Class Sequel::ShardedThreadedConnectionPool
In: lib/sequel/connection_pool/sharded_threaded.rb
Parent: Sequel::ThreadedConnectionPool

The slowest and most advanced connection, dealing with both multi-threaded access and configurations with multiple shards/servers.

In addition, this pool subclass also handles scheduling in-use connections to be removed from the pool when they are returned to it.

Methods

Public Class methods

The following additional options are respected:

  • :servers - A hash of servers to use. Keys should be symbols. If not present, will use a single :default server. The server name symbol will be passed to the connection_proc.

[Source]

    # File lib/sequel/connection_pool/sharded_threaded.rb, line 13
13:   def initialize(opts = {}, &block)
14:     super
15:     @available_connections = {}
16:     @connections_to_remove = []
17:     @servers = Hash.new(:default)
18:     add_servers([:default])
19:     add_servers(opts[:servers].keys) if opts[:servers]
20:   end

Public Instance methods

Adds new servers to the connection pool. Primarily used in conjunction with master/slave or shard configurations. Allows for dynamic expansion of the potential slaves/shards at runtime. servers argument should be an array of symbols.

[Source]

    # File lib/sequel/connection_pool/sharded_threaded.rb, line 25
25:   def add_servers(servers)
26:     sync do
27:       servers.each do |server|
28:         unless @servers.has_key?(server)
29:           @servers[server] = server
30:           @available_connections[server] = []
31:           @allocated[server] = {}
32:         end
33:       end
34:     end
35:   end

A hash of connections currently being used for the given server, key is the Thread, value is the connection. Nonexistent servers will return nil. Treat this as read only, do not modify the resulting object.

[Source]

    # File lib/sequel/connection_pool/sharded_threaded.rb, line 40
40:   def allocated(server=:default)
41:     @allocated[server]
42:   end

An array of connections opened but not currently used, for the given server. Nonexistent servers will return nil. Treat this as read only, do not modify the resulting object.

[Source]

    # File lib/sequel/connection_pool/sharded_threaded.rb, line 47
47:   def available_connections(server=:default)
48:     @available_connections[server]
49:   end

Removes all connections currently available on all servers, 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 connections are being used, they are scheduled to be disconnected as soon as they are returned to the pool.

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

  • :server - Should be a symbol specifing the server to disconnect from, or an array of symbols to specify multiple servers.

[Source]

    # File lib/sequel/connection_pool/sharded_threaded.rb, line 69
69:   def disconnect(opts={}, &block)
70:     block ||= @disconnection_proc
71:     sync do
72:       (opts[:server] ? Array(opts[:server]) : @servers.keys).each do |s|
73:         disconnect_server(s, &block)
74:       end
75:     end
76:   end

Chooses the first available connection to the given server, 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.

[Source]

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 92
 92:   def hold(server=:default)
 93:     sync{server = @servers[server]}
 94:     t = Thread.current
 95:     if conn = owned_connection(t, server)
 96:       return yield(conn)
 97:     end
 98:     begin
 99:       unless conn = acquire(t, server)
100:         time = Time.now
101:         timeout = time + @timeout
102:         sleep_time = @sleep_time
103:         sleep sleep_time
104:         until conn = acquire(t, server)
105:           raise(::Sequel::PoolTimeout) if Time.now > timeout
106:           sleep sleep_time
107:         end
108:       end
109:       yield conn
110:     rescue Sequel::DatabaseDisconnectError
111:       sync{@connections_to_remove << conn} if conn
112:       raise
113:     ensure
114:       sync{release(t, conn, server)} if conn
115:     end
116:   end

Remove servers from the connection pool. Primarily used in conjunction with master/slave or shard configurations. Similar to disconnecting from all given servers, except that after it is used, future requests for the server will use the :default server instead.

[Source]

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 122
122:   def remove_servers(servers)
123:     sync do
124:       raise(Sequel::Error, "cannot remove default server") if servers.include?(:default)
125:       servers.each do |server|
126:         if @servers.include?(server)
127:           disconnect_server(server, &@disconnection_proc)
128:           @available_connections.delete(server)
129:           @allocated.delete(server)
130:           @servers.delete(server)
131:         end
132:       end
133:     end
134:   end

Return an array of symbols for servers in the connection pool.

[Source]

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 137
137:   def servers
138:     sync{@servers.keys}
139:   end

The total number of connections opened for the given server, should be equal to available_connections.length + allocated.length. Nonexistent servers will return the created count of the default server.

[Source]

    # File lib/sequel/connection_pool/sharded_threaded.rb, line 54
54:   def size(server=:default)
55:     server = @servers[server]
56:     @allocated[server].length + @available_connections[server].length
57:   end

[Validate]