Limit linaro mirror Apache cache size

The linaro mirror node only has a 100GB cache volume to be shared
between OpenAFS and Apache. Each cache gets a ~50GB filesystem dedicated
to it. Unfortunately we were telling Apache's cache pruning system to
limit to 60000M which is large than 50GB. THis resulted in the cache
filling up and I think it may also be the source of errors.

Address this my reconfiguring htcacheclean to limit to ~40GB. This limit
is set with some buffer space as htcacheclean runs periodically and has
to keep things low enough to avoid filling up.

Change-Id: I7af3daa396b1631feefed5952460b8a9710b25b5

inventory/service/host_vars/mirror01.regionone.linaro.opendev.org.yaml

@@ -6,3 +6,6 @@ letsencrypt_certs:
 # Allocated 100GB volume for this mirror, so openafs cache has to be <
 # 95%; we go for 45gb
 afs_client_cache_size: '45000000'
+# Simiarly we need to limit the size of the apache mirror to < 50GB
+# and the default is 60000M.
+mirror_apache_cache_limit: '40000M'

playbooks/roles/mirror/defaults/main.yaml

@@ -1,3 +1,4 @@
 mirror_root: '/afs/openstack.org/mirror'
 www_base: '/var/www'
-www_root: '{{ www_base }}/mirror'
+www_root: '{{ www_base }}/mirror'
+mirror_apache_cache_limit: '60000M'

playbooks/roles/mirror/tasks/main.yaml

@@ -168,6 +168,6 @@
   cron:
     name: Apache cache cleanup
     state: present
-    job: /usr/bin/flock -n /var/run/htcacheclean.lock /usr/bin/htcacheclean -n -p /var/cache/apache2/proxy -t -l 60000M > /dev/null
+    job: /usr/bin/flock -n /var/run/htcacheclean.lock /usr/bin/htcacheclean -n -p /var/cache/apache2/proxy -t -l {{ mirror_apache_cache_limit }} > /dev/null
     minute: '0'
     hour: '*'