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HDP-2.5.0: Too many levels of symbolic links when installing Clients

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Installing HDP-2.5.0 Clients using Ambari 2.4.0.1 fails with Warnings/Errors regarding 'Too many levels of symbolic links' when trying to populate /usr/hdp/current/[appName]/conf with configs.

This error is thrown when a targeted working directory is symlinked to a folder which is in turn symlinked back to the original targeted working directory. IE: /usr/hdp/current/[appName]/conf will be symlinked to /etc/[appName]/conf but /etc/[appName]/conf will also be symlinked back to /usr/hdp/current/[appName]/conf.

# hadoop-clients example:

[b84cb1ae teal:hadoop-clients ~] # ll /usr/hdp/current/hadoop-client/conf
lrwxrwxrwx. 1 root root 16 Sep  6 05:31 /usr/hdp/current/hadoop-client/conf -> /etc/hadoop/conf
[b84cb1ae teal:hadoop-clients ~] # ll /etc/hadoop/conf
lrwxrwxrwx. 1 root root 35 Sep  6 05:34 /etc/hadoop/conf -> /usr/hdp/current/hadoop-client/conf
# error thrown in /var/log/ambari-agent/ambari-agent.log:

INFO 2016-09-06 05:43:17,682 ActionQueue.py:104 - Adding STATUS_COMMAND for component HDFS_CLIENT of service HDFS of cluster hart to the queue.
INFO 2016-09-06 05:43:17,690 ActionQueue.py:104 - Adding STATUS_COMMAND for component YARN_CLIENT of service YARN of cluster hart to the queue.
INFO 2016-09-06 05:43:17,699 ActionQueue.py:104 - Adding STATUS_COMMAND for component MAPREDUCE2_CLIENT of service MAPREDUCE2 of cluster hart to the queue.
INFO 2016-09-06 05:43:17,707 ActionQueue.py:104 - Adding STATUS_COMMAND for component TEZ_CLIENT of service TEZ of cluster hart to the queue.
INFO 2016-09-06 05:43:17,715 ActionQueue.py:104 - Adding STATUS_COMMAND for component HCAT of service HIVE of cluster hart to the queue.
INFO 2016-09-06 05:43:17,723 ActionQueue.py:104 - Adding STATUS_COMMAND for component HIVE_CLIENT of service HIVE of cluster hart to the queue.
INFO 2016-09-06 05:43:17,732 ActionQueue.py:104 - Adding STATUS_COMMAND for component PIG of service PIG of cluster hart to the queue.
INFO 2016-09-06 05:43:17,740 ActionQueue.py:104 - Adding STATUS_COMMAND for component SQOOP of service SQOOP of cluster hart to the queue.
INFO 2016-09-06 05:43:17,748 ActionQueue.py:104 - Adding STATUS_COMMAND for component ZOOKEEPER_CLIENT of service ZOOKEEPER of cluster hart to the queue.
INFO 2016-09-06 05:43:17,756 ActionQueue.py:104 - Adding STATUS_COMMAND for component SPARK_CLIENT of service SPARK of cluster hart to the queue.
INFO 2016-09-06 05:43:17,766 ActionQueue.py:104 - Adding STATUS_COMMAND for component SLIDER of service SLIDER of cluster hart to the queue.
INFO 2016-09-06 05:43:17,774 ActionQueue.py:104 - Adding STATUS_COMMAND for component METRICS_MONITOR of service AMBARI_METRICS of cluster hart to the queue.
INFO 2016-09-06 05:43:17,782 ActionQueue.py:104 - Adding STATUS_COMMAND for component HST_AGENT of service SMARTSENSE of cluster hart to the queue.
INFO 2016-09-06 05:43:19,232 PythonReflectiveExecutor.py:65 - Reflective command failed with exception:
Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/ambari_agent/PythonReflectiveExecutor.py", line 57, in run_file
    imp.load_source('__main__', script)
  File "/var/lib/ambari-agent/cache/common-services/HDFS/2.1.0.2.0/package/scripts/hdfs_client.py", line 123, in <module>
    HdfsClient().execute()
  File "/usr/lib/python2.6/site-packages/resource_management/libraries/script/script.py", line 280, in execute
    method(env)
  File "/var/lib/ambari-agent/cache/common-services/HDFS/2.1.0.2.0/package/scripts/hdfs_client.py", line 84, in security_status
    {'core-site.xml': FILE_TYPE_XML})
  File "/usr/lib/python2.6/site-packages/resource_management/libraries/functions/security_commons.py", line 129, in get_params_from_filesystem
    configuration = ET.parse(conf_dir + os.sep + config_file)
  File "/usr/lib64/python2.7/xml/etree/ElementTree.py", line 1182, in parse
    tree.parse(source, parser)
  File "/usr/lib64/python2.7/xml/etree/ElementTree.py", line 647, in parse
    source = open(source, "rb")
IOError: [Errno 40] Too many levels of symbolic links: u'/usr/hdp/current/hadoop-client/conf/core-site.xml'

