GitHub user StephanEwen opened a pull request:
https://github.com/apache/flink/pull/1017
[FLINK-2462] [streaming] Major cleanup of streaming task structure
This pull request addresses exception handling, code duplication, and
missed resource cleanups in the streaming operators.
I mixed multiple issues in this pull request, which would have been better
separated, but many were recognized in the rework, and it was tricky to pull
the fixes apart.
**NOTE** I have not managed to adjust all tests, yet, but I wanted to open
this early for feedback.
## Exception handling
The exceptions are no longer logged by the operators themselves. Operators
perform only cleanup in reaction to exceptions.
Exceptions are reported only the the root Task object, which knows whether
this is the first failure-causing exception (root cause), or is a subsequent
exception, or whether the task was actually canceled already. In the later
case, exceptions are ignored, because many cancellations lead to meaningless
exceptions.
Added more exception in signatures, less exception wrapping where not needed
## Unified setup / teardown structure in streaming tasks
Core resource acquisition/release logic is in `StreamTask`, reducing code
duplication.
Subtasks (e.g., `OneInputStreamTask`, `IterationTailStreamTask`) implement
slim methods for certain parts of the life cycle. The `OneInputStreamTask`
becomes as simple as this
```java
public void init() throws Exception {
TypeSerializer<IN> inSerializer =
configuration.getTypeSerializerIn1(getUserCodeClassLoader());
InputGate[] inputGates = getEnvironment().getAllInputGates();
inputProcessor = new StreamInputProcessor<IN>(inputGates, inSerializer,
getCheckpointBarrierListener(),
configuration.getCheckpointMode(),
getEnvironment().getIOManager(),
getExecutionConfig().areTimestampsEnabled());
// make sure that stream tasks report their I/O statistics
AccumulatorRegistry registry =
getEnvironment().getAccumulatorRegistry();
AccumulatorRegistry.Reporter reporter = registry.getReadWriteReporter();
inputProcessor.setReporter(reporter);
}
protected void run() throws Exception {
while (running && inputProcessor.processInput(streamOperator));
}
protected void cleanup() throws Exception {
inputProcessor.cleanup();
}
protected void cancelTask() {
running = false;
}
```
Guaranteed cleanup of output buffer and input buffer resources (formerly
missed when other exceptions where encountered).
Unified `StreamRecordWriter` and `RecordWriter` usage.
## Cleanup in the StreamSource
Fix mixup in instantiation of source contexts in the stream source task
Auto watermark generators correctly shut down their interval scheduler
## General
Improve use of generics, got rid of many raw types
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/StephanEwen/incubator-flink stream_cleanup
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/1017.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #1017
----
commit 68efed0a3b4184980de956bd57ba301569adac86
Author: Stephan Ewen <[email protected]>
Date: 2015-08-14T21:32:35Z
[FLINK-2462] [streaming] Major cleanup of operator structure for exception
handling and code simplication
- The exceptions are no longer logged by the operators themselves.
Operators perform only cleanup in reaction to exceptions.
Exceptions are reported only the the root Task object, which knows
whether this is the first
failure-causing exception (root cause), or is a subsequent exception,
or whether the task was
actually canceled already. In the later case, exceptions are ignored,
because many
cancellations lead to meaningless exceptions.
- more exception in signatures, less wrapping where not needed
- Core resource acquisition/release logic is in one streaming task,
reducing code duplication
- Guaranteed cleanup of output buffer and input buffer resources
(formerly missed when other exceptions where encountered)
- Fix mixup in instantiation of source contexts in the stream source task
- Auto watermark generators correctly shut down their interval scheduler
- Improve use of generics, got rid of many raw types
----
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