Hmm, I think this approach has some complications:
- Using JobStatus makes it tied to using BigQuery batch load jobs, but the
return type ought to be the same regardless of which method of writing is
used (including potential future BigQuery APIs - they are evolving), or how
many BigQuery load jobs are involved in writing a given window (it can be
multiple).
- Returning a success/failure indicator makes it prone to users ignoring
the failure: the default behavior should be that, if the pipeline succeeds,
that means all data was successfully written - if users want different
error handling, e.g. a deadletter queue, they should have to specify it
explicitly.
I would recommend to return a PCollection of a type that's invariant to
which load method is used (streaming writes, load jobs, multiple load jobs
etc.). If it's unclear what type that should be, you could introduce an
empty type e.g. "class BigQueryWriteResult {}" just for the sake of
signaling success, and later add something to it.
On Tue, Jul 17, 2018 at 12:30 AM Carlos Alonso <car...@mrcalonso.com> wrote:
> All good so far. I've been a bit side tracked but more or less I have the
> idea of using the JobStatus as part of the collection so that not only the
> completion is signaled, but also the result (success/failure) can be
> accessed, how does it sound?
>
> Regards
>
> On Tue, Jul 17, 2018 at 3:07 AM Eugene Kirpichov <kirpic...@google.com>
> wrote:
>
>> Hi Carlos,
>>
>> Any updates / roadblocks you hit?
>>
>>
>> On Tue, Jul 3, 2018 at 7:13 AM Eugene Kirpichov <kirpic...@google.com>
>> wrote:
>>
>>> Awesome!! Thanks for the heads up, very exciting, this is going to make
>>> a lot of people happy :)
>>>
>>> On Tue, Jul 3, 2018, 3:40 AM Carlos Alonso <car...@mrcalonso.com> wrote:
>>>
>>>> + dev@beam.apache.org
>>>>
>>>> Just a quick email to let you know that I'm starting developing this.
>>>>
>>>> On Fri, Apr 20, 2018 at 10:30 PM Eugene Kirpichov <kirpic...@google.com>
>>>> wrote:
>>>>
>>>>> Hi Carlos,
>>>>>
>>>>> Thank you for expressing interest in taking this on! Let me give you a
>>>>> few pointers to start, and I'll be happy to help everywhere along the way.
>>>>>
>>>>> Basically we want BigQueryIO.write() to return something (e.g. a
>>>>> PCollection) that can be used as input to Wait.on().
>>>>> Currently it returns a WriteResult, which only contains a
>>>>> PCollection<TableRow> of failed inserts - that one can not be used
>>>>> directly, instead we should add another component to WriteResult that
>>>>> represents the result of successfully writing some data.
>>>>>
>>>>> Given that BQIO supports dynamic destination writes, I think it makes
>>>>> sense for that to be a PCollection<KV<DestinationT, ???>> so that in
>>>>> theory
>>>>> we could sequence different destinations independently (currently
>>>>> Wait.on()
>>>>> does not provide such a feature, but it could); and it will require
>>>>> changing WriteResult to be WriteResult<DestinationT>. As for what the
>>>>> "???"
>>>>> might be - it is something that represents the result of successfully
>>>>> writing a window of data. I think it can even be Void, or "?" (wildcard
>>>>> type) for now, until we figure out something better.
>>>>>
>>>>> Implementing this would require roughly the following work:
>>>>> - Add this PCollection<KV<DestinationT, ?>> to WriteResult
>>>>> - Modify the BatchLoads transform to provide it on both codepaths:
>>>>> expandTriggered() and expandUntriggered()
>>>>> ...- expandTriggered() itself writes via 2 codepaths: single-partition
>>>>> and multi-partition. Both need to be handled - we need to get a
>>>>> PCollection<KV<DestinationT, ?>> from each of them, and Flatten these two
>>>>> PCollections together to get the final result. The single-partition
>>>>> codepath (writeSinglePartition) under the hood already uses WriteTables
>>>>> that returns a KV<DestinationT, ...> so it's directly usable. The
>>>>> multi-partition codepath ends in WriteRenameTriggered - unfortunately,
>>>>> this
>>>>> codepath drops DestinationT along the way and will need to be refactored a
>>>>> bit to keep it until the end.
