[jira] [Created] (ZOOKEEPER-2553) ZooKeeper cluster unavailable due to corrupted log file during power failures -- java.io.IOException: Unreasonable length

["Ramnatthan Alagappan (JIRA)" <ji...@apache.org>]

Ramnatthan Alagappan created ZOOKEEPER-2553:
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             Summary: ZooKeeper cluster unavailable due to corrupted log file during power failures -- java.io.IOException: Unreasonable length
                 Key: ZOOKEEPER-2553
                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2553
             Project: ZooKeeper
          Issue Type: Bug
          Components: server
    Affects Versions: 3.4.8
         Environment: Normal ZooKeeper cluster with 3 nodes running Linux
            Reporter: Ramnatthan Alagappan


I am running a three node ZooKeeper cluster. 

When a new log file is created by ZooKeeper, I see the following sequence of system calls:

1. creat(new_log)
2. write(new_log, count=16) // This is a log header I believe/
3. truncate(new_log, from 16 bytes to 16 KBytes) // I have configured the log size to be 16K. 

When the above sequence of operations complete, it is reasonable to expect the newly created log file to contain the header(16 bytes) and then filled with zeros till the end of the log.

But when a crash occurs (due to a power failure), while the truncate system call is in progress, it is possible for the log to contain garbage data when the system restarts from a crash. Note that if the crash occurs just after the truncate system call completes, then there is no problem. Basically, the truncate needs to be atomically persisted for ZooKeeper to recover from crashes correctly. 

As mentioned, if a crash occurs during the truncate system call, then ZooKeeper will fail to start with the following exception. Here is the stack trace:

java.io.IOException: Unreasonable length = -295704495
        at org.apache.jute.BinaryInputArchive.checkLength(BinaryInputArchive.java:127)
        at org.apache.jute.BinaryInputArchive.readBuffer(BinaryInputArchive.java:92)
        at org.apache.zookeeper.server.persistence.Util.readTxnBytes(Util.java:233)
        at org.apache.zookeeper.server.persistence.FileTxnLog$FileTxnIterator.next(FileTxnLog.java:625)
        at org.apache.zookeeper.server.persistence.FileTxnLog$FileTxnIterator.next(FileTxnLog.java:652)
        at org.apache.zookeeper.server.persistence.FileTxnLog$FileTxnIterator.init(FileTxnLog.java:552)
        at org.apache.zookeeper.server.persistence.FileTxnLog$FileTxnIterator.<init>(FileTxnLog.java:527)
        at org.apache.zookeeper.server.persistence.FileTxnLog.read(FileTxnLog.java:354)
        at org.apache.zookeeper.server.persistence.FileTxnSnapLog.restore(FileTxnSnapLog.java:132)
        at org.apache.zookeeper.server.ZKDatabase.loadDataBase(ZKDatabase.java:223)
        at org.apache.zookeeper.server.quorum.QuorumPeer.loadDataBase(QuorumPeer.java:510)
        at org.apache.zookeeper.server.quorum.QuorumPeer.start(QuorumPeer.java:500)
        at org.apache.zookeeper.server.quorum.QuorumPeerMain.runFromConfig(QuorumPeerMain.java:153)
        at org.apache.zookeeper.server.quorum.QuorumPeerMain.initializeAndRun(QuorumPeerMain.java:111)
        at org.apache.zookeeper.server.quorum.QuorumPeerMain.main(QuorumPeerMain.java:78)
[myid:1] - ERROR [main:QuorumPeerMain@89] - Unexpected exception, exiting abnormally
java.lang.RuntimeException: Unable to run quorum server
        at org.apache.zookeeper.server.quorum.QuorumPeer.loadDataBase(QuorumPeer.java:558)
        at org.apache.zookeeper.server.quorum.QuorumPeer.start(QuorumPeer.java:500)
        at org.apache.zookeeper.server.quorum.QuorumPeerMain.runFromConfig(QuorumPeerMain.java:153)
        at org.apache.zookeeper.server.quorum.QuorumPeerMain.initializeAndRun(QuorumPeerMain.java:111)
        at org.apache.zookeeper.server.quorum.QuorumPeerMain.main(QuorumPeerMain.java:78)
Caused by: java.io.IOException: Unreasonable length = -295704495
        at org.apache.jute.BinaryInputArchive.checkLength(BinaryInputArchive.java:127)
        at org.apache.jute.BinaryInputArchive.readBuffer(BinaryInputArchive.java:92)
        at org.apache.zookeeper.server.persistence.Util.readTxnBytes(Util.java:233)
        at org.apache.zookeeper.server.persistence.FileTxnLog$FileTxnIterator.next(FileTxnLog.java:625)
        at org.apache.zookeeper.server.persistence.FileTxnLog$FileTxnIterator.next(FileTxnLog.java:652)
        at org.apache.zookeeper.server.persistence.FileTxnLog$FileTxnIterator.init(FileTxnLog.java:552)
        at org.apache.zookeeper.server.persistence.FileTxnLog$FileTxnIterator.<init>(FileTxnLog.java:527)
        at org.apache.zookeeper.server.persistence.FileTxnLog.read(FileTxnLog.java:354)
        at org.apache.zookeeper.server.persistence.FileTxnSnapLog.restore(FileTxnSnapLog.java:132)
        at org.apache.zookeeper.server.ZKDatabase.loadDataBase(ZKDatabase.java:223)
        at org.apache.zookeeper.server.quorum.QuorumPeer.loadDataBase(QuorumPeer.java:510)
        ... 4 more


Next, it is possible for two nodes of a 3-node  ZooKeeper cluster to reach the same state. In that case, they both will fail to startup, rendering the entire cluster unavailable. 



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