[feature] Added settings to configure data dir of InfluxDB

[cbeaujoin-stellar]

I reopened #31 here because it get close automatically when I tried to rebase.

# When "influxdb_data_dir" is set to a path different from the default
# (/var/lib/influxdb), InfluxDB will store its data in the specified directory.
influxdb_data_dir: "/opt/influxdb"

[nemesifier]

What is the rationale for adding this logic to the role itself?

You can already create an alternative data directory using pre_tasks and adjust the InfluxDB configuration with standard tasks or post_tasks in your own playbook.

The role does not overwrite custom InfluxDB settings, so this scenario can be supported without changes on this role.

For this reason, I’m not convinced we should include this feature in the role. It appears to address a system administration use case that is quite specific and not a general need for most OpenWISP users.

Keeping this customization outside the role helps avoid additional maintenance work for the core team but also allows you to change this code freely without waiting for our approval and add more logic if you need.

[cbeaujoin-stellar]

What is the rationale for adding this logic to the role itself?

You can already create an alternative data directory using pre_tasks and adjust the InfluxDB configuration with standard tasks or post_tasks in your own playbook.

The role does not overwrite custom InfluxDB settings, so this scenario can be supported without changes on this role.

For this reason, I’m not convinced we should include this feature in the role. It appears to address a system administration use case that is quite specific and not a general need for most OpenWISP users.

Keeping this customization outside the role helps avoid additional maintenance work for the core team but also allows you to change this code freely without waiting for our approval and add more logic if you need.

The only rational is about the way it is called in ansible-openwisp2:
https://github.com/openwisp/ansible-openwisp2/blob/master/meta/main.yml#L11

Do we want to add pre_tasks or post_tasks in the playbook running ansible-openwisp2 for underlying role that install and configure influxdb or should it be seamlessly integrated in ansible-openwisp2 role.

We have to trade off, but in the case we add it to the role, yes it implies maintenance, for most OpenWISP users the default has no impact, it would be more integrated with the ansible-openwisp2 role & playbook.