class Mongo::Server::ConnectionPool
Represents a connection pool for server connections.
@since 2.0.0, largely rewritten in 2.9.0
Constants
- DEFAULT_MAX_SIZE
The default max size for the connection pool.
@since 2.9.0
- DEFAULT_MIN_SIZE
The default min size for the connection pool.
@since 2.9.0
- DEFAULT_WAIT_TIMEOUT
The default timeout, in seconds, to wait for a connection.
This timeout applies while in flow threads are waiting for background threads to establish connections (and hence they must connect, handshake and auth in the allotted time).
It is currently set to 10 seconds. The default connect timeout is 10 seconds by itself, but setting large timeouts can get applications in trouble if their requests get timed out by the reverse proxy, thus anything over 15 seconds is potentially dangerous.
@since 2.9.0
Attributes
@return [ Integer ] generation Generation of connections currently
being used by the queue.
@since 2.9.0 @api private
@return [ Hash ] options The pool options.
Condition variable broadcast when the size of the pool changes to wake up the populator
@api private
Public Class Methods
Finalize the connection pool for garbage collection.
@param [ List<Mongo::Connection> ] available_connections The available connections. @param [ List<Mongo::Connection> ] pending_connections The pending connections. @param [ Populator
] populator The populator.
@return [ Proc ] The Finalizer.
# File lib/mongo/server/connection_pool.rb, line 652 def self.finalize(available_connections, pending_connections, populator) proc do populator.stop! available_connections.each do |connection| connection.disconnect!(reason: :pool_closed) end available_connections.clear pending_connections.each do |connection| connection.disconnect!(reason: :pool_closed) end pending_connections.clear # Finalizer does not close checked out connections. # Those would have to be garbage collected on their own # and that should close them. end end
Create the new connection pool.
@param [ Server
] server The server which this connection pool is for. @param [ Hash ] options The connection pool options.
@option options [ Integer ] :max_size The maximum pool size. @option options [ Integer ] :max_pool_size Deprecated.
The maximum pool size. If max_size is also given, max_size and max_pool_size must be identical.
@option options [ Integer ] :min_size The minimum pool size. @option options [ Integer ] :min_pool_size Deprecated.
The minimum pool size. If min_size is also given, min_size and min_pool_size must be identical.
@option options [ Float ] :wait_timeout The time to wait, in
seconds, for a free connection.
@option options [ Float ] :wait_queue_timeout Deprecated.
Alias for :wait_timeout. If both wait_timeout and wait_queue_timeout are given, their values must be identical.
@option options [ Float ] :max_idle_time The time, in seconds,
after which idle connections should be closed by the pool.
Note: Additionally, options for connections created by this pool should
be included in the options passed here, and they will be forwarded to any connections created by the pool.
@since 2.0.0, API changed in 2.9.0
# File lib/mongo/server/connection_pool.rb, line 80 def initialize(server, options = {}) unless server.is_a?(Server) raise ArgumentError, 'First argument must be a Server instance' end options = options.dup if options[:min_size] && options[:min_pool_size] && options[:min_size] != options[:min_pool_size] raise ArgumentError, "Min size #{options[:min_size]} is not identical to min pool size #{options[:min_pool_size]}" end if options[:max_size] && options[:max_pool_size] && options[:max_size] != options[:max_pool_size] raise ArgumentError, "Max size #{options[:max_size]} is not identical to max pool size #{options[:max_pool_size]}" end if options[:wait_timeout] && options[:wait_queue_timeout] && options[:wait_timeout] != options[:wait_queue_timeout] raise ArgumentError, "Wait timeout #{options[:wait_timeout]} is not identical to wait queue timeout #{options[:wait_queue_timeout]}" end options[:min_size] ||= options[:min_pool_size] options.delete(:min_pool_size) options[:max_size] ||= options[:max_pool_size] options.delete(:max_pool_size) if options[:min_size] && options[:max_size] && options[:min_size] > options[:max_size] then raise ArgumentError, "Cannot have min size #{options[:min_size]} exceed max size #{options[:max_size]}" end if options[:wait_queue_timeout] options[:wait_timeout] ||= options[:wait_queue_timeout] end options.delete(:wait_queue_timeout) @server = server @options = options.freeze @generation = 1 @closed = false # A connection owned by this pool should be either in the # available connections array (which is used as a stack) # or in the checked out connections set. @available_connections = available_connections = [] @checked_out_connections = Set.new @pending_connections = Set.new # Mutex used for synchronizing access to @available_connections and # @checked_out_connections. The pool object is thread-safe, thus # all methods that retrieve or modify instance variables generally # must do so under this lock. @lock = Mutex.new # Condition variable broadcast when a connection is added to # @available_connections, to wake up any threads waiting for an # available connection when pool is at max size @available_semaphore = Semaphore.new # Background thread reponsible for maintaining the size of # the pool to at least min_size @populator = Populator.new(self, options) @populate_semaphore = Semaphore.new ObjectSpace.define_finalizer(self, self.class.finalize(@available_connections, @pending_connections, @populator)) publish_cmap_event( Monitoring::Event::Cmap::PoolCreated.new(@server.address, options, self) ) @populator.run! if min_size > 0 end
Public Instance Methods
Number of available connections in the pool.
