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.

@since 2.9.0

Attributes

generation[R]

@return [ Integer ] generation Generation of connections currently

being used by the queue.

@since 2.9.0 @api private

options[R]

@return [ Hash ] options The pool options.

Public Class Methods

new(server, options = {}) click to toggle source

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.

@since 2.0.0, API changed in 2.9.0

# File lib/mongo/server/connection_pool.rb, line 63
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

  # 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

  finalizer = proc do
    available_connections.each do |connection|
      connection.disconnect!(reason: :pool_closed)
    end
    available_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
  ObjectSpace.define_finalizer(self, finalizer)

  publish_cmap_event(
    Monitoring::Event::Cmap::PoolCreated.new(@server.address, options)
  )
end

Public Instance Methods

available_count() click to toggle source

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 206
def available_count
  raise_if_closed!

  @lock.synchronize do
    @available_connections.length
  end
end
check_in(connection) click to toggle source

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 319
def check_in(connection)
  @lock.synchronize do
    unless @checked_out_connections.include?(connection)
      raise ArgumentError, "Trying to check in a connection which is not currently checked out by this pool: #{connection}"
    end

    @checked_out_connections.delete(connection)

    # 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.
    publish_cmap_event(
      Monitoring::Event::Cmap::ConnectionCheckedIn.new(@server.address, connection.id)
    )

    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.
    elsif connection.generation != @generation
      connection.disconnect!(reason: :stale)
    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
check_out() click to toggle source

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 [ 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 243
def check_out
  raise_if_closed!

  publish_cmap_event(
    Monitoring::Event::Cmap::ConnectionCheckOutStarted.new(@server.address)
  )

  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)
            next
          end

          if max_idle_time && connection.last_checkin &&
            Time.now - connection.last_checkin > max_idle_time
          then
            connection.disconnect!(reason: :idle)
            next
          end

          throw(:done)
        end

        # Ruby does not allow a thread to lock a mutex which it already
        # holds.
        if unsynchronized_size < max_size
          # This does not currently connect the socket and handshake,
          # but if it did, it would be performing i/o under our lock,
          # which is bad. Fix in the future.
          connection = create_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,
          ),
        )
        raise Error::ConnectionCheckOutTimeout.new(@server.address, wait_timeout)
      end
      @available_semaphore.wait(wait)
    end
  end

  @checked_out_connections << connection
  publish_cmap_event(
    Monitoring::Event::Cmap::ConnectionCheckedOut.new(@server.address, connection.id),
  )
  connection
end
clear(options = nil) click to toggle source

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.

@return [ true ] true.

@since 2.1.0

# File lib/mongo/server/connection_pool.rb, line 369
def clear(options = nil)
  raise_if_closed!

  @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)
      end
    end
  end

  true
end
Also aliased as: disconnect!
close(options = nil) click to toggle source

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 ] true.

@since 2.9.0

# File lib/mongo/server/connection_pool.rb, line 406
def close(options = nil)
  return if closed?

  @lock.synchronize do
    until @available_connections.empty?
      connection = @available_connections.pop
      connection.disconnect!(reason: :pool_closed)
    end

    if options && 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
  end

  @closed = true

  publish_cmap_event(
    Monitoring::Event::Cmap::PoolClosed.new(@server.address)
  )

  true
end
close_idle_sockets() click to toggle source

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 476
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)
          next
        end
      end
      i += 1
    end
  end
end
closed?() click to toggle source

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 219
def closed?
  !!@closed
end
disconnect!(options = nil)

@since 2.1.0 @deprecated

Alias for: clear
inspect() click to toggle source

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 441
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
max_idle_time() click to toggle source

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 166
def max_idle_time
  @max_idle_time ||= options[:max_idle_time]
end
max_size() click to toggle source

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 138
def max_size
  @max_size ||= options[:max_size] || [DEFAULT_MAX_SIZE, min_size].max
end
min_size() click to toggle source

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 147
def min_size
  @min_size ||= options[:min_size] || DEFAULT_MIN_SIZE
end
populate() click to toggle source

Creates up to the min size connections.

Used by the spec test runner.

@api private

# File lib/mongo/server/connection_pool.rb, line 501
def populate
  while size < min_size
    @available_connections << create_connection
  end
end
size() click to toggle source

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 184
def size
  raise_if_closed!

  @lock.synchronize do
    unsynchronized_size
  end
end
wait_timeout() click to toggle source

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 156
def wait_timeout
  @wait_timeout ||= options[:wait_timeout] || DEFAULT_WAIT_TIMEOUT
end
with_connection() { |connection| ... } click to toggle source

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 461
def with_connection
  raise_if_closed!

  connection = check_out
  yield(connection)
ensure
  if connection
    check_in(connection)
  end
end

Private Instance Methods

create_connection() click to toggle source
# File lib/mongo/server/connection_pool.rb, line 509
def create_connection
  connection = Connection.new(@server, options.merge(generation: generation))
  # CMAP spec requires connections to be returned from the pool
  # fully established.
  #connection.connect!
  connection
end
raise_if_closed!() click to toggle source

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 522
def raise_if_closed!
  if closed?
    raise Error::PoolClosedError.new(@server.address)
  end
end
unsynchronized_size() click to toggle source

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 196
def unsynchronized_size
  @available_connections.length + @checked_out_connections.size
end