This is on brand new HDP-2.5.0 clusters and is repeatable. Failures occur on nodes running Clients only without additional applications. I can go through and manually resolve these issues but with the number of applications i am installing and the number of client only nodes i am creating, manual intervention is not practical.

Is this a known issue? Possibly a directory creation race condition?

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6 REPLIES 6

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@Ryan Hanson

The obvious issue is the circular symlink references. Have you created symlinks prior to running the installer?

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Super Collaborator

This seems like a bug, perhaps caused by client-only hosts.

/etc/<component>/conf -> /usr/hdp/current/hadoop-client/conf is correct.

What should have happened is that conf-select should have changed /usr/hdp/current/hadoop-client/conf to point to something like /usr/hdp/2.5.0.0-1234/hadoop/conf/0

I'm guessing that the conf-select step failed. If you could post the entire output from your client install command, that can help us determine why it failed.

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Explorer

@emaxwell - Nope, I haven't tampered with any of the HDP directories prior to, or post, installation.

@Jonathan Hurley - Will do, I destroyed the cluster so will need to respin it back up. Takes a bit. Will post back in a few hours. Also is this the best venue for these logs or should I email/post them elsewhere?

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Super Collaborator

The message boards here are just fine. You can either copy/paste them in a code block or compress them and upload them directly.

What I'm looking for is something like this as part of the hadoop client install on a host with the problem:

2016-08-31 15:50:29,421 - Checking if need to create versioned conf dir /etc/hadoop/2.4.2.0-236/0
2016-08-31 15:50:29,422 - call[('ambari-python-wrap', '/usr/bin/conf-select', 'dry-run-create', '--package', 'hadoop', '--stack-version', '2.4.2.0-236', '--conf-version', '0')] {'logoutput': False, 'sudo': True, 'quiet': False, 'stderr': -1}
2016-08-31 15:50:29,439 - call returned (0, '/etc/hadoop/2.4.2.0-236/0', '')
2016-08-31 15:50:29,439 - Package hadoop will have new conf directories: /etc/hadoop/2.4.2.0-236/0
2016-08-31 15:50:29,439 - Checking if need to create versioned conf dir /etc/hadoop/2.4.2.0-236/0
2016-08-31 15:50:29,440 - call[('ambari-python-wrap', '/usr/bin/conf-select', 'create-conf-dir', '--package', 'hadoop', '--stack-version', '2.4.2.0-236', '--conf-version', '0')] {'logoutput': False, 'sudo': True, 'quiet': False, 'stderr': -1}
2016-08-31 15:50:29,457 - call returned (0, '/etc/hadoop/2.4.2.0-236/0', '')
...

2016-08-31 15:50:29,492 - checked_call[('ambari-python-wrap', '/usr/bin/conf-select', 'set-conf-dir', '--package', 'hadoop', '--stack-version', '2.4.2.0-236', '--conf-version', '0')] {'logoutput': False, 'sudo': True, 'quiet': False}
2016-08-31 15:50:29,509 - checked_call returned (0, '/usr/hdp/2.4.2.0-236/hadoop/conf -> /etc/hadoop/2.4.2.0-236/0')
2016-08-31 15:50:29,510 - Ensuring that hadoop has the correct symlink structure

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Super Collaborator

Very nice! That's exactly what I was looking for and the cause was spot-on. Perhaps Ambari shouldn't fail silently anymore. conf-select used to have a ton of issues which is why we ignored errors invoking it.