Hi Piotr, Thanks for driving this proposal! I strongly agree that the existing metric APIs are not suitable for monitoring restore/checkpoint behavior!
I think the TM-level recovery/checkpointing traces are necessary in the future. In our production environment, we sometimes encounter that job recovery time is very long (30min+), due to several subTask heavy disk traffic. The TM-level recovery trace is helpful for troubleshooting such issues. Best Jinzhong On Wed, Nov 8, 2023 at 5:09 PM Piotr Nowojski <pnowoj...@apache.org> wrote: > Hi Zakelly, > > Thanks for the comments. Quick answer for both of your questions would be > that it probably should be > left as a future work. For more detailed answers please take a look below > :) > > > Does it mean the inclusion and subdivision relationships of spans defined > > by "parent_id" are not supported? I think it is a very necessary feature > > for the trace. > > Yes exactly, that is the current limitation. This could be solved somehow > one way or another in the future. > > Support for reporting multi span traces all at once - for example > `CheckpointStatsTracker` running JM, > could upon checkpoint completion create in one place the whole structure of > parent spans, to have for > example one span per each subtask. This would be a relatively easy follow > up. > > However, if we would like to create true distributed traces, with spans > reported from many different > components, potentially both on JM and TM, the problem is a bit deeper. The > issue in that case is how > to actually fill out `parrent_id` and `trace_id`? Passing some context > entity as a java object would be > unfeasible. That would require too many changes in too many places. I think > the only realistic way > to do it, would be to have a deterministic generator of `parten_id` and > `trace_id` values. > > For example we could create the parent trace/span of the checkpoint on JM, > and set those ids to > something like: `jobId#attemptId#checkpointId`. Each subtask then could > re-generate those ids > and subtasks' checkpoint span would have an id of > `jobId#attemptId#checkpointId#subTaskId`. > Note that this is just an example, as most likely distributed spans for > checkpointing do not make > sense, as we can generate them much easier on the JM anyway. > > > In addition to checkpoint and recovery, I believe the trace would also be > > valuable for performance tuning. If Flink can trace and visualize the > time > > cost of each operator and stage for a sampled record, users would be able > > to easily determine the end-to-end latency and identify performance > issues > > for optimization. Looking forward to seeing these in the future. > > I'm not sure if I understand the proposal - I don't know how traces could > be used for this purpose? > Traces are perfect for one of events (like checkpointing, recovery, etc), > not for continuous monitoring > (like processing records). That's what metrics are. Creating trace and > span(s) per each record would > be prohibitively expensive. > > Unless you mean in batch/bounded jobs? Then yes, we could create a bounded > job trace, with spans > for every stage/task/subtask. > > Best, > Piotrek > > > śr., 8 lis 2023 o 05:30 Zakelly Lan <zakelly....@gmail.com> napisał(a): > > > Hi Piotr, > > > > Happy to see the trace! Thanks for this proposal. > > > > One minor question: It is mentioned in the interface of Span: > > > > Currently we don't support traces with multiple spans. Each span is > > > self-contained and represents things like a checkpoint or recovery. > > > > > > Does it mean the inclusion and subdivision relationships of spans defined > > by "parent_id" are not supported? I think it is a very necessary feature > > for the trace. > > > > In addition to checkpoint and recovery, I believe the trace would also be > > valuable for performance tuning. If Flink can trace and visualize the > time > > cost of each operator and stage for a sampled record, users would be able > > to easily determine the end-to-end latency and identify performance > issues > > for optimization. Looking forward to seeing these in the future. > > > > Best, > > Zakelly > > > > > > On Tue, Nov 7, 2023 at 6:27 PM Piotr Nowojski <pnowoj...