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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 Wed, 22 Apr 2020 17:27:14 GMT
Hi Shachar

The basic rule to remove old data:

  1.  No two running Flink jobs use the same checkpoint directory (at the job-id level).
  2.  Files are not recorded in the latest checkpoint metadata are the candidate to remove.
  3.  If the checkpoint directory is still been written by Flink job, the files which are
newly created than last checkpoint completed time should also been filter out (if you are
not retain multi checkpoints). The rest files are safe to remove.

A simple way is stopping the job, and remove all files not recorded in the checkpoint metadata.

Best
Yun Tang
________________________________
From: Shachar Carmeli <carmeli.dev@gmail.com>
Sent: Tuesday, April 21, 2020 20:46
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 Yun,

First of all sorry for the naming mistake , it was a typo
 How to judge that they are related to specific checkpoint?
  I judged by removing the files and restarting the job - seeing if it fails

in the code below I missed the privateState that is why I was missing files

What about recovery folders how can I know when and what files can I removed?
I see the folder contains recovery -<job-name>  and list of completedCheckpoint3bc1020bb0f9

Best,
Shachar

On 2020/04/20 12:14:35, Yun Tang <myasuka@live.com> wrote:
> 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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