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https://issues.apache.org/jira/browse/FLINK-5544?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15930178#comment-15930178
]
ASF GitHub Bot commented on FLINK-5544:
---------------------------------------
Github user StefanRRichter commented on a diff in the pull request:
https://github.com/apache/flink/pull/3359#discussion_r106669225
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/operators/InternalTimerService.java
---
@@ -18,43 +18,306 @@
package org.apache.flink.streaming.api.operators;
import org.apache.flink.annotation.Internal;
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.core.memory.DataInputViewStreamWrapper;
+import org.apache.flink.core.memory.DataOutputViewStreamWrapper;
+import org.apache.flink.runtime.state.KeyGroupRange;
+import org.apache.flink.streaming.runtime.tasks.EventTimeCallback;
+import org.apache.flink.streaming.runtime.tasks.ProcessingTimeCallback;
+import org.apache.flink.streaming.runtime.tasks.ProcessingTimeService;
+import org.apache.flink.util.InstantiationUtil;
+import org.apache.flink.util.Preconditions;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.ScheduledFuture;
+
+import static org.apache.flink.util.Preconditions.checkArgument;
+import static org.apache.flink.util.Preconditions.checkNotNull;
/**
* Interface for working with time and timers.
*
* <p>This is the internal version of {@link
org.apache.flink.streaming.api.TimerService}
* that allows to specify a key and a namespace to which timers should be
scoped.
*
+ * All d
--- End diff --
Unfinished comment
> Implement Internal Timer Service in RocksDB
> -------------------------------------------
>
> Key: FLINK-5544
> URL: https://issues.apache.org/jira/browse/FLINK-5544
> Project: Flink
> Issue Type: New Feature
> Components: State Backends, Checkpointing
> Reporter: Xiaogang Shi
> Assignee: Xiaogang Shi
>
> Now the only implementation of internal timer service is
> HeapInternalTimerService which stores all timers in memory. In the cases
> where the number of keys is very large, the timer service will cost too much
> memory. A implementation which stores timers in RocksDB seems good to deal
> with these cases.
> It might be a little challenging to implement a RocksDB timer service because
> the timers are accessed in different ways. When timers are triggered, we need
> to access timers in the order of timestamp. But when performing checkpoints,
> we must have a method to obtain all timers of a given key group.
> A good implementation, as suggested by [~StephanEwen], follows the idea of
> merge sorting. We can store timers in RocksDB with the format
> {{KEY_GROUP#TIMER#KEY}}. In this way, the timers under a key group are put
> together and are sorted.
> Then we can deploy an in-memory heap which keeps the first timer of each key
> group to get the next timer to trigger. When a key group's first timer is
> updated, we can efficiently update the heap.
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