mxm commented on a change in pull request #10992: [BEAM-2939] Provide user
facing API for reporting the watermark in SplittableDoFns.
URL: https://github.com/apache/beam/pull/10992#discussion_r392275988
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File path:
sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/DoFn.java
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@@ -1070,6 +1091,120 @@ public Duration getAllowedTimestampSkew() {
@Experimental(Kind.SPLITTABLE_DO_FN)
public @interface NewTracker {}
+ /**
+ * Annotation for the method that maps an element and restriction to initial
watermark estimator
+ * state for a <a
href="https://s.apache.org/splittable-do-fn";>splittable</a> {@link DoFn}.
+ *
+ * <p>Signature: {@code WatermarkEstimatorStateT
getInitialWatermarkState(<arguments>);}
+ *
+ * <p>This method must satisfy the following constraints:
+ *
+ * <ul>
+ * <li>The return type {@code WatermarkEstimatorStateT} defines the
watermark state type used
+ * within this splittable DoFn. All other methods that use a {@link
+ * WatermarkEstimatorState @WatermarkEstimatorState} parameter must
use the same type that
+ * is used here. It is suggested to use as narrow of a return type
definition as possible
+ * (for example prefer to use a square type over a shape type as a
square is a type of a
+ * shape).
+ * <li>If one of its arguments is tagged with the {@link Element}
annotation, then it will be
+ * passed the current element being processed; the argument must be of
type {@code InputT}.
+ * Note that automatic conversion of {@link Row}s and {@link
FieldAccess} parameters are
+ * currently unsupported.
+ * <li>If one of its arguments is tagged with the {@link Restriction}
annotation, then it will
+ * be passed the current restriction being processed; the argument
must be of type {@code
+ * RestrictionT}.
+ * <li>If one of its arguments is tagged with the {@link Timestamp}
annotation, then it will be
+ * passed the timestamp of the current element being processed; the
argument must be of type
+ * {@link Instant}.
+ * <li>If one of its arguments is a subtype of {@link BoundedWindow}, then
it will be passed the
+ * window of the current element. When applied by {@link ParDo} the
subtype of {@link
+ * BoundedWindow} must match the type of windows on the input {@link
PCollection}. If the
+ * window is not accessed a runner may perform additional
optimizations.
+ * <li>If one of its arguments is of type {@link PaneInfo}, then it will
be passed information
+ * about the current triggering pane.
+ * <li>If one of the parameters is of type {@link PipelineOptions}, then
it will be passed the
+ * options for the current pipeline.
+ * </ul>
+ */
+ @Documented
+ @Retention(RetentionPolicy.RUNTIME)
+ @Target(ElementType.METHOD)
+ @Experimental(Kind.SPLITTABLE_DO_FN)
+ public @interface GetInitialWatermarkEstimatorState {}
Review comment:
Note that this terminology deviates from the current `getCheckpointMark()`.
I like it though.
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