[HADOOP-12773] HBase classes fail to load with client/job classloader enabled

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.6.3
• Fix Version/s: 2.8.0, 2.7.3, 2.6.5, 3.0.0-alpha1
• Component/s: util
• Hadoop Flags: Reviewed
• Assignee: Sangjin Lee
• Reporter: Sangjin Lee
• Created: 05/Feb/16 21:36
• Updated: 06/Jan/17 08:05
• Resolved: 08/Feb/16 22:02

Description

Currently if a user uses HBase and enables the client/job classloader, the job fails to load HBase classes. For example,

java.lang.NoClassDefFoundError: Lorg/apache/hadoop/hbase/client/HBaseAdmin;
	at java.lang.Class.getDeclaredFields0(Native Method)
	at java.lang.Class.privateGetDeclaredFields(Class.java:2509)
	at java.lang.Class.getDeclaredField(Class.java:1959)
	at java.io.ObjectStreamClass.getDeclaredSUID(ObjectStreamClass.java:1703)
	at java.io.ObjectStreamClass.access$700(ObjectStreamClass.java:72)
	at java.io.ObjectStreamClass$2.run(ObjectStreamClass.java:484)
	at java.io.ObjectStreamClass$2.run(ObjectStreamClass.java:472)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.io.ObjectStreamClass.<init>(ObjectStreamClass.java:472)
	at java.io.ObjectStreamClass.lookup(ObjectStreamClass.java:369)

It is because the HBase classes (org.apache.hadoop.hbase.*) meet the system classes criteria which are supposed to be loaded strictly from the base classloader. But hadoop does not provide HBase as a dependency.

We should exclude the HBase classes from the system classes until/unless HBase is provided by a future version of hadoop.