Re: Sort Merge Bucket - Action Items
Hi! Wanted to bump this thread with some updated PRs that reflect these discussions (updated IOs that parameterize FileIO#Sink, and re-use ReadableFile). The base pull requests are: - https://github.com/apache/beam/pull/8823 (BucketMetadata implementation) - https://github.com/apache/beam/pull/8824/ (FileOperations/IO implementations) And the actual PTransform implements build on top of those PRs: - https://github.com/apache/beam/pull/9250/ (SMB Sink transform) - https://github.com/apache/beam/pull/9251 (SMB Source transform) Finally we have some benchmarks/style changes (using AutoValue/Builder pattern) for those PTransforms: - https://github.com/apache/beam/pull/9253/ (high-level API classes/style fixes) - https://github.com/apache/beam/pull/9279 (benchmarks for SMB sink and source transform) I know it's a lot of pull requests at once -- let us know if there's anything else we can clarify or streamline. Thanks! - Claire/Neville On Fri, Jul 26, 2019 at 12:45 PM Kenneth Knowles wrote: > There is still considerable value in knowing data sources statically so > you can do things like fetch sizes and other metadata and adjust pipeline > shape. I would not expect to delete these, but to implement them on top of > SDF while still giving them a clear URN and payload so runners can know > that it is a statically-specified source. > > Kenn > > On Fri, Jul 26, 2019 at 3:23 AM Robert Bradshaw > wrote: > >> On Thu, Jul 25, 2019 at 11:09 PM Eugene Kirpichov >> wrote: >> > >> > Hi Gleb, >> > >> > Regarding the future of io.Read: ideally things would go as follows >> > - All runners support SDF at feature parity with Read (mostly this is >> just the Dataflow runner's liquid sharding and size estimation for bounded >> sources, and backlog for unbounded sources, but I recall that a couple of >> other runners also used size estimation) >> > - Bounded/UnboundedSource APIs are declared "deprecated" - it is >> forbidden to add any new implementations to SDK, and users shouldn't use >> them either (note: I believe it's already effectively forbidden to use them >> for cases where a DoFn/SDF at the current level of support will be >> sufficient) >> > - People one by one rewrite existing Bounded/UnboundedSource based >> PTransforms in the SDK to use SDFs instead >> > - Read.from() is rewritten to use a wrapper SDF over the given Source, >> and explicit support for Read is deleted from runners >> > - In the next major version of Beam - presumably 3.0 - the Read >> transform itself is deleted >> > >> > I don't know what's the current status of SDF/Read feature parity, >> maybe Luke or Cham can comment. An alternative path is offered in >> http://s.apache.org/sdf-via-source. >> >> Python supports initial splitting for SDF of all sources on portable >> runners. Dataflow support for batch SDF is undergoing testing, not yet >> rolled out. Dataflow support for streaming SDF is awaiting portable >> state/timer support. >> >> > On Thu, Jul 25, 2019 at 6:39 AM Gleb Kanterov wrote: >> >> >> >> What is the long-term plan for org.apache.beam.sdk.io.Read? Is it >> going away in favor of SDF, or we are always going to have both? >> >> >> >> I was looking into AvroIO.read and AvroIO.readAll, both of them use >> AvroSource. AvroIO.readAll is using SDF, and it's implemented with >> ReadAllViaFileBasedSource that takes AvroSource as a parameter. Looking at >> ReadAllViaFileBasedSource I find it not necessary to use Source, it >> should be enough to have something like (KV, >> OutputReceiver), as we have discussed in this thread, and that should be >> fine for SMB as well. It would require duplicating code from AvroSource, >> but in the end, I don't see it as a problem if AvroSource is going away. >> >> >> >> I'm attaching a small diagram I put for myself to better understand >> the code. >> >> >> >> AvroIO.readAll :: PTransform> -> >> >> >> >> FileIO.matchAll :: PTransform, >> PCollection> >> >> FileIO.readMatches :: PTransform, >> PCollection> >> >> AvroIO.readFiles :: PTransform, >> PCollection> -> >> >> >> >> ReadAllViaFileBasedSource :: PTransform, >> PCollection> -> >> >> >> >> ParDo.of(SplitIntoRangesFn :: DoFn> OffsetRange>>) (splittable do fn) >> >> >> >> Reshuffle.viaRandomKey() >> >> >> >> ParDo.of(ReadFileRangesFn(createSource) :: DoFn> OffsetRange>, T>) where >> >> >> >> createSource :: String -> FileBasedSource >> >> >> >> createSource = AvroSource >> >> >> >> >> >> AvroIO.read without getHintMatchedManyFiles() :: PTransform> PCollection> -> >> >> >> >> Read.Bounded.from(createSource) where >> >> >> >> createSource :: String -> FileBasedSource >> >> >> >> createSource = AvroSource >> >> >> >> >> >> Gleb >> >> >> >> >> >> On Thu, Jul 25, 2019 at 2:41 PM Robert Bradshaw >> wrote: >> >>> >> >>> On Thu, Jul 25, 2019 at 12:35 AM Kenneth Knowles >> wrote: >> >>> > >> >>> > From the peanut gallery, keeping a separate implementation for SMB >> seems fine. Dependencies are serious liabilities for both upstream and >> downstream.
Re: Sort Merge Bucket - Action Items
There is still considerable value in knowing data sources statically so you
can do things like fetch sizes and other metadata and adjust pipeline
shape. I would not expect to delete these, but to implement them on top of
SDF while still giving them a clear URN and payload so runners can know
that it is a statically-specified source.
Kenn
On Fri, Jul 26, 2019 at 3:23 AM Robert Bradshaw wrote:
> On Thu, Jul 25, 2019 at 11:09 PM Eugene Kirpichov
> wrote:
> >
> > Hi Gleb,
> >
> > Regarding the future of io.Read: ideally things would go as follows
> > - All runners support SDF at feature parity with Read (mostly this is
> just the Dataflow runner's liquid sharding and size estimation for bounded
> sources, and backlog for unbounded sources, but I recall that a couple of
> other runners also used size estimation)
> > - Bounded/UnboundedSource APIs are declared "deprecated" - it is
> forbidden to add any new implementations to SDK, and users shouldn't use
> them either (note: I believe it's already effectively forbidden to use them
> for cases where a DoFn/SDF at the current level of support will be
> sufficient)
> > - People one by one rewrite existing Bounded/UnboundedSource based
> PTransforms in the SDK to use SDFs instead
> > - Read.from() is rewritten to use a wrapper SDF over the given Source,
> and explicit support for Read is deleted from runners
> > - In the next major version of Beam - presumably 3.0 - the Read
> transform itself is deleted
> >
> > I don't know what's the current status of SDF/Read feature parity, maybe
> Luke or Cham can comment. An alternative path is offered in
> http://s.apache.org/sdf-via-source.
>
> Python supports initial splitting for SDF of all sources on portable
> runners. Dataflow support for batch SDF is undergoing testing, not yet
> rolled out. Dataflow support for streaming SDF is awaiting portable
> state/timer support.
>
> > On Thu, Jul 25, 2019 at 6:39 AM Gleb Kanterov wrote:
> >>
> >> What is the long-term plan for org.apache.beam.sdk.io.Read? Is it going
> away in favor of SDF, or we are always going to have both?
> >>
> >> I was looking into AvroIO.read and AvroIO.readAll, both of them use
> AvroSource. AvroIO.readAll is using SDF, and it's implemented with
> ReadAllViaFileBasedSource that takes AvroSource as a parameter. Looking at
> ReadAllViaFileBasedSource I find it not necessary to use Source, it
> should be enough to have something like (KV,
> OutputReceiver), as we have discussed in this thread, and that should be
> fine for SMB as well. It would require duplicating code from AvroSource,
> but in the end, I don't see it as a problem if AvroSource is going away.
> >>
> >> I'm attaching a small diagram I put for myself to better understand the
> code.
> >>
> >> AvroIO.readAll :: PTransform> ->
> >>
> >> FileIO.matchAll :: PTransform,
> PCollection>
> >> FileIO.readMatches :: PTransform,
> PCollection>
> >> AvroIO.readFiles :: PTransform,
> PCollection> ->
> >>
> >> ReadAllViaFileBasedSource :: PTransform,
> PCollection> ->
> >>
> >> ParDo.of(SplitIntoRangesFn :: DoFn OffsetRange>>) (splittable do fn)
> >>
> >> Reshuffle.viaRandomKey()
> >>
> >> ParDo.of(ReadFileRangesFn(createSource) :: DoFn OffsetRange>, T>) where
> >>
> >> createSource :: String -> FileBasedSource
> >>
> >> createSource = AvroSource
> >>
> >>
> >> AvroIO.read without getHintMatchedManyFiles() :: PTransform PCollection> ->
> >>
> >> Read.Bounded.from(createSource) where
> >>
> >> createSource :: String -> FileBasedSource
> >>
> >> createSource = AvroSource
> >>
> >>
> >> Gleb
> >>
> >>
> >> On Thu, Jul 25, 2019 at 2:41 PM Robert Bradshaw
> wrote:
> >>>
> >>> On Thu, Jul 25, 2019 at 12:35 AM Kenneth Knowles
> wrote:
> >>> >
> >>> > From the peanut gallery, keeping a separate implementation for SMB
> seems fine. Dependencies are serious liabilities for both upstream and
> downstream. It seems like the reuse angle is generating extra work, and
> potentially making already-complex implementations more complex, instead of
> helping things.
