Thanks for clarifying. Cache-invalidation for side inputs makes sense. In case the Runner fails to checkpoint, could it not re-attempt the checkpoint? At least in the case of Flink, the cache would still be valid until another checkpoint is attempted. For other Runners that may not be the case. Also, rolling back state while keeping the SDK Harness running requires to invalidate the cache.
-Max On 13.08.19 18:09, Lukasz Cwik wrote: > > > On Tue, Aug 13, 2019 at 4:36 AM Maximilian Michels <m...@apache.org > <mailto:m...@apache.org>> wrote: > > Agree that we have to be able to flush before a checkpoint to avoid > caching too many elements. Also good point about checkpoint costs > increasing with flushing the cache on checkpoints. A LRU cache policy in > the SDK seems desirable. > > What is the role of the cache token in the design document[1]? It looks > to me that the token is used to give the Runner control over which and > how many elements can be cached by the SDK. Why is that necessary? > Shouldn't this be up to the SDK? > > > We want to be able to handle the case where the SDK completes the bundle > successfully but the runner fails to checkpoint the information. > We also want the runner to be able to pass in cache tokens for things > like side inputs which may change over time (and the SDK would not know > that this happened). > > > -Max > > [1] > > https://docs.google.com/document/d/1BOozW0bzBuz4oHJEuZNDOHdzaV5Y56ix58Ozrqm2jFg/edit#heading=h.7ghoih5aig5m > > Is it simply to > On 12.08.19 19:55, Lukasz Cwik wrote: > > > > > > On Mon, Aug 12, 2019 at 10:09 AM Thomas Weise <t...@apache.org > <mailto:t...@apache.org> > > <mailto:t...@apache.org <mailto:t...@apache.org>>> wrote: > > > > > > On Mon, Aug 12, 2019 at 8:53 AM Maximilian Michels > <m...@apache.org <mailto:m...@apache.org> > > <mailto:m...@apache.org <mailto:m...@apache.org>>> wrote: > > > > Thanks for starting this discussion Rakesh. An efficient cache > > layer is > > one of the missing pieces for good performance in stateful > > pipelines. > > The good news are that there is a level of caching already > > present in > > Python which batches append requests until the bundle is > finished. > > > > Thomas, in your example indeed we would have to profile to see > > why CPU > > utilization is high on the Flink side but not in the > Python SDK > > harness. > > For example, older versions of Flink (<=1.5) have a high > cost of > > deleting existing instances of a timer when setting a timer. > > Nevertheless, cross-bundle caching would likely result in > increased > > performance. > > > > > > CPU on the Flink side was unchanged, and that's important. The > > throughout improvement comes from the extended bundle caching > on the > > SDK side. That's what tells me that cross-bundle caching is > needed. > > Of course, it will require a good solution for the write also > and I > > like your idea of using the checkpoint boundary for that, > especially > > since that already aligns with the bundle boundary and is under > > runner control. Of course we also want to be careful to not cause > > overly bursty writes. > > > > Profiling will be useful for the timer processing, that is also on > > my list of suspects. > > > > > > Luke, I think the idea to merge pending state requests > could be > > complementary to caching across bundles. > > > > Question: Couldn't we defer flushing back state from the > SDK to the > > Runner indefinitely, provided that we add a way to flush