{"id":39033,"date":"2025-09-18T15:54:32","date_gmt":"2025-09-18T13:54:32","guid":{"rendered":"https:\/\/www.dbi-services.com\/blog\/?p=39033"},"modified":"2025-09-18T16:09:33","modified_gmt":"2025-09-18T14:09:33","slug":"errorhandling-in-ansible","status":"publish","type":"post","link":"https:\/\/www.dbi-services.com\/blog\/errorhandling-in-ansible\/","title":{"rendered":"Errorhandling in Ansible"},"content":{"rendered":"\n
Errors in tasks – abort or ignore?<\/h2>\n\n\n\n
Per default, if a task in a playbook fails, then the execution of the playbook is stopped for that host. <\/p>\n\n\n
\n- name: PLAY1\n hosts: localhost\n gather_facts: no\n tasks:\n - name: let this shell-command fail\n ansible.builtin.shell: exit 1\n\n - name: let this shell-command complete\n ansible.builtin.shell: exit 0\n<\/pre><\/div>\n\n\n<\/figure>\n\n\n\n
As you can see, the 2nd task is not executed. If you want to continue in such a case, the ignore_errors<\/code> parameter is your friend<\/p>\n\n\n
\n - name: let this shell-command fail\n ansible.builtin.shell: exit 1\n ignore_errors: true\n<\/pre><\/div>\n\n\n<\/figure>\n\n\n\n
Custom error conditions<\/h2>\n\n\n\n
Per default, Ansible evaluates the exit-code of the module, in case of the shell-module, the exit-code of the last command.<\/p>\n\n\n\n
But for some commands, that is not adequate. Example: The Oracle commandline tool sqlplus<\/code> to submit sql-commands will have an exit-code of 0 if it can connect to the database-instance. It is not related to the result of your SQL-commands. Error-messages in Oracle are prefixed by ORA-.<\/p>\n\n\n\n
So, if you want to check for application errors, you have to implement it yourself. For that, you can use the failed_when<\/code> option.<\/p>\n\n\n
\n - name: let this shell-command fail\n ansible.builtin.shell: |\n . ~\/.profile\n echo "select count(*) from all_users;" | sqlplus \/ as sysdba\n register: number_of_users\n failed_when: "'ORA-' in number_of_users.stdout"\n<\/pre><\/div>\n\n\n
Caution: In this case the exit-code of the shell is no longer evaluated. To also get the exit-code of the sqlplus call (e.g., sqlplus can not connect to the database, or sqlplus binary not found), you have to add this (default) condition: <\/p>\n\n\n
\n failed_when: "number_of_users.rc != 0 or 'ORA-' in number_of_users.stdout"\n<\/pre><\/div>\n\n\n
But caution! Not all modules will have an rc<\/code> field.<\/p>\n\n\n\n
Tuning: Perform several checks at once<\/h2>\n\n\n\n
Conceptually, Ansible is not the fastest tool. For each task, it will usually login with ssh to the remote server. If you have to run several checks in the shell, then, instead of running each in a separate task, you can run all these check-commands in one shell-task, and evaluate the result afterwards.<\/p>\n\n\n
\n - name: run many check commands\n ansible.builtin.shell: |\n mount | grep ' on \/u00 ' #check if \/u00 is mounted\n rpm -q ksh 2>&1 #check if ksh is installed\n exit 0 # do not fail if rpm exit != 0; we will do our own errorhandling\n register: checks\n\n - name: fail if no \/u00 is mounted\n fail:\n msg: "\/u00 is not mounted"\n when: "' on \/u00 ' not in checks.stdout"\n\n - name: No ksh found, try to install it\n yum:\n name: ksh\n state: present\n when: "'package ksh is not installed' in checks.stdout"\n\n<\/pre><\/div>\n\n\n
If you only want to throw an error, then you can do it directly in the shell-task:<\/p>\n\n\n
\nwhen: "' on \/u00 ' not in checks.stdout" or 'package ksh is not installed' in checks.stdout\n<\/pre><\/div>\n\n\n
But if you parse the output afterwards, you can run tasks to fix the error. <\/p>\n\n\n\n
Sometimes it is difficult to parse the output if some commands return the same output, e.g. “OK”. If your check-commands always return exactly 1 line, then you can directly parse the output of the command. The output of the 3rd command is in checks.stdout_lines[2]<\/code>. In the above example that will not work because grep<\/code> will return the exit-code 0 (not found) or 1 (found) plus the found line. So, expand it as: mount | grep ' on \/u00 ' || echo error<\/code><\/p>\n\n\n\n
Print errormessages more readable<\/h2>\n\n\n\n
Do not fail the task itself, it is very usually unreadable because all information is printed on one line.<\/p>\n\n\n\n<\/figure>\n\n\n\n
Instead, use ignore_errors: true <\/code>and failed_when: false<\/code> in the task. Do the errorhandling in a separate task with a customized errormessage. To print the multiline list of stdout_lines, use debug:<\/code> otherwise you can directy use ansible.builtin.fail: <\/code>with a customized message: <\/code><\/p>\n\n\n
\n - name: force sqlplus to throw error because of missing environment\n ansible.builtin.shell: |\n \/u00\/app\/oracle\/product\/19.7.0\/bin\/sqlplus -L \/ as sysdba @myscript.sql 2>&1\n register: checks\n ignore_errors: true\n failed_when: false\n\n - name: Check for errors of task before\n debug: var=checks.stdout_lines\n failed_when: checks.rc != 0 or 'ORA-' in checks.stdout\n when: checks.rc != 0 or 'ORA-' in checks.stdout\n<\/pre><\/div>\n\n\n<\/figure>\n\n\n\n
Re-run failed hosts<\/h2>\n\n\n\n
As an example for this scenario: A customer of mine will do an offline backup of the development databases. And I have to run an Ansible playbook against all databases. If the playbook for this host is run at the backup time, it will fail because the database is down. But after some minutes the database will be restarted. <\/p>\n\n\n\n
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