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:     @connections_to_disconnect = []
23:     @servers = opts.fetch(:servers_hash, Hash.new(:default))
24:     remove_instance_variable(:@waiter)
25:     @waiters = {}
26: 
27:     add_servers([:default])
28:     add_servers(opts[:servers].keys) if opts[:servers]
29:   end

Public Instance methods

Adds new servers to the connection pool. 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 33
33:   def add_servers(servers)
34:     sync do
35:       servers.each do |server|
36:         unless @servers.has_key?(server)
37:           @servers[server] = server
38:           @available_connections[server] = []
39:           @allocated[server] = {}
40:           @waiters[server] = ConditionVariable.new
41:         end
42:       end
43:     end
44:   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 58
58:   def all_connections
59:     t = Thread.current
60:     sync do
61:       @allocated.values.each do |threads|
62:         threads.each do |thread, conn|
63:           yield conn if t == thread
64:         end
65:       end
66:       @available_connections.values.each{|v| v.each{|c| yield c}}
67:     end
68:   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 49
49:   def allocated(server=:default)
50:     @allocated[server]
51:   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 73
73:   def available_connections(server=:default)
74:     @available_connections[server]
75:   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 94
 94:   def disconnect(opts=OPTS)
 95:     (opts[:server] ? Array(opts[:server]) : sync{@servers.keys}).each do |s|
 96:       if conns = sync{disconnect_server_connections(s)}
 97:         disconnect_connections(conns)
 98:       end
 99:     end
100:   end

[Source]

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 102
102:   def freeze
103:     @servers.freeze
104:     super
105:   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:       while dconn = sync{@connections_to_disconnect.shift}
135:         disconnect_connection(dconn)
136:       end
137:     end
138:   end

[Source]

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 168
168:   def pool_type
169:     :sharded_threaded
170:   end

Remove servers from the connection pool. 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 143
143:   def remove_servers(servers)
144:     conns = nil
145:     sync do
146:       raise(Sequel::Error, "cannot remove default server") if servers.include?(:default)
147:       servers.each do |server|
148:         if @servers.include?(server)
149:           conns = disconnect_server_connections(server)
150:           @waiters.delete(server)
151:           @available_connections.delete(server)
152:           @allocated.delete(server)
153:           @servers.delete(server)
154:         end
155:       end
156:     end
157: 
158:     if conns
159:       disconnect_connections(conns)
160:     end
161:   end

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

[Source]

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 164
164:   def servers
165:     sync{@servers.keys}
166:   end

The total number of connections opened for the given server. Nonexistent servers will return the created count of the default server. The calling code should not have the mutex before calling this.

[Source]

    # File lib/sequel/connection_pool/sharded_threaded.rb, line 80
80:   def size(server=:default)
81:     @mutex.synchronize{_size(server)}
82:   end

[Validate]