the > > state in > > case of a checkpoint? > > > > > > Flushing is needed to prevent the SDK from running out of memory. > Having > > a fixed budget for state inside the SDK would have flushing happen > under > > certain state usage scenarios. > > I could also see that only flushing at checkpoint may lead to slow > > checkpoint performance so we may want to flush state that hasn't been > > used in a while as well. > > > > > > Another performance improvement would be caching read requests > > because > > these first go to the Runner regardless of already cached > appends. > > > > -Max > > > > On 09.08.19 17:12, Lukasz Cwik wrote: > > > > > > > > > On Fri, Aug 9, 2019 at 2:32 AM Robert Bradshaw > > <rober...@google.com <mailto:rober...@google.com> > <mailto:rober...@google.com <mailto:rober...@google.com>> > > > <mailto:rober...@google.com <mailto:rober...@google.com> > <mailto:rober...@google.com <mailto:rober...@google.com>>>> wrote: > > > > > > The question is whether the SDK needs to wait for the > > StateResponse to > > > come back before declaring the bundle done. The proposal > > was to not > > > send the cache token back as part of an append > > StateResponse [1], but > > > pre-provide it as part of the bundle request. > > > > > > > > > Agree, the purpose of the I'm Blocked message is to occur > > during bundle > > > processing. > > > > > > > > > Thinking about this some more, if we assume the state > > response was > > > successfully applied, there's no reason for the SDK to > > block the > > > bundle until it has its hands on the cache token--we can > > update the > > > cache once the StateResponse comes back whether or > not the > > bundle is > > > still active. On the other hand, the runner needs a > way to > > assert it > > > has received and processed all StateRequests from > the SDK > > associated > > > with a bundle before it can declare the bundle complete > > (regardless of > > > the cache tokens), so this might not be safe without > some > > extra > > > coordination (e.g. the ProcessBundleResponse indicating > > the number of > > > state requests associated with a bundle). > > > > > > > > > Since the state request stream is ordered, we can add the id > > of the last > > > state request as part of the ProcessBundleResponse. > > > > > > > > > [1] > > > > > > > https://github.com/apache/beam/blob/release-2.14.0/model/fn-execution/src/main/proto/beam_fn_api.proto#L627 > > > > > > On Thu, Aug 8, 2019 at 6:57 PM Lukasz Cwik > > <lc...@google.com <mailto:lc...@google.com> > <mailto:lc...@google.com <mailto:lc...@google.com>> > > > <mailto:lc...@google.com <mailto:lc...@google.com> > <mailto:lc...@google.com <mailto:lc...@google.com>>>> wrote: > > > > > > > > The purpose of the new state API call in BEAM-7000 > is to > > tell the > > > runner that the SDK is now blocked waiting for the > result of a > > > specific state request and it should be used for > fetches (not > > > updates) and is there to allow for SDKs to differentiate > > readLater > > > (I will need this data at some point in time in the > > future) from > > > read (I need this data now). This comes up commonly > where > > the user > > > prefetches multiple state cells and then looks at their > > content > > > allowing the runner to batch up those calls on its end. > > > > > > > > The way it can be used for clear+append is that the > > runner can > > > store requests in memory up until some time/memory limit > > or until it > > > gets its first "blocked" call and then issue all the > > requests together. > > > > > > > > > > > > On Thu, Aug 8, 2019 at 9:42 AM Robert Bradshaw > > > <rober...