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From Till Rohrmann <trohrm...@apache.org>
Subject Re: Very large _metadata file
Date Mon, 16 Mar 2020 20:53:53 GMT
Hi Jacob,

I think you are running into some deficiencies of Flink's union state here.
The problem is that for every entry in your list state, Flink stores a
separate offset (a long value). The reason for this behaviour is that we
use the same state implementation for the union state as well as for the
split state. For the latter, the offset information is required to split
the state in case of changing the parallelism of your job.

My recommendation would be to try to get rid of union state all together.
The union state has primarily been introduced to checkpoint some source
implementations and might become deprecated due to performance problems
once these sources can be checkpointed differently.

Cheers,
Till

On Sat, Mar 14, 2020 at 3:23 AM Jacob Sevart <jsevart@uber.com> wrote:

> Oh, I should clarify that's 43MB per partition, so with 48 partitions it
> explains my 2GB.
>
> On Fri, Mar 13, 2020 at 7:21 PM Jacob Sevart <jsevart@uber.com> wrote:
>
>> Running *Checkpoints.loadCheckpointMetadata *under a debugger, I found
>> something:
>> *subtaskState.managedOperatorState[0].sateNameToPartitionOffsets("startup-times").offsets.value
*weights
>> 43MB (5.3 million longs).
>>
>> "startup-times" is an operator state of mine (union list of
>> java.time.Instant). I see a way to end up fewer items in the list, but I'm
>> not sure how the actual size is related to the number of offsets. Can you
>> elaborate on that?
>>
>> Incidentally, 42.5MB is the number I got out of
>> https://issues.apache.org/jira/browse/FLINK-14618. So I think my two
>> problems are closely related.
>>
>> Jacob
>>
>> On Mon, Mar 9, 2020 at 6:36 AM Congxian Qiu <qcx978132955@gmail.com>
>> wrote:
>>
>>> Hi
>>>
>>> As Gordon said, the metadata will contain the ByteStreamStateHandle,
>>> when writing out the ByteStreamStateHandle, will write out the handle name
>>> -- which is a path(as you saw). The ByteStreamStateHandle will be created
>>> when state size is small than `state.backend.fs.memory-threshold`(default
>>> is 1024).
>>>
>>> If you want to verify this, you can ref the unit test
>>> `CheckpointMetadataLoadingTest#testLoadAndValidateSavepoint` and load the
>>> metadata, you can find out that there are many `ByteStreamStateHandle`, and
>>> their names are the strings you saw in the metadata.
>>>
>>> Best,
>>> Congxian
>>>
>>>
>>> Jacob Sevart <jsevart@uber.com> 于2020年3月6日周五 上午3:57写道:
>>>
>>>> Thanks, I will monitor that thread.
>>>>
>>>> I'm having a hard time following the serialization code, but if you
>>>> know anything about the layout, tell me if this makes sense. What I see in
>>>> the hex editor is, first, many HDFS paths. Then gigabytes of unreadable
>>>> data. Then finally another HDFS path at the end.
>>>>
>>>> If it is putting state in there, under normal circumstances, does it
>>>> make sense that it would be interleaved with metadata? I would expect all
>>>> the metadata to come first, and then state.
>>>>
>>>> Jacob
>>>>
>>>>
>>>>
>>>> Jacob
>>>>
>>>> On Thu, Mar 5, 2020 at 10:53 AM Kostas Kloudas <kkloudas@gmail.com>
>>>> wrote:
>>>>
>>>>> Hi Jacob,
>>>>>
>>>>> As I said previously I am not 100% sure what can be causing this
>>>>> behavior, but this is a related thread here:
>>>>>
>>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.apache.org_thread.html_r3bfa2a3368a9c7850cba778e4decfe4f6dba9607f32addb69814f43d-2540-253Cuser.flink.apache.org-253E&d=DwIBaQ&c=r2dcLCtU9q6n0vrtnDw9vg&r=lTq5mEceM-U-tVfWzKBngg&m=awEv6FqKY6dZ8NIA4KEFc_qQ6aadR_jTAWnO17wtAus&s=P3Xd0IFKJTDIG2MMeP-hOSfY4ohoCEUMQEJhvGecSlI&e=
