FEATURE: add connnection reaping based on maximum age

This feature ensures connections to the db are always attempted to be closed
after 600 seconds of idle time.

config/discourse_defaults.conf

@@ -123,6 +123,8 @@ new_version_emails = true
 connection_reaper_age = 30
 # run reap check every 30 seconds
 connection_reaper_interval = 30
+# also reap any connections older than this
+connection_reaper_max_age = 600
 
 # set to relative URL (for subdirectory hosting)
 # IMPORTANT: path must not include a trailing /

lib/discourse.rb

@@ -340,7 +340,7 @@ module Discourse
       while true
         begin
           sleep GlobalSetting.connection_reaper_interval
-          reap_connections(GlobalSetting.connection_reaper_age)
+          reap_connections(GlobalSetting.connection_reaper_age, GlobalSetting.connection_reaper_max_age)
         rescue => e
           Discourse.handle_exception(e, {message: "Error reaping connections"})
         end
@@ -348,12 +348,12 @@ module Discourse
     end
   end
 
-  def self.reap_connections(age)
+  def self.reap_connections(idle, max_age)
     pools = []
     ObjectSpace.each_object(ActiveRecord::ConnectionAdapters::ConnectionPool){|pool| pools << pool}
 
     pools.each do |pool|
-      pool.drain(age.seconds)
+      pool.drain(idle.seconds, max_age.seconds)
     end
   end
 

lib/freedom_patches/pool_drainer.rb

@@ -2,11 +2,12 @@
 if Rails.version >= "4.2.0"
   class ActiveRecord::ConnectionAdapters::AbstractAdapter
     module LastUseExtension
-      attr_reader :last_use
+      attr_reader :last_use, :first_use
 
       def initialize(connection, logger = nil, pool = nil)
         super
         @last_use = false
+        @first_use = Time.now
       end
 
       def lease
@@ -26,11 +27,11 @@ end
 class ActiveRecord::ConnectionAdapters::ConnectionPool
   # drain all idle connections
   # if idle_time is specified only connections idle for N seconds will be drained
-  def drain(idle_time=nil)
+  def drain(idle_time=nil, max_age=nil)
     synchronize do
       @available.clear
       @connections.delete_if do |conn|
-        try_drain?(conn, idle_time)
+        try_drain?(conn, idle_time, max_age)
       end
 
       @connections.each do |conn|
@@ -42,9 +43,9 @@ class ActiveRecord::ConnectionAdapters::ConnectionPool
 
   private
 
-  def try_drain?(conn, idle_time)
+  def try_drain?(conn, idle_time, max_age)
     if !conn.in_use?
-      if !idle_time || conn.last_use < idle_time.seconds.ago
+      if !idle_time || conn.last_use < idle_time.seconds.ago || (max_age && conn.first_use < max_age.seconds.ago)
         conn.disconnect!
         return true
       end