>>>>> ...- expandUntriggered() should be treated the same way.
>>>>> - Modify the StreamingWriteTables transform to provide it
>>>>> ...- Here also, the challenge is to propagate the DestinationT type
>>>>> all the way until the end of StreamingWriteTables - it will need to be
>>>>> refactored. After such a refactoring, returning a KV<DestinationT, ...>
>>>>> should be easy.
>>>>>
>>>>> Another challenge with all of this is backwards compatibility in terms
>>>>> of API and pipeline update.
>>>>> Pipeline update is much less of a concern for the BatchLoads codepath,
>>>>> because it's typically used in batch-mode pipelines that don't get
>>>>> updated.
>>>>> I would recommend to start with this, perhaps even with only the
>>>>> untriggered codepath (it is much more commonly used) - that will pave the
>>>>> way for future work.
>>>>>
>>>>> Hope this helps, please ask more if something is unclear!
>>>>>
>>>>> On Fri, Apr 20, 2018 at 12:48 AM Carlos Alonso <car...@mrcalonso.com>
>>>>> wrote:
>>>>>
>>>>>> Hey Eugene!!
>>>>>>
>>>>>> I’d gladly take a stab on it although I’m not sure how much available
>>>>>> time I might have to put into but... yeah, let’s try it.
>>>>>>
>>>>>> Where should I begin? Is there a Jira issue or shall I file one?
>>>>>>
>>>>>> Thanks!
>>>>>> On Thu, 12 Apr 2018 at 00:41, Eugene Kirpichov <kirpic...@google.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> Yes, you're both right - BigQueryIO.write() is currently not
>>>>>>> implemented in a way that it can be used with Wait.on(). It would
>>>>>>> certainly
>>>>>>> be a welcome contribution to change this - many people expressed
>>>>>>> interest
>>>>>>> in specifically waiting for BigQuery writes. Is any of you interested in
>>>>>>> helping out?
>>>>>>>
>>>>>>> Thanks.
>>>>>>>
>>>>>>> On Fri, Apr 6, 2018 at 12:36 AM Carlos Alonso <car...@mrcalonso.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Hi Simon, I think your explanation was very accurate, at least to
>>>>>>>> my understanding. I'd also be interested in getting batch load result's
>>>>>>>> feedback on the pipeline... hopefully someone may suggest something,
>>>>>>>> otherwise we could propose submitting a Jira, or even better, a PR!! :)
>>>>>>>>
>>>>>>>> Thanks!
>>>>>>>>
>>>>>>>> On Thu, Apr 5, 2018 at 2:01 PM Simon Kitching <
>>>>>>>> simon.kitch...@unbelievable-machine.com> wrote:
>>>>>>>>
>>>>>>>>> Hi All,
>>>>>>>>>
>>>>>>>>> I need to write some data to BigQuery (batch-mode) and then send a
>>>>>>>>> Pubsub message to trigger further processing.
>>>>>>>>>
>>>>>>>>> I found this thread titled "Callbacks/other functions run after a
>>>>>>>>> PDone/output transform" on the user-list which was very relevant:
>>>>>>>>>
>>>>>>>>> https://lists.apache.org/thread.html/ddcdf93604396b1cbcacdff49aba60817dc90ee7c8434725ea0d26c0@%3Cuser.beam.apache.org%3E
>>>>>>>>>
>>>>>>>>> Thanks to the author of the Wait transform (Beam 2.4.0)!
>>>>>>>>>
>>>>>>>>> Unfortunately, it appears that the Wait.on transform does not work
>>>>>>>>> with BiqQueryIO in FILE_LOADS mode - or at least I cannot get it to
>>>>>>>>> work.
>>>>>>>>> Advice appreciated.