> >>>
> >>> +1
> >>>
> >>> To be clear, what I care about is that WriteFiles(X) and
> >>> WriteSmbFiles(X) can share the same X, for X in {Avro, Parquet, Text,
> >>> TFRecord, ...}. In other words composability of the API (vs. manually
> >>> filling out the matrix). If WriteFiles and WriteSmbFiles find
> >>> opportunities for (easy, clean) implementation sharing, that'd be
> >>> nice, but not the primary goal.
> >>>
> >>> (Similarly for reading, though that's seem less obvious. Certainly
> >>> whatever T is useful for ReadSmb(T) could be useful for a
> >>> (non-liquid-shading) ReadAll(T) however.)
> >>>
> >>> > On Wed, Jul 24, 2019 at 11:59 AM Neville Li
> wrote:
> >>> >>
> >>> >> I spoke too soon. Turns out for unsharded writes, numShards can't
> be determined until the last finalize transform, which is again different
> from the current SMB proposal (static number of buckets & shards).
> >>> >> I'll end up with more code specialized for SMB in order
Re: Sort Merge Bucket - Action Items
On Thu, Jul 25, 2019 at 11:09 PM Eugene Kirpichov wrote:
>
> Hi Gleb,
>
> Regarding the future of io.Read: ideally things would go as follows
> - All runners support SDF at feature parity with Read (mostly this is just
> the Dataflow runner's liquid sharding and size estimation for bounded
> sources, and backlog for unbounded sources, but I recall that a couple of
> other runners also used size estimation)
> - Bounded/UnboundedSource APIs are declared "deprecated" - it is forbidden to
> add any new implementations to SDK, and users shouldn't use them either
> (note: I believe it's already effectively forbidden to use them for cases
> where a DoFn/SDF at the current level of support will be sufficient)
> - People one by one rewrite existing Bounded/UnboundedSource based
> PTransforms in the SDK to use SDFs instead
> - Read.from() is rewritten to use a wrapper SDF over the given Source, and
> explicit support for Read is deleted from runners
> - In the next major version of Beam - presumably 3.0 - the Read transform
> itself is deleted
>
> I don't know what's the current status of SDF/Read feature parity, maybe Luke
> or Cham can comment. An alternative path is offered in
> http://s.apache.org/sdf-via-source.
Python supports initial splitting for SDF of all sources on portable
runners. Dataflow support for batch SDF is undergoing testing, not yet
rolled out. Dataflow support for streaming SDF is awaiting portable
state/timer support.
> On Thu, Jul 25, 2019 at 6:39 AM Gleb Kanterov wrote:
>>
>> What is the long-term plan for org.apache.beam.sdk.io.Read? Is it going away
>> in favor of SDF, or we are always going to have both?
>>
>> I was looking into AvroIO.read and AvroIO.readAll, both of them use
>> AvroSource. AvroIO.readAll is using SDF, and it's implemented with
>> ReadAllViaFileBasedSource that takes AvroSource as a parameter. Looking at
>> ReadAllViaFileBasedSource I find it not necessary to use Source, it
>> should be enough to have something like (KV,
>> OutputReceiver), as we have discussed in this thread, and that should be
>> fine for SMB as well. It would require duplicating code from AvroSource, but
>> in the end, I don't see it as a problem if AvroSource is going away.
>>
>> I'm attaching a small diagram I put for myself to better understand the code.
>>
>> AvroIO.readAll :: PTransform> ->
>>
>> FileIO.matchAll :: PTransform,
>> PCollection>
>> FileIO.readMatches :: PTransform,
>> PCollection>
>> AvroIO.readFiles :: PTransform,
>> PCollection> ->
>>
>> ReadAllViaFileBasedSource :: PTransform,
>> PCollection> ->
>>
>> ParDo.of(SplitIntoRangesFn :: DoFn> OffsetRange>>) (splittable do fn)
>>
>> Reshuffle.viaRandomKey()
>>
>> ParDo.of(ReadFileRangesFn(createSource) :: DoFn> OffsetRange>, T>) where
>>
>> createSource :: String -> FileBasedSource
>>
>> createSource = AvroSource
>>
>>
>> AvroIO.read without getHintMatchedManyFiles() :: PTransform> PCollection> ->
>>
>> Read.Bounded.from(createSource) where
>>
>> createSource :: String -> FileBasedSource
>>
>> createSource = AvroSource
>>
>>
>> Gleb
>>
>>
>> On Thu, Jul 25, 2019 at 2:41 PM Robert Bradshaw wrote:
>>>
>>> On Thu, Jul 25, 2019 at 12:35 AM Kenneth Knowles wrote:
>>> >
>>> > From the peanut gallery, keeping a separate implementation for SMB seems
>>> > fine. Dependencies are serious liabilities for both upstream and
>>> > downstream. It seems like the reuse angle is generating extra work, and
>>> > potentially making already-complex implementations more complex, instead
>>> > of helping things.
>>>
>>> +1
>>>
>>> To be clear, what I care about is that WriteFiles(X) and
>>> WriteSmbFiles(X) can share the same X, for X in {Avro, Parquet, Text,
>>> TFRecord, ...}. In other words composability of the API (vs. manually
>>> filling out the matrix). If WriteFiles and WriteSmbFiles find
>>> opportunities for (easy, clean) implementation sharing, that'd be
>>> nice, but not the primary goal.
>>>
>>> (Similarly for reading, though that's seem less obvious. Certainly
>>> whatever T is useful for ReadSmb(T) could be useful for a
>>> (non-liquid-shading) ReadAll(T) however.)
>>>
>>> > On Wed, Jul 24, 2019 at 11:59 AM Neville Li wrote:
>>> >>
>>> >> I spoke too soon. Turns out for unsharded writes, numShards can't be
>>> >> determined until the last finalize transform, which is again different
>>> >> from the current SMB proposal (static number of buckets & shards).
>>> >> I'll end up with more code specialized for SMB in order to generalize
>>> >> existing sink code, which I think we all want to avoid.
>>> >>
>>> >> Seems the only option is duplicating some logic like temp file handling,
>>> >> which is exactly what we did in the original PR.
>>> >> I can reuse Compression & Sink for file level writes but that seems
>>> >> about the most I can reuse right now.
>>> >>
>>> >> On Tue, Jul 23, 2019 at 6:36 PM Neville Li wrote:
>>> >>>
>>> >>> So I spent one afternoon trying some ideas for reusing the last few
>>>
Re: Sort Merge Bucket - Action Items
Hi Gleb,
Regarding the future of io.Read: ideally things would go as follows
- All runners support SDF at feature parity with Read (mostly this is just
the Dataflow runner's liquid sharding and size estimation for bounded
sources, and backlog for unbounded sources, but I recall that a couple of
other runners also used size estimation)
- Bounded/UnboundedSource APIs are declared "deprecated" - it is forbidden
to add any new implementations to SDK, and users shouldn't use them either
(note: I believe it's already effectively forbidden to use them for cases
where a DoFn/SDF at the current level of support will be sufficient)
- People one by one rewrite existing Bounded/UnboundedSource based
PTransforms in the SDK to use SDFs instead
- Read.from() is rewritten to use a wrapper SDF over the given Source, and
explicit support for Read is deleted from runners
- In the next major version of Beam - presumably 3.0 - the Read transform
itself is deleted
I don't know what's the current status of SDF/Read feature parity, maybe
Luke or Cham can comment. An alternative path is offered in
http://s.apache.org/sdf-via-source.
On Thu, Jul 25, 2019 at 6:39 AM Gleb Kanterov wrote:
> What is the long-term plan for org.apache.beam.sdk.io.Read? Is it going
> away in favor of SDF, or we are always going to have both?
>
> I was looking into AvroIO.read and AvroIO.readAll, both of them
> use AvroSource. AvroIO.readAll is using SDF, and it's implemented with
> ReadAllViaFileBasedSource that takes AvroSource as a parameter. Looking at
> ReadAllViaFileBasedSource I find it not necessary to use Source, it
> should be enough to have something like (KV,
> OutputReceiver), as we have discussed in this thread, and that should be
> fine for SMB as well. It would require duplicating code from AvroSource,
> but in the end, I don't see it as a problem if AvroSource is going away.
>
> I'm attaching a small diagram I put for myself to better understand the
> code.
>
> AvroIO.readAll :: PTransform> ->
>
> FileIO.matchAll :: PTransform,
> PCollection>
> FileIO.readMatches :: PTransform,
> PCollection>
> AvroIO.readFiles :: PTransform,
> PCollection> ->
>
> ReadAllViaFileBasedSource :: PTransform,
> PCollection> ->
>
> ParDo.of(SplitIntoRangesFn :: DoFn OffsetRange>>) (splittable do fn)
>
> Reshuffle.viaRandomKey()
>
> ParDo.of(ReadFileRangesFn(createSource) :: DoFn OffsetRange>, T>) where
>
> createSource :: String -> FileBasedSource
>
> createSource = AvroSource
>
>
> AvroIO.read without getHintMatchedManyFiles() :: PTransform PCollection> ->
>
> Read.Bounded.from(createSource) where
>
> createSource :: String -> FileBasedSource
>
> createSource = AvroSource
>
>
> Gleb
>
>
> On Thu, Jul 25, 2019 at 2:41 PM Robert Bradshaw
> wrote:
>
>> On Thu, Jul 25, 2019 at 12:35 AM Kenneth Knowles wrote:
>> >
>> > From the peanut gallery, keeping a separate implementation for SMB
>> seems fine. Dependencies are serious liabilities for both upstream and
>> downstream. It seems like the reuse angle is generating extra work, and
>> potentially making already-complex implementations more complex, instead of
>> helping things.
>>
>> +1
>>
>> To be clear, what I care about is that WriteFiles(X) and
>> WriteSmbFiles(X) can share the same X, for X in {Avro, Parquet, Text,
>> TFRecord, ...}. In other words composability of the API (vs. manually
>> filling out the matrix). If WriteFiles and WriteSmbFiles find
>> opportunities for (easy, clean) implementation sharing, that'd be
>> nice, but not the primary goal.
