Hi Jeff
1. " after around 50GB of state, I stop being able to reliably take
checkpoints or savepoints. "
What is the exact reason that job cannot complete checkpoint? Expired before
completing or decline by some tasks? The former one is manly caused by high
back-pressure and the later one is mainly due to some internal error.
2. Have you checked what reason the remote task manager is lost?
If the remote task manager is not crashed, it might be due to GC impact, I
think you might need to check task-manager logs and GC logs.
Best
Yun Tang
________________________________
From: Jeff Henrikson <jehenri...@gmail.com>
Sent: Thursday, June 18, 2020 1:46
To: user <user@flink.apache.org>
Subject: Trouble with large state
Hello Flink users,
I have an application of around 10 enrichment joins. All events are
read from kafka and have event timestamps. The joins are built using
.cogroup, with a global window, triggering on every 1 event, plus a
custom evictor that drops records once a newer record for the same ID
has been processed. Deletes are represented by empty events with
timestamp and ID (tombstones). That way, we can drop records when
business logic dictates, as opposed to when a maximum retention has been
attained. The application runs RocksDBStateBackend, on Kubernetes on
AWS with local SSDs.
Unit tests show that the joins produce expected results. On an 8 node
cluster, watermark output progress seems to indicate I should be able to
bootstrap my state of around 500GB in around 1 day. I am able to save
and restore savepoints for the first half an hour of run time.
My current trouble is that after around 50GB of state, I stop being able
to reliably take checkpoints or savepoints. Some time after that, I
start getting a variety of failures where the first suspicious log event
is a generic cluster connectivity error, such as:
1) java.io.IOException: Connecting the channel failed: Connecting
to remote task manager + '/10.67.7.101:38955' has failed. This
might indicate that the remote task manager has been lost.
2) org.apache.flink.runtime.io.network.netty.exception
.RemoteTransportException: Connection unexpectedly closed by remote
task manager 'null'. This might indicate that the remote task
manager was lost.
3) Association with remote system
[akka.tcp://flink@10.67.6.66:34987] has failed, address is now
gated for [50] ms. Reason: [Association failed with
[akka.tcp://flink@10.67.6.66:34987]] Caused by:
[java.net.NoRouteToHostException: No route to host]
I don't see any obvious out of memory errors on the TaskManager UI.
Adding nodes to the cluster does not seem to increase the maximum
savable state size.
I could enable HA, but for the time being I have been leaving it out to
avoid the possibility of masking deterministic faults.
Below are my configurations.
Thanks in advance for any advice.
Regards,
Jeff Henrikson
Flink version: 1.10
Configuration set via code:
parallelism=8
maxParallelism=64
setStreamTimeCharacteristic(TimeCharacteristic.EventTime)
setCheckpointingMode(CheckpointingMode.AT_LEAST_ONCE)
setTolerableCheckpointFailureNumber(1000)
setMaxConcurrentCheckpoints(1)
enableExternalizedCheckpoints(ExternalizedCheckpointCleanup.RETAIN_ON_CANCELLATION)
RocksDBStateBackend
setPredefinedOptions(PredefinedOptions.FLASH_SSD_OPTIMIZED)
setNumberOfTransferThreads(25)
setDbStoragePath points to a local nvme SSD
Configuration in flink-conf.yaml:
jobmanager.rpc.address: localhost
jobmanager.rpc.port: 6123
jobmanager.heap.size: 28000m
taskmanager.memory.process.size: 28000m
taskmanager.memory.jvm-metaspace.size: 512m
taskmanager.numberOfTaskSlots: 1
parallelism.default: 1
jobmanager.execution.failover-strategy: full
cluster.evenly-spread-out-slots: false
taskmanager.memory.network.fraction: 0.2 # default 0.1
taskmanager.memory.framework.off-heap.size: 2GB
taskmanager.memory.task.off-heap.size: 2GB
taskmanager.network.memory.buffers-per-channel: 32 # default 2
taskmanager.memory.managed.fraction: 0.4 # docs say
default 0.1, but something seems to set 0.4
taskmanager.memory.task.off-heap.size: 2048MB # default 128M
state.backend.fs.memory-threshold: 1048576
state.backend.fs.write-buffer-size: 10240000
state.backend.local-recovery: true
state.backend.rocksdb.writebuffer.size: 64MB
state.backend.rocksdb.writebuffer.count: 8
state.backend.rocksdb.writebuffer.number-to-merge: 4
state.backend.rocksdb.timer-service.factory: heap
state.backend.rocksdb.block.cache-size: 64000000 # default 8MB
state.backend.rocksdb.write-batch-size: 16000000 # default 2MB
web.checkpoints.history: 250
