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From Yun Tang <myas...@live.com>
Subject Re: Flink incremental checkpointing - how long does data is kept in the share folder
Date Mon, 20 Apr 2020 12:14:35 GMT
Hi Shachar

You can refer to [1] to know the directory structure. The files (usually ByteStreamStateHandle)
which are not in the shared folder are exclusive state like operator state or exclusive files
uploaded during each incremental checkpoint. And actually I don't understand why you would
say some files are not mentioned in the metadata file but are related to the checkpoint? How
to judge that they are related to specific checkpoint?

BTW, my name is "Yun" which means cloud in Chinese, not the delicious "Yum" 🙂

Best
Yun Tang
________________________________
From: Shachar Carmeli <carmeli.dev@gmail.com>
Sent: Monday, April 20, 2020 15:36
To: user@flink.apache.org <user@flink.apache.org>
Subject: Re: Flink incremental checkpointing - how long does data is kept in the share folder

Hi Yum
I noticed that the some files are related to the checkpoint but are not mentioned in the metadata
file
and some of the files that are related in the metadata file (usually ByteStreamStateHandle
) are not in the share file
can you explain this behaviour ?

see code I was using
final Savepoint savepoint = Checkpoints.loadCheckpointMetadata(in, CheckpointTool.class.getClassLoader());

                        final Set<String> pathSharedFromMetadata = savepoint.getOperatorStates().stream()
                                        .flatMap(operatorState -> operatorState.getSubtaskStates().values().stream()
                                                        .flatMap(operatorSubtaskState ->
operatorSubtaskState.getManagedKeyedState().stream()
                                                                        .flatMap(keyedStateHandle
-> ((IncrementalKeyedStateHandle) keyedStateHandle).getSharedState().values().stream()
                                                                                        .map(streamStateHandle
-> {
                                                                                         
      totalSize[0] += streamStateHandle.getStateSize();
                                                                                         
      String name = null;
                                                                                         
      if (streamStateHandle instanceof FileStateHandle) {
                                                                                         
              name = ((FileStateHandle) streamStateHandle).getFilePath().getName();
                                                                                         
      } else {
                                                                                         
              final String handleName = ((ByteStreamStateHandle) streamStateHandle).getHandleName();
                                                                                         
              name = new File(handleName).getName();
                                                                                         
      }
                                                                                         
      return name;

                                                                                        }))))
                                        .collect(Collectors.toSet());

Thanks in advance
Shachar

On 2020/04/13 14:30:40, Yun Tang <myasuka@live.com> wrote:
> Hi Shachar
>
> I think you could refer to [1] to know the directory structure of checkpoints. The '_metadata'
file contains all information of which  checkpointed data file belongs, e.g. file paths under
'shared' folder. As I said before, you need to call Checkpoints#loadCheckpointMetadata to
load '_metadata' to know which files belonging to that checkpoint.
>
>
> [1] https://ci.apache.org/projects/flink/flink-docs-stable/ops/state/checkpoints.html#directory-structure
>
> Best
> Yun Tang
>
> ________________________________
> From: Shachar Carmeli <carmeli.dev@gmail.com>
> Sent: Sunday, April 12, 2020 15:32
> To: user@flink.apache.org <user@flink.apache.org>
> Subject: Re: Flink incremental checkpointing - how long does data is kept in the share
folder
>
> Thank you for the quick response
> Your answer related to the checkpoint folder that contains the _metadata file e.g. chk-1829
> What about the "shared" folder , how do I know which  files in that folder are still
relevant and which are left over from a failed checkpoint , they are not directly related
to the _metadata checkpoint or am I missing something?
>
>
> On 2020/04/07 18:37:57, Yun Tang <myasuka@live.com> wrote:
> > Hi Shachar
> >
> > Why do we see data that is older from lateness configuration
> > There might existed three reasons:
> >
> >   1.  RocksDB really still need that file in current checkpoint. If we upload one
file named as 42.sst at 2/4 at some old checkpoint, current checkpoint could still include
that 42.sst file again if that file is never be compacted since then. This is possible in
theory.
> >   2.  Your checkpoint size is large and checkpoint coordinator could not remove
as fast as possible before exit.
> >   3.  That file is created by a crash task manager and not known to checkpoint coordinator.
> >
> > How do I know that the files belong to a valid checkpoint and not a checkpoint of
a crushed job - so we can delete those files
> > You have to call Checkpoints#loadCheckpointMetadata[1] to load latest _metadata
in checkpoint directory and compare the file paths with current files in checkpoint directory.
The ones are not in the checkpoint meta and older than latest checkpoint could be removed.
You could follow this to debug or maybe I could write a tool to help know what files could
be deleted later.
> >
> > [1] https://github.com/apache/flink/blob/693cb6adc42d75d1db720b45013430a4c6817d4a/flink-runtime/src/main/java/org/apache/flink/runtime/checkpoint/Checkpoints.java#L96
> >
> > Best
> > Yun Tang
> >
> > ________________________________
> > From: Shachar Carmeli <carmeli.dev@gmail.com>
> > Sent: Tuesday, April 7, 2020 16:19
> > To: user@flink.apache.org <user@flink.apache.org>
> > Subject: Flink incremental checkpointing - how long does data is kept in the share
folder
> >
> > We are using Flink 1.6.3 and keeping the checkpoint in CEPH ,retaining only one
checkpoint at a time , using incremental and using rocksdb.
> >
> > We run windows with lateness of 3 days , which means that we expect that no data
in the checkpoint share folder will be kept after 3-4 days ,Still We see that there is data
from more than that
> > e.g.
> > If today is 7/4 there are some files from the 2/4
> >
> > Sometime we see checkpoints that we assume (due to the fact that its index number
is not in synch) that it belongs to a job that crushed and the checkpoint was not used to
restore the job
> >
> > My questions are
> >
> > Why do we see data that is older from lateness configuration
> > How do I know that the files belong to a valid checkpoint and not a checkpoint of
a crushed job - so we can delete those files
> >
>
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