>>
>> (Similarly for reading, though that's seem less obvious. Certainly
>> whatever T is useful for ReadSmb(T) could be useful for a
>> (non-liquid-shading) ReadAll(T) however.)
>>
>> > On Wed, Jul 24, 2019 at 11:59 AM Neville Li
>> wrote:
>> >>
>> >> I spoke too soon. Turns out for unsharded writes, numShards can't be
>> determined until the last finalize transform, which is again different from
>> the current SMB proposal (static number of buckets & shards).
>> >> I'll end up with more code specialized for SMB in order to generalize
>> existing sink code, which I think we all want to avoid.
>> >>
>> >> Seems the only option is duplicating some logic like temp file
>> handling, which is exactly what we did in the original PR.
>> >> I can reuse Compression & Sink for file level writes but that seems
>> about the most I can reuse right now.
>> >>
>> >> On Tue, Jul 23, 2019 at 6:36 PM Neville Li
>> wrote:
>> >>>
>> >>> So I spent one afternoon trying some ideas for reusing the last few
>> transforms WriteFiles.
>> >>>
>> >>> WriteShardsIntoTempFilesFn extends DoFn,
>> Iterable>, FileResult>
>> >>> => GatherResults extends PTransform,
>> PCollection>>
>> >>> => FinalizeTempFileBundles extends
>> PTransform>>,
>> WriteFilesResult>
>> >>>
>> >>> I replaced FileResult with KV
>> so I can use pre-compute SMB destination file names for the transforms.
>> >>> I'm also thinking of parameterizing ShardedKey for SMB's
>> bucket/shard to reuse
Re: Sort Merge Bucket - Action Items
As far as I/O code re-use, the consensus seems to be to make the SMB module
as composable as possible using existing Beam components, ideally as-is or
with very basic tweaks.
To be clear, what I care about is that WriteFiles(X) and
> WriteSmbFiles(X) can share the same X, for X in {Avro, Parquet, Text,
> TFRecord, ...}. In other words composability of the API (vs. manually
> filling out the matrix). If WriteFiles and WriteSmbFiles find
> opportunities for (easy, clean) implementation sharing, that'd be
> nice, but not the primary goal.
For SMB writes, it's a pretty easy change to parameterize them by
FileIO.Sink, for which there are already public implementations for
Avro/TFRecord/Parquet/Text! It'll remove a lot of code duplication from the
smb module.
(Similarly for reading, though that's seem less obvious. Certainly
> whatever T is useful for ReadSmb(T) could be useful for a
> (non-liquid-shading) ReadAll(T) however.)
It seems like there isn't an easily composable equivalent for Reader that
isn't coupled with FileBasedSource (+1 on Gleb's question about the
long-term future of org.apache.beam.sdk.io.Read). One thing we could do to
improve parity between SMB reads and Beam's io module is to use ReadableFile
as
our file handles (currently we just use plain ResourceIds + FileSystems api
to open), so our Source transform would more closely resemble the existing
ReadFiles transforms
.
ReadableFile also brings in io.Compression
and
handles opening a ReadableByteChannel for us. We'd still be re-implementing
the I/O operations that deserialize a bytestream into individual elements,
but this seems unavoidable for the time being.
Let me know what you think about these proposed modifications to SMB
read/write!
Thanks,
Claire
On Thu, Jul 25, 2019 at 9:39 AM Gleb Kanterov wrote:
> What is the long-term plan for org.apache.beam.sdk.io.Read? Is it going
> away in favor of SDF, or we are always going to have both?
>
> I was looking into AvroIO.read and AvroIO.readAll, both of them
> use AvroSource. AvroIO.readAll is using SDF, and it's implemented with
> ReadAllViaFileBasedSource that takes AvroSource as a parameter. Looking at
> ReadAllViaFileBasedSource I find it not necessary to use Source, it
> should be enough to have something like (KV,
> OutputReceiver), as we have discussed in this thread, and that should be
> fine for SMB as well. It would require duplicating code from AvroSource,
> but in the end, I don't see it as a problem if AvroSource is going away.
>
> I'm attaching a small diagram I put for myself to better understand the
> code.
>
> AvroIO.readAll :: PTransform> ->
>
> FileIO.matchAll :: PTransform,
> PCollection>
> FileIO.readMatches :: PTransform,
> PCollection>
> AvroIO.readFiles :: PTransform,
> PCollection> ->
>
> ReadAllViaFileBasedSource :: PTransform,
> PCollection> ->
>
> ParDo.of(SplitIntoRangesFn :: DoFn OffsetRange>>) (splittable do fn)
>
> Reshuffle.viaRandomKey()
>
> ParDo.of(ReadFileRangesFn(createSource) :: DoFn OffsetRange>, T>) where
>
> createSource :: String -> FileBasedSource
>
> createSource = AvroSource
>
>
> AvroIO.read without getHintMatchedManyFiles() :: PTransform PCollection> ->
>
> Read.Bounded.from(createSource) where
>
> createSource :: String -> FileBasedSource
>
> createSource = AvroSource
>
>
> Gleb
>
>
> On Thu, Jul 25, 2019 at 2:41 PM Robert Bradshaw
> wrote:
>
>> On Thu, Jul 25, 2019 at 12:35 AM Kenneth Knowles wrote:
>> >
>> > From the peanut gallery, keeping a separate implementation for SMB
>> seems fine. Dependencies are serious liabilities for both upstream and
>> downstream. It seems like the reuse angle is generating extra work, and
>> potentially making already-complex implementations more complex, instead of
>> helping things.
>>
>> +1
>>
>> To be clear, what I care about is that WriteFiles(X) and
>> WriteSmbFiles(X) can share the same X, for X in {Avro, Parquet, Text,
>> TFRecord, ...}. In other words composability of the API (vs. manually
>> filling out the matrix). If WriteFiles and WriteSmbFiles find
>> opportunities for (easy, clean) implementation sharing, that'd be
>> nice, but not the primary goal.
>>
>> (Similarly for reading, though that's seem less obvious. Certainly
>> whatever T is useful for ReadSmb(T) could be useful for a
>> (non-liquid-shading) ReadAll(T) however.)
>>
>> > On Wed, Jul 24, 2019 at 11:59 AM Neville Li
>> wrote:
>> >>
>> >> I spoke too soon. Turns out for unsharded writes, numShards can't be
>> determined until the last finalize transform, which is again different from
>> the current SMB proposal (static
Re: Sort Merge Bucket - Action Items
What is the long-term plan for org.apache.beam.sdk.io.Read? Is it going
away in favor of SDF, or we are always going to have both?
I was looking into AvroIO.read and AvroIO.readAll, both of them
use AvroSource. AvroIO.readAll is using SDF, and it's implemented with
ReadAllViaFileBasedSource that takes AvroSource as a parameter. Looking at
ReadAllViaFileBasedSource I find it not necessary to use Source, it
should be enough to have something like (KV,
OutputReceiver), as we have discussed in this thread, and that should be
fine for SMB as well. It would require duplicating code from AvroSource,
but in the end, I don't see it as a problem if AvroSource is going away.
I'm attaching a small diagram I put for myself to better understand the
code.
AvroIO.readAll :: PTransform> ->
FileIO.matchAll :: PTransform,
PCollection>
FileIO.readMatches :: PTransform,
PCollection>
AvroIO.readFiles :: PTransform,
PCollection> ->
ReadAllViaFileBasedSource :: PTransform,
PCollection> ->
ParDo.of(SplitIntoRangesFn :: DoFn>) (splittable do fn)
Reshuffle.viaRandomKey()
ParDo.of(ReadFileRangesFn(createSource) :: DoFn, T>) where
createSource :: String -> FileBasedSource
createSource = AvroSource
AvroIO.read without getHintMatchedManyFiles() :: PTransform> ->
Read.Bounded.from(createSource) where
createSource :: String -> FileBasedSource
createSource = AvroSource
Gleb
On Thu, Jul 25, 2019 at 2:41 PM Robert Bradshaw wrote:
> On Thu, Jul 25, 2019 at 12:35 AM Kenneth Knowles wrote:
> >
> > From the peanut gallery, keeping a separate implementation for SMB seems
> fine. Dependencies are serious liabilities for both upstream and
> downstream. It seems like the reuse angle is generating extra work, and
> potentially making already-complex implementations more complex, instead of
> helping things.
>
> +1
>
> To be clear, what I care about is that WriteFiles(X) and
> WriteSmbFiles(X) can share the same X, for X in {Avro, Parquet, Text,
> TFRecord, ...}. In other words composability of the API (vs. manually
> filling out the matrix). If WriteFiles and WriteSmbFiles find
> opportunities for (easy, clean) implementation sharing, that'd be
> nice, but not the primary goal.
>
> (Similarly for reading, though that's seem less obvious. Certainly
> whatever T is useful for ReadSmb(T) could be useful for a
> (non-liquid-shading) ReadAll(T) however.)
>
> > On Wed, Jul 24, 2019 at 11:59 AM Neville Li
> wrote:
> >>
> >> I spoke too soon. Turns out for unsharded writes, numShards can't be
> determined until the last finalize transform, which is again different from
> the current SMB proposal (static number of buckets & shards).
> >> I'll end up with more code specialized for SMB in order to generalize
> existing sink code, which I think we all want to avoid.
> >>
> >> Seems the only option is duplicating some logic like temp file
> handling, which is exactly what we did in the original PR.
> >> I can reuse Compression & Sink for file level writes but that seems
> about the most I can reuse right now.
