Awesome summary (seriously) -- would you kindly offer your organizational
skills to every ongoing KIP from henceforth? We need you :P
A few answers/comments:
A2: I think there is a 3rd sub-option here, which is to leave
versioned-ness out of this KIP entirely, return only the non-versioned
stores for now, and then switch over to the versioned stores (only) when
the time comes to flip the switch on making them the default across the
DSL. This has the advantage of retaining the current behavior/semantics
and
provides a clear way to transition smoothly in the future, since it seems
we will want to cut to all versioned state stores rather than offer users
a
choice between versioned or non-versioned stores going forward (similar to
how we only offer timestamped stores presently, and have completely
replaced non-timestamped stores in the DSL.) . In both the timestamped and
versioned cases, the old stores are/will still be available or accessible
to users via the bare StoreSuppliers, should they somehow desire or
require
the old store type. Ultimately, I think either this or option (1) would be
preferable, though I think it should be up to Matthias or anyone else
involved in the versioned stores feature to decide which approach makes
sense in the context of that feature's future plans.
A3: sounds reasonable to me
A5: Also sounds fine to me, though I'll let others chime in with/if they
have an alternative suggestion/preference. I guess the other contender
would be something like DSLStoreImpl or something like that?
On Mon, Jul 24, 2023 at 9:36 AM Almog Gavra <almog.ga...@gmail.com>
wrote:
Lots of thoughts! Happy to see the thriving discussion on this post -
lots
going on so I'm trying to enumerate them to keep things organized
(prefix
"A" for "Almog" so we can use numbers in responses for other things ;P).
A1. Question around closing implementation gaps (e.g. no rocks based
suppression store)
A2. Specifically how to handle Versioned stores
A3. Configuration (new config/reuse old one + new one and ordering of
config resolution)
A4. Drawing a line between what is implementation detail (not exposed in
API) and what is customizable (exposed in API)
A5. Naming of StoreTypeSpec
A6. Param classes in StoreBuilders
------------------------------
Here are summaries for where it seems each of these stands (trying not
to
add any additional opinion yet):
A1. Sophie/Guozhang/Me (if I count hah!) seem to agree that it is worth
pushing this KIP through independently of the implementation gaps as it
doesn't seem to move the intermediate state further from the end state.
Matthias originally had some concerns.
A2. There's questions around whether versioned stores should be their
own
configurable option or whether they are an implementation detail that
the
StoreSpec should decide. It seems like the discussion is converging
here,
this should be an implementation detail.
A3. Matthias/Guozhang prefer adding CUSTOM and then having an additional
config to determine the implementation. Sophie prefers deprecating the
old
config. Guozhang additional suggested flipping the resolution order such
that the old config is only respected in a DefaultStoreSpec
implementation.
A4. This KIP (or rather, the discussion on the KIP) blurs the lines
between
top level store types (KV, windowed, session) and the underlying
implementation of them (timestamped, versioned, kv-list). It seems
everyone
is in alignment to ensure that we keep these two things separate and
that
the line is clearly delineated in the text of the KIP.
A5. Guozhang and Sophie agree that the current name StoreTypeSpec is
misleading, as it's really an implementation spec, not a type
specification.
A6. Agreement that this is an improvement, Sophie believes this can be
done
in a follow up but we should ensure our naming is good here so there's
no
conflicts down the line.
---------------------------------
Ok, phew! Hopefully that covers it all! Now for my thoughts, hopefully
wrapping up some of these discussions:
A1. @Matthias - are you still hesitant here? What would you need to be
convinced here?
A2. Since we are all in agreement that versioned stores should be an
implementation detail, we have two options:
(1) we can extend the KVParams to include a parameter that indicates
whether or not the store should be versioned
(2) we can introduce a configuration for whether or not to use a
versioned
store, and each implementation can choose to read/ignore that config
Any preferences? (1) would align more closely with what we are doing
today
(they are a top-level concept in the Stores API).
A3. I like Guozhang's suggestion of making the "primary" configuration
to
be the new one, and then having a "DefaultStoreTypeSpec" (using the old
naming) which respects the old configuration. That seems to solve nearly
all the concerns (e.g. it'd be easy to see where the enum is used
because
it would only be used within that one class instead of littered
throughout
the code base).
