[HBASE-15686] Add override mechanism for the exempt classes when dynamically loading table coprocessor

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.0.1
• Fix Version/s: 1.4.0, 0.98.20, 2.0.0
• Component/s: Coprocessors
• Hadoop Flags: Reviewed

Release Note

New coprocessor table descriptor attribute, hbase.coprocessor.classloader.included.classes, is added.
User can specify class name prefixes (semicolon separated) which should be loaded by CoprocessorClassLoader through this attribute using the following syntax:
{code}
  hbase> alter 't1', 'coprocessor'=>'hdfs:///foo.jar|com.foo.FooRegionObserver|1001|arg1=1,arg2=2'
{code}

• Assignee: Ted Yu
• Reporter: Sangjin Lee
• Created: 21/Apr/16 19:01
• Updated: 20/Apr/18 16:07
• Resolved: 28/Apr/16 16:23

Description

As part of Hadoop's Timeline Service v.2 (YARN-2928), we're adding a table coprocessor (YARN-4062). However, we're finding that the coprocessor cannot be loaded dynamically. A relevant snippet for the exception:

java.io.IOException: Class org.apache.hadoop.yarn.server.timelineservice.storage.flow.FlowRunCoprocessor cannot be loaded
    at org.apache.hadoop.hbase.master.HMaster.sanityCheckTableDescriptor(HMaster.java:1329)
    at org.apache.hadoop.hbase.master.HMaster.createTable(HMaster.java:1269)
    at org.apache.hadoop.hbase.master.MasterRpcServices.createTable(MasterRpcServices.java:398)
    at org.apache.hadoop.hbase.protobuf.generated.MasterProtos$MasterService$2.callBlockingMethod(MasterProtos.java:42436)
    at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2031)
    at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:107)
    at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:130)
    at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:107)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.io.IOException: Class org.apache.hadoop.yarn.server.timelineservice.storage.flow.FlowRunCoprocessor cannot be loaded
    at org.apache.hadoop.hbase.regionserver.RegionCoprocessorHost.testTableCoprocessorAttrs(RegionCoprocessorHost.java:324)
    at org.apache.hadoop.hbase.master.HMaster.checkClassLoading(HMaster.java:1483)
    at org.apache.hadoop.hbase.master.HMaster.sanityCheckTableDescriptor(HMaster.java:1327)
    ... 8 more
Caused by: java.lang.ClassNotFoundException: org.apache.hadoop.yarn.server.timelineservice.storage.flow.FlowRunCoprocessor
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
    at org.apache.hadoop.hbase.util.CoprocessorClassLoader.loadClass(CoprocessorClassLoader.java:275)
    at org.apache.hadoop.hbase.regionserver.RegionCoprocessorHost.testTableCoprocessorAttrs(RegionCoprocessorHost.java:322)
    ... 10 more

We tracked it down to the fact that CoprocessorClassLoader regarding all hadoop classes as exempt from loading from the coprocessor jar. Since our coprocessor sits in the coprocessor jar, and yet the loading of this class is delegated to the parent which does not have this jar, the classloading fails.

What would be nice is the ability to exclude certain classes from the exempt classes so that they can be loaded via table coprocessor classloader. See hadoop's ApplicationClassLoader for a similar feature.

Is there any other way to load this coprocessor at the table scope?

Issue Links

• is related to: YARN-4062 Add the flush and compaction functionality via coprocessors and scanners for flow run table
• is related to: HBASE-13706 CoprocessorClassLoader should not exempt Hive classes
• is related to: YARN-2928 YARN Timeline Service v.2: alpha 1