> >>
> >> On Tue, Jul 23, 2019 at 6:36 PM Neville Li
> wrote:
> >>>
> >>> So I spent one afternoon trying some ideas for reusing the last few
> transforms WriteFiles.
> >>>
> >>> WriteShardsIntoTempFilesFn extends DoFn,
> Iterable>, FileResult>
> >>> => GatherResults extends PTransform,
> PCollection>>
> >>> => FinalizeTempFileBundles extends
> PTransform>>,
> WriteFilesResult>
> >>>
> >>> I replaced FileResult with KV
> so I can use pre-compute SMB destination file names for the transforms.
> >>> I'm also thinking of parameterizing ShardedKey for SMB's
> bucket/shard to reuse WriteShardsIntoTempFilesFn. These transforms are
> private and easy to change/pull out.
> >>>
> >>> OTOH they are somewhat coupled with the package private
> {Avro,Text,TFRecord}Sink and their WriteOperation impl (where the bulk of
> temp file handing logic lives). Might be hard to decouple either modifying
> existing code or creating new transforms, unless if we re-write most of
> FileBasedSink from scratch.
> >>>
> >>> Let me know if I'm on the wrong track.
> >>>
> >>> WIP Branch https://github.com/spotify/beam/tree/neville/write-files
> >>>
> >>> On Tue, Jul 23, 2019 at 4:22 PM Chamikara Jayalath <
> chamik...@google.com> wrote:
>
>
>
> On Mon, Jul 22, 2019 at 1:41 PM Robert Bradshaw
> wrote:
> >
> > On Mon, Jul 22, 2019 at 7:39 PM Eugene Kirpichov <
> kirpic...@google.com> wrote:
> > >
> > > On Mon, Jul 22, 2019 at 7:49 AM Robert Bradshaw <
> rober...@google.com> wrote:
> > >>
> > >> On Mon, Jul 22, 2019 at 4:04 PM Neville Li
> wrote:
> > >> >
> > >> > Thanks Robert. Agree with the FileIO point. I'll look into it
> and see what needs to be done.
> > >> >
> > >> > Eugene pointed out that we shouldn't build on
> FileBased{Source,Sink}. So for writes I'll probably build on top of
> WriteFiles.
> > >>
> > >> Meaning it could be parameterized by FileIO.Sink, right?
> > >>
> > >>
>
Re: Sort Merge Bucket - Action Items
On Thu, Jul 25, 2019 at 12:35 AM Kenneth Knowles wrote:
>
> From the peanut gallery, keeping a separate implementation for SMB seems
> fine. Dependencies are serious liabilities for both upstream and downstream.
> It seems like the reuse angle is generating extra work, and potentially
> making already-complex implementations more complex, instead of helping
> things.
+1
To be clear, what I care about is that WriteFiles(X) and
WriteSmbFiles(X) can share the same X, for X in {Avro, Parquet, Text,
TFRecord, ...}. In other words composability of the API (vs. manually
filling out the matrix). If WriteFiles and WriteSmbFiles find
opportunities for (easy, clean) implementation sharing, that'd be
nice, but not the primary goal.
(Similarly for reading, though that's seem less obvious. Certainly
whatever T is useful for ReadSmb(T) could be useful for a
(non-liquid-shading) ReadAll(T) however.)
> On Wed, Jul 24, 2019 at 11:59 AM Neville Li wrote:
>>
>> I spoke too soon. Turns out for unsharded writes, numShards can't be
>> determined until the last finalize transform, which is again different from
>> the current SMB proposal (static number of buckets & shards).
>> I'll end up with more code specialized for SMB in order to generalize
>> existing sink code, which I think we all want to avoid.
>>
>> Seems the only option is duplicating some logic like temp file handling,
>> which is exactly what we did in the original PR.
>> I can reuse Compression & Sink for file level writes but that seems about
>> the most I can reuse right now.
>>
>> On Tue, Jul 23, 2019 at 6:36 PM Neville Li wrote:
>>>
>>> So I spent one afternoon trying some ideas for reusing the last few
>>> transforms WriteFiles.
>>>
>>> WriteShardsIntoTempFilesFn extends DoFn,
>>> Iterable>, FileResult>
>>> => GatherResults extends PTransform,
>>> PCollection>>
>>> => FinalizeTempFileBundles extends
>>> PTransform>>,
>>> WriteFilesResult>
>>>
>>> I replaced FileResult with KV so I
>>> can use pre-compute SMB destination file names for the transforms.
>>> I'm also thinking of parameterizing ShardedKey for SMB's
>>> bucket/shard to reuse WriteShardsIntoTempFilesFn. These transforms are
>>> private and easy to change/pull out.
>>>
>>> OTOH they are somewhat coupled with the package private
>>> {Avro,Text,TFRecord}Sink and their WriteOperation impl (where the bulk of
>>> temp file handing logic lives). Might be hard to decouple either modifying
>>> existing code or creating new transforms, unless if we re-write most of
>>> FileBasedSink from scratch.
>>>
>>> Let me know if I'm on the wrong track.
>>>
>>> WIP Branch https://github.com/spotify/beam/tree/neville/write-files
>>>
>>> On Tue, Jul 23, 2019 at 4:22 PM Chamikara Jayalath
>>> wrote:
On Mon, Jul 22, 2019 at 1:41 PM Robert Bradshaw
wrote:
>
> On Mon, Jul 22, 2019 at 7:39 PM Eugene Kirpichov
> wrote:
> >
> > On Mon, Jul 22, 2019 at 7:49 AM Robert Bradshaw
> > wrote:
> >>
> >> On Mon, Jul 22, 2019 at 4:04 PM Neville Li
> >> wrote:
> >> >
> >> > Thanks Robert. Agree with the FileIO point. I'll look into it and
> >> > see what needs to be done.
> >> >
> >> > Eugene pointed out that we shouldn't build on
> >> > FileBased{Source,Sink}. So for writes I'll probably build on top of
> >> > WriteFiles.
> >>
> >> Meaning it could be parameterized by FileIO.Sink, right?
> >>
> >> https://github.com/apache/beam/blob/release-2.13.0/sdks/java/core/src/main/java/org/apache/beam/sdk/io/FileIO.java#L779
> >
> > Yeah if possible, parameterize FileIO.Sink.
> > I would recommend against building on top of WriteFiles either. FileIO
> > being implemented on top of WriteFiles was supposed to be a temporary
> > measure - the longer-term plan was to rewrite it from scratch (albeit
> > with a similar structure) and throw away WriteFiles.
> > If possible, I would recommend to pursue this path: if there are parts
> > of WriteFiles you want to reuse, I would recommend to implement them as
> > new transforms, not at all tied to FileBasedSink (but ok if tied to
> > FileIO.Sink), with the goal in mind that FileIO could be rewritten on
> > top of these new transforms, or maybe parts of WriteFiles could be
> > swapped out for them incrementally.
>
> Thanks for the feedback. There's a lot that was done, but looking at
> the code it feels like there's a lot that was not yet done either, and
> the longer-term plan wasn't clear (though perhaps I'm just not finding
> the right docs).
I'm also a bit unfamiliar with original plans for WriteFiles and for
updating source interfaces, but I prefer not significantly modifying
existing IO transforms to suite the SMB use-case. If there are existing
pieces of code that can be easily re-used that is fine, but existing
sources/sinks are designed to
Re: Sort Merge Bucket - Action Items
>From the peanut gallery, keeping a separate implementation for SMB seems
fine. Dependencies are serious liabilities for both upstream and
downstream. It seems like the reuse angle is generating extra work, and
potentially making already-complex implementations more complex, instead of
helping things.
Kenn
On Wed, Jul 24, 2019 at 11:59 AM Neville Li wrote:
> I spoke too soon. Turns out for unsharded writes, numShards can't be
> determined until the last finalize transform, which is again different from
> the current SMB proposal (static number of buckets & shards).
> I'll end up with more code specialized for SMB in order to generalize
> existing sink code, which I think we all want to avoid.
>
> Seems the only option is duplicating some logic like temp file handling,
> which is exactly what we did in the original PR.
> I can reuse Compression & Sink for file level writes but that seems
> about the most I can reuse right now.
>
> On Tue, Jul 23, 2019 at 6:36 PM Neville Li wrote:
>
>> So I spent one afternoon trying some ideas for reusing the last few
>> transforms WriteFiles.
>>
>> WriteShardsIntoTempFilesFn extends DoFn*,
>> Iterable>, *FileResult*>
>> => GatherResults extends PTransform,
>> PCollection>>
>> => FinalizeTempFileBundles extends PTransform> *FileResult*>>, WriteFilesResult>
>>
>> I replaced FileResult with KV so
>> I can use pre-compute SMB destination file names for the transforms.
>> I'm also thinking of parameterizing ShardedKey for SMB's
>> bucket/shard to reuse WriteShardsIntoTempFilesFn. These transforms are
>> private and easy to change/pull out.
>>
>> OTOH they are somewhat coupled with the package private
>> {Avro,Text,TFRecord}Sink and their WriteOperation impl (where the bulk of
>> temp file handing logic lives). Might be hard to decouple either modifying
>> existing code or creating new transforms, unless if we re-write most of
>> FileBasedSink from scratch.
>>
>> Let me know if I'm on the wrong track.
>>
>> WIP Branch https://github.com/spotify/beam/tree/neville/write-files
>>
>> On Tue, Jul 23, 2019 at 4:22 PM Chamikara Jayalath
>> wrote:
>>
>>>
>>>
>>> On Mon, Jul 22, 2019 at 1:41 PM Robert Bradshaw
>>> wrote:
>>>
On Mon, Jul 22, 2019 at 7:39 PM Eugene Kirpichov
wrote:
>
> On Mon, Jul 22, 2019 at 7:49 AM Robert Bradshaw
wrote:
>>
>> On Mon, Jul 22, 2019 at 4:04 PM Neville Li
wrote:
>> >
>> > Thanks Robert. Agree with the FileIO point. I'll look into it and
see what needs to be done.