>>>>>>>>>
>>>>>>>>> Here's (most of) the relevant test code:
>>>>>>>>> Pipeline p = Pipeline.create(options);
>>>>>>>>> PCollection<String> lines = p.apply("Read Input",
>>>>>>>>> Create.of("line1", "line2", "line3", "line4"));
>>>>>>>>>
>>>>>>>>> TableFieldSchema f1 = new
>>>>>>>>> TableFieldSchema().setName("value").setType("string");
>>>>>>>>> TableSchema s2 = new
>>>>>>>>> TableSchema().setFields(Collections.singletonList(f1));
>>>>>>>>>
>>>>>>>>> WriteResult writeResult = lines.apply("Write and load
>>>>>>>>> data", BigQueryIO.<String>write() //
>>>>>>>>> .to(options.getTableSpec()) //
>>>>>>>>> .withFormatFunction(new SlowFormatter()) //
>>>>>>>>> .withMethod(BigQueryIO.Write.Method.FILE_LOADS) //
>>>>>>>>> //
>>>>>>>>> .withMethod(BigQueryIO.Write.Method.STREAMING_INSERTS) //
>>>>>>>>> .withSchema(s2)
>>>>>>>>>
>>>>>>>>> .withCreateDisposition(BigQueryIO.Write.CreateDisposition.CREATE_IF_NEEDED)
>>>>>>>>> //
>>>>>>>>>
>>>>>>>>> .withWriteDisposition(BigQueryIO.Write.WriteDisposition.WRITE_APPEND));
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> lines.apply(Wait.on(writeResult.getFailedInserts())).apply(ParDo.of(new
>>>>>>>>> OnCompletion()));
>>>>>>>>>
>>>>>>>>> where
>>>>>>>>> + format-function "SlowFormatter" prints out each line and has a
>>>>>>>>> small sleep for testing purposes, and
>>>>>>>>> + DoFn OnCompletion just prints out the contents of each line
>>>>>>>>>
>>>>>>>>> In production code, OnCompletion would be fed some collection
>>>>>>>>> derived from lines, eg min/max record id, and the operation would be
>>>>>>>>> "send
>>>>>>>>> pubsub message" rather than print..
>>>>>>>>>
>>>>>>>>> My expectation is that the "SlowFormatter" would run for each
>>>>>>>>> line, then the data would be uploaded, then OnCompletion would print
>>>>>>>>> each
>>>>>>>>> line. And indeed that happens when STREAMING_INSERTS is used. However
>>>>>>>>> for
>>>>>>>>> FILE_LOADS, LinePrinter runs before the upload takes place.
>>>>>>>>>
>>>>>>>>> I use WriteResult.getFailedInserts as that is the only "output"
>>>>>>>>> that BiqQueryIO.write() generates AFAICT. I don't expect any failed
>>>>>>>>> records, but believe that it can be used as a "signal" for the
>>>>>>>>> Wait.on - ie
>>>>>>>>> the output is "complete for window" only after all data has been
>>>>>>>>> uploaded,
>>>>>>>>> which is what I need. And that does seem to work for STREAMING_LOADS.
>>>>>>>>>
>>>>>>>>> I suspect the reason that this does not work for FILE_LOADS is
>>>>>>>>> that method BatchLoads.writeResult returns a WriteResult that wraps an
>>>>>>>>> "empty" failedInserts collection, ie data which is not connected to
>>>>>>>>> the
>>>>>>>>> batch-load-job that is triggered:
>>>>>>>>> private WriteResult writeResult(Pipeline p) {
>>>>>>>>> PCollection<TableRow> empty =
>>>>>>>>> p.apply("CreateEmptyFailedInserts",
>>>>>>>>> Create.empty(TypeDescriptor.of(TableRow.class)));
>>>>>>>>> return WriteResult.in(p, new TupleTag<>("failedInserts"),
>>>>>>>>> empty);
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>> Note that BatchLoads does "synchronously" invoke BigQuery load
>>>>>>>>> jobs; once a job is submitted the code repeatedly polls the job status
>>>>>>>>> until it reaches DONE or FAILED. However that information does not
>>>>>>>>> appear
>>>>>>>>> to be exposed anywhere (unlike streaming which effectively exposes
>>>>>>>>> completion-state via the failedInserts stream).
>>>>>>>>>
>>>>>>>>> If I have misunderstood something, corrections welcome! If not,
>>>>>>>>> suggestions for workarounds or alternate solutions are also welcome
>>>>>>>>> :-)
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>> Simon
>>>>>>>>>
>>>>>>>>>
