Make the renable optional

Differential Revision: D55366233

fbshipit-source-id: 450a2f6a8285133f5b55064ef4670bd7dd22af72

cookbooks/fb_dnf/README.md

@@ -57,6 +57,11 @@ depending how one wants to use dnf. Set
 `node['fb_dnf']['disable_makecache_timer']` API to `true` to stop this periodic
 refresh of the dnf metadata cache.
 
+To rollback / renable *dnf-makecahce.timer* you also need a second API boolean set:
+- `node['fb_dnf']['enable_makecache_timer']` (set to `true`)
+This is to protect use cases where *dnf-mcachecache.timer* is being disabled/stopped
+another way.
+
 ### Modularity support
 DNF supports modules which may need to be enabled, disabled, or default. You
 can use `node['fb_dnf']['modules']` to configure modules. Do this via:

cookbooks/fb_dnf/attributes/default.rb

@@ -26,6 +26,7 @@
       'skip_if_unavailable' => node.centos? ? false : true,
     },
   },
+  'enable_makecache_timer' => false,
   'disable_makecache_timer' => false,
   'manage_packages' => true,
   'modules' => {},

cookbooks/fb_dnf/recipes/makecache.rb

@@ -5,14 +5,22 @@
 
 MAKECACHE_SYSTEMD_UNIT_NAME = 'dnf-makecache.timer'.freeze
 
+if node['fb_dnf']['disable_makecache_timer'] && node['fb_dnf']['enable_makecache_timer']
+  Chef::Log.error(
+    '[fb_dnf] Something has set BOTH disable + enable makecache timer - Nothing will happen!',
+  )
+end
+
 # If API is set to true, stop + disable the timer
 systemd_unit MAKECACHE_SYSTEMD_UNIT_NAME do
   only_if { node['fb_dnf']['disable_makecache_timer'] }
+  not_if { node['fb_dnf']['enable_makecache_timer'] }
   action [:stop, :disable]
 end
 
 # If API is set to false, start + enable the timer
 systemd_unit MAKECACHE_SYSTEMD_UNIT_NAME do
+  only_if { node['fb_dnf']['enable_makecache_timer'] }
   not_if { node['fb_dnf']['disable_makecache_timer'] }
   action [:start, :enable]
 end