>> >
>> > Eugene pointed out that we shouldn't build on
FileBased{Source,Sink}. So for writes I'll probably build on top of
WriteFiles.
>>
>> Meaning it could be parameterized by FileIO.Sink, right?
>>
>>
https://github.com/apache/beam/blob/release-2.13.0/sdks/java/core/src/main/java/org/apache/beam/sdk/io/FileIO.java#L779
>
> Yeah if possible, parameterize FileIO.Sink.
> I would recommend against building on top of WriteFiles either.
FileIO being implemented on top of WriteFiles was supposed to be a
temporary measure - the longer-term plan was to rewrite it from scratch
(albeit with a similar structure) and throw away WriteFiles.
> If possible, I would recommend to pursue this path: if there are
parts of WriteFiles you want to reuse, I would recommend to implement them
as new transforms, not at all tied to FileBasedSink (but ok if tied to
FileIO.Sink), with the goal in mind that FileIO could be rewritten on top
of these new transforms, or maybe parts of WriteFiles could be swapped out
for them incrementally.
Thanks for the feedback. There's a lot that was done, but looking at
the code it feels like there's a lot that was not yet done either, and
the longer-term plan wasn't clear (though perhaps I'm just not finding
the right docs).
>>>
>>> I'm also a bit unfamiliar with original plans for WriteFiles and for
>>> updating source interfaces, but I prefer not significantly modifying
>>> existing IO transforms to suite the SMB use-case. If there are existing
>>> pieces of code that can be easily re-used that is fine, but existing
>>> sources/sinks are designed to perform a PCollection -> file transformation
>>> and vice versa with (usually) runner determined sharding. Things specific
>>> to SMB such as sharding restrictions, writing metadata to a separate file,
>>> reading multiple files from the same abstraction, does not sound like
>>> features that should be included in our usual file read/write transforms.
>>>
>>>
>> > Read might be a bigger change w.r.t. collocating ordered elements
across files within a bucket and TBH I'm not even sure where to start.
>>
>> Yeah, here we need an interface that gives us ReadableFile ->
>> Iterable. There are existing PTransform,
>> PCollection> but such an interface is insufficient to extract
>> ordered records per shard. It seems
Re: Sort Merge Bucket - Action Items
I spoke too soon. Turns out for unsharded writes, numShards can't be
determined until the last finalize transform, which is again different from
the current SMB proposal (static number of buckets & shards).
I'll end up with more code specialized for SMB in order to generalize
existing sink code, which I think we all want to avoid.
Seems the only option is duplicating some logic like temp file handling,
which is exactly what we did in the original PR.
I can reuse Compression & Sink for file level writes but that seems
about the most I can reuse right now.
On Tue, Jul 23, 2019 at 6:36 PM Neville Li wrote:
> So I spent one afternoon trying some ideas for reusing the last few
> transforms WriteFiles.
>
> WriteShardsIntoTempFilesFn extends DoFn*,
> Iterable>, *FileResult*>
> => GatherResults extends PTransform,
> PCollection>>
> => FinalizeTempFileBundles extends PTransform *FileResult*>>, WriteFilesResult>
>
> I replaced FileResult with KV so I
> can use pre-compute SMB destination file names for the transforms.
> I'm also thinking of parameterizing ShardedKey for SMB's
> bucket/shard to reuse WriteShardsIntoTempFilesFn. These transforms are
> private and easy to change/pull out.
>
> OTOH they are somewhat coupled with the package private
> {Avro,Text,TFRecord}Sink and their WriteOperation impl (where the bulk of
> temp file handing logic lives). Might be hard to decouple either modifying
> existing code or creating new transforms, unless if we re-write most of
> FileBasedSink from scratch.
>
> Let me know if I'm on the wrong track.
>
> WIP Branch https://github.com/spotify/beam/tree/neville/write-files
>
> On Tue, Jul 23, 2019 at 4:22 PM Chamikara Jayalath
> wrote:
>
>>
>>
>> On Mon, Jul 22, 2019 at 1:41 PM Robert Bradshaw
>> wrote:
>>
>>> On Mon, Jul 22, 2019 at 7:39 PM Eugene Kirpichov
>>> wrote:
>>> >
>>> > On Mon, Jul 22, 2019 at 7:49 AM Robert Bradshaw
>>> wrote:
>>> >>
>>> >> On Mon, Jul 22, 2019 at 4:04 PM Neville Li
>>> wrote:
>>> >> >
>>> >> > Thanks Robert. Agree with the FileIO point. I'll look into it and
>>> see what needs to be done.
>>> >> >
>>> >> > Eugene pointed out that we shouldn't build on
>>> FileBased{Source,Sink}. So for writes I'll probably build on top of
>>> WriteFiles.
>>> >>
>>> >> Meaning it could be parameterized by FileIO.Sink, right?
>>> >>
>>> >>
>>> https://github.com/apache/beam/blob/release-2.13.0/sdks/java/core/src/main/java/org/apache/beam/sdk/io/FileIO.java#L779
>>> >
>>> > Yeah if possible, parameterize FileIO.Sink.
>>> > I would recommend against building on top of WriteFiles either. FileIO
>>> being implemented on top of WriteFiles was supposed to be a temporary
>>> measure - the longer-term plan was to rewrite it from scratch (albeit with
>>> a similar structure) and throw away WriteFiles.
>>> > If possible, I would recommend to pursue this path: if there are parts
>>> of WriteFiles you want to reuse, I would recommend to implement them as new
>>> transforms, not at all tied to FileBasedSink (but ok if tied to
>>> FileIO.Sink), with the goal in mind that FileIO could be rewritten on top
>>> of these new transforms, or maybe parts of WriteFiles could be swapped out
>>> for them incrementally.
>>>
>>> Thanks for the feedback. There's a lot that was done, but looking at
>>> the code it feels like there's a lot that was not yet done either, and
>>> the longer-term plan wasn't clear (though perhaps I'm just not finding
>>> the right docs).
>>>
>>
>> I'm also a bit unfamiliar with original plans for WriteFiles and for
>> updating source interfaces, but I prefer not significantly modifying
>> existing IO transforms to suite the SMB use-case. If there are existing
>> pieces of code that can be easily re-used that is fine, but existing
>> sources/sinks are designed to perform a PCollection -> file transformation
>> and vice versa with (usually) runner determined sharding. Things specific
>> to SMB such as sharding restrictions, writing metadata to a separate file,
>> reading multiple files from the same abstraction, does not sound like
>> features that should be included in our usual file read/write transforms.
>>
>>
>>> >> > Read might be a bigger change w.r.t. collocating ordered elements
>>> across files within a bucket and TBH I'm not even sure where to start.
>>> >>
>>> >> Yeah, here we need an interface that gives us ReadableFile ->
>>> >> Iterable. There are existing PTransform,
>>> >> PCollection> but such an interface is insufficient to extract
>>> >> ordered records per shard. It seems the only concrete implementations
>>> >> are based on FileBasedSource, which we'd like to avoid, but there's no
>>> >> alternative. An SDF, if exposed, would likely be overkill and
>>> >> cumbersome to call (given the reflection machinery involved in
>>> >> invoking DoFns).
>>> >
>>> > Seems easiest to just define a new regular Java interface for this.
>>> > Could be either, indeed, ReadableFile -> Iterable, or something
>>> analogous, e.g. (ReadableFile, OutputReceiver) ->
Re: Sort Merge Bucket - Action Items
So I spent one afternoon trying some ideas for reusing the last few
transforms WriteFiles.
WriteShardsIntoTempFilesFn extends DoFn*,
Iterable>, *FileResult*>
=> GatherResults extends PTransform,
PCollection>>
=> FinalizeTempFileBundles extends PTransform*>>, WriteFilesResult>
I replaced FileResult with KV so I
can use pre-compute SMB destination file names for the transforms.
I'm also thinking of parameterizing ShardedKey for SMB's
bucket/shard to reuse WriteShardsIntoTempFilesFn. These transforms are
private and easy to change/pull out.
OTOH they are somewhat coupled with the package private
{Avro,Text,TFRecord}Sink and their WriteOperation impl (where the bulk of
temp file handing logic lives). Might be hard to decouple either modifying
existing code or creating new transforms, unless if we re-write most of
FileBasedSink from scratch.
Let me know if I'm on the wrong track.
WIP Branch https://github.com/spotify/beam/tree/neville/write-files
On Tue, Jul 23, 2019 at 4:22 PM Chamikara Jayalath
wrote:
>
>
> On Mon, Jul 22, 2019 at 1:41 PM Robert Bradshaw
> wrote:
>
>> On Mon, Jul 22, 2019 at 7:39 PM Eugene Kirpichov
>> wrote:
>> >
>> > On Mon, Jul 22, 2019 at 7:49 AM Robert Bradshaw
>> wrote:
>> >>
>> >> On Mon, Jul 22, 2019 at 4:04 PM Neville Li
>> wrote:
>> >> >
>> >> > Thanks Robert. Agree with the FileIO point. I'll look into it and
>> see what needs to be done.
>> >> >
>> >> > Eugene pointed out that we shouldn't build on
>> FileBased{Source,Sink}. So for writes I'll probably build on top of
>> WriteFiles.
>> >>
>> >> Meaning it could be parameterized by FileIO.Sink, right?
