Fetch list of hosts in cluster and do something with them

[Paul Slootman]

I've been wondering what the best way of accomplishing this is:

- We have a number of customers

- Each customer has one or more (Oracle Weblogic) clusters

- Each cluster has an Admin node

- I want to generate an (passphrase-less) ssh key for the "oracle" user on each Admin node

- The public key of the Admin node has to be installed on each node in the cluster so that the "oracle" user on the Admin node can reach each node non-interactively

I have a script that can be run on a host which prints out a list of hostnames in the cluster, iff the host is an Admin node:

 ---

 - hosts: APPS

  sudo: yes

  tasks:

  - name: get cluster host list

    script: /home/paul/ansible-cfg/etc/check-cluster.bash

    register: clusterdata

  - debug: var=clusterdata.stdout_lines

When run, I get the following output:

 TASK: [debug var=clusterdata.stdout_lines] ************************************ 

 ok: [user1.custabc.local] => {

    "clusterdata.stdout_lines": [

        "user1.custabc.local", 

        "user2.custabc.local", 

        "user3.custabc.local", 

        "user4.custabc.local" 

    ]

 }

 ok: [user2.custabc.local] => {

    "clusterdata.stdout_lines": []

 }

 ok: [user4.custabc.local] => {

    "clusterdata.stdout_lines": []

 }

 ok: [user3.custabc.local] => {

    "clusterdata.stdout_lines": []

 }

user1.custabc.local is the Admin node here, APPS is the group of application hosts (I limited the hosts to just one customer here).

Now I'd want to generate an ssh key on user1.custabc.local, and install the public key in authorized_keys on the other hosts (it's not a problem if it's also installed on user1.custabc.local as well.

I just have no idea how to realize this. At the moment the inventory only lists all the hosts, not what hosts are Admin nodes and what nodes belong together in a cluster. We're working on fixing our CMDB to include this data, but it's not yet available. I could of course use the script to fetch this info and then add that info to the inventory. Any tips on what would be the best way to store this info in the inventory? I'm not very at home with Ansible yet :-( so any tips gratefully accepted.

thanks,

Paul

[Brian Coca]

it seems you want something like:


- name: generate ssh key
...
when: clusterdata.stdout_lines

- name: install generated key
...
when: not clusterdata.stdout_lines


or you can check the length of clusterdata.stdout_lines, which seems
to be only populated on the admin node. I would still add it to your
inventory as it is easier to segregate by groups or a group/host var.

--
Brian Coca

[Paul Slootman]

Thanks, something like that might work for me, in combination with setting some local facts on the Admin server. I'll be trying a couple of things...

Am I right in assuming that the following:

  - name: create key for oracle

    user: name=oracle createhome=no generate_ssh_key=yes ssh_key_file=.ssh/id_oracle ssh_key_passphrase="" state=present

will not change anything for an existing oracle user, besides creating an ssh key if it doesn't yet exist?

Paul

[Brian Coca]

sounds right

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--
Brian Coca