[jira] [Comment Edited] (FLINK-10473) State TTL incremental cleanup using Heap backend key iterator

["dalongliu (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-10473?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17067738#comment-17067738 ] 

dalongliu edited comment on FLINK-10473 at 3/26/20, 2:51 PM:
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Hi, [~azagrebin], for the pull request you subimmted, when I debug TtlStateTestBase#

testIncrementalCleanup, I found I can't enter into the *{color:#FF0000}for loop{color}* of TtlIncrementalCleanup#runCleanup method on state access,
{code:java}
private void runCleanup() { int entryNum = 0; Collection<StateEntry<K, N, S>> nextEntries; while ( entryNum < cleanupSize && stateIterator.hasNext() && !(nextEntries = stateIterator.nextEntries()).isEmpty()) { for (StateEntry<K, N, S> state : nextEntries) { S cleanState = ttlState.getUnexpiredOrNull(state.getState()); if (cleanState == null) { stateIterator.remove(state); } else if (cleanState != state.getState()) { stateIterator.update(state, cleanState); } } entryNum += nextEntries.size(); } }


{code}
so I think the incremental  cleanup strategy does not work, the state clean up only in call getWithTtlCheckAndUpdate phase.

Because I want to use this feature to support sql minibatch deduplication state ttl, so first I must understand the principle of incremental clean up,  can you tell me the detailed process of incremental clean up?


was (Author: lsy):
Hi, [~azagrebin], for the pull request you subimmted, when I debug TtlStateTestBase#

testIncrementalCleanup, I found I can't enter into the for loop of TtlIncrementalCleanup#runCleanup method on state access,
{code:java}
private void runCleanup() { int entryNum = 0; Collection<StateEntry<K, N, S>> nextEntries; while ( entryNum < cleanupSize && stateIterator.hasNext() && !(nextEntries = stateIterator.nextEntries()).isEmpty()) { for (StateEntry<K, N, S> state : nextEntries) { S cleanState = ttlState.getUnexpiredOrNull(state.getState()); if (cleanState == null) { stateIterator.remove(state); } else if (cleanState != state.getState()) { stateIterator.update(state, cleanState); } } entryNum += nextEntries.size(); } }


{code}
so I think the incremental  cleanup strategy does not work, the state clean up only in call getWithTtlCheckAndUpdate phase.

Because I want to use this feature to support sql minibatch deduplication state ttl, so first I must understand the principle of incremental clean up,  can you tell me the detailed process of incremental clean up?

> State TTL incremental cleanup using Heap backend key iterator
> -------------------------------------------------------------
>
>                 Key: FLINK-10473
>                 URL: https://issues.apache.org/jira/browse/FLINK-10473
>             Project: Flink
>          Issue Type: New Feature
>          Components: Runtime / State Backends
>    Affects Versions: 1.7.0
>            Reporter: Andrey Zagrebin
>            Assignee: Andrey Zagrebin
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.8.0
>
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> This feature enables lazy background cleanup of state with time-to-live in state keyed backend which stores state in JVM heap. The idea is to keep a global state lazy iterator with loose consistency. Every time a state value for some key is accessed or a record is processed, the iterator is advanced, TTL of iterated state entries is checked and the expired entries are cleaned up. When the iterator reaches the end of state storage it just starts over. This way the state with TTL is regularly cleaned up to prevent ever growing memory consumption. The caveat of this cleanup strategy is that if state is not accessed or no records are processed then accumulated expired state still occupies the storage.



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