Hi, Pretty much just a rephrase of what others said. Flink's state is usually backed some highly available distributed fs and upon checkpoint a consistent view of all local states is written there, so it can be later restored from. As of now, any failure of a Task slot (e.g. if a TM fails, all slots in that TM fail) will result in a job restart. If the remaining TMs have enough slots to restart the job it will be restored onto them. The restoration always starts with the checkpoint as an "entry point". That means all the states written there will be resdistributed to the TMs. With task-local recovery feature [1] flink will try to distribute the state/tasks so that the local snapshot can be reused. Hope that this clears things up.
Best, Dawid [1] https://ci.apache.org/projects/flink/flink-docs-stable/ops/state/large_state_tuning.html#task-local-recovery On 12/01/2019 05:46, Congxian Qiu wrote: > Hi, Siew Wai Yow > > When the job is running, the states are stored in the local RocksDB, > Flink will copy all the needed states to checkpointPath when doing a > Checkpoint. > If there have any failures, the job will be restored from the last > previously *Successfully* checkpoint, and assign the restored states > to all the current TM > (These TMs do not need to be the same as before) . > > Siew Wai Yow <wai_...@hotmail.com <mailto:wai_...@hotmail.com>> > 于2019年1月12日周六 上午11:24写道： > > Thanks. But this is something I know. I would like to know will > the other TM take over the crashed TM's state to ensure data > completion(say the state BYKEY, different key state will be stored > in different TM) OR the crashed TM need to be recovered to continue? > > For example, 5 records, > rec1:KEYA > rec2:KEYB > rec3:KEYA > rec4:KEYC > rec5:KEYB > > TM1 stored state for rec1:KEYA, rec3:KEYA > TM2 stored state for rec2:KEYB, rec5:KEYB <--crashed, what happen > to those state stored inTM2 > TM3 stored state for rec4:KEYC > > In case TM2 crashed, rec2 and rec5 will be assigned to other TM? > Or those record only recover when TM2 being recover? > > Thanks. > > > ------------------------------------------------------------------------ > *From:* Jamie Grier <jgr...@lyft.com <mailto:jgr...@lyft.com>> > *Sent:* Saturday, January 12, 2019 2:26 AM > *To:* Siew Wai Yow > *Cc:* user@flink.apache.org <mailto:user@flink.apache.org> > *Subject:* Re: What happen to state in Flink Task Manager when crash? > > Flink is designed such that local state is backed up to a highly > available system such as HDFS or S3. When a TaskManager fails > state is recovered from there. > > I suggest reading this: > > https://ci.apache.org/projects/flink/flink-docs-release-1.7/ops/state/state_backends.html > > > On Fri, Jan 11, 2019 at 7:33 AM Siew Wai Yow <wai_...@hotmail.com > <mailto:wai_...@hotmail.com>> wrote: > > Hello, > > May i know what happen to state stored in Flink Task Manager > when this Task manager crash. Say the state storage is > rocksdb, would those data transfer to other running Task > Manager so that complete state data is ready for data processing? > > Regards, > Yow > > > > -- > Best, > Congxian
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