[ACCUMULO-623] Data lost with hdfs write ahead log

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Fix Version/s: 1.5.0

Environment

MacOSX, Hadoop 1.0.3, zookeeper 3.3.3

• Assignee: Keith Turner
• Reporter: Keith Turner
• Created: 06/Jun/12 23:09
• Updated: 07/Aug/12 02:09
• Resolved: 16/Jul/12 19:11

Description

I shut my machine down with Accumulo, Zookeeper, and HDFS running. When I restarted it, Accumulo failed to recover its write ahead log because it was zero length. I wondered if this was because I shutdown HDFS so I tried the following on my single node Accumulo instance.

• start HDFS and zookeeper
• init & start Accumulo
• created a table and insert some data
• pkill -f java
• restart everything
• Accumulo fails to start because walog is zero length

Saw excpetions like the following

06 18:58:44,581 [log.SortedLogRecovery] INFO : Looking at mutations from /accumulo/recovery/def72721-5c64-4755-87cc-2e8cfc3002b7 for !0;!0<<
06 18:58:44,590 [tabletserver.TabletServer] WARN : exception trying to assign tablet !0;!0<< /root_tablet
java.lang.RuntimeException: java.io.IOException: java.lang.RuntimeException: Unable to read log entries
        at org.apache.accumulo.server.tabletserver.Tablet.<init>(Tablet.java:1458)
        at org.apache.accumulo.server.tabletserver.Tablet.<init>(Tablet.java:1295)
        at org.apache.accumulo.server.tabletserver.Tablet.<init>(Tablet.java:1134)
        at org.apache.accumulo.server.tabletserver.Tablet.<init>(Tablet.java:1121)
        at org.apache.accumulo.server.tabletserver.TabletServer$AssignmentHandler.run(TabletServer.java:2477)
        at org.apache.accumulo.core.util.LoggingRunnable.run(LoggingRunnable.java:34)
        at java.lang.Thread.run(Thread.java:680)
Caused by: java.io.IOException: java.lang.RuntimeException: Unable to read log entries
        at org.apache.accumulo.server.tabletserver.log.TabletServerLogger.recover(TabletServerLogger.java:428)
        at org.apache.accumulo.server.tabletserver.TabletServer.recover(TabletServer.java:3206)
        at org.apache.accumulo.server.tabletserver.Tablet.<init>(Tablet.java:1426)
        ... 6 more
Caused by: java.lang.RuntimeException: Unable to read log entries
        at org.apache.accumulo.server.tabletserver.log.SortedLogRecovery.findLastStartToFinish(SortedLogRecovery.java:125)
        at org.apache.accumulo.server.tabletserver.log.SortedLogRecovery.recover(SortedLogRecovery.java:89)
        at org.apache.accumulo.server.tabletserver.log.TabletServerLogger.recover(TabletServerLogger.java:426)
        ... 8 more

When trying to run LogReader on the files, it prints nothing.

$ ./bin/accumulo org.apache.accumulo.server.logger.LogReader /accumulo/recovery/def72721-5c64-4755-87cc-2e8cfc3002b7
06 19:04:37,147 [util.NativeCodeLoader] WARN : Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
$ ./bin/accumulo org.apache.accumulo.server.logger.LogReader /accumulo/wal/127.0.0.1+40200/def72721-5c64-4755-87cc-2e8cfc3002b7
$