Sensu is monitoring services like Nagios and the things it should monitor
can be configured with JSON check definition files
<https://sensuapp.org/docs/1.1/guides/getting-started/intro-to-checks.html>.
A JSON check definition file can have one or more check definitions. Here
is a simplified example:
{
"checks": {
"cron": {
"command": "check-process.rb -p cron",
"interval": 60
}
}
}
Let's say I have defined the following template for generating check files:
{
"checks": {
{% for check_def in item.check_defs %}
"{{ check_def.name }}": {
"command": "{{ check_def.command }}",
"interval": {{ check_def.check_interval }}
}{{ ',' if not loop.last else '' }}
{% endfor %}
}
}
I apply this template a task like this:
- copy:
content: "{{ lookup('template', 'check_def.json.j2') | to_nice_json }}"
dest: "{{ somewhere }}"
with_items: "{{ check_sets }}"
notify: Restart Sensu
The check_sets variable is defined similar to:
vars:
services:
- foo
- bar
- baz
tasks:
set_fact:
check_defs: >
{{
check_defs|default([]) + [
{
'name' : 'my-check-def-for' + item.name,
'command' : 'check-process.rb',
'command_args' : '-p ' + item
}
]
}}
with_items: "{{ services }}"
I find this approach to defining check_defs to be ugly for several reasons:
1- It is not declarative (e.g. check_defs|default([]) as well as appending
items to the list are not declarative).
2- I don't like the string concat logic using + and using quotes around
hardcoded strings
3- For newcomers, it is not easy to understand what is going on
If I use a static list, I have to repeat some variables/values. For example:
check_defs:
- name: my-check-def-for-foo
command: check-process.rb
command_args: -p foo
Here foo is repeated twice.
Also users might diverge from the naming convention. For example by
providing:
check_defs:
- name: foo-check
command: check-process.rb
command_args: -p foo
Is there a more elegant way to declare the check_defs variable that doesn't
have any of these drawbacks?
Thanks in advance.
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