Fix inventory group etcd_cluster

[dtrdnk]

Add ability use specific IP. Fix inventory group etcd_cluster: use hostnames instead of ip-address #612

[vitabaks]

Thanks for this PR!

Could you help me understand a bit more about why you've classified this as a fix? This was not a mistake, the requirement to specify the IP address in the inventory was in all releases of this product.

It would be great if you could describe the details of what is offered in this PR.

Also, I'm curious about the decision to create a separate role. Could you share your thoughts on why this approach was chosen over defining variables in vars/main.yml?

[dtrdnk]

Could you help me understand a bit more about why you've classified this as a fix?

Because you use ip-address as hosts in inventory file in etcd_cluster group. Normally, records in group writes like a short hostname or FQDN. You are right, it is not a mistake, because ETCD config require IP-address instead hostname.
My PR allow use hostnames in etcd_cluster group, and get their ip via pg_cluster_default role.

It would be great if you could describe the details of what is offered in this PR.

I wrote some logic, which allow automatically generate variables and properties for configs. My solutions in this PR inspired by Kubespray role
Main goal of this approach - do not write few long vars/* files. Instead, you can write few roles and drop down the monolith approach. I think, kubespray and your role are similar, and there is good opportunity to reuse their practices.
My environment VM's have few ethernet interfaces (for local subnet and management). And currently there is no way, how to use normally hostnames in etcd_cluster and set the IP var with custom interface. My PR also add this ability.

Could you share your thoughts on why this approach was chosen over defining variables in vars/main.yml?

Yeah. I think, better use simple role, which prepare final variables, then write this logic in vars/ files

[vitabaks]

@dtrdnk Thanks for the answer!

I'll review the use of a role to define variables and assess whether it brings any advantages or conveniences. I'll get back to you with my thoughts soon. At first glance, it doesn't appear to be a conventional method for defining variables.

Could you consider this change in a broader context? Perhaps you'd be interested in helping to rethink the logic for all host groups, not just for etcd. As it stands, it seems like this might be only a partial solution.

In the Consul role, we use a different approach to define the listening IP address, not using the 'inventory_hostname' variable. Here are the relevant sections for reference:

• Consul defaults
• Consul config template

Here, the consul_bind_address variable defines the IP address for the interface specified in the consul_iface variable.
This is useful when there are several interfaces on the server, where one is private and the second is public, so we have the opportunity to explicitly specify a private network interface to avoid security risks.

I was thinking of implementing a similar approach for all host groups. What are your thoughts on this?

[vitabaks]

@ThomasSanson I would be grateful if you would take a look at this PR and take part in our discussion.

[dtrdnk]

Could you consider this change in a broader context?

Yeah. I offer two variants for using automatically generated variables:

• globally, if the variable will be used in two roles, as is the case with ETCD.
  The address is used both in the ETCD role itself and in Patroni. For global variant using pg_cluster_defaults role.
• locally in defaults/main.yml, if only automatically generated variables will be used in this role

I was thinking of implementing a similar approach for all host groups. What are your thoughts on this?

With Consul, you took approximately the same approach as I did with ETCD, but did not include the connecting address in the Patroni config. You can globally define the ip variable, and thereby automatically determine the interface on which the service will be launched. This is exactly the approach in the kubespray:

• https://github.com/kubernetes-sigs/kubespray/blob/v2.24.1/inventory/sample/inventory.ini#L1
• https://github.com/kubernetes-sigs/kubespray/blob/v2.24.1/roles/kubernetes/node/defaults/main.yml#L3

P.S
Please, try this Vagrantfile for my work tasks

• https://github.com/dtrdnk/vagrant-powerdns-patroni/tree/3d138cfd76b1c40b681cbce86c58c14460e87537

And after successfully running Vagrant, check the .vagrant/provisioners/ansible/inventory/vagrant_ansible_inventory.
You can see ip var in inventory, which will reused in postgresql_cluster role.

[vitabaks]

@dtrdnk What method do you think will be more convenient?

[dtrdnk]

Take both. As I say above, in roles without reusing vars between roles, just keep them in <role_name>/defaults/main.yml.
In roles with sharing vars, use specific default role

p.s thx for your response

[vitabaks]

@dtrdnk Could you close this PR and prepare a new one that would implement this functionality for all cluster components and not just etcd?

Important! It is necessary to leave backward compatibility so that if the ip variable is not defined, then use the inventory_hostname value as it currently works.