@google.com <mailto:rober...@google.com> > <mailto:rober...@google.com <mailto:rober...@google.com>> > > <mailto:rober...@google.com <mailto:rober...@google.com> > <mailto:rober...@google.com <mailto:rober...@google.com>>>> wrote: > > > >> > > > >> On Tue, Aug 6, 2019 at 12:07 AM Thomas Weise > > <t...@apache.org <mailto:t...@apache.org> > <mailto:t...@apache.org <mailto:t...@apache.org>> > > > <mailto:t...@apache.org <mailto:t...@apache.org> > <mailto:t...@apache.org <mailto:t...@apache.org>>>> wrote: > > > >> > > > > >> > That would add a synchronization point that > forces extra > > > latency especially in streaming mode. > > > >> > > > > >> > Wouldn't it be possible for the runner to > assign the > > token when > > > starting the bundle and for the SDK to pass it along > the state > > > requests? That way, there would be no need to batch and > > wait for a > > > flush. > > > >> > > > >> I think it makes sense to let the runner pre-assign > > these state > > > update > > > >> tokens rather than forcing a synchronization point. > > > >> > > > >> Here's some pointers for the Python implementation: > > > >> > > > >> Currently, when a DoFn needs UserState, a > StateContext > > object is used > > > >> that converts from a StateSpec to the actual value. > > When running > > > >> portably, this is FnApiUserStateContext [1]. The > state > > handles > > > >> themselves are cached at [2] but this context only > > lives for the > > > >> lifetime of a single bundle. Logic could be added > here > > to use the > > > >> token to share these across bundles. > > > >> > > > >> Each of these handles in turn invokes > > state_handler.get* methods when > > > >> its read is called. (Here state_handler is a thin > > wrapper around the > > > >> service itself) and constructs the appropriate result > > from the > > > >> StateResponse. We would need to implement caching at > > this level as > > > >> well, including the deserialization. This will > probably > > require some > > > >> restructoring of how _StateBackedIterable is > > implemented (or, > > > >> possibly, making that class itself cache aware). > > Hopefully that's > > > >> enough to get started. > > > >> > > > >> [1] > > > > > > > https://github.com/apache/beam/blob/release-2.14.0/sdks/python/apache_beam/runners/worker/bundle_processor.py#L402 > > > >> [2] > > > > > > > https://github.com/apache/beam/blob/release-2.14.0/sdks/python/apache_beam/runners/worker/bundle_processor.py#L436 > > > >> . > > > >> > > > >> > On Mon, Aug 5, 2019 at 2:49 PM Lukasz Cwik > > <lc...@google.com <mailto:lc...@google.com> > <mailto:lc...@google.com <mailto:lc...@google.com>> > > > <mailto:lc...@google.com <mailto:lc...@google.com> > <mailto:lc...@google.com <mailto:lc...@google.com>>>> wrote: > > > >> >> > > > >> >> I believe the intent is to add a new state API > call > > telling > > > the runner that it is blocked waiting for a response > > (BEAM-7000). > > > >> >> > > > >> >> This should allow the runner to wait till it sees > > one of these > > > I'm blocked requests and then merge + batch any state > > calls it may > > > have at that point in time allowing it to convert > clear + > > appends > > > into set calls and do any other optimizations as > well. By > > default, > > > the runner would have a time and space based limit > on how many > > > outstanding state calls there are before choosing to > > resolve them. > > > >> >> > > > >> >> On Mon, Aug 5, 2019 at 5:43 PM Lukasz Cwik > > <lc...