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.

available_connections [R]

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

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, line 24
def initialize(db, opts = OPTS)
  @max_size = Integer(opts[:max_connections] || 4)
  raise(Sequel::Error, ':max_connections must be positive') if @max_size < 1
  @mutex =  
  @connection_handling = opts[:connection_handling]
  @available_connections = []
  @allocated = {}
  @timeout = Float(opts[:pool_timeout] || 5)
  @waiter =

Public Instance methods

all_connections ()

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, line 41
def all_connections
  hold do |c|
    sync do
      yield c
      @available_connections.each{|conn| yield conn}
disconnect (opts=OPTS)

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, line 60
def disconnect(opts=OPTS)
  conns = nil
  sync do
    conns = @available_connections.dup
  conns.each{|conn| disconnect_connection(conn)}
hold (server=nil)

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, line 83
def hold(server=nil)
  t = Thread.current
  if conn = owned_connection(t)
    return yield(conn)
    conn = acquire(t)
    yield conn
  rescue Sequel::DatabaseDisconnectError, *@error_classes => e
    if disconnect_error?(e)
      oconn = conn
      conn = nil
      disconnect_connection(oconn) if oconn
      sync do 
    sync{release(t)} if conn
pool_type ()
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# File lib/sequel/connection_pool/threaded.rb, line 107
def pool_type
size ()

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

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# File lib/sequel/connection_pool/threaded.rb, line 113
def size