>> >>
>> >>
>> https://github.com/apache/beam/blob/release-2.13.0/sdks/java/core/src/main/java/org/apache/beam/sdk/io/FileIO.java#L779
>> >
>> > Yeah if possible, parameterize FileIO.Sink.
>> > I would recommend against building on top of WriteFiles either. FileIO
>> being implemented on top of WriteFiles was supposed to be a temporary
>> measure - the longer-term plan was to rewrite it from scratch (albeit with
>> a similar structure) and throw away WriteFiles.
>> > If possible, I would recommend to pursue this path: if there are parts
>> of WriteFiles you want to reuse, I would recommend to implement them as new
>> transforms, not at all tied to FileBasedSink (but ok if tied to
>> FileIO.Sink), with the goal in mind that FileIO could be rewritten on top
>> of these new transforms, or maybe parts of WriteFiles could be swapped out
>> for them incrementally.
>>
>> Thanks for the feedback. There's a lot that was done, but looking at
>> the code it feels like there's a lot that was not yet done either, and
>> the longer-term plan wasn't clear (though perhaps I'm just not finding
>> the right docs).
>>
>
> I'm also a bit unfamiliar with original plans for WriteFiles and for
> updating source interfaces, but I prefer not significantly modifying
> existing IO transforms to suite the SMB use-case. If there are existing
> pieces of code that can be easily re-used that is fine, but existing
> sources/sinks are designed to perform a PCollection -> file transformation
> and vice versa with (usually) runner determined sharding. Things specific
> to SMB such as sharding restrictions, writing metadata to a separate file,
> reading multiple files from the same abstraction, does not sound like
> features that should be included in our usual file read/write transforms.
>
>
>> >> > Read might be a bigger change w.r.t. collocating ordered elements
>> across files within a bucket and TBH I'm not even sure where to start.
>> >>
>> >> Yeah, here we need an interface that gives us ReadableFile ->
>> >> Iterable. There are existing PTransform,
>> >> PCollection> but such an interface is insufficient to extract
>> >> ordered records per shard. It seems the only concrete implementations
>> >> are based on FileBasedSource, which we'd like to avoid, but there's no
>> >> alternative. An SDF, if exposed, would likely be overkill and
>> >> cumbersome to call (given the reflection machinery involved in
>> >> invoking DoFns).
>> >
>> > Seems easiest to just define a new regular Java interface for this.
>> > Could be either, indeed, ReadableFile -> Iterable, or something
>> analogous, e.g. (ReadableFile, OutputReceiver) -> void. Depends on how
>> much control over iteration you need.
>>
>> For this application, one wants to iterate over several files in
>> parallel. The downside of a new interface is that it shares almost
>> nothing with the "normal" sources (e.g. when features (or
>> optimizations) get added to one, they won't get added to the other).
>
>
>
>>
>> > And yes, DoFn's including SDF's are not designed to be used as Java
>> interfaces per se. If you need DoFn machinery in this interface (e.g. side
>> inputs), use Contextful - s.apache.org/context-fn.
>>
>> Yeah, one of the primary downsides to the NewDoFns is how hard it is
>> to build new DoFns out of others (or, really, use them in any context
>> other than as an argument to ParDo).
>>
>>
Re: Sort Merge Bucket - Action Items
On Mon, Jul 22, 2019 at 1:41 PM Robert Bradshaw wrote:
> On Mon, Jul 22, 2019 at 7:39 PM Eugene Kirpichov
> wrote:
> >
> > On Mon, Jul 22, 2019 at 7:49 AM Robert Bradshaw
> wrote:
> >>
> >> On Mon, Jul 22, 2019 at 4:04 PM Neville Li
> wrote:
> >> >
> >> > Thanks Robert. Agree with the FileIO point. I'll look into it and see
> what needs to be done.
> >> >
> >> > Eugene pointed out that we shouldn't build on FileBased{Source,Sink}.
> So for writes I'll probably build on top of WriteFiles.
> >>
> >> Meaning it could be parameterized by FileIO.Sink, right?
> >>
> >>
> https://github.com/apache/beam/blob/release-2.13.0/sdks/java/core/src/main/java/org/apache/beam/sdk/io/FileIO.java#L779
> >
> > Yeah if possible, parameterize FileIO.Sink.
> > I would recommend against building on top of WriteFiles either. FileIO
> being implemented on top of WriteFiles was supposed to be a temporary
> measure - the longer-term plan was to rewrite it from scratch (albeit with
> a similar structure) and throw away WriteFiles.
> > If possible, I would recommend to pursue this path: if there are parts
> of WriteFiles you want to reuse, I would recommend to implement them as new
> transforms, not at all tied to FileBasedSink (but ok if tied to
> FileIO.Sink), with the goal in mind that FileIO could be rewritten on top
> of these new transforms, or maybe parts of WriteFiles could be swapped out
> for them incrementally.
>
> Thanks for the feedback. There's a lot that was done, but looking at
> the code it feels like there's a lot that was not yet done either, and
> the longer-term plan wasn't clear (though perhaps I'm just not finding
> the right docs).
>
I'm also a bit unfamiliar with original plans for WriteFiles and for
updating source interfaces, but I prefer not significantly modifying
existing IO transforms to suite the SMB use-case. If there are existing
pieces of code that can be easily re-used that is fine, but existing
sources/sinks are designed to perform a PCollection -> file transformation
and vice versa with (usually) runner determined sharding. Things specific
to SMB such as sharding restrictions, writing metadata to a separate file,
reading multiple files from the same abstraction, does not sound like
features that should be included in our usual file read/write transforms.
> >> > Read might be a bigger change w.r.t. collocating ordered elements
> across files within a bucket and TBH I'm not even sure where to start.
> >>
> >> Yeah, here we need an interface that gives us ReadableFile ->
> >> Iterable. There are existing PTransform,
> >> PCollection> but such an interface is insufficient to extract
> >> ordered records per shard. It seems the only concrete implementations
> >> are based on FileBasedSource, which we'd like to avoid, but there's no
> >> alternative. An SDF, if exposed, would likely be overkill and
> >> cumbersome to call (given the reflection machinery involved in
> >> invoking DoFns).
> >
> > Seems easiest to just define a new regular Java interface for this.
> > Could be either, indeed, ReadableFile -> Iterable, or something
> analogous, e.g. (ReadableFile, OutputReceiver) -> void. Depends on how
> much control over iteration you need.
>
> For this application, one wants to iterate over several files in
> parallel. The downside of a new interface is that it shares almost
> nothing with the "normal" sources (e.g. when features (or
> optimizations) get added to one, they won't get added to the other).
>
> > And yes, DoFn's including SDF's are not designed to be used as Java
> interfaces per se. If you need DoFn machinery in this interface (e.g. side
> inputs), use Contextful - s.apache.org/context-fn.
>
> Yeah, one of the primary downsides to the NewDoFns is how hard it is
> to build new DoFns out of others (or, really, use them in any context
> other than as an argument to ParDo).
>
> >> > I'll file separate PRs for core changes needed for discussion. WDYT?
> >>
> >> Sounds good.
>
+1
> >>
> >> > On Mon, Jul 22, 2019 at 4:20 AM Robert Bradshaw
> wrote:
> >> >>
> >> >> On Fri, Jul 19, 2019 at 5:16 PM Neville Li
> wrote:
> >> >> >
> >> >> > Forking this thread to discuss action items regarding the change.
> We can keep technical discussion in the original thread.
> >> >> >
> >> >> > Background: our SMB POC showed promising performance & cost saving
> improvements and we'd like to adopt it for production soon (by EOY). We
> want to contribute it to Beam so it's better generalized and maintained. We
> also want to avoid divergence between our internal version and the PR while
> it's in progress, specifically any breaking change in the produced SMB data.
> >> >>
> >> >> All good goals.
> >> >>
> >> >> > To achieve that I'd like to propose a few action items.
> >> >> >
> >> >> > 1. Reach a consensus about bucket and shard strategy, key
> handling, bucket file and metadata format, etc., anything that affect
> produced SMB data.
> >> >> > 2. Revise the existing PR according to #1
> >> >> > 3.
Re: Sort Merge Bucket - Action Items
On Mon, Jul 22, 2019 at 7:39 PM Eugene Kirpichov wrote:
>
> On Mon, Jul 22, 2019 at 7:49 AM Robert Bradshaw wrote:
>>
>> On Mon, Jul 22, 2019 at 4:04 PM Neville Li wrote:
>> >
>> > Thanks Robert. Agree with the FileIO point. I'll look into it and see what
>> > needs to be done.
>> >
>> > Eugene pointed out that we shouldn't build on FileBased{Source,Sink}. So
>> > for writes I'll probably build on top of WriteFiles.
>>
>> Meaning it could be parameterized by FileIO.Sink, right?
>>
>> https://github.com/apache/beam/blob/release-2.13.0/sdks/java/core/src/main/java/org/apache/beam/sdk/io/FileIO.java#L779
>
> Yeah if possible, parameterize FileIO.Sink.
> I would recommend against building on top of WriteFiles either. FileIO being
> implemented on top of WriteFiles was supposed to be a temporary measure - the
> longer-term plan was to rewrite it from scratch (albeit with a similar
> structure) and throw away WriteFiles.
> If possible, I would recommend to pursue this path: if there are parts of
> WriteFiles you want to reuse, I would recommend to implement them as new
> transforms, not at all tied to FileBasedSink (but ok if tied to FileIO.Sink),
> with the goal in mind that FileIO could be rewritten on top of these new
> transforms, or maybe parts of WriteFiles could be swapped out for them
> incrementally.
Thanks for the feedback. There's a lot that was done, but looking at
the code it feels like there's a lot that was not yet done either, and
the longer-term plan wasn't clear (though perhaps I'm just not finding
the right docs).
