How to run command after error occurs in ansible handler - ansible

Question

I have a simple playbook that copies some config files for nginx server and then issues service nginx reload command:
---
- hosts: mirrors
tasks:
- name: Installs nginx web server
apt: pkg=nginx state=installed update_cache=true
notify:
- start nginx
- name: Copy vhost file
copy: src=vhost/test.vhost dest=/etc/nginx/sites-available/ mode=0644
- name: Symlink vhost file to enabled sites
file: src=/etc/nginx/sites-available/test.vhost dest=/etc/nginx/sites-enabled/test.vhost state=link
notify:
- reload nginx
handlers:
- name: start nginx
service: name=nginx state=started
- name: reload nginx
service: name=nginx state=reloaded
Now, the problem is that it might happen that the test.host file contains an error and nginx won't reload properly. If it happens, I'd like to run a command systemctl status nginx.service and see it's output when ansible playbook executes. How can I add this "error handler"?

Answer 1

If the handler output tells you about the failure, you can put together a nice bit of error handling with the ignore_errors and register keywords.
Set your handler not to end to fail and end the play when it gets an error code back, but to register the output as a variable:
handlers:
- name: reload nginx
service: name=nginx state=reloaded
ignore_errors: True
register: nginx_reloaded
Then back in the tasks section, call flush_handlers to execute all the queued handlers that would otherwise wait until the end of the play. Add a task in to go and ask the server about the status of Nginx when your nginx_reloaded variable has a non-zero return code, and then print the information from that with the debug module:
- name: Symlink vhost file to enabled sites
file: src=/etc/nginx/sites-available/test.vhost dest=/etc/nginx/sites-enabled/test.vhost state=link
notify:
- reload nginx
- meta: flush_handlers
- name: Get the Nginx service status if it failed to failed.
command: "systemctl status nginx.service"
register: nginx_status
when: nginx_reloaded.rc != 0
- debug: var=nginx_status
when: nginx_reloaded.rc != 0
Of course, a better solution would be to fix those errors in your configuration files - and figuring them out through Ansible output has limitations compared to SSHing onto the target host to check it out.

Answer 2

Why don't use Ansible modules ability to validate configuration?:
http://docs.ansible.com/ansible/template_module.html
http://docs.ansible.com/ansible/replace_module.html
http://docs.ansible.com/ansible/lineinfile_module.html
For example:
- template: src=/mine/sudoers dest=/etc/sudoers validate='visudo -cf %s'
- lineinfile: dest=/etc/sudoers state=present regexp='^%ADMIN ALL\=' line='%ADMIN ALL=(ALL) NOPASSWD:ALL' validate='visudo -cf %s'
- replace: dest=/etc/apache/ports regexp='^(NameVirtualHost|Listen)\s+80\s*$' replace='\1 127.0.0.1:8080' validate='/usr/sbin/apache2ctl -f %s -t'