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jsonansibleinventoryvsphere

Custom dynamic inventory scripts/plugins in Ansible

Ansible allows devs to write programs (in any language) that will return JSON describing the dynamic “snapshot” of current hosts. I’m using vSphere, which is currently not supported by Ansible OSS, and so I need to write such a "custom inventory plugin".

I can handle the querying of vSphere for a list of hosts, as well as constructing the JSON that is compatible with what Ansible is expecting.

Where the documentation completely (seemingly) falls flat is:

  • How do I “connect” Ansible with my inventory app? That is, say my inventory app is a simple bash script (inventory.sh)..how do I configure Ansible to call bash inventory.sh and obtain JSON from it? In reality the app will likely be a Java executable (inventory.jar) but I figure that if I can figure out how to get it working with bash, I can extrapolate to Java; and
  • How does Ansible actually capture/fetch the JSON back from the app? STDOUT? Is this all supposed to happen over an HTTP connection? Examples? How does inventory.sh or inventory.jar communicate that JSON back to Ansible?
Solution

  • The inventory script has to be located on the same machine where Ansible runs. It is not communicating through http, Ansible will simply parse the STDOUT of your program. The location does not matter at all, you have to pass the path to Ansible when you call Ansible:

    ansible-playbook ... -i /path/to/your/inventory.sh

    To avoid passing the inventory location every time you could add this to you ansible.cfg:

    inventory = /path/to/your/inventory.sh

    You could also copy the script to /etc/ansible/hosts, which is the default location Ansible will look for inventory files/scripts, but I prefer to keep things together so I suggest to place it close to your playbooks/roles etc.

    And (3) Is any of this documented, anywhere? Don't see anything in the Ansible docs...

    It is not mentioned on the page Developing Dynamic Inventory Sources but it is to be seen on some examples on the page Dynamic Inventory. The docs are community managed and from times litte unstructured and lacking important information.

    BTW, there is a VMware inventory script included. By looking at the source I have seen it imports some vSphere stuff. I have little experience with VMware so I can't judge if this is actually what you need and don't need to write your own.