Class: Sequel::ThreadedConnectionPool

Inherits:
ConnectionPool show all
Defined in:
lib/sequel/connection_pool/threaded.rb

Overview

A connection pool allowing multi-threaded access to a pool of connections. This is the default connection pool used by Sequel.

Direct Known Subclasses

ShardedThreadedConnectionPool

Constant Summary collapse

USE_WAITER =
RUBY_VERSION >= '1.9'

Constants inherited from ConnectionPool

ConnectionPool::CONNECTION_POOL_MAP, ConnectionPool::DEFAULT_SERVER, ConnectionPool::OPTS

Instance Attribute Summary collapse

Attributes inherited from ConnectionPool

#after_connect, #db

Instance Method Summary collapse

Methods inherited from ConnectionPool

#created_count, #servers

Methods included from ConnectionPool::ClassMethods

#get_pool

Constructor Details

#initialize(db, opts = OPTS) ⇒ ThreadedConnectionPool

The following additional options are respected:

  • :connection_handling - Set how to handle available connections. By default, uses a a queue for fairness. Can be set to :stack to use a stack, which may offer better performance.

  • :max_connections - The maximum number of connections the connection pool will open (default 4)

  • :pool_sleep_time - The amount of time to sleep before attempting to acquire a connection again, only used on ruby 1.8. (default 0.001)

  • :pool_timeout - The amount of seconds to wait to acquire a connection before raising a PoolTimeoutError (default 5)

Raises:


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# File 'lib/sequel/connection_pool/threaded.rb', line 32

def initialize(db, opts = OPTS)
  super
  @max_size = Integer(opts[:max_connections] || 4)
  raise(Sequel::Error, ':max_connections must be positive') if @max_size < 1
  @mutex = Mutex.new  
  @connection_handling = opts[:connection_handling]
  @available_connections = []
  @allocated = {}
  @timeout = Float(opts[:pool_timeout] || 5)

  if USE_WAITER
    @waiter = ConditionVariable.new
  else
    # :nocov:
    @sleep_time = Float(opts[:pool_sleep_time] || 0.001)
    # :nocov:
  end
end

Instance Attribute Details

#allocatedObject (readonly)

A hash with thread keys and connection values for currently allocated connections.


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# File 'lib/sequel/connection_pool/threaded.rb', line 20

def allocated
  @allocated
end

#available_connectionsObject (readonly)

An array of connections that are available for use by the pool.


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# File 'lib/sequel/connection_pool/threaded.rb', line 16

def available_connections
  @available_connections
end

#max_sizeObject (readonly)

The maximum number of connections this pool will create (per shard/server if sharding).


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# File 'lib/sequel/connection_pool/threaded.rb', line 13

def max_size
  @max_size
end

Instance Method Details

#all_connectionsObject

Yield all of the available connections, and the one currently allocated to this thread. This will not yield connections currently allocated to other threads, as it is not safe to operate on them. This holds the mutex while it is yielding all of the available connections, which means that until the method's block returns, the pool is locked.


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# File 'lib/sequel/connection_pool/threaded.rb', line 56

def all_connections
  hold do |c|
    sync do
      yield c
      @available_connections.each{|conn| yield conn}
    end
  end
end

#disconnect(opts = OPTS) ⇒ Object

Removes all connections currently available, optionally yielding each connection to the given block. This method has the effect of disconnecting from the database, assuming that no connections are currently being used. If you want to be able to disconnect connections that are currently in use, use the ShardedThreadedConnectionPool, which can do that. This connection pool does not, for performance reasons. To use the sharded pool, pass the :servers=>{} option when connecting to the database.

Once a connection is requested using #hold, the connection pool creates new connections to the database.


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# File 'lib/sequel/connection_pool/threaded.rb', line 75

def disconnect(opts=OPTS)
  sync do
    @available_connections.each{|conn| db.disconnect_connection(conn)}
    @available_connections.clear
  end
end

#hold(server = nil) ⇒ Object

Chooses the first available connection, or if none are available, creates a new connection. Passes the connection to the supplied block:

pool.hold {|conn| conn.execute('DROP TABLE posts')}

Pool#hold is re-entrant, meaning it can be called recursively in the same thread without blocking.

If no connection is immediately available and the pool is already using the maximum number of connections, Pool#hold will block until a connection is available or the timeout expires. If the timeout expires before a connection can be acquired, a Sequel::PoolTimeout is raised.


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# File 'lib/sequel/connection_pool/threaded.rb', line 96

def hold(server=nil)
  t = Thread.current
  if conn = owned_connection(t)
    return yield(conn)
  end
  begin
    conn = acquire(t)
    yield conn
  rescue Sequel::DatabaseDisconnectError
    oconn = conn
    conn = nil
    db.disconnect_connection(oconn) if oconn
    @allocated.delete(t)
    raise
  ensure
    sync{release(t)} if conn
  end
end

#pool_typeObject


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# File 'lib/sequel/connection_pool/threaded.rb', line 115

def pool_type
  :threaded
end

#sizeObject

The total number of connections opened, either available or allocated. This may not be completely accurate as it isn't protected by the mutex.


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# File 'lib/sequel/connection_pool/threaded.rb', line 121

def size
  @allocated.length + @available_connections.length
end