Weiwei Yang created YARN-7800:
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Summary: Bind node constraint once a container is proposed to be
placed on this node
Key: YARN-7800
URL: https://issues.apache.org/jira/browse/YARN-7800
Project: Hadoop YARN
Issue Type: Sub-task
Components: RM
Reporter: Weiwei Yang
We found when there is circular dependency between multiple scheduling
requests, allocation decisions made by placement constraint algorithm might be
conflicting with related tags. More describing of the issue please refer to
YARN-7783.
To solve this issue, a possible solution is to bind *node constraint*. If the
algorithm wants to place any new container to this node, except for checking if
it satisfies the placement constraint, it also check if it satisfies the node
constraint. For example
1) "foo", anti-affinity with "foo"
+Implies node constraint:+ on each node, it cannot have more than 1 foo tags
2) "bar", anti-affinity with "foo"
+Implies node constraint:+ on each node, it cannot have both "bar" and "foo"
tags
With such constraint, it works like
* req2 is placed on any of nodes, e.g n2, +a node constraint[1] is added to n2
that constrains this node cannot have both "bar" and "foo" tags+
* when the algorithm wants to place req1 on n2, it checks if its placement
constraint is satisfied. It should be as there is no foo container on this node
yet.
* Then the algorithm checks if the node constraint is satisfied. It is not
because it violate node constraint [1].
This avoids to do additional re-attempt like what was done in YARN-7783.
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