class 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
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.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 18 def initialize(db, opts = OPTS) super @available_connections = {} @connections_to_remove = [] @servers = opts.fetch(:servers_hash, Hash.new(:default)) if USE_WAITER @waiter = nil @waiters = {} end add_servers([:default]) add_servers(opts[:servers].keys) if opts[:servers] 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.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 36 def add_servers(servers) sync do servers.each do |server| unless @servers.has_key?(server) @servers[server] = server @available_connections[server] = [] @allocated[server] = {} @waiters[server] = ConditionVariable.new if USE_WAITER end end end 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.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 61 def all_connections t = Thread.current sync do @allocated.values.each do |threads| threads.each do |thread, conn| yield conn if t == thread end end @available_connections.values.each{|v| v.each{|c| yield c}} end 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.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 52 def allocated(server=:default) @allocated[server] 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.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 76 def available_connections(server=:default) @available_connections[server] 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.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 98 def disconnect(opts=OPTS) (opts[:server] ? Array(opts[:server]) : sync{@servers.keys}).each do |s| if conns = sync{disconnect_server_connections(s)} disconnect_connections(conns) end end end
# File lib/sequel/connection_pool/sharded_threaded.rb, line 106 def freeze @servers.freeze super 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.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 125 def hold(server=:default) server = pick_server(server) t = Thread.current if conn = owned_connection(t, server) return yield(conn) end begin conn = acquire(t, server) yield conn rescue Sequel::DatabaseDisconnectError, *@error_classes => e sync{@connections_to_remove << conn} if conn && disconnect_error?(e) raise ensure sync{release(t, conn, server)} if conn end end
# File lib/sequel/connection_pool/sharded_threaded.rb, line 171 def pool_type :sharded_threaded 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.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 146 def remove_servers(servers) conns = nil sync do raise(Sequel::Error, "cannot remove default server") if servers.include?(:default) servers.each do |server| if @servers.include?(server) conns = disconnect_server_connections(server) @waiters.delete(server) if USE_WAITER @available_connections.delete(server) @allocated.delete(server) @servers.delete(server) end end end if conns disconnect_connections(conns) end end
Return an array of symbols for servers in the connection pool.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 167 def servers sync{@servers.keys} 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.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 83 def size(server=:default) server = @servers[server] @allocated[server].length + @available_connections[server].length end
Private Instance Methods
Assigns a connection to the supplied thread for the given server, if one is available. The calling code should already have the mutex when calling this.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 180 def _acquire(thread, server) if conn = available(server) allocated(server)[thread] = conn end end
Assigns a connection to the supplied thread, if one is available. The calling code should NOT already have the mutex when calling this.
This should return a connection is one is available within the timeout, or nil if a connection could not be acquired within the timeout.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 193 def acquire(thread, server) sync do if conn = _acquire(thread, server) return conn end time = Time.now @waiters[server].wait(@mutex, @timeout) Thread.pass until conn = _acquire(thread, server) deadline ||= time + @timeout current_time = Time.now raise_pool_timeout(current_time - time, server) if current_time > deadline # :nocov: # It's difficult to get to this point, it can only happen if there is a race condition # where a connection cannot be acquired even after the thread is signalled by the condition # variable that a connection is ready. @waiters[server].wait(@mutex, deadline - current_time) Thread.pass # :nocov: end conn end end
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 240 def available(server) next_available(server) || make_new(server) end
Return a connection to the pool of available connections for the server, returns the connection. The calling code should already have the mutex before calling this.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 247 def checkin_connection(server, conn) available_connections(server) << conn if USE_WAITER @waiters[server].signal Thread.pass end conn end
Disconnect all given connections.
immediately, and schedules currently allocated connections for disconnection as soon as they are returned to the pool. The calling code should not have the mutex before calling this.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 274 def disconnect_connections(conns) conns.each{|conn| disconnect_connection(conn)} end
Clear the array of available connections for the server, returning an array of previous available connections that should be disconnected (or nil if none should be). Mark any allocated connections to be removed when they are checked back in. The calling code should already have the mutex before calling this.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 260 def disconnect_server_connections(server) @connections_to_remove.concat(allocated(server).values) if dis_conns = available_connections(server) conns = dis_conns.dup dis_conns.clear end conns end
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 281 def make_new(server) if (n = size(server)) >= @max_size allocated(server).to_a.each{|t, c| release(t, c, server) unless t.alive?} n = nil end default_make_new(server) if (n || size(server)) < @max_size end
Return the next available connection in the pool for the given server, or nil if there is not currently an available connection for the server. The calling code should already have the mutex before calling this.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 292 def next_available(server) case @connection_handling when :stack available_connections(server).pop else available_connections(server).shift end end
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 303 def owned_connection(thread, server) sync{@allocated[server][thread]} end
If the server given is in the hash, return it, otherwise, return the default server.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 308 def pick_server(server) sync{@servers[server]} end
Create the maximum number of connections to each server immediately.
# File lib/sequel/connection_pool/sharded_threaded.rb, line 313 def preconnect(concurrent = false) conn_servers = @servers.keys.map{|s| Array.new(max_size - size(s), s)}.flatten if concurrent conn_servers.map{|s| Thread.new{[s, make_new(s)]}}.map(&:join).each{|t| checkin_connection(*t.value)} else conn_servers.each{|s| checkin_connection(s, make_new(s))} end end
Raise a PoolTimeout error showing the current timeout, the elapsed time, the server the connection attempt was made to, and the database's name (if any).
# File lib/sequel/connection_pool/sharded_threaded.rb, line 325 def raise_pool_timeout(elapsed, server) name = db.opts[:name] raise ::Sequel::PoolTimeout, "timeout: #{@timeout}, elapsed: #{elapsed}, server: #{server}#{", database name: #{name}" if name}" end
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 334 def release(thread, conn, server) if @connections_to_remove.include?(conn) remove(thread, conn, server) else conn = allocated(server).delete(thread) if @connection_handling == :disconnect disconnect_connection(conn) else checkin_connection(server, conn) end end end
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 350 def remove(thread, conn, server) @connections_to_remove.delete(conn) allocated(server).delete(thread) if @servers.include?(server) disconnect_connection(conn) end