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

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 53
53:   def all_connections
54:     t = Thread.current
55:     sync do
56:       @allocated.values.each do |threads|
57:         threads.each do |thread, conn|
58:           yield conn if t == thread
59:         end
60:       end
61:       @available_connections.values.each{|v| v.each{|c| yield c}}
62:     end
63:   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 68
68:   def available_connections(server=:default)
69:     @available_connections[server]
70:   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 90
90:   def disconnect(opts={}, &block)
91:     block ||= @disconnection_proc
92:     sync do
93:       (opts[:server] ? Array(opts[:server]) : @servers.keys).each do |s|
94:         disconnect_server(s, &block)
95:       end
96:     end
97:   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 113
113:   def hold(server=:default)
114:     server = pick_server(server)
115:     t = Thread.current
116:     if conn = owned_connection(t, server)
117:       return yield(conn)
118:     end
119:     begin
120:       unless conn = acquire(t, server)
121:         time = Time.now
122:         timeout = time + @timeout
123:         sleep_time = @sleep_time
124:         sleep sleep_time
125:         until conn = acquire(t, server)
126:           raise(::Sequel::PoolTimeout) if Time.now > timeout
127:           sleep sleep_time
128:         end
129:       end
130:       yield conn
131:     rescue Sequel::DatabaseDisconnectError
132:       sync{@connections_to_remove << conn} if conn
133:       raise
134:     ensure
135:       sync{release(t, conn, server)} if conn
136:     end
137:   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 143
143:   def remove_servers(servers)
144:     sync do
145:       raise(Sequel::Error, "cannot remove default server") if servers.include?(:default)
146:       servers.each do |server|
147:         if @servers.include?(server)
148:           disconnect_server(server, &@disconnection_proc)
149:           @available_connections.delete(server)
150:           @allocated.delete(server)
151:           @servers.delete(server)
152:         end
153:       end
154:     end
155:   end

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

[Source]

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 158
158:   def servers
159:     sync{@servers.keys}
160:   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 75
75:   def size(server=:default)
76:     server = @servers[server]
77:     @allocated[server].length + @available_connections[server].length
78:   end

[Validate]