@Sophie, unless you have objections here I will update the KIP to do
that.
A4. I will make these changes to the KIP to make it clear.
A5. I will rename it `DslStorePlugin` - any objections to this name?
A6. Let's punt this ;) I agree with everyone that this would be a
welcome
improvement and that this KIP is aligned with moving in that direction.
Given how much discussion there was on this KIP, which is minor
relative to
making the changes to StoreBuilder API, I'd rather not tie the two
together.
Cheers & Thanks everyone for the thoughts!
- Almog
On Sun, Jul 23, 2023 at 5:15 PM Sophie Blee-Goldman <
ableegold...@gmail.com>
wrote:
Guozhang:
On your 2nd point:
"impl types" (in hindsight it may not be a good name) for rocksdb /
memory / custom, and we used "store types" for kv / windowed /
sessioned
etc,
First off, thanks so much for this clarification -- using "store type"
here
was definitely making me uncomfortable as this usually refers to KV vs
window, etc -- but I just couldn't for the life of me think of the
right
term for rocks vs IM. We should 100% change to something like
StoreImplSpec
for this kind of interface.
As for list-value store (for stream-stream Join)
Again, glad you mentioned this -- I forgot how the extra stream-stream
join
store is not a "regular" KV Store but rather this special list-value
store.
If we proceed with something like the current approach, perhaps that
should
be a boolean (or enum) parameter in the KVConfig, similar to the
EmitStrategy? After all, the high-level goal of this KIP is to be
able to
fully customize all DSL state stores, and this is currently not
possible
due to KAFKA-14976 <https://issues.apache.org/jira/browse/KAFKA-14976
.
If we expect there to be further customizations like this going
forward,
perhaps we could instead have each of the three StoreConfig classes
accept
a single enum parameter for the "sub-type" (or whatever you want to
call
it), which would encompass (and replace) things like the EmitStrategy
as
well as the list-value type (we could define one enum for each Config
class
so there is no accidentally requesting a LIST_VALUE subtype on a
WindowStore). Thoughts?
Lastly, regarding 3.b:
I love that you brought this up because that is actually what I first
proposed to Almog, ie introducing a param class to clean up the
StoreBuilder API, during our chat that led to this KIP. He pushed
back,
claiming (rightly so) that this change would be huge in scope for a
purely
aesthetic/API change that doesn't add any functionality, and that it
makes
more sense to start with the DSL config since there is a clear gap in
functionality there, particularly when it comes to custom state stores
(reasons 1 & 3 in the Motivation section). He did agree that the param
classes were a better API, which is why you see them in this KIP. In
other
words: I fully agree that we should apply this improvement to the
PAPI/StoreBuilder interface as well, but I think that's a distinct
concept
for the time-being and should not block the DSL improvement. Rather, I
consider this KIP as setting the stage for a followup KIP down the
line
to
clean up the StoreBuilders and bring them in line with the new
param/config
class approach.
That said, A) we should definitely make sure whatever we introduce
here
can be extended to the PAPI StoreBuilders in a natural way, and B) I
should
clarify that I personally would be happy to see this included in the
current KIP, but as Almog's KIP it's up to him to decide whether he's
comfortable expanding the scope like this. If you can convince him
where
I
could not, more power to you! :P
On Sun, Jul 23, 2023 at 4:48 PM Sophie Blee-Goldman <
ableegold...@gmail.com>
wrote:
Matthias:
I'm not sure I agree with (or maybe don't follow) this take:
we need all kind of `StoreTypeSpec` implementations,
and it might also imply that we need follow up KIPs for new feature
(like in-memory versioned store) that might not need a KIP
otherwise.
I see this feature as being a nice add-on/convenience API for any
store
types which have a full DSL implementation. I don't think it's
unreasonable
to just say that this feature is only going to be available for
store
types
that have KV, Window, and Session implementations. I can't think of
any
case besides versioned stores where this would force a KIP for a new
feature that would not otherwise have to go through a KIP, and even
for
versioned state stores, the only issue is that the KIP for that was
already
accepted.
