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https://issues.apache.org/jira/browse/HDDS-2026?focusedWorklogId=301784&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-301784
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ASF GitHub Bot logged work on HDDS-2026:
----------------------------------------
Author: ASF GitHub Bot
Created on: 27/Aug/19 08:37
Start Date: 27/Aug/19 08:37
Worklog Time Spent: 10m
Work Description: bshashikant commented on issue #1349: HDDS-2026.
Overlapping chunk region cannot be read concurrently
URL: https://github.com/apache/hadoop/pull/1349#issuecomment-525200958
Thanks @adoroszlai for working on this. The locking logic seems good to me.
But in Ozone world, a chunk once written is immutable , and hence we might
not need the lock at all
while reading a chunk.
@anuengineer @elek @mukul1987 what do you think?
There is also a race condition which exists in the system where a chunk
might get deleted by BlockDeleting service in Datanode while readChunk is
happening which is where i think we need to have synchronization on a container
level (not precisely at the chunk level) for closed containers but this problem
is beyond the scope of this jira.
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Issue Time Tracking
-------------------
Worklog Id: (was: 301784)
Time Spent: 1.5h (was: 1h 20m)
> Overlapping chunk region cannot be read concurrently
> ----------------------------------------------------
>
> Key: HDDS-2026
> URL: https://issues.apache.org/jira/browse/HDDS-2026
> Project: Hadoop Distributed Data Store
> Issue Type: Bug
> Components: Ozone Datanode
> Reporter: Doroszlai, Attila
> Assignee: Doroszlai, Attila
> Priority: Critical
> Labels: pull-request-available
> Attachments: HDDS-2026-repro.patch, changes.diff,
> first-cut-proposed.diff
>
> Time Spent: 1.5h
> Remaining Estimate: 0h
>
> Concurrent requests to datanode for the same chunk may result in the
> following exception in datanode:
> {code}
> java.nio.channels.OverlappingFileLockException
> at java.base/sun.nio.ch.FileLockTable.checkList(FileLockTable.java:229)
> at java.base/sun.nio.ch.FileLockTable.add(FileLockTable.java:123)
> at
> java.base/sun.nio.ch.AsynchronousFileChannelImpl.addToFileLockTable(AsynchronousFileChannelImpl.java:178)
> at
> java.base/sun.nio.ch.SimpleAsynchronousFileChannelImpl.implLock(SimpleAsynchronousFileChannelImpl.java:185)
> at
> java.base/sun.nio.ch.AsynchronousFileChannelImpl.lock(AsynchronousFileChannelImpl.java:118)
> at
> org.apache.hadoop.ozone.container.keyvalue.helpers.ChunkUtils.readData(ChunkUtils.java:175)
> at
> org.apache.hadoop.ozone.container.keyvalue.impl.ChunkManagerImpl.readChunk(ChunkManagerImpl.java:213)
> at
> org.apache.hadoop.ozone.container.keyvalue.KeyValueHandler.handleReadChunk(KeyValueHandler.java:574)
> at
> org.apache.hadoop.ozone.container.keyvalue.KeyValueHandler.handle(KeyValueHandler.java:195)
> at
> org.apache.hadoop.ozone.container.common.impl.HddsDispatcher.dispatchRequest(HddsDispatcher.java:271)
> at
> org.apache.hadoop.ozone.container.common.impl.HddsDispatcher.dispatch(HddsDispatcher.java:148)
> at
> org.apache.hadoop.ozone.container.common.transport.server.GrpcXceiverService$1.onNext(GrpcXceiverService.java:73)
> at
> org.apache.hadoop.ozone.container.common.transport.server.GrpcXceiverService$1.onNext(GrpcXceiverService.java:61)
> {code}
> It seems this is covered by retry logic, as key read is eventually successful
> at client side.
> The problem is that:
> bq. File locks are held on behalf of the entire Java virtual machine. They
> are not suitable for controlling access to a file by multiple threads within
> the same virtual machine.
> ([source|https://docs.oracle.com/javase/8/docs/api/java/nio/channels/FileLock.html])
> code ref:
> [{{ChunkUtils.readData}}|https://github.com/apache/hadoop/blob/c92de8209d1c7da9e7ce607abeecb777c4a52c6a/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/keyvalue/helpers/ChunkUtils.java#L175]
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