From e4018a00fdfb6b0586c42d4a25a005b5ca416173 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Rafael=20Mendon=C3=A7a=20Fran=C3=A7a?= Date: Thu, 20 Sep 2012 19:04:37 -0300 Subject: Revert "backport fair connection pool 02b2335563 to 3-2-stable" This reverts commit 0693e079708a52b777f2b7872b8e3d467b880a0d. Revert "Cache columns metadata to avoid extra while testing" This reverts commit a82f1e3f5d11c8dfba9f4c911745ec40a7965216. Reason: This is causing failures in the postgresql build. See http://travis-ci.org/#!/rails/rails/builds/2485584 Related with #7675 --- .../abstract/connection_pool.rb | 239 +++++---------------- 1 file changed, 49 insertions(+), 190 deletions(-) (limited to 'activerecord/lib') 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 235efc12f6..d4649102df 100644 --- a/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb +++ b/activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb @@ -57,141 +57,10 @@ 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 - - # Threadsafe, fair, FIFO queue. Meant to be used by ConnectionPool - # with which it shares a Monitor. But could be a generic Queue. - # - # The Queue in stdlib's 'thread' could replace this class except - # stdlib's doesn't support waiting with a timeout. - class Queue - def initialize(lock = Monitor.new) - @lock = lock - @cond = @lock.new_cond - @num_waiting = 0 - @queue = [] - end - - # Test if any threads are currently waiting on the queue. - def any_waiting? - synchronize do - @num_waiting > 0 - end - end - - # Return the number of threads currently waiting on this - # queue. - def num_waiting - synchronize do - @num_waiting - end - end - - # Add +element+ to the queue. Never blocks. - def add(element) - synchronize do - @queue.push element - @cond.signal - end - end - - # If +element+ is in the queue, remove and return it, or nil. - def delete(element) - synchronize do - @queue.delete(element) - end - end - - # Remove all elements from the queue. - def clear - synchronize do - @queue.clear - end - end - - # Remove the head of the queue. - # - # If +timeout+ is not given, remove and return the head the - # queue if the number of available elements is strictly - # greater than the number of threads currently waiting (that - # is, don't jump ahead in line). Otherwise, return nil. - # - # If +timeout+ is given, block if it there is no element - # available, waiting up to +timeout+ seconds for an element to - # become available. - # - # Raises: - # - ConnectionTimeoutError if +timeout+ is given and no element - # becomes available after +timeout+ seconds, - def poll(timeout = nil) - synchronize do - if timeout - no_wait_poll || wait_poll(timeout) - else - no_wait_poll - end - end - end - - private - - def synchronize(&block) - @lock.synchronize(&block) - end - - # Test if the queue currently contains any elements. - def any? - !@queue.empty? - end - - # A thread can remove an element from the queue without - # waiting if an only if the number of currently available - # connections is strictly greater than the number of waiting - # threads. - def can_remove_no_wait? - @queue.size > @num_waiting - end - - # Removes and returns the head of the queue if possible, or nil. - def remove - @queue.shift - end - - # Remove and return the head the queue if the number of - # available elements is strictly greater than the number of - # threads currently waiting. Otherwise, return nil. - def no_wait_poll - remove if can_remove_no_wait? - end - - # Waits on the queue up to +timeout+ seconds, then removes and - # returns the head of the queue. - def wait_poll(timeout) - @num_waiting += 1 - - t0 = Time.now - elapsed = 0 - loop do - @cond.wait(timeout - elapsed) - - return remove if any? - - elapsed = Time.now - t0 - - if elapsed >= timeout - msg = 'could not obtain a database connection within %0.3f seconds (waited %0.3f seconds)' % - [timeout, elapsed] - raise ConnectionTimeoutError, msg - end - end - ensure - @num_waiting -= 1 - end - end - include MonitorMixin attr_accessor :automatic_reconnect - attr_reader :spec, :connections, :size + attr_reader :spec, :connections # Creates a new ConnectionPool object. +spec+ is a ConnectionSpecification # object which describes database connection information (e.g. adapter, @@ -207,6 +76,7 @@ module ActiveRecord # The cache of reserved connections mapped to threads @reserved_connections = {} + @queue = new_cond @timeout = spec.config[:wait_timeout] || 5 # default max pool size to 5 @@ -214,16 +84,6 @@ module ActiveRecord @connections = [] @automatic_reconnect = true - - @available = Queue.new self - end - - # Hack for tests to be able to add connections. Do not call outside of tests - def insert_connection_for_test!(c) #:nodoc: - synchronize do - @connections << c - @available.add c - end end # Retrieve the connection associated with the current thread, or call @@ -279,7 +139,6 @@ module ActiveRecord conn.disconnect! end @connections = [] - @available.clear end end @@ -291,15 +150,9 @@ module ActiveRecord checkin conn conn.disconnect! if conn.requires_reloading? end - @connections.delete_if do |conn| conn.requires_reloading? end - @available.clear - @connections.each do |conn| - @available.add conn - end - end end @@ -363,22 +216,58 @@ connection. For example: ActiveRecord::Base.connection.close # 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 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. + # 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. # # Returns: an AbstractAdapter object. # # Raises: - # - PoolFullError: no connection can be obtained from the pool. + # - ConnectionTimeoutError: no connection can be obtained from the pool + # within the timeout period. def checkout synchronize do - conn = acquire_connection - conn.lease - checkout_and_verify(conn) + waited_time = 0 + + 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 + + if waited_time >= @timeout + raise ConnectionTimeoutError, "could not obtain a database connection#{" within #{@timeout} seconds" if @timeout} (waited #{waited_time} seconds). The max pool size is currently #{@size}; consider increasing it." + end + + # Sometimes our wait can end because a connection is available, + # but another thread can snatch it up first. If timeout hasn't + # passed but no connection is avail, looks like that happened -- + # loop and wait again, for the time remaining on our timeout. + before_wait = Time.now + @queue.wait( [@timeout - waited_time, 0].max ) + waited_time += (Time.now - before_wait) + + # Will go away in Rails 4, when we don't clean up + # after leaked connections automatically anymore. Right now, clean + # up after we've returned from a 'wait' if it looks like it's + # needed, then loop and try again. + if(active_connections.size >= @connections.size) + clear_stale_cached_connections! + end + end end end @@ -391,40 +280,10 @@ connection. For example: ActiveRecord::Base.connection.close synchronize do conn.run_callbacks :checkin do conn.expire + @queue.signal end release conn - - @available.add conn - end - end - - # Acquire a connection by one of 1) immediately removing one - # from the queue of available connections, 2) creating a new - # connection if the pool is not at capacity, 3) waiting on the - # queue for a connection to become available (first calling - # clear_stale_cached_connections! to clean up leaked connections, - # this cleanup will prob be going away in Rails4). - # - # Raises: - # - ConnectionTimeoutError if a connection could not be acquired - def acquire_connection - if conn = @available.poll - conn - elsif @connections.size < @size - checkout_new_connection - else - # this conditional clear_stale will go away in Rails 4, when we don't - # clean up after leaked connections automatically anymore. Right now, - # clean up after we've returned from a 'wait' if it looks like it's - # needed before trying to wait for a connection. - synchronize do - if(active_connections.size >= @connections.size) - clear_stale_cached_connections! - end - end - - @available.poll(@timeout) end end -- cgit v1.2.3