>> > Read might be a bigger change w.r.t. collocating ordered elements across
>> > files within a bucket and TBH I'm not even sure where to start.
>>
>> Yeah, here we need an interface that gives us ReadableFile ->
>> Iterable. There are existing PTransform,
>> PCollection> but such an interface is insufficient to extract
>> ordered records per shard. It seems the only concrete implementations
>> are based on FileBasedSource, which we'd like to avoid, but there's no
>> alternative. An SDF, if exposed, would likely be overkill and
>> cumbersome to call (given the reflection machinery involved in
>> invoking DoFns).
>
> Seems easiest to just define a new regular Java interface for this.
> Could be either, indeed, ReadableFile -> Iterable, or something analogous,
> e.g. (ReadableFile, OutputReceiver) -> void. Depends on how much control
> over iteration you need.
For this application, one wants to iterate over several files in
parallel. The downside of a new interface is that it shares almost
nothing with the "normal" sources (e.g. when features (or
optimizations) get added to one, they won't get added to the other).
> And yes, DoFn's including SDF's are not designed to be used as Java
> interfaces per se. If you need DoFn machinery in this interface (e.g. side
> inputs), use Contextful - s.apache.org/context-fn.
Yeah, one of the primary downsides to the NewDoFns is how hard it is
to build new DoFns out of others (or, really, use them in any context
other than as an argument to ParDo).
>> > I'll file separate PRs for core changes needed for discussion. WDYT?
>>
>> Sounds good.
>>
>> > On Mon, Jul 22, 2019 at 4:20 AM Robert Bradshaw
>> > wrote:
>> >>
>> >> On Fri, Jul 19, 2019 at 5:16 PM Neville Li wrote:
>> >> >
>> >> > Forking this thread to discuss action items regarding the change. We
>> >> > can keep technical discussion in the original thread.
>> >> >
>> >> > Background: our SMB POC showed promising performance & cost saving
>> >> > improvements and we'd like to adopt it for production soon (by EOY). We
>> >> > want to contribute it to Beam so it's better generalized and
>> >> > maintained. We also want to avoid divergence between our internal
>> >> > version and the PR while it's in progress, specifically any breaking
>> >> > change in the produced SMB data.
>> >>
>> >> All good goals.
>> >>
>> >> > To achieve that I'd like to propose a few action items.
>> >> >
>> >> > 1. Reach a consensus about bucket and shard strategy, key handling,
>> >> > bucket file and metadata format, etc., anything that affect produced
>> >> > SMB data.
>> >> > 2. Revise the existing PR according to #1
>> >> > 3. Reduce duplicate file IO logic by reusing FileIO.Sink, Compression,
>> >> > etc., but keep the existing file level abstraction
>> >> > 4. (Optional) Merge code into extensions::smb but mark clearly as
>> >> > @experimental
>> >> > 5. Incorporate ideas from the discussion, e.g. ShardingFn,
>> >> > GroupByKeyAndSortValues, FileIO generalization, key URN, etc.
>> >> >
>> >> > #1-4 gives us something usable in the short term, while #1 guarantees
>> >> > that production data produced today are usable when #5 lands on master.
>> >> > #4 also gives early adopters a chance to give feedback.
>> >> > Due to the scope of #5, it might take much longer and a couple of big
>> >> > PRs to achieve, which we can keep iterating on.
>> >> >
>> >> > What are your thoughts
Re: Sort Merge Bucket - Action Items
On Mon, Jul 22, 2019 at 7:49 AM Robert Bradshaw wrote:
> On Mon, Jul 22, 2019 at 4:04 PM Neville Li wrote:
> >
> > Thanks Robert. Agree with the FileIO point. I'll look into it and see
> what needs to be done.
> >
> > Eugene pointed out that we shouldn't build on FileBased{Source,Sink}. So
> for writes I'll probably build on top of WriteFiles.
>
> Meaning it could be parameterized by FileIO.Sink, right?
>
>
> https://github.com/apache/beam/blob/release-2.13.0/sdks/java/core/src/main/java/org/apache/beam/sdk/io/FileIO.java#L779
Yeah if possible, parameterize FileIO.Sink.
I would recommend against building on top of WriteFiles either. FileIO
being implemented on top of WriteFiles was supposed to be a temporary
measure - the longer-term plan was to rewrite it from scratch (albeit with
a similar structure) and throw away WriteFiles.
If possible, I would recommend to pursue this path: if there are parts of
WriteFiles you want to reuse, I would recommend to implement them as new
transforms, not at all tied to FileBasedSink (but ok if tied to
FileIO.Sink), with the goal in mind that FileIO could be rewritten on top
of these new transforms, or maybe parts of WriteFiles could be swapped out
for them incrementally.
>
>
> > Read might be a bigger change w.r.t. collocating ordered elements across
> files within a bucket and TBH I'm not even sure where to start.
>
> Yeah, here we need an interface that gives us ReadableFile ->
> Iterable. There are existing PTransform,
> PCollection> but such an interface is insufficient to extract
> ordered records per shard. It seems the only concrete implementations
> are based on FileBasedSource, which we'd like to avoid, but there's no
> alternative. An SDF, if exposed, would likely be overkill and
> cumbersome to call (given the reflection machinery involved in
> invoking DoFns).
>
Seems easiest to just define a new regular Java interface for this.
Could be either, indeed, ReadableFile -> Iterable, or something
analogous, e.g. (ReadableFile, OutputReceiver) -> void. Depends on how
much control over iteration you need.
And yes, DoFn's including SDF's are not designed to be used as Java
interfaces per se. If you need DoFn machinery in this interface (e.g. side
inputs), use Contextful - s.apache.org/context-fn.
>
> > I'll file separate PRs for core changes needed for discussion. WDYT?
>
> Sounds good.
>
> > On Mon, Jul 22, 2019 at 4:20 AM Robert Bradshaw
> wrote:
> >>
> >> On Fri, Jul 19, 2019 at 5:16 PM Neville Li
> wrote:
> >> >
> >> > Forking this thread to discuss action items regarding the change. We
> can keep technical discussion in the original thread.
> >> >
> >> > Background: our SMB POC showed promising performance & cost saving
> improvements and we'd like to adopt it for production soon (by EOY). We
> want to contribute it to Beam so it's better generalized and maintained. We
> also want to avoid divergence between our internal version and the PR while
> it's in progress, specifically any breaking change in the produced SMB data.
> >>
> >> All good goals.
> >>
> >> > To achieve that I'd like to propose a few action items.
> >> >
> >> > 1. Reach a consensus about bucket and shard strategy, key handling,
> bucket file and metadata format, etc., anything that affect produced SMB
> data.
> >> > 2. Revise the existing PR according to #1
> >> > 3. Reduce duplicate file IO logic by reusing FileIO.Sink,
> Compression, etc., but keep the existing file level abstraction
> >> > 4. (Optional) Merge code into extensions::smb but mark clearly as
> @experimental
> >> > 5. Incorporate ideas from the discussion, e.g. ShardingFn,
> GroupByKeyAndSortValues, FileIO generalization, key URN, etc.
> >> >
> >> > #1-4 gives us something usable in the short term, while #1 guarantees
> that production data produced today are usable when #5 lands on master. #4
> also gives early adopters a chance to give feedback.
> >> > Due to the scope of #5, it might take much longer and a couple of big
> PRs to achieve, which we can keep iterating on.
> >> >
> >> > What are your thoughts on this?
> >>
> >> I would like to see some resolution on the FileIO abstractions before
> >> merging into experimental. (We have a FileBasedSink that would mostly
> >> already work, so it's a matter of coming up with an analogous Source
> >> interface.) Specifically I would not want to merge a set of per file
> >> type smb IOs without a path forward to this or the determination that
> >> it's not possible/desirable.
>
Re: Sort Merge Bucket - Action Items
On Mon, Jul 22, 2019 at 4:04 PM Neville Li wrote:
>
> Thanks Robert. Agree with the FileIO point. I'll look into it and see what
> needs to be done.
>
> Eugene pointed out that we shouldn't build on FileBased{Source,Sink}. So for
> writes I'll probably build on top of WriteFiles.
Meaning it could be parameterized by FileIO.Sink, right?
https://github.com/apache/beam/blob/release-2.13.0/sdks/java/core/src/main/java/org/apache/beam/sdk/io/FileIO.java#L779
> Read might be a bigger change w.r.t. collocating ordered elements across
> files within a bucket and TBH I'm not even sure where to start.
Yeah, here we need an interface that gives us ReadableFile ->
Iterable. There are existing PTransform,
PCollection> but such an interface is insufficient to extract
ordered records per shard. It seems the only concrete implementations
are based on FileBasedSource, which we'd like to avoid, but there's no
alternative. An SDF, if exposed, would likely be overkill and
cumbersome to call (given the reflection machinery involved in
invoking DoFns).
> I'll file separate PRs for core changes needed for discussion. WDYT?
Sounds good.
> On Mon, Jul 22, 2019 at 4:20 AM Robert Bradshaw wrote:
>>
>> On Fri, Jul 19, 2019 at 5:16 PM Neville Li wrote:
>> >
>> > Forking this thread to discuss action items regarding the change. We can
>> > keep technical discussion in the original thread.
>> >
>> > Background: our SMB POC showed promising performance & cost saving
>> > improvements and we'd like to adopt it for production soon (by EOY). We
>> > want to contribute it to Beam so it's better generalized and maintained.
>> > We also want to avoid divergence between our internal version and the PR
>> > while it's in progress, specifically any breaking change in the produced
>> > SMB data.
>>
>> All good goals.
