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Posted to issues@flink.apache.org by "prashantbh (via GitHub)" <gi...@apache.org> on 2025/04/11 09:45:52 UTC
[PR] [FLINK-37655][runtime] Convert WindowStagger into an interface for ea… [flink]
prashantbh opened a new pull request, #26441:
URL: https://github.com/apache/flink/pull/26441
…sy extensibility
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## What is the purpose of the change
To provide users the flexibility to implement custom window staggering behaviours beyond the standard options (ALIGNED, RANDOM, NATURAL), this PR convert the WindowStagger enum into an interface. The current enum structure restricts extension because enums are final. By adopting an interface, we allow users to define and plug in their own staggering strategies, catering to more diverse use cases. The original enum constants will be provided as default implementations of this new interface.
## Brief change log
Converts WindowStagger into an interface from ENUM.
## Verifying this change
This change is a trivial rework, since existing ENUM constants are retained as standard implementation, all the existing test will work as it is.
## Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): No
- The public API, i.e., is any changed class annotated with `@Public(Evolving)`: No
## Documentation
- Does this pull request introduce a new feature?
- If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)
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Re: [PR] [FLINK-37655][runtime] Convert WindowStagger into an interface [flink]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on PR #26441:
URL: https://github.com/apache/flink/pull/26441#issuecomment-4385867052
This PR is being marked as stale since it has not had any activity in the last 90 days.
If you would like to keep this PR alive, please leave a comment asking for a review.
If the PR has merge conflicts, update it with the latest from the base branch.
If you are having difficulty finding a reviewer, please reach out to the
community, contact details can be found here: https://flink.apache.org/what-is-flink/community/
If this PR is no longer valid or desired, please feel free to close it.
If no activity occurs in the next 30 days, it will be automatically closed.
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Re: [PR] [FLINK-37655][runtime] Convert WindowStagger into an interface [flink]
Posted by "prashantbh (via GitHub)" <gi...@apache.org>.
prashantbh commented on code in PR #26441:
URL: https://github.com/apache/flink/pull/26441#discussion_r2039503996
##########
flink-runtime/src/main/java/org/apache/flink/streaming/api/windowing/assigners/WindowStagger.java:
##########
@@ -21,43 +21,81 @@
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.streaming.api.windowing.windows.TimeWindow;
+import java.io.Serializable;
import java.util.concurrent.ThreadLocalRandom;
-/** A {@code WindowStagger} staggers offset in runtime for each window assignment. */
+/**
+ * Interface for defining how window assignments should be staggered to distribute load over time.
+ * Implementations determine the offset applied during window assignment.
+ */
@PublicEvolving
-public enum WindowStagger {
- /** Default mode, all panes fire at the same time across all partitions. */
- ALIGNED {
- @Override
- public long getStaggerOffset(final long currentProcessingTime, final long size) {
- return 0L;
- }
- },
+public interface WindowStagger extends Serializable {
+
+ /**
+ * Calculates the stagger offset for a window assignment based on the current processing time
+ * and the window size.
+ *
+ * @param currentProcessingTime The current processing time.
+ * @param size The size of the window.
+ * @return The calculated stagger offset in milliseconds.
+ */
+ long getStaggerOffset(final long currentProcessingTime, final long size);
+
+ // Pre-defined Staggering Strategies
+ /** Default mode: No staggering, all panes fire at the same time across all partitions. */
+ WindowStagger ALIGNED =
+ new WindowStagger() {
+ private static final long serialVersionUID = 1L;
+
+ @Override
+ public long getStaggerOffset(final long currentProcessingTime, final long size) {
+ return 0L;
+ }
+
+ @Override
+ public String toString() {
+ return "ALIGNED";
+ }
+ };
/**
* Stagger offset is sampled from uniform distribution U(0, WindowSize) when first event
* ingested in the partitioned operator.
