Ansible Playbook Error Handling
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In this lesson, we will focus on managing errors within an Ansible playbook, particularly when an error is expected or planned as part of the playbook's logic. We'll use the scenario of the conditional_test.yml playbook, where the absence of a file is an expected outcome based on a conditional statement.
You will learn how to handle errors gracefully in Ansible playbooks, ensuring that your automation continues smoothly even when certain tasks fail.
Understanding Error Handling in Ansible
Error handling in Ansible is important when executing tasks that might fail under expected conditions. For example, in our conditional_test.yml playbook, the task to check for a file's existence might fail if the file was deliberately removed. Instead of letting this stop our playbook, we can configure our playbook to ignore / skip the error.
Modifying the Playbook for Error Handling
We will update the conditional_test.yml playbook to include a task that checks for the file's existence using the ls command. To handle potential errors, we'll use the ignore_errors directive, which tells Ansible to continue executing the playbook even if the task fails.
Open conditional_test.yml and add the following task at the end:
- name: Check if the file exists
command: ls ~/conditional_test_file.txt
ignore_errors: True
register: file_checkIn this task, we're using the command module to run ls ~/conditional_test_file.txt. The ignore_errors: yes line ensures that even if the command fails (which it will if the file doesn't exist), the playbook will not stop executing. The output of the command is registered in the file_check variable.
Adding a Conditional Success Message
Next, let's add a task to display a success message if the file was correctly removed (i.e., if the previous task failed). We can use the file_check variable to determine if the command was successful or not.
Add this task below the file check task:
- name: Confirm file removal
debug:
msg: "File was successfully removed"
when: file_check.failedThis task uses the debug module to print a message confirming the file's removal. The when: file_check.failed condition checks if the previous task failed (which indicates that the file was successfully removed).
Testing the Updated Playbook
Run the playbook normally which will not delete the file
ansible-playbook conditional_test.ymlYou should see output like the following:
Run the updated playbook with the command to delete the file:
ansible-playbook conditional_test.yml -e '{create_file: False}'You should see that the playbook is completed. It should show some errors, but it will state ...ignoring after the error, and you should see a debug message stating the file was removed:
Conclusion
In this lesson, you have learned how to handle errors in Ansible playbooks. By using ignore_errors and conditional statements, you can ensure your playbooks are robust and capable of handling scenarios where certain failures are expected.
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