Bharath Kumarasubramanian created SAMZA-2597:
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Summary: Maintain traversal order for registered operators
Key: SAMZA-2597
URL: https://issues.apache.org/jira/browse/SAMZA-2597
Project: Samza
Issue Type: Bug
Reporter: Bharath Kumarasubramanian
Assignee: Bharath Kumarasubramanian
*Problem*: Currently, we have a deterministic way of creating the operator DAG
by having a LinkedHashMap so that during our runtime, we ensure the lifecycle
of operators follow a deterministic order.
While we use the same order to traverse the graph and create the DAG, we lose
the order within the sub DAG as the registered operators is a HashSet. The
implication is result of an operator is dispatched non-deterministically to its
sub-DAG. i.e
Op A --> Op B --> Op C
|--> Op D --> Op E
Output of Op A can be dispatched to Op B or Op D depending how we iterate the
`registeredOperators` set of Op A.
While this is not a guarantee Samza provides to applications, we want to be
consistent with graph traversal order, DAG insertion order and DAG traversal
order.
*Change*: Use `LinkedHashSet` instead of `HashSet` to make it consistent.
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