However, I think I agree on your main point -- that things like
"regular"
vs timestamped vs versioned are/should be an implementation detail
that's
hidden from the user. As I noted previously, the current KIP
actually
greatly improves the situation for timestamped stores, as this
would be
handled completely transparently by the OOTB RocksDBStoreSpec. To
me,
this
provides a very natural way to let the DSL operators using the
default
store type/spec to specify which kind of store (eg
versioned/timestamped/etc) it wants, and choose the correct
default. If
the
eventual intention is to have versioned state stores replace
timestamped
stores as the default in the DSL, then we can simply swap out the
versioned
stores for the timestamped stores in the RocksDBStoreTypeSpec, when
that
time comes. Until then, users who want to use the versioned store
will
have
to do what they do today, which is individually override operators
via
Materialized/StoreSuppliers.
All in all, it sounds like we should not offer a versioned store
type
spec, as "versioned" is more akin to "timestamped" than to a true
difference in underlying store implementation type (eg rocks vs
in-memory).
W.r.t whether to deprecate the old config or introduce a new CUSTOM
enum
type, either seems fine to me, and we can go with that alternative
instead.
The only other con to this approach that I can think of, and I'm
honestly
not sure if this is something users would care about or only devs,
is
that
the advantage to moving rocks and IM to the store type spec
interface
is
that it helps to keep the relevant logic encapsulated in one easy
place
you
can quickly check to tell what kind of state store is used where. In
the
current code, I found it extremely annoying and difficult to track
down
all
usages of the StoreType enum to see which actual rocksdb store was
being
used where (for example some stores using the TimeOrderedBuffer
variants
in
some special cases, or to understand whether the DSL was defaulting
to
plain, timestamped, or versioned stores for RocksDB vs InMemory --
both
of
which seem like they could be of interest to a user). This would be
much
easier if everything was handled in one place, and you can just go
to
the
(eg) RocksDBStoreTypeSpec and see what it's doing, or find usages of
the
methods to understand what stores are being handed to which DSL
operators.
I suppose we could still clean up the API and solve this problem by
having
the old (and new) config delegate to a StoreTypeSpec no matter what,
but
make RocksDBStoreTypeSpec and InMemoryStoreTypeSpec internal classes
that
are simply implementation details of the ROCKSDB vs IN_MEMORY enums.
WDYT?
On Sun, Jul 23, 2023 at 11:14 AM Guozhang Wang <
guozhang.wang...@gmail.com>
wrote:
Thanks everyone for the great discussions so far! I first saw the
JIRA
and left some quick thoughts without being aware of the
already-written KIP (kudos to Almog, very great one) and the
DISCUSS
thread here. And I happily find some of my initial thoughts align
with
the KIP already :)
Would like to add a bit more of my 2c after reading through the KIP
and the thread here:
1. On the high level, I'm in favor of pushing this KIP through
without
waiting on the other gaps to be closed. In my back pocket's
"dependency graph" of Kafka Streams roadmap of large changes or
feature gaps, the edges of dependencies are defined based on my
understanding of whether doing one first would largely complicate /
negate the effort of the other but not vice versa, in which case we
should consider getting the other done first. In this case, I feel
such a dependency is not strong enough, so encouraging the KIP
contributor to finish what he/she would love to do to close some
gaps
early would be higher priorities. I did not see by just doing this
we
could end up in a worse intermediate stage yet, but I could be
corrected.
2. Regarding the store types --- gain here I'd like to just clarify
the terms a bit since in the past it has some confusions: we used
"impl types" (in hindsight it may not be a good name) for rocksdb /
memory / custom, and we used "store types" for kv / windowed /
sessioned etc, as I said in the JIRA I think the current proposal
also
have a good side effect as quality bar to really enforce us think
twice when trying to add more store types in the future as it will
impact API instantiations. In the ideal world, I would consider:
* We have (timestamped) kv store, versioned kv store, window store,
session store as first-class DSL store types. Some DSL operators
could
accept multiple store types (e.g. versioned and non versioned
kv-store) for semantics / efficiency trade-offs. But I think we
would
remove un-timestamped kv stores eventually since that efficiency
trade-off is so minimal compared to its usage limitations.