@return [ Integer ] Number of available connections.
@since 2.9.0
# File lib/mongo/server/connection_pool.rb, line 225 def available_count raise_if_closed! @lock.synchronize do @available_connections.length end end
Check a connection back into the pool.
The connection must have been previously created by this pool.
@param [ Mongo::Server::Connection
] connection The connection.
@since 2.9.0
# File lib/mongo/server/connection_pool.rb, line 392 def check_in(connection) @lock.synchronize do unless connection.connection_pool == self raise ArgumentError, "Trying to check in a connection which was not checked out by this pool: #{connection} checked out from pool #{connection.connection_pool} (for #{self})" end unless @checked_out_connections.include?(connection) raise ArgumentError, "Trying to check in a connection which is not currently checked out by this pool: #{connection} (for #{self})" end # Note: if an event handler raises, resource will not be signaled. # This means threads waiting for a connection to free up when # the pool is at max size may time out. # Threads that begin waiting after this method completes (with # the exception) should be fine. @checked_out_connections.delete(connection) publish_cmap_event( Monitoring::Event::Cmap::ConnectionCheckedIn.new(@server.address, connection.id, self) ) if closed? connection.disconnect!(reason: :pool_closed) return end if connection.closed? # Connection was closed - for example, because it experienced # a network error. Nothing else needs to be done here. @populate_semaphore.signal elsif connection.generation != @generation connection.disconnect!(reason: :stale) @populate_semaphore.signal else connection.record_checkin! @available_connections << connection # Wake up only one thread waiting for an available connection, # since only one connection was checked in. @available_semaphore.signal end end end
Checks a connection out of the pool.
If there are active connections in the pool, the most recently used connection is returned. Otherwise if the connection pool size is less than the max size, creates a new connection and returns it. Otherwise waits up to the wait timeout and raises Timeout::Error if there are still no active connections and the pool is at max size.
The returned connection counts toward the pool's max size. When the caller is finished using the connection, the connection should be checked back in via the check_in
method.
@return [ Mongo::Server::Connection
] The checked out connection. @raise [ Error::PoolClosedError
] If the pool has been closed. @raise [ Timeout::Error ] If the connection pool is at maximum size
and remains so for longer than the wait timeout.
@since 2.9.0
# File lib/mongo/server/connection_pool.rb, line 277 def check_out publish_cmap_event( Monitoring::Event::Cmap::ConnectionCheckOutStarted.new(@server.address) ) if closed? publish_cmap_event( Monitoring::Event::Cmap::ConnectionCheckOutFailed.new( @server.address, Monitoring::Event::Cmap::ConnectionCheckOutFailed::POOL_CLOSED ), ) raise Error::PoolClosedError.new(@server.address, self) end deadline = Time.now + wait_timeout connection = nil # It seems that synchronize sets up its own loop, thus a simple break # is insufficient to break the outer loop catch(:done) do loop do # Lock must be taken on each iteration, rather for the method # overall, otherwise other threads will not be able to check in # a connection while this thread is waiting for one. @lock.synchronize do until @available_connections.empty? connection = @available_connections.pop if connection.generation != generation # Stale connections should be disconnected in the clear # method, but if any don't, check again here connection.disconnect!(reason: :stale) @populate_semaphore.signal next end if max_idle_time && connection.last_checkin && Time.now - connection.last_checkin > max_idle_time then connection.disconnect!(reason: :idle) @populate_semaphore.signal next end @pending_connections << connection throw(:done) end # Ruby does not allow a thread to lock a mutex which it already # holds. if unsynchronized_size < max_size connection = create_connection @pending_connections << connection throw(:done) end end wait = deadline - Time.now if wait <= 0 publish_cmap_event( Monitoring::Event::Cmap::ConnectionCheckOutFailed.new( @server.address, Monitoring::Event::Cmap::ConnectionCheckOutFailed::TIMEOUT, ), ) msg = @lock.synchronize do "Timed out attempting to check out a connection " + "from pool for #{@server.address} after #{wait_timeout} sec. " + "Connections in pool: #{@available_connections.length} available, " + "#{@checked_out_connections.length} checked out, " + "#{@pending_connections.length} pending" end raise Error::ConnectionCheckOutTimeout.new(msg, address: @server.address) end @available_semaphore.wait(wait) end end begin connect_connection(connection) rescue Exception # Handshake or authentication failed @lock.synchronize do @pending_connections.delete(connection) end @populate_semaphore.signal publish_cmap_event( Monitoring::Event::Cmap::ConnectionCheckOutFailed.new( @server.address, Monitoring::Event::Cmap::ConnectionCheckOutFailed::CONNECTION_ERROR ), ) raise end @lock.synchronize do @checked_out_connections << connection @pending_connections.delete(connection) end publish_cmap_event( Monitoring::Event::Cmap::ConnectionCheckedOut.new(@server.address, connection.id, self), ) connection end
Closes all idle connections in the pool and schedules currently checked out connections to be closed when they are checked back into the pool. The pool remains operational and can create new connections when requested.
