[jira] [Created] (OAK-4504) Retry query with index hint for query involving _modified and _id

["Chetan Mehrotra (JIRA)" <ji...@apache.org>]

Chetan Mehrotra created OAK-4504:
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             Summary: Retry query with index hint for query involving _modified and _id
                 Key: OAK-4504
                 URL: https://issues.apache.org/jira/browse/OAK-4504
             Project: Jackrabbit Oak
          Issue Type: Improvement
          Components: mongomk
            Reporter: Chetan Mehrotra
            Assignee: Chetan Mehrotra
             Fix For: 1.6


With OAK-3071 a compound index was added for _modified and _id. Earlier we have seen with OAK-1966 that Mongo might not pick correct index and with introduction of new index we have seen cases where query times out as Mongo picks _id index

Below stacktrace if from a 1.0.28 Oak version based setup
{noformat}
17.06.2016 08:38:58.255 *WARN* [pool-10-thread-2] org.apache.jackrabbit.oak.plugins.index.AsyncIndexUpdate [async] The index update failed
com.mongodb.MongoExecutionTimeoutException: operation exceeded time limit
	at com.mongodb.QueryResultIterator.throwOnQueryFailure(QueryResultIterator.java:211)
	at com.mongodb.QueryResultIterator.init(QueryResultIterator.java:198)
	at com.mongodb.QueryResultIterator.initFromQueryResponse(QueryResultIterator.java:176)
	at com.mongodb.QueryResultIterator.<init>(QueryResultIterator.java:64)
	at com.mongodb.DBCollectionImpl.find(DBCollectionImpl.java:86)
	at com.mongodb.DBCollectionImpl.find(DBCollectionImpl.java:66)
	at com.mongodb.DBCursor._check(DBCursor.java:458)
	at com.mongodb.DBCursor._hasNext(DBCursor.java:546)
	at com.mongodb.DBCursor.hasNext(DBCursor.java:571)
	at org.apache.jackrabbit.oak.plugins.document.mongo.MongoDocumentStore.queryInternal(MongoDocumentStore.java:585)
	at org.apache.jackrabbit.oak.plugins.document.mongo.MongoDocumentStore.query(MongoDocumentStore.java:516)
	at org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.diffManyChildren(DocumentNodeStore.java:2207)
{noformat}

To account for such cases we should add a retry with hint logic
# Invoke the query normally 
# In case of timeout and if target Mongo has compound index configured retry the query with explicit hint



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