fb_networkd: setup a way to stop and start services around a networkd…

… change

Differential Revision: D54094219

fbshipit-source-id: 1f13316e4ba957309552a079a946f0da8bfbe046

cookbooks/fb_networkd/README.md

@@ -157,6 +157,15 @@ will result in:
 notifies :restart, 'service[some_service]'
 ```
 
+If you need to stop a service before a networkd change is made (and then start
+it against afterwards) you can use `node['fb_networkd']['stop_before']`.
+This is a list of resource names which will be issued a :stop before the
+networkd change is made, than a :start at the end of the run.
+
+```ruby
+node.default['fb_networkd']['stop_before'] << 'service[cool_service]'
+```
+
 ### When can Chef make network changes
 Network changes can be disruptive and have potential for major impact. To
 mitigate this, `node.interface_change_allowed?(interface)` from `fb_helpers`

cookbooks/fb_networkd/attributes/default.rb

@@ -31,4 +31,5 @@
   'links' => {},
   'devices' => {},
   'notify_resources' => {},
+  'stop_before' => [],
 }

cookbooks/fb_networkd/recipes/default.rb

@@ -25,7 +25,11 @@
 node.default['fb_systemd']['networkd']['enable'] = true
 
 fb_networkd 'manage configuration' do
+  # Trigger deferred actions (e.g. :restart)
   notifies :trigger, 'fb_networkd_notify[doit]'
+  # Trigger service stops (and starts) around networkd changes
+  notifies :stop, 'fb_networkd_notify[doit]', :before
+  notifies :start, 'fb_networkd_notify[doit]'
 end
 
 fb_networkd_notify 'doit' do

cookbooks/fb_networkd/resources/notify.rb

@@ -36,3 +36,39 @@
     end
   end
 end
+
+action :stop do
+  if Chef::VERSION.to_i >= 16
+    notify_group 'stop resources before networkd change' do # rubocop:disable Chef/Meta/Chef16
+      node['fb_networkd']['stop_before'].each do |r|
+        notifies :stop, r, :immediately
+      end
+      action :run
+    end
+  else
+    log 'stop resources before networkd change' do
+      node['fb_networkd']['stop_before'].each do |r|
+        notifies :stop, r, :immediately
+      end
+      action :write
+    end
+  end
+end
+
+action :start do
+  if Chef::VERSION.to_i >= 16
+    notify_group 'start resources after networkd change' do # rubocop:disable Chef/Meta/Chef16
+      node['fb_networkd']['stop_before'].each do |r|
+        notifies :start, r
+      end
+      action :run
+    end
+  else
+    log 'start resources after networkd change' do
+      node['fb_networkd']['stop_before'].each do |r|
+        notifies :start, r
+      end
+      action :write
+    end
+  end
+end