Github user sandeshh commented on a diff in the pull request:
https://github.com/apache/incubator-apex-core/pull/185#discussion_r48757578
--- Diff: api/src/main/java/com/datatorrent/api/Operator.java ---
@@ -99,6 +99,25 @@ public String toString()
}
/**
+ * DelayOperator is an operator of which the outgoing streaming window
id is incremented by *one* by the
+ * engine, thus allowing loops in the "DAG". The output ports of a
DelayOperator, if connected, *must*
+ * immediately connect to an upstream operator in the data flow path.
Note that at least one output port of
+ * DelayOperator should be connected in order for the DelayOperator to
serve its purpose.
+ *
+ * This is meant for iterative algorithms in the topology. A larger
window increment can be simulated by an
+ * implementation of this interface.
+ */
+ interface DelayOperator extends Operator
+ {
+ /**
+ * This method gets called at the first window of the execution.
+ * The implementation is expected to emit tuples for initialization
and/or
+ * recovery.
+ */
+ void firstWindow();
--- End diff --
Should this function have "Window ID" as an argument?
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