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.

Constants

USE_WAITER = true  

Attributes

allocated [R]

A hash with thread/fiber 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:

:max_connections

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

:pool_timeout

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

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

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
46 def all_connections
47   hold do |c|
48     sync do
49       yield c
50       @available_connections.each{|conn| yield conn}
51     end
52   end
53 end
disconnect(opts=OPTS)

Removes all connections currently available. 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
64 def disconnect(opts=OPTS)
65   conns = nil
66   sync do
67     conns = @available_connections.dup
68     @available_connections.clear
69     @waiter.signal
70   end
71   conns.each{|conn| disconnect_connection(conn)}
72 end
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
 87 def hold(server=nil)
 88   t = Sequel.current
 89   if conn = owned_connection(t)
 90     return yield(conn)
 91   end
 92   begin
 93     conn = acquire(t)
 94     yield conn
 95   rescue Sequel::DatabaseDisconnectError, *@error_classes => e
 96     if disconnect_error?(e)
 97       oconn = conn
 98       conn = nil
 99       disconnect_connection(oconn) if oconn
100       sync do 
101         @allocated.delete(t)
102         @waiter.signal
103       end
104     end
105     raise
106   ensure
107     if conn
108       sync{release(t)}
109       if @connection_handling == :disconnect
110         disconnect_connection(conn)
111       end
112     end
113   end
114 end
pool_type()
[show source] 
    # File lib/sequel/connection_pool/threaded.rb
116 def pool_type
117   :threaded
118 end
size()

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
122 def size
123   @mutex.synchronize{_size}
124 end