@option options [ true | false ] :lazy If true, do not close any of
the idle connections and instead let them be closed during a subsequent check out operation.
@option options [ true | false ] :stop_populator Whether to stop
the populator background thread. For internal driver use only.
@return [ true ] true.
@since 2.1.0
# File lib/mongo/server/connection_pool.rb, line 450 def clear(options = nil) raise_if_closed! if options && options[:stop_populator] stop_populator end @lock.synchronize do @generation += 1 publish_cmap_event( Monitoring::Event::Cmap::PoolCleared.new(@server.address) ) unless options && options[:lazy] until @available_connections.empty? connection = @available_connections.pop connection.disconnect!(reason: :stale) @populate_semaphore.signal end end end true end
Marks the pool closed, closes all idle connections in the pool and schedules currently checked out connections to be closed when they are checked back into the pool. If force option is true, checked out connections are also closed. Attempts to use the pool after it is closed will raise Error::PoolClosedError
.
@option options [ true | false ] :force Also close all checked out
connections.
@return [ true ] Always true.
@since 2.9.0
# File lib/mongo/server/connection_pool.rb, line 492 def close(options = nil) return if closed? options ||= {} stop_populator @lock.synchronize do until @available_connections.empty? connection = @available_connections.pop connection.disconnect!(reason: :pool_closed) end if options[:force] until @checked_out_connections.empty? connection = @checked_out_connections.take(1).first connection.disconnect!(reason: :pool_closed) @checked_out_connections.delete(connection) end end # mark pool as closed before releasing lock so # no connections can be created, checked in, or checked out @closed = true end publish_cmap_event( Monitoring::Event::Cmap::PoolClosed.new(@server.address, self) ) true end
Close sockets that have been open for longer than the max idle time,
if the option is set.
@since 2.5.0
# File lib/mongo/server/connection_pool.rb, line 568 def close_idle_sockets return if closed? return unless max_idle_time @lock.synchronize do i = 0 while i < @available_connections.length connection = @available_connections[i] if last_checkin = connection.last_checkin if (Time.now - last_checkin) > max_idle_time connection.disconnect!(reason: :idle) @available_connections.delete_at(i) @populate_semaphore.signal next end end i += 1 end end end
Whether the pool has been closed.
@return [ true | false ] Whether the pool is closed.
@since 2.9.0
# File lib/mongo/server/connection_pool.rb, line 238 def closed? !!@closed end
Get a pretty printed string inspection for the pool.
@example Inspect the pool.
pool.inspect
@return [ String ] The pool inspection.
@since 2.0.0
# File lib/mongo/server/connection_pool.rb, line 533 def inspect if closed? "#<Mongo::Server::ConnectionPool:0x#{object_id} min_size=#{min_size} max_size=#{max_size} " + "wait_timeout=#{wait_timeout} closed>" else "#<Mongo::Server::ConnectionPool:0x#{object_id} min_size=#{min_size} max_size=#{max_size} " + "wait_timeout=#{wait_timeout} current_size=#{size} available=#{available_count}>" end end
The maximum seconds a socket can remain idle since it has been checked in to the pool, if set.
@return [ Float | nil ] The max socket idle time in seconds.
@since 2.9.0
# File lib/mongo/server/connection_pool.rb, line 185 def max_idle_time @max_idle_time ||= options[:max_idle_time] end
Get the maximum size of the connection pool.
@return [ Integer ] The maximum size of the connection pool.
@since 2.9.0
# File lib/mongo/server/connection_pool.rb, line 157 def max_size @max_size ||= options[:max_size] || [DEFAULT_MAX_SIZE, min_size].max end
Get the minimum size of the connection pool.
@return [ Integer ] The minimum size of the connection pool.