*/
- RANDOM {
- @Override
- public long getStaggerOffset(final long currentProcessingTime, final long size) {
- return (long) (ThreadLocalRandom.current().nextDouble() * size);
- }
- },
+ WindowStagger RANDOM =
+ new WindowStagger() {
+ private static final long serialVersionUID = 1L;
+
+ @Override
+ public long getStaggerOffset(final long currentProcessingTime, final long size) {
+ return (long) (ThreadLocalRandom.current().nextDouble() * size);
+ }
+
+ @Override
+ public String toString() {
+ return "RANDOM";
+ }
+ };
/**
* When the first event is received in the window operator, take the difference between the
* start of the window and current procesing time as the offset. This way, windows are staggered
* based on when each parallel operator receives the first event.
*/
- NATURAL {
- @Override
- public long getStaggerOffset(final long currentProcessingTime, final long size) {
- final long currentProcessingWindowStart =
- TimeWindow.getWindowStartWithOffset(currentProcessingTime, 0, size);
- return Math.max(0, currentProcessingTime - currentProcessingWindowStart);
- }
- };
-
- public abstract long getStaggerOffset(final long currentProcessingTime, final long size);
+ WindowStagger NATURAL =
+ new WindowStagger() {
+ private static final long serialVersionUID = 1L; // Add serialVersionUID
+
+ @Override
+ public long getStaggerOffset(final long currentProcessingTime, final long size) {
+ final long currentProcessingWindowStart =
+ TimeWindow.getWindowStartWithOffset(currentProcessingTime, 0, size);
+ return Math.max(0, currentProcessingTime - currentProcessingWindowStart);
+ }
+
+ @Override
+ public String toString() {
+ return "NATURAL"; // Optional: for better readability
Review Comment:
I will remove this.
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Re: [PR] [FLINK-37655][runtime] Convert WindowStagger into an interface [flink]
Posted by "flinkbot (via GitHub)" <gi...@apache.org>.
flinkbot commented on PR #26441:
URL: https://github.com/apache/flink/pull/26441#issuecomment-2796411490
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## CI report:
* c3c4894e2208dfe9adda8fd23044041a2079e153 UNKNOWN
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Re: [PR] [FLINK-37655][runtime] Convert WindowStagger into an interface [flink]
Posted by "prashantbh (via GitHub)" <gi...@apache.org>.
prashantbh commented on PR #26441:
URL: https://github.com/apache/flink/pull/26441#issuecomment-2796875876
> I have some questions:
>
> * I assume this means the user will need to recompile their programs to pick up the interface version.
> * I am inclined to leave this as an enum, until there is a need to extend it. Otherwise we are creating an extension point that may never be used.
This change affects only new Flink versions and isn’t backported. So, if you upgrade, you'll need to recompile any programs that use it—but since you're already updating Flink, that's expected, unless you are changing Flink version at runtime.
We're switching from an enum to an interface to give us a flexible extension point for future needs without breaking backward compatibility. For example, we’re working on a custom WindowAssigner (a variant of `TumblingEventTimeWindows` with our own `WindowStagger` logic), and with this change, we only need to provide our custom `WindowStagger` rather than re-implementing the whole assigner.
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Re: [PR] [FLINK-37655][runtime] Convert WindowStagger into an interface [flink]
Posted by "prashantbh (via GitHub)" <gi...@apache.org>.
prashantbh commented on PR #26441:
URL: https://github.com/apache/flink/pull/26441#issuecomment-2796820453
@flinkbot run azure
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Re: [PR] [FLINK-37655][runtime] Convert WindowStagger into an interface [flink]
Posted by "davidradl (via GitHub)" <gi...@apache.org>.
davidradl commented on code in PR #26441:
URL: https://github.com/apache/flink/pull/26441#discussion_r2039502534
##########
flink-runtime/src/main/java/org/apache/flink/streaming/api/windowing/assigners/WindowStagger.java:
##########
@@ -21,43 +21,81 @@
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.streaming.api.windowing.windows.TimeWindow;
+import java.io.Serializable;
import java.util.concurrent.ThreadLocalRandom;
-/** A {@code WindowStagger} staggers offset in runtime for each window assignment. */
+/**
+ * Interface for defining how window assignments should be staggered to distribute load over time.