* As for list-value store (for stream-stream Join),
memory-lru-cache
(for PAPI use only), memory-time-ordered-buffer (for suppression),
they would not be exposed as DSL first-class store types in the
future. Instead, they would be treated as internal used stores
(e.g.
list-value store is built on key-value store with specialized serde
and putInternal), or continue to be just convenient OOTB PAPI used
stores only.
* As we move on, we will continue to be very, very strict on what
would be added as DSL store types (and hence requires changes to
the
proposed APIs), what to be added as convenient OOTB PAPI store
impls
only, what to be added as internal used store types that should
not be
exposed to users nor customizable at all.
3. Some more detailed thoughts below:
3.a) I originally also think that we can extend the existing
config,
rather than replacing it. The difference was that I was thinking
that
order-wise, the runtime would look at the API first, and then the
config, whereas in your rejected alternative it was looking at the
config first, and then the API --- that I think is a minor thing
and
either is fine. I'm in agreement that having two configs would be
more
confusing to users to learn about their precedence rather than
helpful, but if we keep both a config and a public API, then the
precedence ordering would not be so confusing as long as we state
them
clearly. For example:
* We have DefaultStoreTypeSpec OOTB, in that impl we look at the
config only, and would only expect either ROCKS or MEMORY, and
return
corresponding OOTB store impls; if any other values configured, we
error out.
* Users extend that by having MyStoreTypeSpec, in which they could
do
arbituray things without respecting the config at all, but our
recommended pattern in docs would still say "look into the config,
if
it is ROCKS or MEMORY just return fall back to
DefaultStoreTypeSepc;
otherwise if it's some String you recognize, then return your
customized store based on the string value, otherwise error out".
3.b) About the struct-like Params classes, I like the idea a lot
and
wished we would pursue this in the first place, but if we only do
this
in Spec it would leave some inconsistencies with the StoreBuilders
though arguably the latter is only for PAPI. I'm wondering if we
should consider including the changes in StoreBuilders (e.g.
WindowStoreBuilder(WindowSupplierParams)), and if yes, maybe we
should
also consider renaming that e.g. `WindowSupplierParams` to
`WindowStoreSpecParams` too? For this one I only have a "weak
feeling"
so I can be convinced otherwise :P
Thanks,
Guozhang
On Sun, Jul 23, 2023 at 9:52 AM Matthias J. Sax <mj...@apache.org>
wrote:
Thanks for all the input. My intention was not to block the KIP,
but
just to take a step back and try get a holistic picture and
discussion,
to explore if there are good/viable alternative designs. As said
originally, I really like to close this gap, and was always aware
that
the current config is not flexible enough.
I guess, my "concern" is that the KIP does increase the API
surface
area
significantly, as we need all kind of `StoreTypeSpec`
implementations,
and it might also imply that we need follow up KIPs for new
feature
(like in-memory versioned store) that might not need a KIP
otherwise.
The second question is if it might make the already "patchy"
situation
with regard to customization worse.
We did de-scope the original KIP-591 for this reason, and given
the
new
situation of the DSL, it seems that it actually got worse
compared
to
back in the days.
Lastly, I hope to make the new versioned stores the default in
the
DSL
and we did not do it in the previous KIP due to backward
compatibility
issues. Thus, from a DSL point of view, I believe there should be
only
"RocksDB", "InMemory", and "Custom" in an ideal world.
Introducing
(I
am
exaggerating to highlight my point) "KvRocksDbSpec",
"TimestampeKvRocksDbSpec", "VersionedRocksDbSpec", plus the
corresponding in-memory specs seems to head into the opposite
direction.
-- My goal is to give users a handle of the _physical_ store
(RocksDB
vs
InMemory vs Custom) but not the _logical_ stores (plain kv,
ts-kv,
versioned) which is "dictated" by the DSL itself and should not
be
customizable (we are just in a weird intermediate situation that
we
need
to clean up, but not "lean into" IMHO).
Thus, I am also not sure if adding "VersionedRocksDbSpec" would
be
ideal
(also, given that it only changes a single store, but not the two
windowed stores)?
