Ansible - creating a list of IPs and ports

Ansible tip - creating a list of IPs:Ports with Jinja2 loops

While working on setting up an ansible-playbook for a Kafka cluster, a few challenges came up. In this, setting up the zookeeper.connect value in the Kafka server configuration file: "/server.properties"

The line should look something like this:

zookeeper.connect=kafkaserver1:2181,kafkaserver2:2181,kafkaserver3:2181

jinja2 loop

The simple loop will look something like this:

{% for host in groups['kafkaservers'] %}
  {{ host }}:2181,
{% endfor %}

Thy issue here is that you will get redundant comma at the end of the line like so:

zookeeper.connect=kafkaserver1:2181,kafkaserver2:2181,kafkaserver3:2181,

In order to resolve this we will use if not loop.last

{% for host in groups['kafkaservers'] %}
  {{ host }}:2181
    {% if not loop.last %}
       ,
    {% endif %}
{% endfor %}

Ansible example task

- name: Set zookeeper.connect in server.properties
  lineinfile:
    path: "{{ kafka_server_config_file_path }}"
    regexp: "^zookeeper.connect"
    line: "zookeeper.connect={% for host in groups['kafkaservers'] %}{{ host }}:2181{% if not loop.last %},{% endif %}{% endfor %}"
  become: yes