Marcel Reutegger created OAK-2621:
-------------------------------------
Summary: Too many reads for child nodes
Key: OAK-2621
URL: https://issues.apache.org/jira/browse/OAK-2621
Project: Jackrabbit Oak
Issue Type: Bug
Affects Versions: 1.0
Reporter: Marcel Reutegger
Priority: Minor
Fix For: 1.1.9
The DocumentNodeStore issues a lot of reads when sibling nodes are deleted,
which are also index with a property index.
The following calls will become a hotspot:
{noformat}
at
org.apache.jackrabbit.oak.plugins.document.mongo.MongoDocumentStore.query(MongoDocumentStore.java:406)
at
org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.readChildDocs(DocumentNodeStore.java:846)
at
org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.readChildren(DocumentNodeStore.java:788)
at
org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.getChildren(DocumentNodeStore.java:753)
at
org.apache.jackrabbit.oak.plugins.document.DocumentNodeState.getChildNodeCount(DocumentNodeState.java:194)
at
org.apache.jackrabbit.oak.plugins.memory.ModifiedNodeState.getChildNodeCount(ModifiedNodeState.java:198)
at
org.apache.jackrabbit.oak.plugins.memory.MutableNodeState.getChildNodeCount(MutableNodeState.java:265)
at
org.apache.jackrabbit.oak.plugins.memory.MemoryNodeBuilder.getChildNodeCount(MemoryNodeBuilder.java:293)
at
org.apache.jackrabbit.oak.plugins.index.property.strategy.ContentMirrorStoreStrategy.prune(ContentMirrorStoreStrategy.java:456)
{noformat}
I think the code triggering this issue is in
{{ModifiedNodeState.getChildNodeCount()}}. It keeps track of already deleted
children and requests {{max += deleted}}. The actual {{max}} is always 1 as
requested from {{ContentMirrorStoreStrategy.prune()}}, but as more nodes get
deleted, the higher {{max}} gets passed to
{{DocumentNodeState.getChildNodeCount()}}. The DocumentNodeStore then checks if
it has the children in the cache, only to find out the cache entry has too few
entries and it needs to fetch one more.
It would be best to have a minimum number of child nodes to fetch from MongoDB
in this case. E.g. when NodeState.getChildNodeEntries() is called, the
DocumentNodeState fetches 100 children.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
