Ansible and ControlMaster file naming

This is a short story of how Ansible and SSH (using the default ControlMaster path format) bite me.

Lets take this network layout for example, where we have the same IP behind different machines.

And we have this lines in our ssh config file,

Now the problem is that dc1-db and dc2-db share the same IP, and the master socket file which is created (based on the above placeholders %[email protected]%h:%p) will use the same file name, so if you try to connect to dc1-db right after you have connected to dc2-db, guess where you well end up ?

I only notice this after I saw my Ansible playbook is changing the same file over and over, the file was a simple yum repo definition, which should not change after the first setup, but this repo template had a ansible fact as place holder which was the distro version (rhel6/rhel7), and based on which connection was establish first (dc1-db vs dc2-db) this fact was set based on the first machine which was connected. So each run one of the machine will register a change.

After looking into ssh documentation I found out there are other place holders I can use. There is %C which didn’t help in my case, as it seem to generate the same string, but using %n did the trick as it used the connection name and not the Hostname name/ip for the socket file.

 

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