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Sequel::ShardedThreadedConnectionPool

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.

Public Class Methods

new(opts = {}, &block) click to toggle source

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.

    # 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

add_servers(servers) click to toggle source

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.

    # 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
all_connections() click to toggle source

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.

    # 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
allocated(server=:default) click to toggle source

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.

    # File lib/sequel/connection_pool/sharded_threaded.rb, line 44
44:   def allocated(server=:default)
45:     @allocated[server]
46:   end
available_connections(server=:default) click to toggle source

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.

    # File lib/sequel/connection_pool/sharded_threaded.rb, line 68
68:   def available_connections(server=:default)
69:     @available_connections[server]
70:   end
disconnect(opts={}, &block) click to toggle source

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 #, 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.

    # 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
hold(server=:default) click to toggle source

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.

     # 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(servers) click to toggle source

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.

     # 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
servers() click to toggle source

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

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 158
158:   def servers
159:     sync{@servers.keys}
160:   end
size(server=:default) click to toggle source

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.

    # 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

Private Instance Methods

acquire(thread, server) click to toggle source

Assigns a connection to the supplied thread for the given server, if one is available. The calling code should NOT already have the mutex when calling this.

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 167
167:   def acquire(thread, server)
168:     sync do
169:       if conn = available(server)
170:         allocated(server)[thread] = conn
171:       end
172:     end
173:   end
available(server) click to toggle source

Returns an available connection to the given server. If no connection is available, tries to create a new connection. The calling code should already have the mutex before calling this.

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 178
178:   def available(server)
179:     available_connections(server).pop || make_new(server)
180:   end
disconnect_server(server, &block) click to toggle source

Disconnect from the given server. Disconnects available connections immediately, and schedules currently allocated connections for disconnection as soon as they are returned to the pool. The calling code should already have the mutex before calling this.

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 186
186:   def disconnect_server(server, &block)
187:     if conns = available_connections(server)
188:       conns.each{|conn| block.call(conn)} if block
189:       conns.clear
190:     end
191:     @connections_to_remove.concat(allocated(server).values)
192:   end
make_new(server) click to toggle source

Creates a new connection to the given server if the size of the pool for the server is less than the maximum size of the pool. The calling code should already have the mutex before calling this.

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 197
197:   def make_new(server)
198:     if (n = size(server)) >= @max_size
199:       allocated(server).to_a.each{|t, c| release(t, c, server) unless t.alive?}
200:       n = nil
201:     end
202:     default_make_new(server) if (n || size(server)) < @max_size
203:   end
owned_connection(thread, server) click to toggle source

Returns the connection owned by the supplied thread for the given server, if any. The calling code should NOT already have the mutex before calling this.

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 207
207:   def owned_connection(thread, server)
208:     sync{@allocated[server][thread]}
209:   end
pick_server(server) click to toggle source

If the server given is in the hash, return it, otherwise, return the default server.

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 212
212:   def pick_server(server)
213:     sync{@servers[server]}
214:   end
release(thread, conn, server) click to toggle source

Releases the connection assigned to the supplied thread and server. If the server or connection given is scheduled for disconnection, remove the connection instead of releasing it back to the pool. The calling code should already have the mutex before calling this.

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 220
220:   def release(thread, conn, server)
221:     if @connections_to_remove.include?(conn)
222:       remove(thread, conn, server)
223:     else
224:       if @queue
225:         available_connections(server).unshift(allocated(server).delete(thread))
226:       else
227:         available_connections(server) << allocated(server).delete(thread)
228:       end
229:     end
230:   end
remove(thread, conn, server) click to toggle source

Removes the currently allocated connection from the connection pool. The calling code should already have the mutex before calling this.

     # File lib/sequel/connection_pool/sharded_threaded.rb, line 234
234:   def remove(thread, conn, server)
235:     @connections_to_remove.delete(conn)
236:     allocated(server).delete(thread) if @servers.include?(server)
237:     @disconnection_proc.call(conn) if @disconnection_proc
238:   end

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