Flink rocksdb compaction filter not working

Mohammad Hossein Gerami :

I have a Flink Cluster. I enabled the compaction filter and using state TTL. but Rocksdb Compaction Filter does not free states from memory.

I have about 300 record / s in my Flink Pipeline

My state TTL config:

@Override
public void open(Configuration parameters) throws Exception {
    ListStateDescriptor<ObjectNode> descriptor = new ListStateDescriptor<ObjectNode>(
            "my-state",
            TypeInformation.of(new TypeHint<ObjectNode>() {})
    );


    StateTtlConfig ttlConfig = StateTtlConfig
            .newBuilder(Time.seconds(600))
            .cleanupInRocksdbCompactFilter(2)
            .build();

    descriptor.enableTimeToLive(ttlConfig);

    myState = getRuntimeContext().getListState(descriptor);
}

flink-conf.yaml:

state.backend: rocksdb
state.backend.rocksdb.ttl.compaction.filter.enabled: true
state.backend.rocksdb.block.blocksize: 16kb
state.backend.rocksdb.compaction.level.use-dynamic-size: true
state.backend.rocksdb.thread.num: 4
state.checkpoints.dir: file:///opt/flink/checkpoint
state.backend.rocksdb.timer-service.factory: rocksdb
state.backend.rocksdb.checkpoint.transfer.thread.num: 2
state.backend.local-recovery: true
state.backend.rocksdb.localdir: /opt/flink/rocksdb
jobmanager.execution.failover-strategy: region
rest.port: 8081
state.backend.rocksdb.memory.managed: true
# state.backend.rocksdb.memory.fixed-per-slot: 20mb
state.backend.rocksdb.memory.write-buffer-ratio: 0.9
state.backend.rocksdb.memory.high-prio-pool-ratio: 0.1
taskmanager.memory.managed.fraction: 0.6
taskmanager.memory.network.fraction: 0.1
taskmanager.memory.network.min: 500mb
taskmanager.memory.network.max: 700mb
taskmanager.memory.process.size: 5500mb
taskmanager.memory.task.off-heap.size: 800mb

metrics.reporter.influxdb.class: org.apache.flink.metrics.influxdb.InfluxdbReporter
metrics.reporter.influxdb.host: ####
metrics.reporter.influxdb.port: 8086
metrics.reporter.influxdb.db: ####
metrics.reporter.influxdb.username: ####
metrics.reporter.influxdb.password: ####
metrics.reporter.influxdb.consistency: ANY
metrics.reporter.influxdb.connectTimeout: 60000
metrics.reporter.influxdb.writeTimeout: 60000

state.backend.rocksdb.metrics.estimate-num-keys: true
state.backend.rocksdb.metrics.num-running-compactions: true
state.backend.rocksdb.metrics.background-errors: true
state.backend.rocksdb.metrics.block-cache-capacity: true
state.backend.rocksdb.metrics.block-cache-pinned-usage: true
state.backend.rocksdb.metrics.block-cache-usage: true
state.backend.rocksdb.metrics.compaction-pending: true

Monitoring by Influxdb and Grafana:

azagrebin :

As the name of this TTL cleanup implies (cleanupInRocksdbCompactFilter), it relies on the custom RocksDB compaction filter which runs only during compactions. More details in docs.

The metrics in the screenshot show that there have been no running compactions all the time. I suppose that the size of data is just not big enough to start any compaction at this point of time.

Compaction Filter does not free states from memory.

I assume that the main RAM memory is meant by saying 'from memory'. If so, the compaction is not running there at all. The size of data, kept by RocksDB in main memory, is always limited. It is basically a cache and the expired untouched state should just get evicted from it eventually. The rest is periodically spilled to disk and gets compacted over time. This is when this TTL cleanup is supposed to remove the expired state from the system.