@google.com <mailto:lc...@google.com> > <mailto:lc...@google.com <mailto:lc...@google.com>> > > > <mailto:lc...@google.com <mailto:lc...@google.com> > <mailto:lc...@google.com <mailto:lc...@google.com>>>> wrote: > > > >> >>> > > > >> >>> Now I see what you mean. > > > >> >>> > > > >> >>> On Mon, Aug 5, 2019 at 5:42 PM Thomas Weise > > <t...@apache.org <mailto:t...@apache.org> > <mailto:t...@apache.org <mailto:t...@apache.org>> > > > <mailto:t...@apache.org <mailto:t...@apache.org> > <mailto:t...@apache.org <mailto:t...@apache.org>>>> wrote: > > > >> >>>> > > > >> >>>> Hi Luke, > > > >> >>>> > > > >> >>>> I guess the answer is that it depends on the > state > > backend. > > > If a set operation in the state backend is available > that > > is more > > > efficient than clear+append, then it would be beneficial > > to have a > > > dedicated fn api operation to allow for such > optimization. > > That's > > > something that needs to be determined with a profiler :) > > > >> >>>> > > > >> >>>> But the low hanging fruit is cross-bundle > caching. > > > >> >>>> > > > >> >>>> Thomas > > > >> >>>> > > > >> >>>> On Mon, Aug 5, 2019 at 2:06 PM Lukasz Cwik > > <lc...@google.com <mailto:lc...@google.com> > <mailto:lc...@google.com <mailto:lc...@google.com>> > > > <mailto:lc...@google.com <mailto:lc...@google.com> > <mailto:lc...@google.com <mailto:lc...@google.com>>>> wrote: > > > >> >>>>> > > > >> >>>>> Thomas, why do you think a single round trip is > > needed? > > > >> >>>>> > > > >> >>>>> clear + append can be done blindly from the SDK > > side and it > > > has total knowledge of the state at that point in time > > till the end > > > of the bundle at which point you want to wait to get the > > cache token > > > back from the runner for the append call so that for the > > next bundle > > > you can reuse the state if the key wasn't processed > elsewhere. > > > >> >>>>> > > > >> >>>>> Also, all state calls are "streamed" over > gRPC so > > you don't > > > need to wait for clear to complete before being able to > > send append. > > > >> >>>>> > > > >> >>>>> On Tue, Jul 30, 2019 at 12:58 AM jincheng sun > > > <sunjincheng...@gmail.com > <mailto:sunjincheng...@gmail.com> > > <mailto:sunjincheng...@gmail.com > <mailto:sunjincheng...@gmail.com>> > > <mailto:sunjincheng...@gmail.com > <mailto:sunjincheng...@gmail.com> > > <mailto:sunjincheng...@gmail.com > <mailto:sunjincheng...@gmail.com>>>> wrote: > > > >> >>>>>> > > > >> >>>>>> Hi Rakesh, > > > >> >>>>>> > > > >> >>>>>> Glad to see you pointer this problem out! > > > >> >>>>>> +1 for add this implementation. Manage > State by > > > write-through-cache is pretty important for > Streaming job! > > > >> >>>>>> > > > >> >>>>>> Best, Jincheng > > > >> >>>>>> > > > >> >>>>>> Thomas Weise <t...@apache.org > <mailto:t...@apache.org> > > <mailto:t...@apache.org <mailto:t...@apache.org>> > <mailto:t...@apache.org <mailto:t...@apache.org> > > <mailto:t...@apache.org <mailto:t...