Ansible: exception handling ... error handling ..

Ansible: exception handling ...

1. Lets create a simple playbook and run

[root@master dec15]# cat error.yaml

- hosts: w1

  tasks:

  - package:

      name: "httpd"

      state: present

  - debug:

      msg: "This is a test run .."

[root@master dec15]# ansible-playbook error.yaml

2. Lets make a mistake on one of the variable.

say pkg name is nane

# cat error.yaml

- hosts: w1

  tasks:

  - package:

        nane: "httpd"

        state: present

- debug:

    msg: "This is just a test run ..."

[root@master dec15]# alias 'ap=ansible-playbook'

[root@master dec15]# ap error.yaml

we saw fatal error. we know its because the keyword we wrote, ansible does not that that keyword defined.

in fact it didn't recognize the parameter e=we supply.

3. What we can do is tell ansible to ignore if you find error. do not just throw error, continue.

# cat error.yaml

- hosts: w1

  tasks:

  - package:

        nane: "httpd"

        state: present

    ignore_errors: yes # ignore this error and go to next task

- debug:

    msg: "This is just a test run ..."

[root@master dec15]# ap error.yaml

You see, error is ignored this time.

4. Now, lets try something else, lets download a file from internet..

[root@master dec15]# ansible-doc -l uri

# cat errors.yaml

- hosts: w1

  tasks:

    - package:

        name: "httpd"

        state: present

debug: 

   msg: "This is just testing msg"

Before running the playbook to download a file from internet, lets look into some docs

or google for ansible uri or get-uri

look for example 

Image source: https://hips.hearstapps.com/hmg-prod.s3.amazonaws.com/images/quotes-about-change-1580499303.jpg

[root@master dec15]# cat error.yaml

- hosts: w1

  tasks:

  - package:

      nane: "httpd"

      state: present

    ignore_errors: yes

  #- get_uri:

  - uri:

      url: https://hips.hearstapps.com/hmg-prod.s3.amazonaws.com/images/quotes-about-change-1580499303.jpg

      dest: "/var/www/html/life_l.jpg"

  - debug:

      msg: "This is a test run .."

[root@master dec15]#

[root@master dec15]# ap error.yaml

[root@worker1 ~]# ls -l /var/www/html/life_l.jpg

-rw-r--r--. 1 root root 206868 Dec  8 05:10 /var/www/html/life_l.jpg

The result above shows that its successful.

5. Now, say we have a problem with internet connection, and if you run this playbook,, it will fail.

It will throw error, so how do you handle the error?

The best thing you can do is ignore the error. How? look at the yaml file below..

[root@master dec15]# netstat -rn

Kernel IP routing table

Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface

0.0.0.0         192.168.10.1    0.0.0.0         UG        0 0          0 enp0s3

for lab purpose, you can remove the 0.0.0.0

[root@master dec15]# cat error.yaml

- hosts: w1

  tasks:

  - package:

      nane: "httpd"

      state: present

    ignore_errors: yes

  #- get_uri:

  - uri:

      url: https://hips.hearstapps.com/hmg-prod.s3.amazonaws.com/images/quotes-about-change-1580499303.jpg

      dest: "/var/www/html/life_l.jpg"

    ignore_errors: yes

  - debug:

      msg: "This is a test run .."

[root@master dec15]# ap error.yaml

If you are disconnected from internet, it will fail with error unreachable network. 

so, you can use ignore_errors keyword to ignore the error.

it will continue to run it. But it might be an important piece of information, that you can't ignore it.

so,  you have to be very careful while dealing with ignore_errors.

6. Using block.

On block, your code in block and at the end, include rescue.

[root@master dec15]# ap error.yaml

/usr/lib/python3.6/site-packages/requests/__init__.py:91: RequestsDependencyWarning: urllib3 (1.26.2) or chardet (3.0.4) doesn't match a supported version!

  RequestsDependencyWarning)

PLAY [w1] *********************************************************************************************************************

TASK [Gathering Facts] ********************************************************************************************************

ok: [w1]

TASK [package] ****************************************************************************************************************

ok: [w1]

TASK [uri] ********************************************************************************************************************

changed: [w1]

TASK [service] ****************************************************************************************************************

changed: [w1]

TASK [debug] ******************************************************************************************************************

ok: [w1] => {

    "msg": "This is a test run .."

}

TASK [debug] ******************************************************************************************************************

ok: [w1] => {

    "msg": "This is a test run .."

}

PLAY RECAP ********************************************************************************************************************

w1                         : ok=6    changed=2    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

[root@worker1 ~]# systemctl status httpd

● httpd.service - The Apache HTTP Server

   Loaded: loaded (/usr/lib/systemd/system/httpd.service; disabled; vendor preset: disabled)

   Active: active (running) since Tue 2020-12-08 06:01:59 EST; 42s ago

     Docs: man:httpd.service(8)

 Main PID: 59114 (httpd)

[root@worker1 html]# ls -ltr

total 212

-rw-r--r--. 1 root root      8 Dec  7 03:19 index.html

-rw-r--r--. 1 root root     12 Dec  8 05:51 webap.htm

-rw-r--r--. 1 root root 206868 Dec  8 05:53 life_l.jpg

[root@worker1 html]# cat webap.htm

This is cool