[ https://issues.apache.org/jira/browse/JCR-2345?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12762971#action_12762971 ] 

Andrey Adamovich commented on JCR-2345:
---------------------------------------

Thanks for your reply Stefan. And good point about several bundle caches having different versions of the same content. I will try to write the pooled version and see how it goes as in our application it's mostly reading data at the moment and that's very unfortunate that one reading operation from PM may block other reading operations.

> Many threads are blocked trying to get lock: org/apache/jackrabbit/core/persistence/bundle/OraclePersistenceManager@0x2b71b2c979c0[fat lock]
> --------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: JCR-2345
>                 URL: https://issues.apache.org/jira/browse/JCR-2345
>             Project: Jackrabbit Content Repository
>          Issue Type: Bug
>          Components: jackrabbit-core, JCR 1.0.1
>    Affects Versions: 1.5.5
>         Environment: HP Unix
>            Reporter: Andrey Adamovich
>         Attachments: dump1.txt, dump2.txt, dump3.txt
>
>
> We implemented a multi-threaded export functionlity for our JR repository, but it turns out that intended parallel behavior can't be achieved becuase most of the threads seemed to be waiting for OraclePersistenceManager. 
> This is the stack trace for most of the waiting threads:
>     -- Blocked trying to get lock: org/apache/jackrabbit/core/persistence/bundle/OraclePersistenceManager@0x2b71b2c979c0[fat lock]
>     at jrockit/vm/Threads.waitForUnblockSignal()V(Native Method)
>     at jrockit/vm/Locks.fatLockBlockOrSpin(Locks.java:1675)[optimized]
>     at jrockit/vm/Locks.lockFat(Locks.java:1776)[optimized]
>     at jrockit/vm/Locks.monitorEnterSecondStageHard(Locks.java:1312)[optimized]
>     at jrockit/vm/Locks.monitorEnterSecondStage(Locks.java:1259)[optimized]
>     at org/apache/jackrabbit/core/persistence/bundle/AbstractBundlePersistenceManager.exists(AbstractBundlePersistenceManager.java:506)[optimized]
>     at org/apache/jackrabbit/core/state/SharedItemStateManager.hasNonVirtualItemState(SharedItemStateManager.java:1343)[inlined]
>     at org/apache/jackrabbit/core/state/SharedItemStateManager.hasItemState(SharedItemStateManager.java:297)[optimized]
>     at org/apache/jackrabbit/core/state/XAItemStateManager.hasItemState(XAItemStateManager.java:295)[optimized]
>     at org/apache/jackrabbit/core/state/SessionItemStateManager.getItemState(SessionItemStateManager.java:181)[optimized]
>     at org/apache/jackrabbit/core/ItemManager.getItemData(ItemManager.java:282)[inlined]
>     at org/apache/jackrabbit/core/ItemManager.getItemData(ItemManager.java:249)[inlined]
>     at org/apache/jackrabbit/core/ItemManager.getNode(ItemManager.java:513)[inlined]
>     at org/apache/jackrabbit/core/LazyItemIterator.prefetchNext(LazyItemIterator.java:109)[inlined]
>     at org/apache/jackrabbit/core/LazyItemIterator.next(LazyItemIterator.java:230)[inlined]
>     at org/apache/jackrabbit/core/LazyItemIterator.nextNode(LazyItemIterator.java:137)[optimized]
>     ^-- Holding lock: org/apache/jackrabbit/core/ItemManager@0x2b71ec068f58[thin lock]
>     at org/apache/jackrabbit/commons/xml/Exporter.exportNodes(Exporter.java:212)[optimized]
>     at org/apache/jackrabbit/commons/xml/DocumentViewExporter.exportNode(DocumentViewExporter.java:77)[inlined]
>     at org/apache/jackrabbit/commons/xml/Exporter.exportNode(Exporter.java:294)[inlined]
>     at org/apache/jackrabbit/commons/xml/Exporter.export(Exporter.java:143)[optimized]
>     at org/apache/jackrabbit/commons/AbstractSession.export(AbstractSession.java:462)[inlined]
>     at org/apache/jackrabbit/commons/AbstractSession.exportDocumentView(AbstractSession.java:236)[inlined]
>     at org/apache/jackrabbit/commons/AbstractSession.exportDocumentView(AbstractSession.java:281)[optimized]
>     ^-- Holding lock: org/apache/jackrabbit/core/XASessionImpl@0x2b71ec068950[thin lock]
> This is the stack trace for blocking thread:
>     at jrockit/net/SocketNativeIO.readBytesPinned(Ljava/io/FileDescriptor;[BIII)I(Native Method)
>     at jrockit/net/SocketNativeIO.socketRead(SocketNativeIO.java:46)[optimized]
>     at java/net/SocketInputStream.socketRead0(Ljava/io/FileDescriptor;[BIII)I(SocketInputStream.java)[inlined]