@apache.org>>>> 于 > > > 2019年7月29日周一 下午8:54写道： > > > >> >>>>>>> > > > >> >>>>>>> FYI a basic test appears to confirm the > > importance of the > > > cross-bundle caching: I found that the throughput can be > > increased > > > by playing with the bundle size in the Flink runner. > > Default caps at > > > 1000 elements (or 1 second). So on a high throughput > > stream the > > > bundles would be capped by the count limit. Bumping the > > count limit > > > increases the throughput by reducing the chatter > over the > > state > > > plane (more cache hits due to larger bundle). > > > >> >>>>>>> > > > >> >>>>>>> The next level of investigation would involve > > profiling. > > > But just by looking at metrics, the CPU utilization > on the > > Python > > > worker side dropped significantly while on the Flink > side > > it remains > > > nearly same. There are no metrics for state > operations on > > either > > > side, I think it would be very helpful to get these in > > place also. > > > >> >>>>>>> > > > >> >>>>>>> Below the stateful processing code for > reference. > > > >> >>>>>>> > > > >> >>>>>>> Thomas > > > >> >>>>>>> > > > >> >>>>>>> > > > >> >>>>>>> class StatefulFn(beam.DoFn): > > > >> >>>>>>> count_state_spec = > > userstate.CombiningValueStateSpec( > > > >> >>>>>>> 'count', > > > > beam.coders.IterableCoder(beam.coders.VarIntCoder()), sum) > > > >> >>>>>>> timer_spec = userstate.TimerSpec('timer', > > > userstate.TimeDomain.WATERMARK) > > > >> >>>>>>> > > > >> >>>>>>> def process(self, kv, > > > count=beam.DoFn.StateParam(count_state_spec), > > > timer=beam.DoFn.TimerParam(timer_spec), > > window=beam.DoFn.WindowParam): > > > >> >>>>>>> count.add(1) > > > >> >>>>>>> timer_seconds = (window.end.micros // > > 1000000) - 1 > > > >> >>>>>>> timer.set(timer_seconds) > > > >> >>>>>>> > > > >> >>>>>>> @userstate.on_timer(timer_spec) > > > >> >>>>>>> def process_timer(self, > > > count=beam.DoFn.StateParam(count_state_spec), > > > window=beam.DoFn.WindowParam): > > > >> >>>>>>> if count.read() == 0: > > > >> >>>>>>> logging.warning("###timer fired > > with count > > > %d, window %s" % (count.read(), window)) > > > >> >>>>>>> > > > >> >>>>>>> > > > >> >>>>>>> > > > >> >>>>>>> On Thu, Jul 25, 2019 at 5:09 AM Robert > Bradshaw > > > <rober...@google.com <mailto:rober...@google.com> > <mailto:rober...@google.com <mailto:rober...@google.com>> > > <mailto:rober...@google.com <mailto:rober...@google.com> > <mailto:rober...@google.com <mailto:rober...@google.com>>>> wrote: > > > >> >>>>>>>> > > > >> >>>>>>>> On Wed, Jul 24, 2019 at 6:21 AM Rakesh Kumar > > > <rakeshku...@lyft.com <mailto:rakeshku...@lyft.com> > <mailto:rakeshku...@lyft.com <mailto:rakeshku...@lyft.com>> > > <mailto:rakeshku...@lyft.com <mailto:rakeshku...@lyft.com> > <mailto:rakeshku...@lyft.com <mailto:rakeshku...@lyft.com>>>> wrote: > > > >> >>>>>>>> > > > > >> >>>>>>>> > Thanks Robert, > > > >> >>>>>>>> > > > > >> >>>>>>>> > I stumble on the jira that you have > created > > some time ago > > > >> >>>>>>>> > > https://jira.apache.org/jira/browse/BEAM-5428 > > > >> >>>>>>>> > > > > >> >>>>>>>> > You also marked code where code > changes are > > required: > > > >> >>>>>>>> > > > > > > > > https://github.com/apache/beam/blob/7688bcfc8ebb4bedf26c5c3b3fe0e13c0ec2aa6d/sdks/python/apache_beam/runners/worker/bundle_processor.py#L291 > > > >> >>>>>>>> > > > > > > > > https://github.com/apache/beam/blob/7688bcfc8ebb4bedf26c5c3b3fe0e13c0ec2aa6d/sdks/python/apache_beam/runners/worker/bundle_processor.py#L349 > > > >> >>>>>>>> > > > > > > > > https://github.com/apache/beam/blob/7688bcfc8ebb4bedf26c5c3b3fe0e13c0ec2aa6d/sdks/python/apache_beam/runners/worker/bundle_processor.py#L465 > > > >> >>>>>>>> > > > > >> >>>>>>>> > I am willing to provide help to implement > > this. Let me > > > know how I can help. > > > >> >>>>>>>> > > > >> >>>>>>>> As far as I'm aware, no one is actively > > working on it > > > right now. > > > >> >>>>>>>> Please feel free to assign yourself the JIRA > > entry and > > > I'll be happy > > > >> >>>>>>>> to answer any questions you might have if > > (well probably > > > when) these > > > >> >>>>>>>> pointers are insufficient. > > > >> >>>>>>>> > > > >> >>>>>>>> > On Tue, Jul 23, 2019 at 3:47 AM Robert > Bradshaw > > > <rober...