Furthermore, I actually hope that we could use the new versioned
store
to replace the window- and sessions- stores, and thus to decrease
the
number of required store types.
Admittedly, I am talking a lot about a potential future, but the
goal
is
only to explore opportunities to not get into "worse"
intermediate
state, that will require a huge deprecation surface area later
on.
Of
course, if there is no better way, and my concerns are not
shared, I
am
ok to move forward with the KIP.
Bottom line: I would personally prefer to keep the current config
and
add a `Custom` option to it, plus adding one new config that
allows
people to set their custom `StoreTypeSpec` class. -- I would not
add a
built-in spec for versioned stores at this point (or any other
built-in
`StorytypeSpec` implementations). I guess, users could write a
custom
spec if they want to enable versioned store across the board for
now
(until we make them the default anyway)?
Hope my train of thoughts is halfway reasonable and not totally
off
track?
-Matthias
On 7/21/23 15:27, Sophie Blee-Goldman wrote:
I agree with everything Almog said above, and will just add on
to
two
points:
1. Regarding whether to block this KIP on the completion of
any or
all
future implementations of in-memory version stores (or persist
suppression
buffers), I feel that would be unfair to this feature which is
completely
unrelated to the semantic improvements offered by versioned
state
stores.
It seems like the responsibility of those driving the versioned
state
stores feature, not Almog/this KIP, to make sure that those
bases
are
covered. Further, if anything, this KIP will help with the
massive
proliferation of StoreSuppliers on the Stores factory class,
and
provide
users with a much easier way to leverage the versioned stores
without
having to muck around directly with the StoreSuppliers.
I also thought about it a bit, and really like Almog's
suggestion
to
introduce an additional StoreSpec for the Versioned state
stores.
Obviously
we can add the RocksDB one to this KIP now, and then as he
mentioned,
there's an easy way to get users onto the IMVersionedStateStore
types
once
they are completed.
Lastly, on this note, I want to point out how smoothly this
solved
the
issue of timestamped stores, which are intended to be the DSL
default
but
are only a special case for RocksDB. Right now it can be
confusing
for a
user scrolling through the endless Stores class and seeing a
timestamped
version of the persistent but not in-memory stores. One could
easily
assume
there was no timestamped option for IM stores and that this
feature
was
incomplete, if they weren't acutely aware of the internal
implementation
details (namely that it's only required for RocksDB for
compatibility
reasons). However, with this KIP, all that is handled
completely
transparently to the user, and we the devs, who *are* aware of
the
internal
implementation details, are now appropriately the ones
responsible
for
handing the correct store type to a particular operator. While
versioned
state stores may not be completely comparable, depending on
whether
we want
users to remain able to easily choose between using them or not
(vs
timestamped which should be used by all), I still feel this KIP
is a
great
step in the right direction that not only should not be
blocked on
the
completion of the IM implementations, but in fact should
specifically
be
done first as it enables an easier way to utilize those IM
versioned
stores. Just my 2 cents :)
2. The idea to expand the existing the config with a CUSTOM
enum
without
introducing another config to specify the CUSTOM store spec
does
not
seem
appropriate, or even possible (for the reasons Almog mentioned
above
about
config types, though perhaps there is a way I'm not seeing). I
do
not
buy
the argument that we should optimize the API to make it easy
for
users who
just want to switch to all in-memory stores, as I truly believe
this
is a
very small fraction of the potential userbase of this feature
(anyone
who's
actually using this should please chime in!). It seems very
likely
that the
majority of users of this feature are actually those with
custom
state
stores, as to my knowledge, this has been the case any/every
time
this
feature was requested by users.
That said, while I don't see any way to get around introducing
a
new
config, I don't personally have a preference w.r.t whether to
keep
around
the old config or deprecate it. I simply don't get the
impression
it
is
very heavily used as it stands today, while it only works for
those
who
want all in-memory stores. Again, input from actual users
would be
very
valuable here. In the absence of that data, I will just point
to
the
fact
that this KIP was proposed by a Streams dev (you :P),
abandoned,
picked up
by another Streams dev, and finally implemented without ever
hearing
from a
user that they would find this useful. This is not to disparage
the
original KIP, but just to say again, as I stated back then, it
seemed
like
a major opportunity loss to leave out custom state stores
Cheers,
Sophie
On Fri, Jul 21, 2023 at 1:52 PM Almog Gavra <
almog.ga...@gmail.com>
wrote:
Thanks for all the feedback folk! Responses inline.
