Kinesis Connector and Savepoint/Checkpoint restore.
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Kinesis Connector and Savepoint/Checkpoint restore.
 
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Hello, we currently use Flink 1.9.0 with Kinesis to process data.
We have extended data retention on the Kinesis stream, which gives us 7 days of data. We have found that when a savepoint/checkpoint is restored that it appears to be restarting the Kinesis Consumer from the start of the stream. The flink_taskmanager_job_task_operator_KinesisConsumer_stream_shardId_millisBehindLatest property reports to Prometheus that it is behind by 7 days when the process starts back up from a savepoint. We have some logs that say: Subtask 3 will start consuming seeded shard StreamShardHandle{streamName='TheStream', shard='{ShardId: shardId-000000000083,HashKeyRange: {StartingHashKey: 220651847300296034902031972006537199616,EndingHashKey: 223310303291865866647839586127097888767},SequenceNumberRange: {StartingSequenceNumber: 49597946220601502339755334362523522663986150244033234226,}}'} from sequence number EARLIEST_SEQUENCE_NUM with ShardConsumer 20 This seems to indicate that this shard is starting from the beginning of the stream and some logs that say: Subtask 3 will start consuming seeded shard StreamShardHandle{streamName='
TheStream ', shard='{ShardId: shardId-000000000087,HashKeyRange: {StartingHashKey: 231285671266575361885262428488779956224,EndingHashKey: 233944127258145193631070042609340645375},SequenceNumberRange: {StartingSequenceNumber: 49597946220690705320549456855089665537076743690057155954,}}'} from sequence number 49599841594208637293623823226010128300928335129272649074 with ShardConsumer 21 This shard seems to be resuming from a specific point. I am assuming that this might be caused by no data being available on the shard for the entire stream (possible with this application stage). Is this the expected behavior? I had thought it would checkpoint with the most recent sequence number, regardless of if it got data or not. -Steve |
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Hi Steven
If you restore savepoint/checkpoint successfully, I think this might due to the shard wasn't discovered in the previous run, therefore it would be consumed from the beginning. Please refer to the implementation here: [1]
Best
Yun Tang
From: Steven Nelson <[hidden email]>
Sent: Wednesday, October 16, 2019 4:31 To: user <[hidden email]> Subject: Kinesis Connector and Savepoint/Checkpoint restore. Hello, we currently use Flink 1.9.0 with Kinesis to process data.
We have extended data retention on the Kinesis stream, which gives us 7 days of data.
We have found that when a savepoint/checkpoint is restored that it appears to be restarting the Kinesis Consumer from the start of the stream. The flink_taskmanager_job_task_operator_KinesisConsumer_stream_shardId_millisBehindLatest property reports to
Prometheus that it is behind by 7 days when the process starts back up from a savepoint.
We have some logs that say:
Subtask 3 will start
consuming
seeded
shard
StreamShardHandle{streamName='TheStream', shard='{ShardId: shardId-000000000083,HashKeyRange: {StartingHashKey: 220651847300296034902031972006537199616,EndingHashKey:
223310303291865866647839586127097888767},SequenceNumberRange: {StartingSequenceNumber: 49597946220601502339755334362523522663986150244033234226,}}'} from sequence number EARLIEST_SEQUENCE_NUM with ShardConsumer 20
This seems to indicate that this shard is starting from the beginning of the stream
and some logs that say:
Subtask 3 will start
consuming
seeded
shard
StreamShardHandle{streamName=' TheStream ',
shard='{ShardId: shardId-000000000087,HashKeyRange: {StartingHashKey: 231285671266575361885262428488779956224,EndingHashKey: 233944127258145193631070042609340645375},SequenceNumberRange: {StartingSequenceNumber: 49597946220690705320549456855089665537076743690057155954,}}'}
from sequence number 49599841594208637293623823226010128300928335129272649074 with ShardConsumer 21
This shard seems to be resuming from a specific point.
I am assuming that this might be caused by no data being available on the shard for the entire stream (possible with this application stage). Is this the expected behavior? I had thought it would checkpoint with the most recent sequence number, regardless
of if it got data or not.
-Steve
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Re: Kinesis Connector and Savepoint/Checkpoint restore.
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Hi, I am also facing the same problem. I am using Flink 1.9.0 and consuming from Kinesis source with retention of 1 day. I am observing that when the job is submitted with "latest" initial stream position, the job starts well and keep on processing data from all the shards for very long period of time without any lag. When the job fails then it also recovery well with last successful checkpointed state. But i am also experiencing that very rarely when the job fails and it recovers from the last successful checkpointed state, i noticed a hug lag( 1 day as per retention) on one of the stream. For me, to reproduce this issue is still unknown to defined a step by step process. So far now, as per the analysis i gathered some more information by customizing the FlinkKinesisConsumer to put additional log message, I noticed that the number of shards details which is loaded from checkpoint data during recovering is less than than the actual number of shards in the stream. I have fixed number of shards in kinesis stream. i added one line of debug log at line 408 to print the size of variable "sequenceNumsToRestore" which was populated with shard details from checkpoint data. In this consumer class, when the "run" method is called, it does following
As in my case, the recovered number of shard details from the checkpoint data is less than the actual number of shards which results into scheduling those shards with earliest stream position. I am suspecting that somehow the checkpoint is missing state for some of the shards. But if this is the case then that checkpoint should had failed. Any further information to resolve this issue would be highly appreciated... Regards, Ravi On Wed, Oct 16, 2019 at 5:57 AM Yun Tang <[hidden email]> wrote:
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Re: Kinesis Connector and Savepoint/Checkpoint restore.
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I have verified this behavior in 1.9.0, 1.8.1 and 1.7.2. About half my shards start over at trim horizon. Why would some shard statuses appear to not exist in a savepoints? This seems like a big problem. -Steve On Wed, Oct 16, 2019 at 12:08 AM Ravi Bhushan Ratnakar <[hidden email]> wrote:
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Re: Kinesis Connector and Savepoint/Checkpoint restore.
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Do you know step by step process to reproduce this problem? -Ravi On Wed 16 Oct, 2019, 17:40 Steven Nelson, <[hidden email]> wrote:
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Re: Kinesis Connector and Savepoint/Checkpoint restore.
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In my situation I believe it's because we have idle shards (it's a testing environment). I dug into the connector code and it looks like it only updates the shard state when a record is processed or when the shard hits shard_end. So, for an idle shard it would never get a checkpointed state. I guess this is okay since in production we won't have idle shards, but it might be better to send through a empty record that doesn't get emitted, but it does trigger a state update. -Steve On Wed, Oct 16, 2019 at 12:54 PM Ravi Bhushan Ratnakar <[hidden email]> wrote:
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Re: Kinesis Connector and Savepoint/Checkpoint restore.
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Hi For idle shards, I think restore from the previous not consumed data is ok, because Flink did not consume any data before, but for not idle shards this is problematic. From my experience of other connectors, could you check whether the "error" shards are newly split? maybe the newly split shards were not contained in the checkpoint. Best, Congxian Steven Nelson <[hidden email]> 于2019年10月17日周四 上午2:19写道：
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Re: Kinesis Connector and Savepoint/Checkpoint restore.
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Hi congxian, Thank you for your reply. As I shared details in my previous mail, in my case, last successful checkpoint is missing details for some of the shards. I am not doing any up scale or down scale of kinesis shard. I always run with fix number of shards, so there is no possibility of new shard discovery which could cause such problem. Thanks, Ravi On Fri 22 Nov, 2019, 02:53 Congxian Qiu, <[hidden email]> wrote:
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