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.
  • :servers_hash - The base hash to use for the servers. By default, Sequel uses Hash.new(:default). You can use a hash with a default proc that raises an error if you want to catch all cases where a nonexistent server is used.

[Source]

    # File lib/sequel/connection_pool/sharded_threaded.rb, line 17
17:   def initialize(opts = {}, &block)
18:     super
19:     @available_connections = {}
20:     @connections_to_remove = []
21:     @servers = opts.fetch(:servers_hash, Hash.new(:default))
22:     add_servers([:default])
23:     add_servers(opts[:servers].keys) if opts[:servers]
24:   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 29
29:   def add_servers(servers)
30:     sync do
31:       servers.each do |server|
32:         unless @servers.has_key?(server)
33:           @servers[server] = server
34:           @available_connections[server] = []
35:           @allocated[server] = {}
36:         end
37:       end
38:     end
39:   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 44
44:   def allocated(server=:default)
45:     @allocated[server]
46:   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 51
51:   def available_connections(server=:default)
52:     @available_connections[server]
53:   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 73
73:   def disconnect(opts={}, &block)
74:     block ||= @disconnection_proc
75:     sync do
76:       (opts[:server] ? Array(opts[:server]) : @servers.keys).each do |s|
77:         disconnect_server(s, &block)
78:       end
79:     end
80:   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 96
 96:   def hold(server=:default)
 97:     sync{server = @servers[server]}
 98:     t = Thread.current
 99:     if conn = owned_connection(t, server)
100:       return yield(conn)
101:     end
102:     begin
103:       unless conn = acquire(t, server)
104:         time = Time.now
105:         timeout = time + @timeout
106:         sleep_time = @sleep_time
107:         sleep sleep_time
108:         until conn = acquire(t, server)
109:           raise(::Sequel::PoolTimeout) if Time.now > timeout
110:           sleep sleep_time
111:         end
112:       end
113:       yield conn
114:     rescue Sequel::DatabaseDisconnectError
115:       sync{@connections_to_remove << conn} if conn
116:       raise
117:     ensure
118:       sync{release(t, conn, server)} if conn
119:     end
120:   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 126
126:   def remove_servers(servers)
127:     sync do
128:       raise(Sequel::Error, "cannot remove default server") if servers.include?(:default)
129:       servers.each do |server|
130:         if @servers.include?(server)
131:           disconnect_server(server, &@disconnection_proc)
132:           @available_connections.delete(server)
133:           @allocated.delete(server)
134:           @servers.delete(server)
135:         end
136:       end
137:     end
138:   end

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

[Source]

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 141
141:   def servers
142:     sync{@servers.keys}
143:   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 58
58:   def size(server=:default)
59:     server = @servers[server]
60:     @allocated[server].length + @available_connections[server].length
61:   end

[Validate]