>>>>>
>>>>> Which you can re-post your problem and monitor for answers.
>>>>>
>>>>> Cheers,
>>>>> Kostas
>>>>>
>>>>> On Wed, Mar 4, 2020 at 7:02 PM Jacob Sevart <jsevart@uber.com>
wrote:
>>>>> >
>>>>> > Kostas and Gordon,
>>>>> >
>>>>> > Thanks for the suggestions! I'm on RocksDB. We don't have that
>>>>> setting configured so it should be at the default 1024b. This is the
full
>>>>> "state.*" section showing in the JobManager UI.
>>>>> >
>>>>> >
>>>>> >
>>>>> > Jacob
>>>>> >
>>>>> > On Wed, Mar 4, 2020 at 2:45 AM Tzu-Li (Gordon) Tai <
>>>>> tzulitai@apache.org> wrote:
>>>>> >>
>>>>> >> Hi Jacob,
>>>>> >>
>>>>> >> Apart from what Klou already mentioned, one slightly possible
>>>>> reason:
>>>>> >>
>>>>> >> If you are using the FsStateBackend, it is also possible that
your
>>>>> state is small enough to be considered to be stored inline within the
>>>>> metadata file.
>>>>> >> That is governed by the "state.backend.fs.memory-threshold"
>>>>> configuration, with a default value of 1024 bytes, or can also be
>>>>> configured with the `fileStateSizeThreshold` argument when constructing
the
>>>>> `FsStateBackend`.
>>>>> >> The purpose of that threshold is to ensure that the backend
does
>>>>> not create a large amount of very small files, where potentially the
file
>>>>> pointers are actually larger than the state itself.
>>>>> >>
>>>>> >> Cheers,
>>>>> >> Gordon
>>>>> >>
>>>>> >>
>>>>> >>
>>>>> >> On Wed, Mar 4, 2020 at 6:17 PM Kostas Kloudas <kkloudas@gmail.com>
>>>>> wrote:
>>>>> >>>
>>>>> >>> Hi Jacob,
>>>>> >>>
>>>>> >>> Could you specify which StateBackend you are using?
>>>>> >>>
>>>>> >>> The reason I am asking is that, from the documentation in
[1]:
>>>>> >>>
>>>>> >>> "Note that if you use the MemoryStateBackend, metadata and
>>>>> savepoint
>>>>> >>> state will be stored in the _metadata file. Since it is
>>>>> >>> self-contained, you may move the file and restore from any
>>>>> location."
>>>>> >>>
>>>>> >>> I am also cc'ing Gordon who may know a bit more about state
>>>>> formats.
>>>>> >>>
>>>>> >>> I hope this helps,
>>>>> >>> Kostas
>>>>> >>>
>>>>> >>> [1]
>>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__ci.apache.org_projects_flink_flink-2Ddocs-2Drelease-2D1.6_ops_state_savepoints.html&d=DwIBaQ&c=r2dcLCtU9q6n0vrtnDw9vg&r=lTq5mEceM-U-tVfWzKBngg&m=awEv6FqKY6dZ8NIA4KEFc_qQ6aadR_jTAWnO17wtAus&s=fw0c-Ct21HHJv4MzZRicIaltqHLQOrNvqchzNgCdwkA&e=
>>>>> >>>
>>>>> >>> On Wed, Mar 4, 2020 at 1:25 AM Jacob Sevart <jsevart@uber.com>
>>>>> wrote:
>>>>> >>> >
>>>>> >>> > Per the documentation:
>>>>> >>> >
>>>>> >>> > "The meta data file of a Savepoint contains (primarily)
pointers
>>>>> to all files on stable storage that are part of the Savepoint, in form
of
>>>>> absolute paths."
>>>>> >>> >
>>>>> >>> > I somehow have a _metadata file that's 1.9GB. Running
strings on
>>>>> it I find 962 strings, most of which look like HDFS paths, which leaves
a
>>>>> lot of that file-size unexplained. What else is in there, and how exactly
>>>>> could this be happening?
>>>>> >>> >
>>>>> >>> > We're running 1.6.
>>>>> >>> >
>>>>> >>> > Jacob
>>>>> >
>>>>> >
>>>>> >
>>>>> > --
>>>>> > Jacob Sevart
>>>>> > Software Engineer, Safety
>>>>>
>>>>
>>>>
>>>> --
>>>> Jacob Sevart
>>>> Software Engineer, Safety
>>>>
>>>
>>
>> --
>> Jacob Sevart
>> Software Engineer, Safety
>>
>
>
> --
> Jacob Sevart
> Software Engineer, Safety
>

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