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https://issues.apache.org/jira/browse/FLINK-29577?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17615803#comment-17615803
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Yun Tang commented on FLINK-29577:
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I wonder will the full snapshot restoring duration would be reduced with this
patch?
> Disable rocksdb wal when restore from full snapshot
> ---------------------------------------------------
>
> Key: FLINK-29577
> URL: https://issues.apache.org/jira/browse/FLINK-29577
> Project: Flink
> Issue Type: Improvement
> Components: Runtime / State Backends
> Reporter: Cai Liuyang
> Assignee: Cai Liuyang
> Priority: Major
> Labels: pull-request-available
>
> For now, RocksDBFullRestoreOperation and
> RocksDBHeapTimersFullRestoreOperation does's pass RocksDB::WriteOptions to
> RocksDBWriteBatchWrapper when restore kv-data, which will use
> RocksDBWriteBatchWrapper‘s default WriteOptions(doesn't disable rocksdb wal
> explicitly, see code below), so during restoring from full snapshot, wal is
> enabled(use more disk and affect rocksdb-write-performance when restoring)
>
> {code:java}
> // First: RocksDBHeapTimersFullRestoreOperation::restoreKVStateData() doesn't
> pass WriteOptions to RocksDBWriteBatchWrapper(null as default)
> private void restoreKVStateData(
> ThrowingIterator<KeyGroup> keyGroups,
> Map<Integer, ColumnFamilyHandle> columnFamilies,
> Map<Integer, HeapPriorityQueueSnapshotRestoreWrapper<?>>
> restoredPQStates)
> throws IOException, RocksDBException, StateMigrationException {
> // for all key-groups in the current state handle...
> try (RocksDBWriteBatchWrapper writeBatchWrapper =
> new RocksDBWriteBatchWrapper(this.rocksHandle.getDb(),
> writeBatchSize)) {
> HeapPriorityQueueSnapshotRestoreWrapper<HeapPriorityQueueElement>
> restoredPQ = null;
> ColumnFamilyHandle handle = null;
> ......
> }
> // Second: RocksDBWriteBatchWrapper::flush function doesn't disable wal
> explicitly when user doesn't pass WriteOptions to RocksDBWriteBatchWrapper
> public void flush() throws RocksDBException {
> if (options != null) {
> db.write(options, batch);
> } else {
> // use the default WriteOptions, if wasn't provided.
> try (WriteOptions writeOptions = new WriteOptions()) {
> db.write(writeOptions, batch);
> }
> }
> batch.clear();
> }
> {code}
>
>
> As we known, rocksdb's wal is usesless for flink, so i think we can disable
> wal for RocksDBWriteBatchWrapper's default WriteOptions.
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