Harunobu Daikoku created YARN-9826:
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Summary: Blocked threads at
EntityGroupFSTimelineStore#getCachedStore
Key: YARN-9826
URL: https://issues.apache.org/jira/browse/YARN-9826
Project: Hadoop YARN
Issue Type: Improvement
Components: timelineserver
Affects Versions: 2.7.3
Reporter: Harunobu Daikoku
We have observed this case several times on our production cluster where 100s
of TimelineServer threads are blocked at the following synchronized block in
EntityGroupFSTimelineStore#getCachedStore when our HDFS NameNode is under high
load.
{code:java}
synchronized (this.cachedLogs) {
// Note that the content in the cache log storage may be stale.
cacheItem = this.cachedLogs.get(groupId);
if (cacheItem == null) {
LOG.debug("Set up new cache item for id {}", groupId);
cacheItem = new EntityCacheItem(groupId, getConfig());
AppLogs appLogs = getAndSetAppLogs(groupId.getApplicationId());
if (appLogs != null) {
LOG.debug("Set applogs {} for group id {}", appLogs, groupId);
cacheItem.setAppLogs(appLogs);
this.cachedLogs.put(groupId, cacheItem);
} else {
LOG.warn("AppLogs for groupId {} is set to null!", groupId);
}
}
}
{code}
One thread inside the synchronized block performs multiple fs operations
(fs.exists) inside getAndSetAppLogs, which could block other threads when, for
instance, the NameNode RPC queue is full.
One possible solution is to move getAndSetAppLogs outside the synchronized
block.
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