Chapter 15. Troubleshooting and Debugging Apache HBase

Table of Contents

15.1. General Guidelines
15.2. Logs
15.2.1. Log Locations
15.2.2. Log Levels
15.2.3. JVM Garbage Collection Logs
15.3. Resources
15.3.2. Mailing Lists
15.3.3. IRC
15.3.4. JIRA
15.4. Tools
15.4.1. Builtin Tools
15.4.2. External Tools
15.5. Client
15.5.1. ScannerTimeoutException or UnknownScannerException
15.5.2. Performance Differences in Thrift and Java APIs
15.5.3. LeaseException when calling
15.5.4. Shell or client application throws lots of scary exceptions during normal operation
15.5.5. Long Client Pauses With Compression
15.5.6. Secure Client Connect ([Caused by GSSException: No valid credentials provided...])
15.5.7. ZooKeeper Client Connection Errors
15.5.8. Client running out of memory though heap size seems to be stable (but the off-heap/direct heap keeps growing)
15.5.9. Client Slowdown When Calling Admin Methods (flush, compact, etc.)
15.5.10. Secure Client Cannot Connect ([Caused by GSSException: No valid credentials provided (Mechanism level: Failed to find any Kerberos tgt)])
15.6. MapReduce
15.6.1. You Think You're On The Cluster, But You're Actually Local
15.6.2. Launching a job, you get java.lang.IllegalAccessError: com/google/protobuf/HBaseZeroCopyByteString or class cannot access its superclass
15.7. NameNode
15.7.1. HDFS Utilization of Tables and Regions
15.7.2. Browsing HDFS for HBase Objects
15.8. Network
15.8.1. Network Spikes
15.8.2. Loopback IP
15.8.3. Network Interfaces
15.9. RegionServer
15.9.1. Startup Errors
15.9.2. Runtime Errors
15.9.3. Snapshot Errors Due to Reverse DNS
15.9.4. Shutdown Errors
15.10. Master
15.10.1. Startup Errors
15.10.2. Shutdown Errors
15.11. ZooKeeper
15.11.1. Startup Errors
15.11.2. ZooKeeper, The Cluster Canary
15.12. Amazon EC2
15.12.1. ZooKeeper does not seem to work on Amazon EC2
15.12.2. Instability on Amazon EC2
15.12.3. Remote Java Connection into EC2 Cluster Not Working
15.13. HBase and Hadoop version issues
15.13.1. NoClassDefFoundError when trying to run 0.90.x on hadoop-0.20.205.x (or hadoop-1.0.x)
15.13.2. ...cannot communicate with client version...
15.14. IPC Configuration Conflicts with Hadoop
15.15. HBase and HDFS
15.16. Running unit or integration tests
15.16.1. Runtime exceptions from MiniDFSCluster when running tests
15.17. Case Studies
15.18. Cryptographic Features
15.19. Operating System Specific Issues
15.19.1. Page Allocation Failure
15.20. JDK Issues
15.20.1. NoSuchMethodError: java.util.concurrent.ConcurrentHashMap.keySet

15.1. General Guidelines

Always start with the master log (TODO: Which lines?). Normally it’s just printing the same lines over and over again. If not, then there’s an issue. Google or should return some hits for those exceptions you’re seeing.

An error rarely comes alone in Apache HBase, usually when something gets screwed up what will follow may be hundreds of exceptions and stack traces coming from all over the place. The best way to approach this type of problem is to walk the log up to where it all began, for example one trick with RegionServers is that they will print some metrics when aborting so grepping for Dump should get you around the start of the problem.

RegionServer suicides are “normal”, as this is what they do when something goes wrong. For example, if ulimit and max transfer threads (the two most important initial settings, see Limits on Number of Files and Processes (ulimit) and Section, “dfs.datanode.max.transfer.threads) aren’t changed, it will make it impossible at some point for DataNodes to create new threads that from the HBase point of view is seen as if HDFS was gone. Think about what would happen if your MySQL database was suddenly unable to access files on your local file system, well it’s the same with HBase and HDFS. Another very common reason to see RegionServers committing seppuku is when they enter prolonged garbage collection pauses that last longer than the default ZooKeeper session timeout. For more information on GC pauses, see the 3 part blog post by Todd Lipcon and Section, “Long GC pauses” above.

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