ansible - template json for environmental variable in docker container

Question

I'm trying to assign a one-liner json string to an environmental variable in a docker container. This is what the json look like:

{"ip_access": {"IP_whitelist": {"192.168.99.19/32": "grafana/status (Provider)"}}, "vhosts": {"prometheus1": {"dns_names": ["prometheus1.company.internal"], "add_lines_443": ["include IP_whitelist;", "set $prometheus http://prometheus:9090;", "location / { proxy_pass $prometheus; }"], "options": {"cert_path": "/etc/ssl/certs/prometheus1.crt", "key_path": "/etc/ssl/private/prometheus1.key"}}}}

So instead of ["prometheus1.company.internal"] I want to have ["{{ inventory_hostname }} .company.internal"] (and also for the other instances of prometheus1.

I'm using docker_container as follows:

- name: create nginx reverse proxy container
  docker_container:
    image: registry.company.com/devops/nginx-reverseproxy:{{ nginx_version }}
    name: nginx-reverseproxy
    labels:
      role=metrics
    volumes:
      - /etc/ssl/certs/{{ inventory_hostname }}.crt:/etc/ssl/certs/{{ inventory_hostname }}.crt
      - /etc/ssl/private/{{ inventory_hostname }}.key:/etc/ssl/private/{{ inventory_hostname }}.key
    container_default_behavior: compatibility
    networks_cli_compatible: yes
    network_mode: default
    purge_networks: yes
    networks:
      - name: metrics-net
      - name: proxy-net
    env:
      STAGING_ENVIRONMENT: 'production'
      NGINX_VHOSTS_JSON: '{{ lookup("template", "rproxy/nginx_vhosts_prometheus_develop.j2") }}'

Unfortunately, I keep getting:

TASK [prometheus : create nginx reverse proxy container] **********************************************
fatal: [prometheus_vag]: FAILED! => {"changed": false, "msg": "Non-string value found for env option. Ambiguous env options must be wrapped in quotes to avoid them being interpreted. Key: NGINX_VHOSTS_JSON"}

The weird thing is, if I simply use the template module, it works as expected:

  template:
    src: rproxy/nginx_vhosts_prometheus_develop.j2
    dest: /tmp/tempo.json
  when: "prometheus_host in inventory_hostname"
  tags:
    - copytmp

inventory_hostname will be replaced by the actual value in the inventory and I get the right thing. Moreover, if I paste this exact result into the playbook as the value of NGINX_VHOSTS_JSON in the yaml playbook, it also works without any issues.

But lookup template seems not to be delivering the expected string.

Any ideas how I can get around the problem?

score 1 · Accepted Answer · answered Apr 06 '21 at 14:20

Ansible's templating often automatically converts things to a data structure when they look like string representations of a structure.

You can avoid this in this case by explicitly turning it into JSON when you need it:

NGINX_VHOSTS_JSON: '{{ lookup("template", "rproxy/nginx_vhosts_prometheus_develop.j2") | to_json }}'

Personally, I would template it in a more human-friendly representation such as YAML, then convert it to JSON:

test.j2:

ip_access:
  IP_whitelist:
    192.168.99.19/32: grafana/status (Provider)
vhosts:
  {{ inventory_hostname }}.company.internal:
    add_lines_443:
    - include IP_whitelist;
    - set $prometheus http://prometheus:9090;
    - location / { proxy_pass $prometheus; }
    dns_names:
    - {{ inventory_hostname }}.company.internal
    options:
      cert_path: /etc/ssl/certs/{{ inventory_hostname }}.company.internal.crt
      key_path: /etc/ssl/private/{{ inventory_hostname }}.company.internal.key

test.yml:

- hosts: localhost
  gather_facts: false
  tasks:
    - debug:
        msg: "{{ lookup('template', 'test.j2') | from_yaml | to_json }}"

Result:

ok: [localhost] => {
    "msg": "{\"ip_access\": {\"IP_whitelist\": {\"192.168.99.19/32\": \"grafana/status (Provider)\"}}, \"vhosts\": {\"localhost.company.internal\": {\"add_lines_443\": [\"include IP_whitelist;\", \"set $prometheus http://prometheus:9090;\", \"location / { proxy_pass $prometheus; }\"], \"dns_names\": [\"localhost.company.internal\"], \"options\": {\"cert_path\": \"/etc/ssl/certs/localhost.company.internal.crt\", \"key_path\": \"/etc/ssl/private/localhost.company.internal.key\"}}}}"
}

Thank you. Very useful answer, indeed! – Lethargos Apr 06 '21 at 16:55 — Lethargos, Apr 06 '21 at 16:55

score 0 · Answer 2 · answered Apr 06 '21 at 14:07

0

I was able to solve it eventually by turning it into json as follows:

NGINX_VHOSTS_JSON: '{{ lookup("template", "rproxy/nginx_vhosts_prometheus_develop.j2") | to_json }}'

I didn't need to change anything else.

answered Apr 06 '21 at 14:07

Lethargos

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ansible - template json for environmental variable in docker container

2 Answers2