So I guess AsyncFSStorageAgent.copyToHdfs is a synchronous write. My mistake. However I think AsyncFSStorageAgent needs to be documented properly. Even the public methods have no documentation also this piece of code in GenericNode.
For Exactly once, we are enforcing synchronous checkpointing which is ok. Chandni On Tue, Nov 10, 2015 at 3:20 PM, Chandni Singh <[email protected]> wrote: > Chetan, > > I am pasting the code here and highlighting the lines. The last statement > is NOT a 'return' if Processing_Mode == EXACTLY_ONCE > > > void checkpoint(long windowId) > { > if (!context.stateless) { > StorageAgent ba = context.getValue(OperatorContext.STORAGE_AGENT); > if (ba != null) { > try { > checkpointStats = new Stats.CheckpointStats(); > checkpointStats.checkpointStartTime = System.currentTimeMillis(); > ba.save(operator, id, windowId); > if (ba instanceof AsyncFSStorageAgent) { > AsyncFSStorageAgent asyncFSStorageAgent = (AsyncFSStorageAgent) ba; > if (!asyncFSStorageAgent.isSyncCheckpoint()) { > if(PROCESSING_MODE != ProcessingMode.EXACTLY_ONCE) { > CheckpointHandler checkpointHandler = new CheckpointHandler(); > checkpointHandler.agent = asyncFSStorageAgent; > checkpointHandler.operatorId = id; > checkpointHandler.windowId = windowId; > checkpointHandler.stats = checkpointStats; > FutureTask<Stats.CheckpointStats> futureTask = new > FutureTask<Stats.CheckpointStats>(checkpointHandler); > taskQueue.add(new Pair<FutureTask<Stats.CheckpointStats>, > Long>(futureTask, windowId)); > executorService.submit(futureTask); > checkpoint = null; > checkpointStats = null; > return; > }else{ > > * asyncFSStorageAgent.copyToHDFS(id, windowId);* } > } > } > checkpointStats.checkpointTime = System.currentTimeMillis() - > checkpointStats.checkpointStartTime; > } > catch (IOException ie) { > try { > logger.warn("Rolling back checkpoint {} for Operator {} due to the > exception {}", > Codec.getStringWindowId(windowId), operator, ie); > ba.delete(id, windowId); > } > catch (IOException ex) { > logger.warn("Error while rolling back checkpoint", ex); > } > throw new RuntimeException(ie); > } > } > } > > checkpoint = new Checkpoint(windowId, applicationWindowCount, > checkpointWindowCount); > if (operator instanceof Operator.CheckpointListener) { > > * ((Operator.CheckpointListener) operator).checkpointed(windowId);* } > } > > > Chandni > > > On Tue, Nov 10, 2015 at 3:05 PM, Chetan Narsude (cnarsude) < > [email protected]> wrote: > >> There are a lot of things which are different when it comes to async >> checkpointing. I was evaluating it in the morning and expect that either I >> am able to explain or open jira issues. With my partial observation is >> that with Async checkpointing, checkpointed is not issued (chandni, the >> last statement in the if block is ³return²). I am digging into it but feel >> free to chime in if someone else is able to find that. >> >> Also I realized that my morning email applies as it is to committed but >> checkpointed has deviated a little bit from that. Will post the revised >> response soon. >> >> ‹ >> Chetan >> >> >> >> >> On 11/10/15, 2:04 PM, "Chandni Singh" <[email protected]> wrote: >> >> >Chetan, >> > >> >Looking at the checkpoint(windowId) in Node.java, I don't think the steps >> >you mentioned are followed. >> > >> >*if (using AsyncFSStorageAgent) {* >> >* asyncFSStorageAgent.copyToHdfs(...)* >> >*}* >> >*operator.checkpointed(windowId);* >> > >> >This means even copyToHdfs fails the operator is notified that the window >> >is check-pointed. >> > >> >Are we saying that copyToHdfs will never fail with AsyncFSStorageAgent >> for >> >a window since the operator is notified that the window is checkpointed? >> > >> >Chandni >> > >> >On Tue, Nov 10, 2015 at 11:33 AM, Timothy Farkas <[email protected]> >> >wrote: >> > >> >> Will do >> >> >> >> On Tue, Nov 10, 2015 at 11:01 AM, Pramod Immaneni >> >><[email protected]> >> >> wrote: >> >> >> >> > Is there a unit test covering it? Otherwise can you write one to test >> >>the >> >> > hypothesis. >> >> > >> >> > On Tue, Nov 10, 2015 at 11:00 AM, Timothy Farkas < >> [email protected]> >> >> > wrote: >> >> > >> >> > > That is what it is looking