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Sequel::ThreadedConnectionPool

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

Attributes

max_size[R]

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

available_connections[R]

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

allocated[R]

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

Public Class Methods

new(opts = {}, &block) click to toggle source

The following additional options are respected:

  • :connection_handling - Set how to handle available connections. By default, uses a a stack for performance. Can be set to :queue to use a queue, which reduces the chances of connections becoming stale.

  • :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 (default 0.001)

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

    # File lib/sequel/connection_pool/threaded.rb, line 25
25:   def initialize(opts = {}, &block)
26:     super
27:     @max_size = Integer(opts[:max_connections] || 4)
28:     raise(Sequel::Error, ':max_connections must be positive') if @max_size < 1
29:     @mutex = Mutex.new  
30:     @queue = opts[:connection_handling] == :queue
31:     @available_connections = []
32:     @allocated = {}
33:     @timeout = Integer(opts[:pool_timeout] || 5)
34:     @sleep_time = Float(opts[:pool_sleep_time] || 0.001)
35:   end

Public Instance Methods

all_connections() click to toggle source

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.

    # File lib/sequel/connection_pool/threaded.rb, line 48
48:   def all_connections
49:     hold do |c|
50:       sync do
51:         yield c
52:         @available_connections.each{|c| yield c}
53:       end
54:     end
55:   end
disconnect(opts={}, &block) click to toggle source

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 #, the connection pool creates new connections to the database.

    # File lib/sequel/connection_pool/threaded.rb, line 67
67:   def disconnect(opts={}, &block)
68:     block ||= @disconnection_proc
69:     sync do
70:       @available_connections.each{|conn| block.call(conn)} if block
71:       @available_connections.clear
72:     end
73:   end
hold(server=nil) click to toggle source

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.

     # File lib/sequel/connection_pool/threaded.rb, line 89
 89:   def hold(server=nil)
 90:     t = Thread.current
 91:     if conn = owned_connection(t)
 92:       return yield(conn)
 93:     end
 94:     begin
 95:       unless conn = acquire(t)
 96:         time = Time.now
 97:         timeout = time + @timeout
 98:         sleep_time = @sleep_time
 99:         sleep sleep_time
100:         until conn = acquire(t)
101:           raise(::Sequel::PoolTimeout) if Time.now > timeout
102:           sleep sleep_time
103:         end
104:       end
105:       yield conn
106:     rescue Sequel::DatabaseDisconnectError
107:       oconn = conn
108:       conn = nil
109:       @disconnection_proc.call(oconn) if @disconnection_proc && oconn
110:       @allocated.delete(t)
111:       raise
112:     ensure
113:       sync{release(t)} if conn
114:     end
115:   end
size() click to toggle source

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

    # File lib/sequel/connection_pool/threaded.rb, line 39
39:   def size
40:     @allocated.length + @available_connections.length
41:   end

Private Instance Methods

acquire(thread) click to toggle source

Assigns a connection to the supplied thread, if one is available. The calling code should NOT already have the mutex when calling this.

     # File lib/sequel/connection_pool/threaded.rb, line 122
122:   def acquire(thread)
123:     sync do
124:       if conn = available
125:         @allocated[thread] = conn
126:       end
127:     end
128:   end
available() click to toggle source

Returns an available connection. If no connection is available, tries to create a new connection. The calling code should already have the mutex before calling this.

     # File lib/sequel/connection_pool/threaded.rb, line 133
133:   def available
134:     @available_connections.pop || make_new(DEFAULT_SERVER)
135:   end
default_make_new(server) click to toggle source

Alias the default make_new method, so subclasses can call it directly.

Alias for: make_new
make_new(server) click to toggle source

Creates a new connection to the given server if the size of the pool for the server is less than the maximum size of the pool. The calling code should already have the mutex before calling this.

     # File lib/sequel/connection_pool/threaded.rb, line 143
143:   def make_new(server)
144:     if (n = size) >= @max_size
145:       @allocated.keys.each{|t| release(t) unless t.alive?}
146:       n = nil
147:     end
148:     super if (n || size) < @max_size
149:   end
Also aliased as: default_make_new
owned_connection(thread) click to toggle source

Returns the connection owned by the supplied thread, if any. The calling code should NOT already have the mutex before calling this.

     # File lib/sequel/connection_pool/threaded.rb, line 153
153:   def owned_connection(thread)
154:     sync{@allocated[thread]}
155:   end
release(thread) click to toggle source

Releases the connection assigned to the supplied thread back to the pool. The calling code should already have the mutex before calling this.

     # File lib/sequel/connection_pool/threaded.rb, line 159
159:   def release(thread)
160:     if @queue
161:       @available_connections.unshift(@allocated.delete(thread))
162:     else
163:       @available_connections << @allocated.delete(thread)
164:     end
165:   end
sync() click to toggle source

Yield to the block while inside the mutex. The calling code should NOT already have the mutex before calling this.

     # File lib/sequel/connection_pool/threaded.rb, line 169
169:   def sync
170:     @mutex.synchronize{yield}
171:   end

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