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opening a connection will block if the pool is full

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1 parent 9a4bfd0 commit b8f748269584c1475f6e06aec48fce627f603880 @tenderlove tenderlove committed Apr 15, 2012
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59 activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb
@@ -2,6 +2,7 @@
require 'monitor'
require 'set'
require 'active_support/core_ext/module/deprecation'
+require 'timeout'
module ActiveRecord
# Raised when a connection could not be obtained within the connection
@@ -11,9 +12,6 @@ class ConnectionTimeoutError < ConnectionNotEstablished
# 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
@@ -94,6 +92,21 @@ def run
attr_accessor :automatic_reconnect, :timeout
attr_reader :spec, :connections, :size, :reaper
+ class Latch # :nodoc:
+ def initialize
+ @mutex = Mutex.new
+ @cond = ConditionVariable.new
+ end
+
+ def release
+ @mutex.synchronize { @cond.broadcast }
+ end
+
+ def await
+ @mutex.synchronize { @cond.wait @mutex }
+ end
+ end
+
# Creates a new ConnectionPool object. +spec+ is a ConnectionSpecification
# object which describes database connection information (e.g. adapter,
# host name, username, password, etc), as well as the maximum size for
@@ -115,6 +128,7 @@ def initialize(spec)
# default max pool size to 5
@size = (spec.config[:pool] && spec.config[:pool].to_i) || 5
+ @latch = Latch.new
@connections = []
@automatic_reconnect = true
end
@@ -139,8 +153,10 @@ def active_connection?
# #release_connection releases the connection-thread association
# and returns the connection to the pool.
def release_connection(with_id = current_connection_id)
- conn = @reserved_connections.delete(with_id)
- checkin conn if conn
+ synchronize do
+ conn = @reserved_connections.delete(with_id)
+ checkin conn if conn
+ end
end
# If a connection already exists yield it to the block. If no connection
@@ -205,23 +221,23 @@ def clear_stale_cached_connections! # :nodoc:
# Raises:
# - PoolFullError: no connection can be obtained from the pool.
def checkout
- # Checkout an available connection
- synchronize do
- # 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
+ loop do
+ # Checkout an available connection
+ synchronize do
+ # 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)
+ return checkout_and_verify(conn) if conn
end
+
+ Timeout.timeout(@timeout, PoolFullError) { @latch.await }
end
end
@@ -238,6 +254,7 @@ def checkin(conn)
release conn
end
+ @latch.release
end
# Remove a connection from the connection pool. The connection will
@@ -250,6 +267,7 @@ def remove(conn)
# from the reserved hash will be a little easier.
release conn
end
+ @latch.release
end
# Removes dead connections from the pool. A dead connection can occur
@@ -262,6 +280,7 @@ def reap
remove conn if conn.in_use? && stale > conn.last_use && !conn.active?
end
end
+ @latch.release
end
private
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24 activerecord/test/cases/connection_pool_test.rb
@@ -96,6 +96,30 @@ def test_full_pool_exception
end
end
+ def test_full_pool_blocks
+ cs = @pool.size.times.map { @pool.checkout }
+ t = Thread.new { @pool.checkout }
+
+ # make sure our thread is in the timeout section
+ Thread.pass until t.status == "sleep"
+
+ connection = cs.first
+ connection.close
+ assert_equal connection, t.join.value
+ end
+
+ def test_removing_releases_latch
+ cs = @pool.size.times.map { @pool.checkout }
+ t = Thread.new { @pool.checkout }
+
+ # make sure our thread is in the timeout section
+ Thread.pass until t.status == "sleep"
+
+ connection = cs.first
+ @pool.remove connection
+ assert_respond_to t.join.value, :execute
+ end
+
def test_reap_and_active
@pool.checkout
@pool.checkout

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