Basically, I'm suggesting two things: first, call out in some
way
(perhaps the StoreTypeSpec javadocs) that each StoreTypeSpec
is
considered
a public contract in itself and should outline any semantic
guarantees it
does, or does not, make. Second, we should add a note on
ordering
guarantees in the two OOTB specs: for RocksDB we assert that
range
queries
will honor serialized byte ordering, whereas the InMemory
flavor
gives no
ordering guarantee whatsoever at this time.
That makes sense to me Sophie! I'll make the changes to the
KIP.
And
@Colt,
yes I believe that would be the new javadoc for the generic
ReadOnlyKeyValueStore.
However, I am wondering if we should close others gaps first?
@Matthias, thanks for the review and thoughts! I think we
should
separate
closing other gaps in the product from providing this as
useful
functionality to avoid feature creep so long as the API
proposed
here will
be suitable for when we want to close those implementation
gaps!
My
general
proposal is that for things that are not customizable today by
default.dsl.store they remain not customizable after this KIP.
The
good
news is, however, that there's no reason why this cannot be
extended
to
cover those in the future if we want to - see specifics below.
Comments on the specifics below
In particular, this holds for the new versioned-store ...
Should
versioned stores also be covered by the KIP
Is there a reason why we can't introduce a
VersionedRocksDBStoreTypeSpec
and if we ever support an in-memory an equivalent
VersionedInMemoryRocksDBStoreTypeSpec? If so, then there would
not
need to
be any additional changes to the API proposed in this KIP.
For `suppress()` it's actually other way around we only have
an
in-memory
implementation. Do you aim to allow custom stores for
`suppress()`,
too?
We have three options here:
1) we can decide to maintain existing behavior and use the
in-memory
implementation for all stores (not even going through the API
at
all)
2a) we can introduce a new parameter to the KeyValueParams
class
(boolean
isTimeOrderedBuffer or something like that) and return an
in-memory
store
in the implementation of RocksDBStoreTypeSpec (this maintains
the
existing
behavior, and would allow us in the future to make the change
to
return a
RocksDB store if we ever provide one)
2b) same as 2a but we throw an exception if the requested
store
type
does
not support that (this is backwards incompatible, and since
ROCKS_DB
is the
default we probably shouldn't do this)
My proposal for now is 1) because as of KIP-825
EmitStrategy#ON_WINDOW_CLOSE is the preferred way of
suppressing
and
that
is accounted for in this API already.
Last, I am not sure if the new parameter replacing the
existing
one
is
the
best way to go?
I'm happy either way, just let me know which you prefer - the
discussion
around CUSTOM is in the rejected alternatives but I'm happy to
differ to
whatever the project conventions are :)
If it's matches existing `ROCKS_DB` or `IN_MEMORY` we just
process
it as
we
do know, and if know we assume it's a fully qualified class
name
and
try to
instantiate it?
Note that there is no functionality for this kind of thing in
AbstractConfig (it's either a String validated enum or a
class)
so
this
would be a departure from convention. Again, I'm happy to
implement
that if
it's preferred.
Also wondering how it would related to the existing `Stores`
factory?
StoreTypeSpec will depend on Stores factory - they're one
layer
removed.
You can imagine that StoreTypeSpec is just a grouping of
methods
from the
Stores factory into a convenient package for default
configuration
purposes.
Thanks again for all the detailed thoughts Matthias!
On Fri, Jul 21, 2023 at 11:50 AM Matthias J. Sax <
mj...@apache.org
wrote:
Thanks for the KIP. Overall I like the idea to close this
gap.
However, I am wondering if we should close others gaps
first? In
particular, IIRC, we have a few cases for which we only have
a
RocksDB
implementation for a store, and thus, adding an in-memory
version
for
these stores first, to make the current `IN_MEMORY` parameter
work,
might be the first step?
