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.
: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 18
18:   def initialize(db, opts = OPTS)
19:     super
20:     @available_connections = {}
21:     @connections_to_remove = []
22:     @servers = opts.fetch(:servers_hash, Hash.new(:default))
23: 
24:     if USE_WAITER
25:       @waiter = nil
26:       @waiters = {}
27:     end
28: 
29:     add_servers([:default])
30:     add_servers(opts[:servers].keys) if opts[:servers]
31:   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 36
36:   def add_servers(servers)
37:     sync do
38:       servers.each do |server|
39:         unless @servers.has_key?(server)
40:           @servers[server] = server
41:           @available_connections[server] = []
42:           @allocated[server] = {}
43:           @waiters[server] = ConditionVariable.new if USE_WAITER
44:         end
45:       end
46:     end
47:   end

Yield all of the available connections, and the ones 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 connections, which means that until the method‘s block returns, the pool is locked.

[Source]

    # File lib/sequel/connection_pool/sharded_threaded.rb, line 61
61:   def all_connections
62:     t = Thread.current
63:     sync do
64:       @allocated.values.each do |threads|
65:         threads.each do |thread, conn|
66:           yield conn if t == thread
67:         end
68:       end
69:       @available_connections.values.each{|v| v.each{|c| yield c}}
70:     end
71:   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 52
52:   def allocated(server=:default)
53:     @allocated[server]
54:   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 76
76:   def available_connections(server=:default)
77:     @available_connections[server]
78:   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 98
 98:   def disconnect(opts=OPTS)
 99:     (opts[:server] ? Array(opts[:server]) : sync{@servers.keys}).each do |s|
100:       if conns = sync{disconnect_server_connections(s)}
101:         disconnect_connections(conns)
102:       end
103:     end
104:   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 120
120:   def hold(server=:default)
121:     server = pick_server(server)
122:     t = Thread.current
123:     if conn = owned_connection(t, server)
124:       return yield(conn)
125:     end
126:     begin
127:       conn = acquire(t, server)
128:       yield conn
129:     rescue Sequel::DatabaseDisconnectError, *@error_classes => e
130:       sync{@connections_to_remove << conn} if conn && disconnect_error?(e)
131:       raise
132:     ensure
133:       sync{release(t, conn, server)} if conn
134:     end
135:   end

[Source]

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 166
166:   def pool_type
167:     :sharded_threaded
168:   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 141
141:   def remove_servers(servers)
142:     conns = nil
143:     sync do
144:       raise(Sequel::Error, "cannot remove default server") if servers.include?(:default)
145:       servers.each do |server|
146:         if @servers.include?(server)
147:           conns = disconnect_server_connections(server)
148:           @waiters.delete(server) if USE_WAITER
149:           @available_connections.delete(server)
150:           @allocated.delete(server)
151:           @servers.delete(server)
152:         end
153:       end
154:     end
155: 
156:     if conns
157:       disconnect_connections(conns)
158:     end
159:   end

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

[Source]

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 162
162:   def servers
163:     sync{@servers.keys}
164:   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 83
83:   def size(server=:default)
84:     server = @servers[server]
85:     @allocated[server].length + @available_connections[server].length
86:   end

[Validate]