@apache.org> > > wrote: > > > > > Hi Rui, > > > > > > Thanks for the comments! > > > > > > > 1. I see the trace just supports Span? Does it support trace events? > > > > I'm not sure whether tracing events is reasonable for TraceReporter. > > > > If it supports, flink can report checkpoint and checkpoint path > > > proactively. > > > > Currently, checkpoint lists or the latest checkpoint can only be > > fetched > > > > by external components or platforms. And report is more timely and > > > > efficient than fetch. > > > > > > No, currently the `TraceReporter` that I'm introducing supports only > > single > > > span traces. > > > So currently neither events on their own, nor events inside spans are > not > > > supported. > > > This is done just for the sake of simplicity, and test out the basic > > > functionality. But I think, > > > those currently missing features should be added at some point in > > > the future. > > > > > > About structured logging (basically events?) I vaguely remember some > > > discussions about > > > that. It might be a much larger topic, so I would prefer to leave it > out > > of > > > the scope of this > > > FLIP. > > > > > > > 2. This FLIP just monitors the checkpoint and task recovery, right? > > > > > > Yes, it only adds single span traces for checkpointing and > > > recovery/initialisation - one > > > span per whole job per either recovery/initialization process or per > each > > > checkpoint. > > > > > > > Could we add more operations in this FLIP? In our production, we > > > > added a lot of trace reporters for job starts and scheduler > operation. > > > > They are useful if some jobs start slowly, because they will affect > > > > the job availability. For example: > > > > - From JobManager process is started to JobGraph is created > > > > - From JobGraph is created to JobMaster is created > > > > - From JobMaster is created to job is running > > > > - From start request tm from yarn or kubernetes to all tms are ready > > > > - etc > > > > > > I think those could be indeed useful. If you would like to contribute > > them > > > in the future, > > > I would be happy to review the FLIP for it :) > > > > > > > Of course, this FLIP doesn't include them is fine for me. The first > > > version > > > > only initializes the interface and common operations, and we can add > > > > more operations in the future > > > > > > Yes, that's exactly my thinking :) > > > > > > Best, > > > Piotrek > > > > > > wt., 7 lis 2023 o 10:05 Rui Fan <1996fan...@gmail.com> napisał(a): > > > > > > > Hi Piotr, > > > > > > > > Thanks for driving this proposal! The trace reporter is useful to > > > > check a lot of duration monitors inside of Flink. > > > > > > > > I have some questions about this proposal: > > > > > > > > 1. I see the trace just supports Span? Does it support trace events? > > > > I'm not sure whether tracing events is reasonable for TraceReporter. > > > > If it supports, flink can report checkpoint and checkpoint path > > > > proactively. > > > > Currently, checkpoint lists or the latest checkpoint can only be > > fetched > > > > by external components or platforms. And report is more timely and > > > > efficient than fetch. > > > > > > > > 2. This FLIP just monitors the checkpoint and task recovery, right? > > > > Could we add more operations in this FLIP? In our production, we > > > > added a lot of trace reporters for job starts and scheduler > operation. > > > > They are useful if some jobs start slowly, because they will affect > > > > the job availability. For example: > > > > - From JobManager process is started to JobGraph is created > > > > - From JobGraph is created to JobMaster is created > > > > - From JobMaster is created to job is running > > > > - From start request tm from yarn or kubernetes to all tms are ready > > > > - etc > > > > > > > > Of course, this FLIP doesn't include them is fine for me. The first > > > version > > > > only initializes the interface and common operations, and we can add > > > > more operations in the future. > > > > > > > > Best, > > > > Rui > > > > > > > > On Tue, Nov 7, 2023 at 4:31 PM Piotr Nowojski <pnowoj...@apache.org> > > > > wrote: > > > > > > > > > Hi all! > > > > > > > > > > I would like to start a discussion on FLIP-384: Introduce > > TraceReporter > > > > and > > > > > use it to create checkpointing and recovery traces [1]. > > > > > > > > > > This proposal intends to improve observability of Flink's > > Checkpointing > > > > and > > > > > Recovery/Initialization operations, by adding support for reporting > > > > traces > > > > > from Flink. In the future, reporting traces can be of course used > for > > > > other > > > > > use cases and also by users. > > > > > > > > > > There are also two other follow up FLIPS, FLIP-385 [2] and FLIP-386 > > > [3], > > > > > which expand the basic functionality introduced in FLIP-384 [1]. > > > > > > > > > > Please let me know what you think! > > > > > > > > > > Best, > > > > > Piotr Nowojski > > > > > > > > > > [1] > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-384%3A+Introduce+TraceReporter+and+use+it+to+create+checkpointing+and+recovery+traces > > > > > [2] > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-385%3A+Add+OpenTelemetryTraceReporter+and+OpenTelemetryMetricReporter > > > > > [3] > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/FLINK/FLIP-386%3A+Support+adding+custom+metrics+in+Recovery+Spans > > > > > > > > > > > > > > >
