For example, I want to find all nodes with a certain tag, grab their IP address, then generate a config file to distribute to those nodes.
A use case might be a database that needs to know about every other node, but can have nodes added and removed at any time.
You can use Salt Mine to do it. First, distribute this configuration to all the Minions:
mine_functions:
grains.item:
- roles
- fqdn_ip4
With that configuration, every Minion will publish those two grains to all other minions. More details about Mine here.
Now, we can create a file with all the names with role=db.
/tmp/mydbhosts:
file:
- managed
- source: salt://example/myhosts
- template: mako
The template example/myhosts:
% for minion, peer_grains in salt['mine.get']('*', 'grains.items').items():
% if "db" in peer_grains["role"]:
minion peer_grains["fqdn_ip4"]
% endif
% endfor
I have a hacky solution, so hopefully someone else can find a better answer.
The approach is to create a Python script that runs salt to grab the YAML output of network.ip_addrs eth0 then use that to call a particular sls with a pillar.
I made an example prototype which still needs to be implemented and tweaked:
#!/usr/bin/env python
import subprocess
import yaml
# Query all db nodes for their ip addresses
data = subprocess.check_output(
'salt -G "role:db" network.ip_addrs eth0',
shell=True
)
data = yaml.load(data)
# Parse and reshuffle for pillar input
addrs = []
for a in data.values():
addrs.append(a[0])
addrs = yaml.dump({'db_peers': addrs})
# Update configuration file on each node
data = subprocess.check_output(
'salt -G "role:db" state.sls db.configure pillar="{}"'.format(addrs),
shell=True
)
This will execute something along the lines of:
salt -G "role:db" state.sls db.configure pillar="db_peers: [1.2.3.4, 2.3.4.5]"
This could potentially be put into a module, but I'm not sure how to nicely ask salt-minion to communicate to the master to run db.configure on other nodes. I could simply execute the command similar to the script above.