zhihai xu created YARN-3655:
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Summary: FairScheduler: potential deadlock due to maxAMShare
limitation and container reservation
Key: YARN-3655
URL: https://issues.apache.org/jira/browse/YARN-3655
Project: Hadoop YARN
Issue Type: Bug
Components: fairscheduler
Affects Versions: 2.7.0
Reporter: zhihai xu
Assignee: zhihai xu
FairScheduler: potential deadlock due to maxAMShare limitation and container
reservation.
If a node is reserved by an application, all the other applications don't have
any chance to assign a new container on this node, unless the application which
reserves the node assigns a new container on this node or releases the reserved
container on this node.
The problem is if an application tries to call assignReservedContainer and fail
to get a new container due to maxAMShare limitation, it will block all other
applications to use the nodes it reserves. If all other running applications
can't release their AM containers due to being blocked by these reserved
containers. A dead lock situation can happen.
The following is the code at FSAppAttempt#assignContainer which can cause this
potential dead lock.
{code}
// Check the AM resource usage for the leaf queue
if (!isAmRunning() && !getUnmanagedAM()) {
List<ResourceRequest> ask = appSchedulingInfo.getAllResourceRequests();
if (ask.isEmpty() || !getQueue().canRunAppAM(
ask.get(0).getCapability())) {
if (LOG.isDebugEnabled()) {
LOG.debug("Skipping allocation because maxAMShare limit would " +
"be exceeded");
}
return Resources.none();
}
}
{code}
To fix this issue, we can unreserve the node if we can't allocate the AM
container on the node due to Max AM share limitation and the node is reserved
by the application.
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