class Sequel::ThreadedConnectionPool

  1. lib/sequel/connection_pool/threaded.rb
Superclass: ConnectionPool

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


USE_WAITER = true  


allocated [R]

A hash with thread keys and connection values for currently allocated connections. The calling code should already have the mutex before calling this.

available_connections [R]

An array of connections that are available for use by the pool. The calling code should already have the mutex before calling this.

max_size [R]

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

Public Class methods

new(db, opts = OPTS)

The following additional options are respected:


The maximum number of connections the connection pool will open (default 4)


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

[show source]
   # File lib/sequel/connection_pool/threaded.rb
26 def initialize(db, opts = OPTS)
27   super
28   @max_size = Integer(opts[:max_connections] || 4)
29   raise(Sequel::Error, ':max_connections must be positive') if @max_size < 1
30   @mutex =  
31   @connection_handling = opts[:connection_handling]
32   @available_connections = []
33   @allocated = {}
34   @timeout = Float(opts[:pool_timeout] || 5)
35   @waiter =
36 end

Public Instance methods


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.

[show source]
   # File lib/sequel/connection_pool/threaded.rb
43 def all_connections
44   hold do |c|
45     sync do
46       yield c
47       @available_connections.each{|conn| yield conn}
48     end
49   end
50 end

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.

[show source]
   # File lib/sequel/connection_pool/threaded.rb
62 def disconnect(opts=OPTS)
63   conns = nil
64   sync do
65     conns = @available_connections.dup
66     @available_connections.clear
67     @waiter.signal
68   end
69   conns.each{|conn| disconnect_connection(conn)}
70 end

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.

[show source]
    # File lib/sequel/connection_pool/threaded.rb
 85 def hold(server=nil)
 86   t = Sequel.current
 87   if conn = owned_connection(t)
 88     return yield(conn)
 89   end
 90   begin
 91     conn = acquire(t)
 92     yield conn
 93   rescue Sequel::DatabaseDisconnectError, *@error_classes => e
 94     if disconnect_error?(e)
 95       oconn = conn
 96       conn = nil
 97       disconnect_connection(oconn) if oconn
 98       sync do 
 99         @allocated.delete(t)
100         @waiter.signal
101       end
102     end
103     raise
104   ensure
105     if conn
106       sync{release(t)}
107       if @connection_handling == :disconnect
108         disconnect_connection(conn)
109       end
110     end
111   end
112 end
[show source]
    # File lib/sequel/connection_pool/threaded.rb
114 def pool_type
115   :threaded
116 end

The total number of connections opened, either available or allocated. The calling code should not have the mutex before calling this.

[show source]
    # File lib/sequel/connection_pool/threaded.rb
120 def size
121   @mutex.synchronize{_size}
122 end