>     at java/net/SocketInputStream.read(SocketInputStream.java:129)[optimized]
>     at oracle/net/ns/Packet.receive()V(Unknown Source)[inlined]
>     at oracle/net/ns/DataPacket.receive()V(Unknown Source)[optimized]
>     at oracle/net/ns/NetInputStream.getNextPacket()V(Unknown Source)[optimized]
>     at oracle/net/ns/NetInputStream.read([BII)I(Unknown Source)[inlined]
>     at oracle/net/ns/NetInputStream.read([B)I(Unknown Source)[inlined]
>     at oracle/net/ns/NetInputStream.read()I(Unknown Source)[optimized]
>     at oracle/jdbc/driver/T4CMAREngine.unmarshalUB1(T4CMAREngine.java:1104)[inlined]
>     at oracle/jdbc/driver/T4CMAREngine.unmarshalSB1(T4CMAREngine.java:1075)[inlined]
>     at oracle/jdbc/driver/T4C8TTILob.receiveReply(T4C8TTILob.java:872)[optimized]
>     at oracle/jdbc/driver/T4C8TTILob.getChunkSize(T4C8TTILob.java:329)[inlined]
>     at oracle/jdbc/driver/T4CConnection.getChunkSize(T4CConnection.java:2026)[optimized]
>     ^-- Holding lock: oracle/jdbc/driver/T4CConnection@0x2b71b2ce0650[thin lock]
>     at oracle/sql/BLOB.getChunkSize(BLOB.java:389)[inlined]
>     at oracle/sql/BLOB.getBufferSize(BLOB.java:410)[inlined]
>     at oracle/sql/BLOB.getBinaryStream(BLOB.java:229)[optimized]
>     at org/apache/jackrabbit/core/persistence/bundle/BundleDbPersistenceManager.getBytes(BundleDbPersistenceManager.java:1110)[inlined]
>     at org/apache/jackrabbit/core/persistence/bundle/BundleDbPersistenceManager.loadBundle(BundleDbPersistenceManager.java:1142)[inlined]
>     at org/apache/jackrabbit/core/persistence/bundle/BundleDbPersistenceManager.loadBundle(BundleDbPersistenceManager.java:1094)[inlined]
>     at org/apache/jackrabbit/core/persistence/bundle/AbstractBundlePersistenceManager.getBundle(AbstractBundlePersistenceManager.java:701)[inlined]
>     at org/apache/jackrabbit/core/persistence/bundle/AbstractBundlePersistenceManager.exists(AbstractBundlePersistenceManager.java:506)[optimized]
>     ^-- Holding lock: org/apache/jackrabbit/core/persistence/bundle/OraclePersistenceManager@0x2b71b2c979c0[fat lock]
>     at org/apache/jackrabbit/core/state/SharedItemStateManager.hasNonVirtualItemState(SharedItemStateManager.java:1343)[inlined]
>     at org/apache/jackrabbit/core/state/SharedItemStateManager.hasItemState(SharedItemStateManager.java:297)[optimized]
>     at org/apache/jackrabbit/core/state/XAItemStateManager.hasItemState(XAItemStateManager.java:295)[optimized]
>     at org/apache/jackrabbit/core/state/SessionItemStateManager.getItemState(SessionItemStateManager.java:181)[optimized]
>     at org/apache/jackrabbit/core/ItemManager.getItemData(ItemManager.java:282)[inlined]
>     at org/apache/jackrabbit/core/ItemManager.getItemData(ItemManager.java:249)[inlined]
>     at org/apache/jackrabbit/core/ItemManager.getNode(ItemManager.java:513)[inlined]
>     at org/apache/jackrabbit/core/LazyItemIterator.prefetchNext(LazyItemIterator.java:109)[inlined]
>     at org/apache/jackrabbit/core/LazyItemIterator.next(LazyItemIterator.java:230)[inlined]
>     at org/apache/jackrabbit/core/LazyItemIterator.nextNode(LazyItemIterator.java:137)[optimized]
>     ^-- Holding lock: org/apache/jackrabbit/core/ItemManager@0x2b71dcf8c668[thin lock]
>     at org/apache/jackrabbit/commons/xml/Exporter.exportNodes(Exporter.java:212)[optimized]
>     at org/apache/jackrabbit/commons/xml/DocumentViewExporter.exportNode(DocumentViewExporter.java:77)[inlined]
>     at org/apache/jackrabbit/commons/xml/Exporter.exportNode(Exporter.java:294)[inlined]
>     at org/apache/jackrabbit/commons/xml/Exporter.export(Exporter.java:143)[optimized]
>     at org/apache/jackrabbit/commons/AbstractSession.export(AbstractSession.java:462)[inlined]
>     at org/apache/jackrabbit/commons/AbstractSession.exportDocumentView(AbstractSession.java:236)[inlined]
>     at org/apache/jackrabbit/commons/AbstractSession.exportDocumentView(AbstractSession.java:281)[optimized]
>     ^-- Holding lock: org/apache/jackrabbit/core/XASessionImpl@0x2b71dcf8c3c0[thin lock]
> Oracle database performfs as usual. So, I doubt that it is an Oracle problem. In any case is there any way to avoid other threads blocking each other while performing read operations from PM?

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