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From Stephan Ewen <se...@apache.org>
Subject Re: Exception when restoring state from RocksDB - how to recover?
Date Tue, 11 Oct 2016 16:37:59 GMT
Hi Josh!

I think the master has gotten more stable with respect to that. The issue
you mentioned should be fixed.

Another big set of changes (the last big batch) is going in in the next
days - this time for re-sharding timers (window operator) and other state
that is not organized by key.

If you want to be a bit conservative, give it a few days before jumping
onto the latest master. If you are brave, give it a shot now ;-)

Greetings,
Stephan


On Tue, Oct 11, 2016 at 5:43 PM, Josh <jofo90@gmail.com> wrote:

> Hi Stephan,
>
> Thanks, that sounds good!
>
> I'm planning to upgrade to Flink 1.2-SNAPSHOT as soon as possible - I was
> delaying upgrading due to the issues with restoring operator state you
> mentioned on my other thread here:
> http://apache-flink-user-mailing-list-archive.2336050.
> n4.nabble.com/Flink-job-fails-to-restore-RocksDB-state-
> after-upgrading-to-1-2-SNAPSHOT-td9110.html
>
> Sorry to jump around but do you know if that's fixed in the latest
> 1.2-SNAPSHOT? Was it resolved by Flink-4788?
>
> Thanks,
> Josh
>
> On Tue, Oct 11, 2016 at 4:13 PM, Stephan Ewen <sewen@apache.org> wrote:
>
>> Hi Josh!
>>
>> There are two ways to improve the RocksDB / S3 behavior
>>
>> (1) Use the FullyAsync mode. It stores the data in one file, not in a
>> directory. Since directories are the "eventual consistent" part of S3, this
>> prevents many issues.
>>
>> (2) Flink 1.2-SNAPSHOT has some additional fixes that circumvent
>> additional S3 issues.
>>
>> Hope that helps,
>> Stephan
>>
>>
>> On Tue, Oct 11, 2016 at 4:42 PM, Josh <jofo90@gmail.com> wrote:
>>
>>> Hi Aljoscha,
>>>
>>> Yeah I'm using S3. Is this a known problem when using S3? Do you have
>>> any ideas on how to restore my job from this state, or prevent it from
>>> happening again?
>>>
>>> Thanks,
>>> Josh
>>>
>>>
>>> On Tue, Oct 11, 2016 at 1:58 PM, Aljoscha Krettek <aljoscha@apache.org>
>>> wrote:
>>>
>>>> Hi,
>>>> you are using S3 to store the checkpoints, right? It might be that
>>>> you're running into a problem with S3 "directory listings" not being
>>>> consistent.
>>>>
>>>> Cheers,
>>>> Aljoscha
>>>>
>>>> On Tue, 11 Oct 2016 at 12:40 Josh <jofo90@gmail.com> wrote:
>>>>
>>>> Hi all,
>>>>
>>>>
>>>> I just have a couple of questions about checkpointing and restoring state
from RocksDB.
>>>>
>>>>
>>>> 1) In some cases, I find that it is impossible to restore a job from a checkpoint,
due to an exception such as the one pasted below[*]. In this case, it appears that the last
checkpoint is somehow corrupt. Does anyone know why this might happen?
>>>>
>>>>
>>>> 2) When the above happens, I have no choice but to cancel the job, as it
repeatedly attempts to restart and keeps getting the same exception. Given that no savepoint
was taken recently, is it possible for me to restore the job from an older checkpoint (e.g.
the second-last checkpoint)?
>>>>
>>>>
>>>> The version of Flink I'm using Flink-1.1-SNAPSHOT, from mid-June.
>>>>
>>>>
>>>> Thanks,
>>>>
>>>> Josh
>>>>
>>>>
>>>> [*]The exception when restoring state:
>>>>
>>>> java.lang.Exception: Could not restore checkpointed state to operators and
functions
>>>> 	at org.apache.flink.streaming.runtime.tasks.StreamTask.restoreState(StreamTask.java:480)
>>>> 	at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:219)
>>>> 	at org.apache.flink.runtime.taskmanager.Task.run(Task.java:588)
>>>> 	at java.lang.Thread.run(Thread.java:745)
>>>> Caused by: java.lang.RuntimeException: Error while restoring RocksDB state
from /mnt/yarn/usercache/hadoop/appcache/application_1476181294189_0001/flink-io-09ad1cb1-8dff-4f9a-9f61-6cae27ee6f1d/d236820a793043bd63360df6f175cae9/StreamFlatMap_9_8/dummy_state/dc5beab1-68fb-48b3-b3d6-272497d15a09/chk-1
>>>> 	at org.apache.flink.contrib.streaming.state.RocksDBStateBackend.restoreFromSemiAsyncSnapshot(RocksDBStateBackend.java:537)
>>>> 	at org.apache.flink.contrib.streaming.state.RocksDBStateBackend.injectKeyValueStateSnapshots(RocksDBStateBackend.java:489)
>>>> 	at org.apache.flink.streaming.api.operators.AbstractStreamOperator.restoreState(AbstractStreamOperator.java:204)
>>>> 	at org.apache.flink.streaming.api.operators.AbstractUdfStreamOperator.restoreState(AbstractUdfStreamOperator.java:154)
>>>> 	at org.apache.flink.streaming.runtime.tasks.StreamTask.restoreState(StreamTask.java:472)
>>>> 	... 3 more
>>>> Caused by: org.rocksdb.RocksDBException: NotFound: Backup not found
>>>> 	at org.rocksdb.BackupEngine.restoreDbFromLatestBackup(Native Method)
>>>> 	at org.rocksdb.BackupEngine.restoreDbFromLatestBackup(BackupEngine.java:177)
>>>> 	at org.apache.flink.contrib.streaming.state.RocksDBStateBackend.restoreFromSemiAsyncSnapshot(RocksDBStateBackend.java:535)
>>>> 	... 7 more
>>>>
>>>>
>>>>
>>>
>>
>

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