[HADOOP-104] Reflexive access to non-public class with public ctor requires setAccessible (with some JVMs)

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Duplicate
• Fix Version/s: 0.5.0
• Assignee: Hairong Kuang
• Reporter: Michel Tourn
• Created: 25/Mar/06 07:07
• Updated: 13/Sep/06 03:53
• Resolved: 13/Sep/06 03:53

Description

Multiple times I have hit this problem which prevents the NameNode from starting.
The only fix I had so far was to loose all my DFS data...

Exception in thread "main" java.lang.RuntimeException: java.lang.IllegalAccessException:
Class org.apache.hadoop.io.WritableFactories can not access a member of
class org.apache.hadoop.dfs.Block with modifiers "public"
at org.apache.hadoop.io.WritableFactories.newInstance(WritableFactories.java:49)
at org.apache.hadoop.io.ArrayWritable.readFields(ArrayWritable.java:81)
at org.apache.hadoop.dfs.FSDirectory.loadFSEdits(FSDirectory.java:374)
at org.apache.hadoop.dfs.FSDirectory.loadFSImage(FSDirectory.java:347)
at org.apache.hadoop.dfs.FSDirectory.<init>(FSDirectory.java:258)
at org.apache.hadoop.dfs.FSNamesystem.<init>(FSNamesystem.java:151)
at org.apache.hadoop.dfs.NameNode.<init>(NameNode.java:82)

According to this,
http://forum.java.sun.com/thread.jspa?threadID=704100&messageID=4082902
this is a known issue when using
reflexive access to a non-public class with public ctor
(class org.apache.hadoop.dfs.Block is such a class)

This problem may not occur with all JVM releases.
(I build on 1.5.0-b64 and run on 1.5.0_05-b05)

This problem only occured for me when
I upgrade code or change XML configuration AND
have existing files in the DFS.
This problem does not occur when I just stop / restart the NameServer.

In any case, the attached patch fixes it by calling setAccessible
before constructing the instance with reflection.

Issue Links

• duplicates: HADOOP-367 Static blocks do not automatically run when a class is loaded in Java 5.0