1 files changed, 85 insertions, 55 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
index ea738cb305..b8f99adc22 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -9,6 +9,13 @@ module ActiveRecord
   class ConnectionTimeoutError < ConnectionNotEstablished
   end
 
+  # Raised when a connection pool is full and another connection is requested
+  class PoolFullError < ConnectionNotEstablished
+    def initialize size, timeout
+      super("Connection pool of size #{size} and timeout #{timeout}s is full")
+    end
+  end
+
   module ConnectionAdapters
     # Connection pool base class for managing Active Record database
     # connections.
@@ -57,10 +64,35 @@ module ActiveRecord
     # * +wait_timeout+: number of seconds to block and wait for a connection
     #   before giving up and raising a timeout error (default 5 seconds).
     class ConnectionPool
+      # Every +frequency+ seconds, the reaper will call +reap+ on +pool+.
+      # A reaper instantiated with a nil frequency will never reap the
+      # connection pool.
+      #
+      # Configure the frequency by setting "reaping_frequency" in your
+      # database yaml file.
+      class Reaper
+        attr_reader :pool, :frequency
+
+        def initialize(pool, frequency)
+          @pool      = pool
+          @frequency = frequency
+        end
+
+        def run
+          return unless frequency
+          Thread.new(frequency, pool) { |t, p|
+            while true
+              sleep t
+              p.reap
+            end
+          }
+        end
+      end
+
       include MonitorMixin
 
-      attr_accessor :automatic_reconnect
-      attr_reader :spec, :connections
+      attr_accessor :automatic_reconnect, :timeout
+      attr_reader :spec, :connections, :size, :reaper
 
       # Creates a new ConnectionPool object. +spec+ is a ConnectionSpecification
       # object which describes database connection information (e.g. adapter,
@@ -76,8 +108,9 @@ module ActiveRecord
         # The cache of reserved connections mapped to threads
         @reserved_connections = {}
 
-        @queue = new_cond
         @timeout = spec.config[:wait_timeout] || 5
+        @reaper  = Reaper.new self, spec.config[:reaping_frequency]
+        @reaper.run
 
         # default max pool size to 5
         @size = (spec.config[:pool] && spec.config[:pool].to_i) || 5
@@ -155,76 +188,47 @@ module ActiveRecord
       # associated with stale threads.
       def verify_active_connections! #:nodoc:
         synchronize do
-          clear_stale_cached_connections!
           @connections.each do |connection|
             connection.verify!
           end
         end
       end
 
-      # Return any checked-out connections back to the pool by threads that
-      # are no longer alive.
-      def clear_stale_cached_connections!
-        keys = @reserved_connections.keys - Thread.list.find_all { |t|
-          t.alive?
-        }.map { |thread| thread.object_id }
-        keys.each do |key|
-          conn = @reserved_connections[key]
-          ActiveSupport::Deprecation.warn(<<-eowarn) if conn.in_use?
-Database connections will not be closed automatically, please close your
-database connection at the end of the thread by calling `close` on your
-connection.  For example: ActiveRecord::Base.connection.close
-          eowarn
-          checkin conn
-          @reserved_connections.delete(key)
-        end
+      def clear_stale_cached_connections! # :nodoc:
       end
+      deprecate :clear_stale_cached_connections!
 
       # Check-out a database connection from the pool, indicating that you want
       # to use it. You should call #checkin when you no longer need this.
       #
-      # This is done by either returning an existing connection, or by creating
-      # a new connection. If the maximum number of connections for this pool has
-      # already been reached, but the pool is empty (i.e. they're all being used),
-      # then this method will wait until a thread has checked in a connection.
-      # The wait time is bounded however: if no connection can be checked out
-      # within the timeout specified for this pool, then a ConnectionTimeoutError
-      # exception will be raised.
+      # This is done by either returning and leasing existing connection, or by
+      # creating a new connection and leasing it.
+      #
+      # If all connections are leased and the pool is at capacity (meaning the
+      # number of currently leased connections is greater than or equal to the
+      # size limit set), an ActiveRecord::PoolFullError exception will be raised.
       #
       # Returns: an AbstractAdapter object.
       #
       # Raises:
-      # - ConnectionTimeoutError: no connection can be obtained from the pool
-      #   within the timeout period.
+      # - PoolFullError: no connection can be obtained from the pool.
       def checkout
         # Checkout an available connection
         synchronize do
-          loop do
-            conn = @connections.find { |c| c.lease }
-
-            unless conn
-              if @connections.size < @size
-                conn = checkout_new_connection
-                conn.lease
-              end
-            end
-
-            if conn
-              checkout_and_verify conn
-              return conn
-            end
-
-            @queue.wait(@timeout)
-
-            if(active_connections.size < @connections.size)
-              next
-            else
-              clear_stale_cached_connections!
-              if @size == active_connections.size
-                raise ConnectionTimeoutError, "could not obtain a database connection#{" within #{@timeout} seconds" if @timeout}. The max pool size is currently #{@size}; consider increasing it."
-              end
-            end
+          # Try to find a connection that hasn't been leased, and lease it
+          conn = connections.find { |c| c.lease }
+
+          # If all connections were leased, and we have room to expand,
+          # create a new connection and lease it.
+          if !conn && connections.size < size
+            conn = checkout_new_connection
+            conn.lease
+          end
 
+          if conn
+            checkout_and_verify conn
+          else
+            raise PoolFullError.new(size, timeout)
           end
         end
       end
@@ -238,7 +242,33 @@ connection.  For example: ActiveRecord::Base.connection.close
         synchronize do
           conn.run_callbacks :checkin do
             conn.expire
-            @queue.signal
+          end
+        end
+      end
+
+      # Remove a connection from the connection pool.  The connection will
+      # remain open and active but will no longer be managed by this pool.
+      def remove(conn)
+        synchronize do
+          @connections.delete conn
+
+          # FIXME: we might want to store the key on the connection so that removing
+          # from the reserved hash will be a little easier.
+          thread_id = @reserved_connections.keys.find { |k|
+            @reserved_connections[k] == conn
+          }
+          @reserved_connections.delete thread_id if thread_id
+        end
+      end
+
+      # Removes dead connections from the pool.  A dead connection can occur
+      # if a programmer forgets to close a connection at the end of a thread
+      # or a thread dies unexpectedly.
+      def reap
+        synchronize do
+          stale = Time.now - @timeout
+          connections.dup.each do |conn|
+            remove conn if conn.in_use? && stale > conn.last_use && !conn.active?
           end
         end
       end