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Troubleshooting

This section provides information for troubleshooting and recovery.

Diagnosing issues from log files

Whenever you face any issues during installation, you should first check the following log files to diagnose the issues:

The installation process is broken

Issue:

The installation process gets broken.

Solution:

Whenever the installation process gets broken, do the following:

  1. Stop Unravel.

    manager stop

    If the manager does not work, open the services directory, each service has a stop.sh script. Stop the service monitor (monit). and then run the stop.sh script.

    In case you do not have stop.sh scripts, send SIGTERM to all the services starting with the service monitor (monit)

    Caution

    Avoid using SIGKILL since that may cause some file corruption.

  2. Reinstall Unravel using the content in the data directory.

Files got deleted or corrupted

Issue:

The files got deleted or corrupted

Solution:

  1. Stop Unravel.

  2. Assuming that you have installed Unravel in /opt, run the following command:

    /opt/unravel/manager refresh files

    This regenerates all the scripts and configuration files.

    In case the refresh command did not regenerate the files or the manager is broken, then check <Unravel installation directory>/data/conf/current.yaml and run the following. The current.yaml file shows the current version that is installed.

    <Unravel installation directory>/versions/X.Y.Z/setup --config=<Unravel installation directory>/data/conf/unravel.yaml

  3. Start Unravel.

    <Unravel installation directory>/unravel/manager start

Unravel software got deleted

Issue:

Unravel software got deleted.

Solution:

  1. Stop Unravel.

  2. Check <Unravel installation directory>/data/conf/current.yaml for the current version that is installed.

  3. Unpack that same version in the exact location where it was deployed earlier.

    tar zxf unravel-SAME-VERSION.tar.gz -C /opt

  4. Run the following:

    <Unravel installation directory>/versions/X.Y.Z/setup --config=<Unravel installation directory>/unravel/data/conf/unravel.yaml

  5. Start the manager.

    <Unravel installation directory>/unravel/manager start

Restoring Unravel from a backup

Issue:

How to restore Unravel from a backup?

Solution:

  1. Stop Unravel.

  2. Restore the backup of the data directory.

  3. Open data/conf/unravel.effective.yaml and check for the following key paths:

    • base: <Unravel installation directory>

    • data: <Unravel installation directory>/data

  4. Make sure that the data is restored to the right location.

  5. Make sure the unravel user has full access and ownership of the base location and everything in it.

  6. Check< Unravel installation directory>/data/conf/current.yaml for the current version that is installed.

  7. Unpack that same version in the exact location where it was deployed earlier.

    tar zxf unravel-SAME-VERSION.tar.gz -C /opt

  8. Run the following:

    <Unravel installation directory>/versions/X.Y.Z/setup --config=<Unravel installation directory>/data/conf/unravel.yaml

  9. Start Unravel.

    <Unravel installation directory>/manager start

On-demand services not starting

Issue:

The On-demand services are not starting.

Solution:

If Unravel is installed in RHEL 7.7 environment, the following issues can occur while starting OnDemand service:

  • Unsafe symlink failure: To resolve this issue, you must manually edit the /etc/init.d and /etc/systemd/system files and change the location for PID file creation from usr/local/unravel/ondemand to /var/run.

    rhel77errorondemand.png

  • /lib/lsb/init-functions not existing: To resolve this issue, you must remove the existing /lib/lsb/init-functions file and install the redhat-lsb-core package:

    rmdir /lib/lsb/init-functions
yum install redhat-lsb-core

Troubleshooting Cloudera Distribution of Apache Hadoop (CDH) issues

Symptom

Problem

Remedy

hadoop fs -ls /user/unravel/HOOK_RESULT_DIR/ indicates that the directory does not exist

  • Unravel Server RPM is not yet installed, or

  • Unravel Server RPM is installed on a different HDFS cluster, or

  • HDFS home directory for Unravel does not exist, or

  • kerberos/sentry actions are needed

Install Unravel RPM on Unravel host.

or

Verify that user unravel user exists and has a /user/unravel/ directory in HDFS with write access to it.

ClassNotFound error for com.unraveldata.dataflow.hive.hook.UnravelHiveHook during Hive query execution

Unravel hive hook JAR was not found in in $HIVE_HOME/lib/.

Confirm that the UNRAVEL_SENSOR parcel was distributed and activated in Cloudera Manager.

or

Put the Unravel hive-hook JAR corresponding to hive-version in jar-destination on each gateway as follows:

cd /usr/local/unravel/hive-hook/;
cp unravel-hive-hive-version*hook.jar jar-destination

Oozie shell action fails with ClassNotFoundException on Hcat call after Unravel Hive Hooks were added to the cluster

HCatalog is part of Apache Hive. In such a case, the Hive Hook configuration is found, but the libraries that execute Hive Hook are missing.

Since this is a shell action, libraries need to exist on every node locally so that Sqoop command can locate it during command execution. You can add Unravel Hive Hook jar in /var/lib/sqoop or wherever the hive-hcatalog jars are located in the cluster.

Unravel stop and start fails with an error

Issue:

When Unravel is stopped and restarted immediately, the following error is displayed:

[Errno 1] Operation not permitted
[Errno 1] Operation not permitted
INS00160: Process '3366' is not owned by unravel
INS00161: Process '3366' is not owned by unravel, this can come from a stale pid file '/opt/unravel/run/mysql.pid'
Solution

When you do an ungraceful shutdown, the PID files will remain and if the PID is reused it may cause problems. You should ensure that unravel is stopped (it will if the server was just restarted) and delete the PID files in /opt/unravel/run

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