@google.com <mailto:rober...@google.com> > <mailto:rober...@google.com <mailto:rober...@google.com>> > > <mailto:rober...@google.com <mailto:rober...@google.com> > <mailto:rober...@google.com <mailto:rober...@google.com>>>> wrote: > > > >> >>>>>>>> >> > > > >> >>>>>>>> >> This is documented at > > > >> >>>>>>>> >> > > > > > > > https://docs.google.com/document/d/1BOozW0bzBuz4oHJEuZNDOHdzaV5Y56ix58Ozrqm2jFg/edit#heading=h.7ghoih5aig5m > > > >> >>>>>>>> >> . Note that it requires participation of > > both the > > > runner and the SDK > > > >> >>>>>>>> >> (though there are no correctness > issues if > > one or the > > > other side does > > > >> >>>>>>>> >> not understand the protocol, caching just > > won't be used). > > > >> >>>>>>>> >> > > > >> >>>>>>>> >> I don't think it's been implemented > > anywhere, but > > > could be very > > > >> >>>>>>>> >> beneficial for performance. > > > >> >>>>>>>> >> > > > >> >>>>>>>> >> On Wed, Jul 17, 2019 at 6:00 PM > Rakesh Kumar > > > <rakeshku...@lyft.com <mailto:rakeshku...@lyft.com> > <mailto:rakeshku...@lyft.com <mailto:rakeshku...@lyft.com>> > > <mailto:rakeshku...@lyft.com <mailto:rakeshku...@lyft.com> > <mailto:rakeshku...@lyft.com <mailto:rakeshku...@lyft.com>>>> wrote: > > > >> >>>>>>>> >> > > > > >> >>>>>>>> >> > I checked the python sdk[1] and it has > > similar > > > implementation as Java SDK. > > > >> >>>>>>>> >> > > > > >> >>>>>>>> >> > I would agree with Thomas. In case of > > high volume > > > event stream and bigger cluster size, network call can > > potentially > > > cause a bottleneck. > > > >> >>>>>>>> >> > > > > >> >>>>>>>> >> > @Robert > > > >> >>>>>>>> >> > I am interested to see the > proposal. Can you > > > provide me the link of the proposal? > > > >> >>>>>>>> >> > > > > >> >>>>>>>> >> > [1]: > > > > > > > https://github.com/apache/beam/blob/db59a3df665e094f0af17fe4d9df05fe420f3c16/sdks/python/apache_beam/transforms/userstate.py#L295 > > > >> >>>>>>>> >> > > > > >> >>>>>>>> >> > > > > >> >>>>>>>> >> > On Tue, Jul 16, 2019 at 9:43 AM > Thomas Weise > > > <t...@apache.org <mailto:t...@apache.org> > <mailto:t...@apache.org <mailto:t...@apache.org>> > > <mailto:t...@apache.org <mailto:t...@apache.org> > <mailto:t...@apache.org <mailto:t...@apache.org>>>> wrote: > > > >> >>>>>>>> >> >> > > > >> >>>>>>>> >> >> Thanks for the pointer. For streaming, > > it will be > > > important to support caching across bundles. It appears > > that even > > > the Java SDK doesn't support that yet? > > > >> >>>>>>>> >> >> > > > >> >>>>>>>> >> >> > > > > > > > https://github.com/apache/beam/blob/77b295b1c2b0a206099b8f50c4d3180c248e252c/sdks/java/harness/src/main/java/org/apache/beam/fn/harness/FnApiDoFnRunner.java#L221 > > > >> >>>>>>>> >> >> > > > >> >>>>>>>> >> >> Regarding clear/append: It would > be nice > > if both > > > could occur within a single Fn Api roundtrip when > the state is > > > persisted. > > > >> >>>>>>>> >> >> > > > >> >>>>>>>> >> >> Thanks, > > > >> >>>>>>>> >> >> Thomas > > > >> >>>>>>>> >> >> > > > >> >>>>>>>> >> >> > > > >> >>>>>>>> >> >> > > > >> >>>>>>>> >> >> On Tue, Jul 16, 2019 at 6:58 AM > Lukasz Cwik > > > <lc...