like to me. The task is submitted >> >> > > GenericNode#checkpoint line 504, then at the end of the >> >> > > GenericNode#checkpoint line 531 checkpointed is called. I am likely >> >> > missing >> >> > > something, just would like to know what :) >> >> > > >> >> > > Tim >> >> > > >> >> > > On Tue, Nov 10, 2015 at 10:51 AM, Pramod Immaneni < >> >> > [email protected]> >> >> > > wrote: >> >> > > >> >> > > > Tim, >> >> > > > >> >> > > > Are you suggesting that checkpointed is called before the >> >>checkpoint >> >> is >> >> > > > completely persisted in the storage. >> >> > > > >> >> > > > Thanks >> >> > > > >> >> > > > On Tue, Nov 10, 2015 at 10:49 AM, Timothy Farkas < >> >> [email protected]> >> >> > > > wrote: >> >> > > > >> >> > > > > Chetan, >> >> > > > > >> >> > > > > I do not see the process of reporting the checkpoint to stram, >> >> > > receiving >> >> > > > > the ack, and then calling checkpointed. The logic I'm seeing in >> >> > > > GenericNode >> >> > > > > line 484 is that the checkpoint method is called, it spawns >> >>another >> >> > > > thread >> >> > > > > that writes to hdfs, and then checkpointed is immediately >> called >> >> > > > > afterwards. I am missing something, can you give me some >> >>pointers >> >> so >> >> > > > that I >> >> > > > > can better understand the flow? >> >> > > > > >> >> > > > > Tim >> >> > > > > >> >> > > > > On Tue, Nov 10, 2015 at 10:33 AM, Munagala Ramanath < >> >> > > [email protected] >> >> > > > > >> >> > > > > wrote: >> >> > > > > >> >> > > > > > Chetan's answer provides a good explanation as well as >> >>clarifying >> >> > > that >> >> > > > > > the difference can be more than 1. >> >> > > > > > >> >> > > > > > Since checkpointing (i.e. "commit notification" as Thomas >> >>refers >> >> to >> >> > > > > > it) is asynchronous, I'm curious >> >> > > > > > about whether the window ids in the checkpointed call are >> >> > guaranteed >> >> > > > > > to be sequential or if they could >> >> > > > > > be out of order, i.e. can the checkpointed call see window id >> >>101 >> >> > > > > > before it sees 100 ? >> >> > > > > > >> >> > > > > > Ram >> >> > > > > > >> >> > > > > > On Tue, Nov 10, 2015 at 10:27 AM, Bhupesh Chawda >> >> > > > > > <[email protected]> wrote: >> >> > > > > > > Hi Tim, >> >> > > > > > > Thanks for the detailed explanation. >> >> > > > > > > I understand that the sequence would be >> >> > > > > > > beginWindow (x) -> endWindow (x) -> checkpointed (x) -> >> >> > > beginWindow >> >> > > > > > > (x+1) >> >> > > > > > > >> >> > > > > > > However when I try to print out the window ids in >> >>beginWindow, >> >> > > > > endWindow >> >> > > > > > > and checkpointed calls, I see x and x-1 respectively. >> >> > > > > > > I.e. If the window just before checkpoint is 100, I see >> that >> >> the >> >> > > > > > > checkpointed call had window id 99. >> >> > > > > > > >> >> > > > > > > Note: This is observed in the local mode of Apex. >> >> > > > > > > >> >> > > > > > > Thanks >> >> > > > > > > -Bhupesh >> >> > > > > > > On 10-Nov-2015 11:25 pm, "Timothy Farkas" >> >><[email protected] >> >> > >> >> > > > wrote: >> >> > > > > > > >> >> > > > > > >> Hi Bhupesh, >> >> > > > > > >> >> >> > > > > > >> The sequencing of checkpoint called in relation to >> >>beginWindow >> >> > and >> >> > > > > > >> endWindow depends on how your APPLICATION_WINDOW_COUNT and >> >> > > > > > >> CHECKPOINT_WINDOW_COUNT are configured. If the two >> >> WINDOW_COUNTs >> >> > > are >> >> > > > > not >> >> > > > > > >> configured to be the same then it is possible that >> >> checkpointed >> >> > is >> >> > > > > > called >> >> > > > > > >> within an application window. So the sequence of events >> >>would >> >> be >> >> > > > this: >> >> > > > > > >> >> >> > > > > > >> beginWindow -> checkpointed -> endWindow >> >> > > > > > >> >> >> > > > > > >> If the APPLICATION_WINDOW_COUNT and >> CHECKPOINT_WINDOW_COUNT >> >> are >> >> > > the >> >> > > > > same >> >> > > > > > >> (default). Then the sequence of calls would be this: >> >> > > > > > >> >> >> > > > > > >> beginWindow (100) -> endWindow (100) -> checkpointed >> (100) >> >> -> >> >> > > > > > beginWindow >> >> > > > > > >> (101) >> >> > > > > > >> >> >> > > > > > >> The numbers in the sequence represent possible streaming >> >> window >> >> > > Ids >> >> > > > > that >> >> > > > > > >> each call would be associated with. >> >> > > > > > >> >> >> > > > > > >> The StateMachine which calls these callbacks for non-input >> >> > > operators >> >> > > > > is >> >> > > > > > in >> >> > > > > > >> GenericNode.java. >> >> > > > > > >> >> >> > > > > > >> Tim >> >> > > > > > >> >> >> > > > > > >> On Tue, Nov 10, 2015 at 3:36 AM, Bhupesh Chawda < >> >> > > > > > [email protected]> >> >> > > > > > >> wrote: >> >> > > > > > >> >> >> > > > > > >> > Hi Chetan / Community, >> >> > > > > > >> > >> >> > > > > > >> > Can someone please elaborate on why the window id >> >>supplied >> >> to >> >> > > > > > >> > CheckpointListener and the Operator would differ. >> >> > > > > > >> > I tried looking at the window ids of checkpointed() and >> >>the >> >> > > > > > beginWindow() >> >> > > > > > >> > calls and they differ by 1. Don't know why this should >> be >> >> the >> >> > > > case. >> >> > > > > > >> > >> >> > > > > > >> > Thanks. >> >> > > > > > >> > -Bhupesh >> >> > > > > > >> > >> >> > > > > > >> > On Thu, Sep 17, 2015 at 5:56 AM, Chetan Narsude < >> >> > > > > > [email protected]> >> >> > > > > > >> > wrote: >> >> > > > > > >> > >> >> > > > > > >> > > Short answer is yes. >> >> > > > > > >> > > >> >> > > > > > >> > > All the control tuples are scheduled to be delivered >> >> outside >> >> > > of >> >> > > > > the >> >> > > > > > >> > window. >> >> > > > > > >> > > As checkpointed callback is triggered because of >> >> CHECKPOINT >> >> > > > > control >> >> > > > > > >> > tuple, >> >> > > > > > >> > > it will happen after endWindow and before the next >> >> > > beginWindow. >> >> > > > > > >> > > >> >> > > > > > >> > > The windowId supplied to CheckpointListener and the >> one >> >> > > provided >> >> > > > > to >> >> > > > > > >> > > Operator need not match even though the sequence is >> >> defined. >> >> > > So >> >> > > > I >> >> > > > > am >> >> > > > > > >> > > curious how you intend to use this knowledge. >> >> > > > > > >> > > >> >> > > > > > >> > > -- >> >> > > > > > >> > > Chetan >> >> > > > > > >> > > >> >> > > > > > >> > > >> >> > > > > > >> > > On Tue, Sep 15, 2015 at 8:31 AM, Thomas Weise < >> >> > > > > > [email protected]> >> >> > > > > > >> > > wrote: >> >> > > > > > >> > > >> >> > > > > > >> > > > It has not changed the operator execution model. >> >>State >> >> > > > > > serialization >> >> > > > > > >> is >> >> > > > > > >> > > > still synchronous, write to HDFS is taken out of the >> >> > > operator >> >> > > > > > thread. >> >> > > > > > >> > > > >> >> > > > > > >> > > > On Tue, Sep 15, 2015 at 8:18 AM, Amol Kekre < >> >> > > > > [email protected] >> >> > > > > > > >> >> > > > > > >> > > wrote: >> >> > > > > > >> > > > >> >> > > > > > >> > > > > >> >> > > > > > >> > > > > Sent too soon. Has asynchronous checkpointing >> >>changed >> >> > > this? >> >> > > > > > >> > > > > >> >> > > > > > >> > > > > Amol >> >> > > > > > >> > > > > >> >> > > > > > >> > > > > Sent from my iPhone >> >> > > > > > >> > > > > >> >> > > > > > >> > > > > > On Sep 15, 2015, at 12:38 AM, Bhupesh Chawda < >> >> > > > > > >> > > [email protected]> >> >> > > > > > >> > > > > wrote: >> >> > > > > > >> > > > > > >> >> > > > > > >> > > > > > Hi All, >> >> > > > > > >> > > > > > >> >> > > > > > >> > > > > > Is it safe to assume that the checkpointed() and >> >>the >> >> > > > > > >> beginWindow() >> >> > > > > > >> > > > calls >> >> > > > > > >> > > > > > are sequenced? >> >> > > > > > >> > > > > > In other words, are these calls part of the same >> >> > thread >> >> > > > and >> >> > > > > > may >> >> > > > > > >> not >> >> > > > > > >> > > run >> >> > > > > > >> > > > > in >> >> > > > > > >> > > > > > parallel? >> >> > > > > > >> > > > > > >> >> > > > > > >> > > > > > Thanks. >> >> > > > > > >> > > > > > >> >> > > > > > >> > > > > > -- >> >> > > > > > >> > > > > > -Bhupesh >> >> > > > > > >> > > > > >> >> > > > > > >> > > > >> >> > > > > > >> > > >> >> > > > > > >> > >> >> > > > > > >> >> >> > > > > > >> >> > > > > >> >> > > > >> >> > > >> >> > >> >> >> >> >