+ * Implementations determine the offset applied during window assignment.
+ */
@PublicEvolving
-public enum WindowStagger {
- /** Default mode, all panes fire at the same time across all partitions. */
- ALIGNED {
- @Override
- public long getStaggerOffset(final long currentProcessingTime, final long size) {
- return 0L;
- }
- },
+public interface WindowStagger extends Serializable {
+
+ /**
+ * Calculates the stagger offset for a window assignment based on the current processing time
+ * and the window size.
+ *
+ * @param currentProcessingTime The current processing time.
+ * @param size The size of the window.
+ * @return The calculated stagger offset in milliseconds.
+ */
+ long getStaggerOffset(final long currentProcessingTime, final long size);
+
+ // Pre-defined Staggering Strategies
+ /** Default mode: No staggering, all panes fire at the same time across all partitions. */
+ WindowStagger ALIGNED =
+ new WindowStagger() {
+ private static final long serialVersionUID = 1L;
+
+ @Override
+ public long getStaggerOffset(final long currentProcessingTime, final long size) {
+ return 0L;
+ }
+
+ @Override
+ public String toString() {
+ return "ALIGNED";
+ }
+ };
/**
* Stagger offset is sampled from uniform distribution U(0, WindowSize) when first event
* ingested in the partitioned operator.
*/
- RANDOM {
- @Override
- public long getStaggerOffset(final long currentProcessingTime, final long size) {
- return (long) (ThreadLocalRandom.current().nextDouble() * size);
- }
- },
+ WindowStagger RANDOM =
+ new WindowStagger() {
+ private static final long serialVersionUID = 1L;
+
+ @Override
+ public long getStaggerOffset(final long currentProcessingTime, final long size) {
+ return (long) (ThreadLocalRandom.current().nextDouble() * size);
+ }
+
+ @Override
+ public String toString() {
+ return "RANDOM";
+ }
+ };
/**
* When the first event is received in the window operator, take the difference between the
* start of the window and current procesing time as the offset. This way, windows are staggered
* based on when each parallel operator receives the first event.
*/
- NATURAL {
- @Override
- public long getStaggerOffset(final long currentProcessingTime, final long size) {
- final long currentProcessingWindowStart =
- TimeWindow.getWindowStartWithOffset(currentProcessingTime, 0, size);
- return Math.max(0, currentProcessingTime - currentProcessingWindowStart);
- }
- };
-
- public abstract long getStaggerOffset(final long currentProcessingTime, final long size);
+ WindowStagger NATURAL =
+ new WindowStagger() {
+ private static final long serialVersionUID = 1L; // Add serialVersionUID
+
+ @Override
+ public long getStaggerOffset(final long currentProcessingTime, final long size) {
+ final long currentProcessingWindowStart =
+ TimeWindow.getWindowStartWithOffset(currentProcessingTime, 0, size);
+ return Math.max(0, currentProcessingTime - currentProcessingWindowStart);
+ }
+
+ @Override
+ public String toString() {
+ return "NATURAL"; // Optional: for better readability
Review Comment:
nit: why does this toString have a comment but this others do not?
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Re: [PR] [FLINK-37655][runtime] Convert WindowStagger into an interface [flink]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on PR #26441:
URL: https://github.com/apache/flink/pull/26441#issuecomment-4629319596
This PR has been closed since it has not had any activity in 120 days.
If you feel like this was a mistake, or you would like to continue working on it,
please feel free to re-open the PR and ask for a review.
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Re: [PR] [FLINK-37655][runtime] Convert WindowStagger into an interface [flink]
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] closed pull request #26441: [FLINK-37655][runtime] Convert WindowStagger into an interface
URL: https://github.com/apache/flink/pull/26441
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