@google.com <mailto:lc...@google.com> > <mailto:lc...@google.com <mailto:lc...@google.com>> > > <mailto:lc...@google.com <mailto:lc...@google.com> > <mailto:lc...@google.com <mailto:lc...@google.com>>>> wrote: > > > >> >>>>>>>> >> >>> > > > >> >>>>>>>> >> >>> User state is built on top of read, > > append and > > > clear and not off a read and write paradigm to allow for > > blind appends. > > > >> >>>>>>>> >> >>> > > > >> >>>>>>>> >> >>> The optimization you speak of can > be done > > > completely inside the SDK without any additional > protocol > > being > > > required as long as you clear the state first and then > > append all > > > your new data. The Beam Java SDK does this for all > runners > > when > > > executed portably[1]. You could port the same logic > to the > > Beam > > > Python SDK as well. > > > >> >>>>>>>> >> >>> > > > >> >>>>>>>> >> >>> 1: > > > > > > > https://github.com/apache/beam/blob/41478d00d34598e56471d99d0845ac16efa5b8ef/sdks/java/harness/src/main/java/org/apache/beam/fn/harness/state/BagUserState.java#L84 > > > >> >>>>>>>> >> >>> > > > >> >>>>>>>> >> >>> On Tue, Jul 16, 2019 at 5:54 AM > Robert > > Bradshaw > > > <rober...@google.com <mailto:rober...@google.com> > <mailto:rober...@google.com <mailto:rober...@google.com>> > > <mailto:rober...@google.com <mailto:rober...@google.com> > <mailto:rober...@google.com <mailto:rober...@google.com>>>> wrote: > > > >> >>>>>>>> >> >>>> > > > >> >>>>>>>> >> >>>> Python workers also have a > per-bundle > > SDK-side > > > cache. A protocol has > > > >> >>>>>>>> >> >>>> been proposed, but hasn't yet been > > implemented > > > in any SDKs or runners. > > > >> >>>>>>>> >> >>>> > > > >> >>>>>>>> >> >>>> On Tue, Jul 16, 2019 at 6:02 AM > Reuven Lax > > > <re...@google.com <mailto:re...@google.com> > <mailto:re...@google.com <mailto:re...@google.com>> > > <mailto:re...@google.com <mailto:re...@google.com> > <mailto:re...@google.com <mailto:re...@google.com>>>> wrote: > > > >> >>>>>>>> >> >>>> > > > > >> >>>>>>>> >> >>>> > It's runner dependent. Some > runners > > (e.g. the > > > Dataflow runner) do have such a cache, though I > think it's > > currently > > > has a cap for large bags. > > > >> >>>>>>>> >> >>>> > > > > >> >>>>>>>> >> >>>> > Reuven > > > >> >>>>>>>> >> >>>> > > > > >> >>>>>>>> >> >>>> > On Mon, Jul 15, 2019 at 8:48 PM > > Rakesh Kumar > > > <rakeshku...@lyft.com <mailto:rakeshku...@lyft.com> > <mailto:rakeshku...@lyft.com <mailto:rakeshku...@lyft.com>> > > <mailto:rakeshku...@lyft.com <mailto:rakeshku...@lyft.com> > <mailto:rakeshku...@lyft.com <mailto:rakeshku...@lyft.com>>>> wrote: > > > >> >>>>>>>> >> >>>> >> > > > >> >>>>>>>> >> >>>> >> Hi, > > > >> >>>>>>>> >> >>>> >> > > > >> >>>>>>>> >> >>>> >> I have been using python sdk > for the > > > application and also using BagState in production. I was > > wondering > > > whether state logic has any write-through-cache > > implemented or not. > > > If we are sending every read and write request through > > network then > > > it comes with a performance cost. We can avoid network > > call for a > > > read operation if we have write-through-cache. > > > >> >>>>>>>> >> >>>> >> I have superficially looked > into the > > > implementation and I didn't see any cache > implementation. > > > >> >>>>>>>> >> >>>> >> > > > >> >>>>>>>> >> >>>> >> is it possible to have this > cache? > > would it > > > cause any issue if we have the caching layer? > > > >> >>>>>>>> >> >>>> >> > > > > > >
