Iterating over a list in a dictionary within a Jinja2 template

[cmacrae]

Hi guys,

I've got something I'd really like some help on, not just the solution, but the understanding and perhaps any related documentation/articles.

I'm writing a role for deployment of Hubot.
To define bots to be deployed, I'm using a dictionary, like so:

hubot_bots:
  testbot:
    owner: 'Bot Wrangler <b...@example.com>'
    name: Hubot
    descr: Delightfully aware robutt
    adapter: rocketchat
    environment:
      - rocketchat_room: GENERAL
      - rocketchat_user: Hubot
      - rocketchat_password: Hubot

Using 'with_items' I can iterate over items in 'hubot_bots', like 'testbot' here, and create resources, such as directories named after the key 'testbot' and then run commands accessing the values using 'item.value.owner' and 'item.value.adapter', etc.

Now, for each of these bot definitions, I want to deploy a Systemd service file, for management of each bot process.
Within this template, I want to refer to some of the values as defined above, including iterating over each key/value in the 'environment' list.

I tried my best the other evening with a few combinations of 'with_dict' and 'with_nested' and felt I was making some progress, but definitely not getting the desired results, nor understanding how it was working.

Here's the task I'm deploying the template with:

  - name: Deploy service files for each Hubot
    template:
      src: hubot.service.j2
      dest: /usr/lib/systemd/system/hubot-{{ item.key }}.service
      owner: root
      group: root
      mode: 0644
    with_dict: hubot_bots

And here's the template I'm using:

[Unit]
Description=Hubot-{{ item }}
Requires=network.target
After=network.target

[Service]
Type=simple
WorkingDirectory={{ hubot_village_path }}/{{ item }}
User={{ hubot_admin_user }}

Restart=always
RestartSec=10

{% for env in item.value.environment %}
Environment={{ env|upper}}={{ env.value }}
{% endfor %}

ExecStart={{ hubot_village_path }}/{{ item }}/bin/hubot --adapter {{ item.value.adapter }}

[Install]
WantedBy=multi-user.target

As you can see, I want to refer to each bot defined under 'hubot_bots' and then some other values.

Would anyone be able to point me in the right direction on how to get the desired outcome, and understand how this works.
Any documentation or articles would be great. I'm still grasping concepts with YAML structures and the Jinja2 template engine - I'd love to learn as much as I can about it, as I can see it can be very powerful.

So, thank you so much in advance if anyone can help me on this!

Kind Regards,
Calum

[Mike Biancaniello]

First, in your j2, you can't ever reference `item` without `item.key` or `item.value`.

However, I think your amin problem is that your first iteration is a dict (not a list) and the second is a list of dicts without deterministic keys.

Try this:

hubot_bots:
  testbot:
    owner: 'Bot Wrangler <b...@example.com>'
    name: Hubot
    descr: Delightfully aware robutt
    adapter: rocketchat
    environment:

      - key: rocketchat_room
        value: GENERAL
      - key: rocketchat_user
        value: Hubot
      - key: rocketchat_password
        value: Hubot

or:

hubot_bots:
  testbot:
    owner: 'Bot Wrangler <b...@example.com>'
    name: Hubot
    descr: Delightfully aware robutt
    adapter: rocketchat
    environment:

      rocketchat_room: GENERAL
      rocketchat_user: Hubot
      rocketchat_password: Hubot

You could also go with with_items and change the vars to:

hubot_bots:
  - label: testbot
    owner: 'Bot Wrangler <b...@example.com>'

    name: Hubot
    descr: Delightfully aware robutt
    adapter: rocketchat
    environment:

      rocketchat_room: GENERAL
      rocketchat_user: Hubot
      rocketchat_password: Hubot

[cmacrae]

Thanks Mike! I'll take a go at using this :)

[cmacrae]

So, I solved what I wanted to do :)  

For anyone interested, here's how I got it working:

Bot definition looks like this:

hubot_bots:

  testbot:

    owner: 'Bot Wrangler <b...@example.com>'

    name: Hubot

    descr: Delightfully aware robutt

    adapter: rocketchat

    environment:

      - rocketchat_room: GENERAL

      - rocketchat_user: Hubot

      - rocketchat_password: Hubot

Task that deploys the template which reads the above values, looks like this:

  - name: Deploy service files for each Hubot

    template:

      src: hubot.service.j2

      dest: /usr/lib/systemd/system/hubot-{{ item.key }}.service

      owner: root

      group: root

      mode: 0644

    with_dict: hubot_bots

And finally, the Jinja2 code that does what I need (the significant part being the for loops):

[Unit]

Description=Hubot-{{ item.key }}

Requires=network.target

After=network.target

[Service]

Type=simple

WorkingDirectory={{ hubot_village_path }}/{{ item.key }}

User={{ hubot_admin_user }}

Restart=always

RestartSec=10

{% for env in item.value.environment %}

{% for k, v in env.items() %}

Environment={{ k |upper }}={{ v }}

{% endfor %}

{% endfor %}  

 

ExecStart={{ hubot_village_path }}/{{ item.key }}/bin/hubot --adapter {{ item.value.adapter }}

[Install]

WantedBy=multi-user.target

Hope this helps anyone that stumbles upon it!