[HADOOP-13770] Shell.checkIsBashSupported swallowed an interrupted exception

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 2.8.0, 3.0.0-alpha2
• Component/s: util
• Labels: oct16-easy shell supportability
• Target Version/s: 2.8.0
• Hadoop Flags: Reviewed
• Assignee: Wei-Chiu Chuang
• Reporter: Wei-Chiu Chuang
• Created: 16/Dec/15 22:28
• Updated: 02/Oct/19 17:14
• Resolved: 28/Oct/16 15:11

Description

Shell.checkIsBashSupported() creates a bash shell command to verify if the system supports bash. However, its error message is misleading, and the logic should be updated.

If the shell command throws an IOException, it does not imply the bash did not run successfully. If the shell command process was interrupted, its internal logic throws an InterruptedIOException, which is a subclass of IOException.

Shell.checkIsBashSupported

    ShellCommandExecutor shexec;
    boolean supported = true;
    try {
      String[] args = {"bash", "-c", "echo 1000"};
      shexec = new ShellCommandExecutor(args);
      shexec.execute();
    } catch (IOException ioe) {
      LOG.warn("Bash is not supported by the OS", ioe);
      supported = false;
    }

An example of it appeared in a recent jenkins job
https://builds.apache.org/job/PreCommit-HADOOP-Build/8257/testReport/org.apache.hadoop.ipc/TestRPCWaitForProxy/testInterruptedWaitForProxy/

The test logic in TestRPCWaitForProxy.testInterruptedWaitForProxy starts a thread, wait it for 1 second, and interrupt the thread, expecting the thread to terminate. However, the method Shell.checkIsBashSupported swallowed the interrupt, and therefore failed.

2015-12-16 21:31:53,797 WARN  util.Shell (Shell.java:checkIsBashSupported(718)) - Bash is not supported by the OS
java.io.InterruptedIOException: java.lang.InterruptedException
	at org.apache.hadoop.util.Shell.runCommand(Shell.java:930)
	at org.apache.hadoop.util.Shell.run(Shell.java:838)
	at org.apache.hadoop.util.Shell$ShellCommandExecutor.execute(Shell.java:1117)
	at org.apache.hadoop.util.Shell.checkIsBashSupported(Shell.java:716)
	at org.apache.hadoop.util.Shell.<clinit>(Shell.java:705)
	at org.apache.hadoop.util.StringUtils.<clinit>(StringUtils.java:79)
	at org.apache.hadoop.security.SecurityUtil.getAuthenticationMethod(SecurityUtil.java:639)
	at org.apache.hadoop.security.UserGroupInformation.initialize(UserGroupInformation.java:273)
	at org.apache.hadoop.security.UserGroupInformation.ensureInitialized(UserGroupInformation.java:261)
	at org.apache.hadoop.security.UserGroupInformation.loginUserFromSubject(UserGroupInformation.java:803)
	at org.apache.hadoop.security.UserGroupInformation.getLoginUser(UserGroupInformation.java:773)
	at org.apache.hadoop.security.UserGroupInformation.getCurrentUser(UserGroupInformation.java:646)
	at org.apache.hadoop.ipc.RPC.waitForProtocolProxy(RPC.java:397)
	at org.apache.hadoop.ipc.RPC.waitForProtocolProxy(RPC.java:350)
	at org.apache.hadoop.ipc.RPC.waitForProxy(RPC.java:330)
	at org.apache.hadoop.ipc.TestRPCWaitForProxy$RpcThread.run(TestRPCWaitForProxy.java:115)
Caused by: java.lang.InterruptedException
	at java.lang.Object.wait(Native Method)
	at java.lang.Object.wait(Object.java:503)
	at java.lang.UNIXProcess.waitFor(UNIXProcess.java:264)
	at org.apache.hadoop.util.Shell.runCommand(Shell.java:920)
	... 15 more

The original design is not desirable, as it swallowed a potential interrupt, causing TestRPCWaitForProxy.testInterruptedWaitForProxy to fail. Unfortunately, Java does not allow this static method to throw exception. We should removed the static member variable, so that the method can throw the interrupt exception. The node manager should call the static method, instead of using the static member variable.

This fix has an associated benefit: the tests could run faster, because it will no longer need to spawn a bash process when it uses a Shell static method variable (which happens quite often for checking what operating system Hadoop is running on)

Issue Links

• is broken by: HADOOP-12441 Fix kill command behavior under some Linux distributions.