In particular, this holds for the new versioned-store (but I
actually
believe the is some other internal store with no in-memory
implementation). -- For `suppress()` it's actually other way
around
we
we only have an in-memory implementation. Do you aim to allow
custom
stores for `suppress()`, too?
Btw: Should versioned stores also be covered by the KIP (ie,
`StoreTypeSpec`)? We did consider to add a new option
`VERSIONED`
to the
existing `default.dsl.store` config, but opted out for
various
reasons.
Last, I am not sure if the new parameter replacing the
existing
one
is
the best way to go? Did you put the idea to add `CUSTOM` to
the
existing
config into rejected alternative. Personally, I would prefer
to
add
`CUSTOM` as I would like to optimize to easy of use for the
majority of
users (which don't implement a custom store), but only
switch to
in-memory sometimes. -- As an alternative, you would also
just
extend
`dsl.default.store` (it's just a String) and allow to pass in
anything.
If it's matches existing `ROCKS_DB` or `IN_MEMORY` we just
process
it as
we do know, and if know we assume it's a fully qualified
class
name
and
try to instantiate it? -- Given that we plan to keep the
store-enum, is
seems cleaner to keep the existing config and keep both the
config
and
enum aligned to each other?
It's just preliminary thought. I will need to go back an
take a
more
detailed look into the code to grok how the propose
`StoreTypeSpec`
falls into place. Also wondering how it would related to the
existing
`Stores` factory?
-Matthias
On 7/21/23 6:45 AM, Colt McNealy wrote:
Sophie—
Thanks for chiming in here. +1 to the idea of specifying the
ordering
guarantees that we make in the StorageTypeSpec javadocs.
Quick question then. Is the javadoc that says:
Order is not guaranteed as bytes lexicographical ordering
might
not
represent key order.
no longer correct, and should say:
Order guarantees depend on the underlying implementation of
the
ReadOnlyKeyValueStore. For more information, please consult
the
[StorageTypeSpec javadocs](....)
Thanks,
Colt McNealy
*Founder, LittleHorse.dev*
On Thu, Jul 20, 2023 at 9:28 PM Sophie Blee-Goldman <
ableegold...@gmail.com>
wrote:
Hey Almog, first off, thanks for the KIP! I (and others)
raised
concerns
over how restrictive the default.dsl.store config would be
if
not
extendable to custom store types, especially given that
this
seems to
be
the primary userbase of such a feature. At the time we
didn't
really
have
any better ideas for a clean way to achieve that, but what
you
proposed
makes a lot of sense to me. Happy to see a good solution to
this,
and
hopefully others will share my satisfaction :P
I did have one quick piece of feedback which arose from an
unrelated
question posed to the dev mailing list w/ subject line
"ReadOnlyKeyValueStore#range()
Semantics"
<
https://lists.apache.org/thread/jbckmth8d3mcgg0rd670cpvsgwzqlwrm>.
I
recommend checking out the full thread for context, but it
made
me
think
about how we can leverage the new StoreTypeSpec concept as
an
answer
to
the
long-standing question in Streams: where can we put
guarantees
of
the
public contract for RocksDB (or other store
implementations)
when
all
the
RocksDB stuff is technically internal.
Basically, I'm suggesting two things: first, call out in
some
way
(perhaps
the StoreTypeSpec javadocs) that each StoreTypeSpec is
considered
a
public
contract in itself and should outline any semantic
guarantees
it
does,
or
does not, make. Second, we should add a note on ordering
guarantees in
the
two OOTB specs: for RocksDB we assert that range queries
will
honor
serialized byte ordering, whereas the InMemory flavor
gives no
ordering
guarantee whatsoever at this time.
Thoughts?
-Sophie
On Thu, Jul 20, 2023 at 4:28 PM Almog Gavra <
almog.ga...@gmail.com>
wrote:
Hi All,
I would like to propose a KIP to expand support for
default
store
types
(KIP-591) to encompass custom store implementations:
https://cwiki.apache.org/confluence/display/KAFKA/KIP-954%3A+expand+default+DSL+store+configuration+to+custom+types
Looking forward to your feedback!
Cheers,
Almog