@since 2.9.0
# File lib/mongo/server/connection_pool.rb, line 166 def min_size @min_size ||= options[:min_size] || DEFAULT_MIN_SIZE end
Creates and adds a connection to the pool, if the pool's size is below min_size. Retries once if a socket-related error is encountered during this process and raises if a second error or a non socket-related error occurs.
Used by the pool populator background thread.
@return [ true | false ] Whether this method should be called again
to create more connections.
@raise [ Error::AuthError
, Error
] The second socket-related error raised if a retry occured, or the non socket-related error
@api private
# File lib/mongo/server/connection_pool.rb, line 626 def populate return false if closed? begin return create_and_add_connection rescue Error::SocketError, Error::SocketTimeoutError => e # an error was encountered while connecting the connection, # ignore this first error and try again. log_warn("Populator failed to connect a connection for #{address}: #{e.class}: #{e}. It will retry.") end return create_and_add_connection rescue Error::AuthError, Error # wake up one thread waiting for connections, since one could not # be created here, and can instead be created in flow @available_semaphore.signal raise end
Size of the connection pool.
Includes available and checked out connections.
@return [ Integer ] Size of the connection pool.
@since 2.9.0
# File lib/mongo/server/connection_pool.rb, line 203 def size raise_if_closed! @lock.synchronize do unsynchronized_size end end
Stop the background populator thread and clean up any connections created which have not been connected yet.
Used when closing the pool or when terminating the bg thread for testing purposes. In the latter case, this method must be called before the pool is used, to ensure no connections in pending_connections were created in-flow by the check_out
method.
@api private
# File lib/mongo/server/connection_pool.rb, line 598 def stop_populator @populator.stop! @lock.synchronize do # If stop_populator is called while populate is running, there may be # connections waiting to be connected, connections which have not yet # been moved to available_connections, or connections moved to available_connections # but not deleted from pending_connections. These should be cleaned up. until @pending_connections.empty? connection = @pending_connections.take(1).first connection.disconnect! @pending_connections.delete(connection) end end end
@note This method is experimental and subject to change.
@api experimental @since 2.11.0
# File lib/mongo/server/connection_pool.rb, line 246 def summary @lock.synchronize do "#<ConnectionPool size=#{unsynchronized_size} (#{min_size}-#{max_size}) " + "used=#{@checked_out_connections.length} avail=#{@available_connections.length} pending=#{@pending_connections.length}>" end end
The time to wait, in seconds, for a connection to become available.
@return [ Float ] The queue wait timeout.
@since 2.9.0
# File lib/mongo/server/connection_pool.rb, line 175 def wait_timeout @wait_timeout ||= options[:wait_timeout] || DEFAULT_WAIT_TIMEOUT end
Yield the block to a connection, while handling check in/check out logic.
@example Execute with a connection.
pool.with_connection do |connection| connection.read end
@return [ Object ] The result of the block.
@since 2.0.0
# File lib/mongo/server/connection_pool.rb, line 553 def with_connection raise_if_closed! connection = check_out yield(connection) ensure if connection check_in(connection) end end
Private Instance Methods
Attempts to connect (handshake and auth) the connection. If an error is encountered, closes the connection and raises the error.
# File lib/mongo/server/connection_pool.rb, line 729 def connect_connection(connection) begin connection.connect! rescue Exception connection.disconnect!(reason: :error) raise end end
Create a connection, connect it, and add it to the pool.
@return [ true | false ] True if a connection was created and
added to the pool, false otherwise
@raise [ Mongo::Error
] An error encountered during connection connect
# File lib/mongo/server/connection_pool.rb, line 684 def create_and_add_connection connection = nil @lock.synchronize do if !closed? && unsynchronized_size < min_size connection = create_connection @pending_connections << connection else return false end end begin connect_connection(connection) rescue Exception @lock.synchronize do @pending_connections.delete(connection) end raise end @lock.synchronize do @available_connections << connection @pending_connections.delete(connection) # wake up one thread waiting for connections, since one was created @available_semaphore.signal end true end
# File lib/mongo/server/connection_pool.rb, line 674 def create_connection connection = Connection.new(@server, options.merge(generation: generation, connection_pool: self)) end
Asserts that the pool has not been closed.
@raise [ Error::PoolClosedError
] If the pool has been closed.
@since 2.9.0
# File lib/mongo/server/connection_pool.rb, line 721 def raise_if_closed! if closed? raise Error::PoolClosedError.new(@server.address, self) end end
Returns the size of the connection pool without acquiring the lock. This method should only be used by other pool methods when they are already holding the lock as Ruby does not allow a thread holding a lock to acquire this lock again.
# File lib/mongo/server/connection_pool.rb, line 215 def unsynchronized_size @available_connections.length + @checked_out_connections.length + @pending_connections.length end