Rinat Sharipov created FLINK-9592:
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Summary: Notify on moving into pending/ final state
Key: FLINK-9592
URL: https://issues.apache.org/jira/browse/FLINK-9592
Project: Flink
Issue Type: New Feature
Components: filesystem-connector
Reporter: Rinat Sharipov
Hi mates, I got a proposal about functionality of BucketingSink.
During implementation of one of our tasks we got the following need - create a
meta-file, with the path and additional information about the file, created by
BucketingSink, when it’s been moved into final place.
Unfortunately such behaviour is currently not available for us.
We’ve implemented our own Sink, that provides an opportunity to register
notifiers, that will be called, when file state is changing, but current API
doesn’t allow us to add such behaviour using inheritance ...
It seems, that such functionality could be useful, and could be a part of
BucketingSink API
What do you sink, should I make a PR ?
Sincerely yours,
*Rinat Sharipov*
Software Engineer at 1DMP CORE Team
email: [[email protected]|mailto:[email protected]]
mobile: +7 (925) 416-37-26
Clever{color:#4f8f00}DATA{color}
make your data clever
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Hi,
I see that could be a useful feature. What exactly now is preventing you from
inheriting from BucketingSink? Maybe it would be just enough to make the
BucketingSink easier extendable.
One thing now that could collide with such feature is that Kostas is now
working on larger BucketingSink rework/refactor.
Piotrek
________________________________________________________________________
Hi guys, thx for your reply.
The following code info is actual for *release-1.5.0 tag,
org.apache.flink.streaming.connectors.fs.bucketing.BucketingSink class*
For now, BucketingSink has the following lifecycle of files
When moving files from opened to pending state:
# on each item (*method* *invoke:434* *line*), we check that suitable bucket
exist, and contain opened file, in case, when opened file doesn’t exist, we
create one, and write item to it
# on each item (*method* *invoke:434* *line*), we check that suitable opened
file doesn’t exceed the limits, and if limits are exceeded, we close it and
move into pending state using *closeCurrentPartFile:568 line - private method*
# on each timer request (*onProcessingTime:482 line*), we check, if items
haven't been added to the opened file longer, than specified period of time, we
close it, using the same private method *closeCurrentPartFile:588 line*
So, the only way, that we have, is to call our hook from
*closeCurrentPartFile*, that is private, so we copy-pasted the current impl and
injected our logic there
Files are moving from pending state into final, during checkpointing lifecycle,
in *notifyCheckpointComplete:657 line*, that is public, and contains a lot of
logic, including discovery of files in pending states, synchronization of state
access and it’s modification, etc …
So we couldn’t override it, or call super method and add some logic, because
when current impl changes the state of files, it removes them from state, and
we don’t have any opportunity to know,
for which files state have been changed.
To solve such problem, we've created the following interface
/**
* The {@code FileStateChangeCallback} is used to perform any additional
operations, when {@link BucketingSink}
* moves file from one state to another. For more information about state
management of {@code BucketingSink}, look
* through it's official documentation.
*/
public interface FileStateChangeCallback extends Serializable {
/**
* Used to perform any additional operations, related with moving of file into
next state.
*
* @param fs provides access for working with file system
* @param path path to the file, moved into next state
*
* @throws IOException if something went wrong, while performing any operations
with file system
*/
void call(FileSystem fs, Path path) throws IOException;
}
And have added an ability to register this callbacks in BucketingSink impl in
the following manner
public BucketingSink<T>
registerOnFinalStateChangeCallback(FileStateChangeCallback… callbacks) \{...}
public BucketingSink<T>
registerOnPendingStateChangeCallback(FileStateChangeCallback... callbacks)
\{...}
I’m ready to discuss the best ways, how such hooks could be implemented in the
core impl or any other improvements, that will help us to add such
functionality into our extension, using public api, instead of copy-pasting the
source code.
Thx for your help, mates =)
[*See More* from Piotr Nowojski|x-redundant-cluster-toggle://0]
Sincerely yours,
*Rinat Sharipov*
Software Engineer at 1DMP CORE Team
email: [[email protected]|mailto:[email protected]]
mobile: +7 (925) 416-37-26
Clever{color:#4f8f00}DATA{color}
make your data clever
________________________________________________________________________
Hi,
Couple of things:
1. Please create a Jira ticket with this proposal, so we can move discussion
from user mailing list.
I haven’t thought it through, so take my comments with a grain of salt, however:
2. If we were to go with such callback, I would prefer to have one
BucketStateChangeCallback, with methods like `onInProgressToPending(…)`,
`onPendingToFinal`, `onPendingToCancelled(…)`, etc, in oppose to having one
interface passed three times/four times for different purposes.
3. Other thing that I had in mind is that BucketingSink could be rewritten to
extend TwoPhaseCommitSinkFunction. In that case, with
public class BucketingSink2 extends TwoPhaseCommitSinkFunction<???>
user could add his own hooks by overriding following methods
BucketingSink2#beginTransaction, BucketingSink2#preCommit,
BucketingSink2#commit, BucketingSink2#abort. For example:
public class MyBucketingSink extends BucketingSink2 {
@Override
protected void commit(??? txn) {
super.commit(txn);
// My hook on moving file from pending to commit state
};
}
Alternatively, we could implement before mentioned callbacks support in
TwoPhaseCommitSinkFunction and provide such feature to
Kafka/Pravega/BucketingSink at once.
Piotrek
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