Backtrace Information

This section explains how to generate backtrace logs on your Exasol system.

If you are experiencing performance problems or operations that hang, you need to provide all the backtrace information for the time period when the problem occurred.

Prerequisites

You must have enough free disk space for the logs. For more information, see EXAsupport.

Procedure

The following examples use ConfD through the command-line tool confd_client, which is available on all database nodes. For more information, see ConfD.

Placeholder values are indicated with UPPERCASE characters. Replace the placeholders with your own values.

  1. Connect to EXAClusterOS (COS) on the cluster using c4 connect -t <DEPLOYMENT>[.<NODE>]/cos. For example:

    c4 connect -t 1.11/cos

    If you do not specify a node, c4 will connect to the first active node in the deployment.

    For more information about how to use c4 connect, see How to use c4.

  2. To find the name of the database, use the ConfD job db_list. For example:

    confd_client db_list
    - MY_DATABASE

  3. To create a backtrace log, use the EXAsupport tool . Specify the start date (-s) and end date (-t) using the format YYYY-MM-DD. For example:

    exasupport -s 2022-08-11 -t 2022-08-11 -e MY_DATABASE -b1,2,3,4

    If the log file was created successfully, you will see the following message containing the file name:

    Successfully stored debug information into file /exa/tmp/support/exacluster_debuginfo_2022_08_11-23_27_20.tar.gz
  4. To disconnect from EXAClusterOS, use CTRL+D or type exit.

  5. Copy the log file to your local computer using the scp command (secure copy). 

    scp -P $COS_PORT -i ~/.ssh/$KEY root@$DATABASE_IP:/exa/tmp/support/$FILENAME $LOCAL_FOLDER
    Parameter Description
    $COS_PORT

    The SSH port for connecting to EXAClusterOS (COS). Default = 20002

    To find the port number in the configuration, use c4 config | grep CCC_PLAY_SSHD_PORT.
    $KEY

    The filename of the SSH private key.

    To find the filename in the configuration, use c4 config | grep CCC_AWS_KEY_PAIR_FILE.
    $DATABASE_IP

    The external IP address of the cluster node that you were connected to when creating the log file.

    To find the IP addresses of all nodes, use c4 ps.

    $FILENAME The name of the log file that was generated by EXAsupport in the previous step.
    $LOCAL_FOLDER Path to a folder on your computer where the log file will be stored.
    Example

    Get the necessary info: 

    c4 config | grep CCC_AWS_KEY_PAIR_FILE
    CCC_AWS_KEY_PAIR_FILE=my_private_key.pem

    c4 config | grep CCC_PLAY_SSHD_PORT
    CCC_PLAY_SSHD_PORT=20002

    c4 ps 
          N  PLAY_ID   NODE  MEDIUM  INSTANCE     EXTERNAL_IP     INTERNAL_IP  STAGE  STATE      UPTIME    TTL
      ┌─  1  3a4a7d8d  10    awscf   c5d.large    203.0.113.10    10.0.0.10    c      running    04:35:15  +∞
      │   1  3a4a7d8d  11    awscf   c5d.2xlarge  203.0.113.11    10.0.0.11    d      running    04:35:16  +∞
      └─  1  3a4a7d8d  12    awscf   c5d.2xlarge  203.0.113.12    10.0.0.12    d      running    04:35:15  +∞

    Copy the file to your local machine:

    scp -P 2002 -i ~/.ssh/my_private_key.pem \
      root@203.0.113.10:/exa/tmp/support/exacluster_debuginfo_2022_08_11-23_27_20.tar.gz ~/my_logs/

Verification

To verify that the log was successfully copied, use the ls command in the target folder on your local machine.

Example
ls -lahtr ~/mylogs | grep exacluster_debuginfo
-rwxr-xr-x  1 user group 9.8K Sep 20 17:38 exacluster_debuginfo_2022_08_11-23_27_20.tar.gz