Add apache connection tuning back to apache

This was missed in the migration.

Change-Id: I09ac1f117b62b659f93ce01b73a4270378d2e25d

playbooks/roles/etherpad/files/apache-connection-tuning

@@ -0,0 +1,39 @@
+# worker MPM
+# StartServers: initial number of server processes to start
+# MinSpareThreads: minimum number of worker threads which are kept spare
+# MaxSpareThreads: maximum number of worker threads which are kept spare
+# ThreadLimit: ThreadsPerChild can be changed to this maximum value during a
+#              graceful restart. ThreadLimit can only be changed by stopping
+#              and starting Apache.
+# ThreadsPerChild: constant number of worker threads in each server process
+# MaxClients: maximum number of simultaneous client connections
+# MaxRequestsPerChild: maximum number of requests a server process serves
+#
+# Etherpad Lite clients create a lot of connections. To be able to support
+# Several hundred concurrent users we need to make sure that we allow a few
+# thousand concurrent connections. This should be ok as typical etherpad use
+# involves a couple writers then a bunch of lurkers. The cost of lurkers
+# is basically the TCP connection as they don't create DB writes and so on.
+# In addition to allowing for connection growth, keep a healthy number of
+# spare threads around to better handle thundering herds of users (eg at the
+# start of summit sessions).
+<IfModule mpm_worker_module>
+    ServerLimit         128
+    StartServers          3
+    MinSpareThreads      96
+    MaxSpareThreads     192
+    ThreadLimit          64
+    ThreadsPerChild      32
+    MaxClients         4096
+    MaxRequestsPerChild   0
+</IfModule>
+<IfModule mpm_event_module>
+    ServerLimit         128
+    StartServers          3
+    MinSpareThreads      96
+    MaxSpareThreads     192
+    ThreadLimit          64
+    ThreadsPerChild      32
+    MaxClients         4096
+    MaxRequestsPerChild   0
+</IfModule>

playbooks/roles/etherpad/tasks/main.yaml

@@ -52,6 +52,15 @@
     - headers
     - proxy_wstunnel
 
+- name: Copy apache tuning
+  copy:
+    src: apache-connection-tuning
+    dest: /etc/apache2/conf-enabled/connection-tuning.conf
+    owner: root
+    group: root
+    mode: 0644
+  notify: etherpad Reload apache2
+
 - name: Copy apache config
   template:
     src: etherpad.vhost.j2