>>
>> > To achieve that I'd like to propose a few action items.
>> >
>> > 1. Reach a consensus about bucket and shard strategy, key handling, bucket
>> > file and metadata format, etc., anything that affect produced SMB data.
>> > 2. Revise the existing PR according to #1
>> > 3. Reduce duplicate file IO logic by reusing FileIO.Sink, Compression,
>> > etc., but keep the existing file level abstraction
>> > 4. (Optional) Merge code into extensions::smb but mark clearly as
>> > @experimental
>> > 5. Incorporate ideas from the discussion, e.g. ShardingFn,
>> > GroupByKeyAndSortValues, FileIO generalization, key URN, etc.
>> >
>> > #1-4 gives us something usable in the short term, while #1 guarantees that
>> > production data produced today are usable when #5 lands on master. #4 also
>> > gives early adopters a chance to give feedback.
>> > Due to the scope of #5, it might take much longer and a couple of big PRs
>> > to achieve, which we can keep iterating on.
>> >
>> > What are your thoughts on this?
>>
>> I would like to see some resolution on the FileIO abstractions before
>> merging into experimental. (We have a FileBasedSink that would mostly
>> already work, so it's a matter of coming up with an analogous Source
>> interface.) Specifically I would not want to merge a set of per file
>> type smb IOs without a path forward to this or the determination that
>> it's not possible/desirable.
Re: Sort Merge Bucket - Action Items
Thanks Robert. Agree with the FileIO point. I'll look into it and see what
needs to be done.
Eugene pointed out that we shouldn't build on FileBased{Source,Sink}. So
for writes I'll probably build on top of WriteFiles. Read might be a bigger
change w.r.t. collocating ordered elements across files within a bucket and
TBH I'm not even sure where to start.
I'll file separate PRs for core changes needed for discussion. WDYT?
On Mon, Jul 22, 2019 at 4:20 AM Robert Bradshaw wrote:
> On Fri, Jul 19, 2019 at 5:16 PM Neville Li wrote:
> >
> > Forking this thread to discuss action items regarding the change. We can
> keep technical discussion in the original thread.
> >
> > Background: our SMB POC showed promising performance & cost saving
> improvements and we'd like to adopt it for production soon (by EOY). We
> want to contribute it to Beam so it's better generalized and maintained. We
> also want to avoid divergence between our internal version and the PR while
> it's in progress, specifically any breaking change in the produced SMB data.
>
> All good goals.
>
> > To achieve that I'd like to propose a few action items.
> >
> > 1. Reach a consensus about bucket and shard strategy, key handling,
> bucket file and metadata format, etc., anything that affect produced SMB
> data.
> > 2. Revise the existing PR according to #1
> > 3. Reduce duplicate file IO logic by reusing FileIO.Sink, Compression,
> etc., but keep the existing file level abstraction
> > 4. (Optional) Merge code into extensions::smb but mark clearly as
> @experimental
> > 5. Incorporate ideas from the discussion, e.g. ShardingFn,
> GroupByKeyAndSortValues, FileIO generalization, key URN, etc.
> >
> > #1-4 gives us something usable in the short term, while #1 guarantees
> that production data produced today are usable when #5 lands on master. #4
> also gives early adopters a chance to give feedback.
> > Due to the scope of #5, it might take much longer and a couple of big
> PRs to achieve, which we can keep iterating on.
> >
> > What are your thoughts on this?
>
> I would like to see some resolution on the FileIO abstractions before
> merging into experimental. (We have a FileBasedSink that would mostly
> already work, so it's a matter of coming up with an analogous Source
> interface.) Specifically I would not want to merge a set of per file
> type smb IOs without a path forward to this or the determination that
> it's not possible/desirable.
>
Re: Sort Merge Bucket - Action Items
On Fri, Jul 19, 2019 at 5:16 PM Neville Li wrote: > > Forking this thread to discuss action items regarding the change. We can keep > technical discussion in the original thread. > > Background: our SMB POC showed promising performance & cost saving > improvements and we'd like to adopt it for production soon (by EOY). We want > to contribute it to Beam so it's better generalized and maintained. We also > want to avoid divergence between our internal version and the PR while it's > in progress, specifically any breaking change in the produced SMB data. All good goals. > To achieve that I'd like to propose a few action items. > > 1. Reach a consensus about bucket and shard strategy, key handling, bucket > file and metadata format, etc., anything that affect produced SMB data. > 2. Revise the existing PR according to #1 > 3. Reduce duplicate file IO logic by reusing FileIO.Sink, Compression, etc., > but keep the existing file level abstraction > 4. (Optional) Merge code into extensions::smb but mark clearly as > @experimental > 5. Incorporate ideas from the discussion, e.g. ShardingFn, > GroupByKeyAndSortValues, FileIO generalization, key URN, etc. > > #1-4 gives us something usable in the short term, while #1 guarantees that > production data produced today are usable when #5 lands on master. #4 also > gives early adopters a chance to give feedback. > Due to the scope of #5, it might take much longer and a couple of big PRs to > achieve, which we can keep iterating on. > > What are your thoughts on this? I would like to see some resolution on the FileIO abstractions before merging into experimental. (We have a FileBasedSink that would mostly already work, so it's a matter of coming up with an analogous Source interface.) Specifically I would not want to merge a set of per file type smb IOs without a path forward to this or the determination that it's not possible/desirable.
Sort Merge Bucket - Action Items
Forking this thread to discuss action items regarding the change. We can keep technical discussion in the original thread. Background: our SMB POC showed promising performance & cost saving improvements and we'd like to adopt it for production soon (by EOY). We want to contribute it to Beam so it's better generalized and maintained. We also want to avoid divergence between our internal version and the PR while it's in progress, specifically any breaking change in the produced SMB data. To achieve that I'd like to propose a few action items. 1. Reach a consensus about bucket and shard strategy, key handling, bucket file and metadata format, etc., anything that affect produced SMB data. 2. Revise the existing PR according to #1 3. Reduce duplicate file IO logic by reusing FileIO.Sink, Compression, etc., but keep the existing file level abstraction 4. (Optional) Merge code into extensions::smb but mark clearly as @experimental 5. Incorporate ideas from the discussion, e.g. ShardingFn, GroupByKeyAndSortValues, FileIO generalization, key URN, etc. #1-4 gives us something usable in the short term, while #1 guarantees that production data produced today are usable when #5 lands on master. #4 also gives early adopters a chance to give feedback. Due to the scope of #5, it might take much longer and a couple of big PRs to achieve, which we can keep iterating on. What are your thoughts on this? On Thu, Jul 18, 2019 at 5:32 AM Robert Bradshaw wrote: > On Wed, Jul 17, 2019 at 9:12 PM Gleb Kanterov wrote: > >> > >> Suppose one assigns a sharding function to a PCollection. Is it lazy, > >> or does it induce a reshuffle right at that point? In either case, > >> once the ShardingFn has been applied, how long does it remain in > >> effect? Does it prohibit the runner (or user) from doing subsequent > >> resharding (including dynamic load balancing)? What happens when one > >> has a DoFn that changes the value? (Including the DoFns in our sinks > >> that assign random keys.) > > > > > > What if we would reason about sharding in the same way as we reason > about timestamps? > > > > Please correct me if I am wrong, as I know, in Beam, timestamps exist > for each element. You can get timestamp by using Reify.timestamps. If there > are timestamped values, and they go through ParDo, timestamps are preserved. > > That is correct. > > > We can think of the same with sharding, where Reify.shards would be > PTransform, ShardedValue> and ShardedValue would > contain shard and a grouping key. > > Meaning the shard that the PCollection is currently sharded by, or the > one that it should be sharded by in the future. (Your use case is a > bit strange in that a single key may be spread across multiple shards, > as long as they're part of the same "bucket.") > > > ParDo wouldn't change sharding and would propagate ShardingFn. > > The ShardingFn may not be applicable to downstream (mutated) elements. > > FYI, internally this is handled by having annotations on DoFns as > being key-preserving, and only reasoning about operations separated by > such DoFns. > > > CoGroupByKey on such PTransforms would reify grouping key, and do > regular CoGroupByKey, or be rewritten to a regular ParDo if sharding of > inputs is compatible. > > > > As you mentioned, it requires dynamic work rebalancing to preserve > sharding. What if we do dynamic work rebalancing for each shard > independently, as, I guess, it's done today for fixed windows. > > Currently, the unit of colocation is by key. Generally sharding > introduces a notion of colocation where multiple keys (or mulitple > elements, I suppose it need not be keyed) are promised to be processed > by the same machine. This is both to constraining (wrt dynamic > reshrading) and not needed (with respect to SMB, as your "colocation" > is per bucket, but buckets themselves can be processed in a > distributed manner). > > > When we do a split, we would split one shard into two. It should be > possible to do consistently if values within buckets are sorted, in this > case, we would split ranges of possible values. > > I'm not quite following here. Suppose one processes element a, m, and > z. Then one decides to split the bundle, but there's not a "range" we > can pick for the "other" as this bundle already spans the whole range. > But maybe I'm just off in the weeds here. > > > On Wed, Jul 17, 2019 at 6:37 PM Robert Bradshaw > wrote: > >> > >> On Wed, Jul 17, 2019 at 4:26 PM Gleb Kanterov wrote: > >> > > >> > I find there is an interesting point in the comments brought by Ahmed > Eleryan. Similar to WindowFn, having a concept of ShardingFn, that enables > users to implement a class for sharding data. Each Beam node can have > ShardingFn set, similar to WindowFn (or WindowingStrategy). Sinks and > sources are aware of that and preserve this information. Using that it's > possible to do optimization on Beam graph, removing redundant CoGroupByKey, > and it would be
