A connection pool allowing multi-threaded access to a sharded pool of connections, using a timed queue (only available in Ruby 3.2+).
Methods
Public Class
Public Instance
Attributes
| max_size | [R] |
The maximum number of connections this pool will create per shard. |
Public Class methods
The following additional options are respected:
| :max_connections |
The maximum number of connections the connection pool will open (default 4) |
| :pool_timeout |
The amount of seconds to wait to acquire a connection before raising a PoolTimeout (default 5) |
| :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, |
# File lib/sequel/connection_pool/sharded_timed_queue.rb 24 def initialize(db, opts = OPTS) 25 super 26 27 @max_size = Integer(opts[:max_connections] || 4) 28 raise(Sequel::Error, ':max_connections must be positive') if @max_size < 1 29 @mutex = Mutex.new 30 @timeout = Float(opts[:pool_timeout] || 5) 31 32 @allocated = {} 33 @sizes = {} 34 @queues = {} 35 @servers = opts.fetch(:servers_hash, Hash.new(:default)) 36 37 add_servers([:default]) 38 add_servers(opts[:servers].keys) if opts[:servers] 39 end
Public Instance methods
Adds new servers to the connection pool. Allows for dynamic expansion of the potential replicas/shards at runtime. servers argument should be an array of symbols.
# File lib/sequel/connection_pool/sharded_timed_queue.rb 43 def add_servers(servers) 44 sync do 45 servers.each do |server| 46 next if @servers.has_key?(server) 47 48 @servers[server] = server 49 @sizes[server] = 0 50 @queues[server] = Queue.new 51 (@allocated[server] = {}).compare_by_identity 52 end 53 end 54 nil 55 end
Yield all of the available connections, and the one currently allocated to this thread (if one is allocated). This will not yield connections currently allocated to other threads, as it is not safe to operate on them.
# File lib/sequel/connection_pool/sharded_timed_queue.rb 60 def all_connections 61 thread = Sequel.current 62 sync{@queues.to_a}.each do |server, queue| 63 if conn = owned_connection(thread, server) 64 yield conn 65 end 66 67 # Use a hash to record all connections already seen. As soon as we 68 # come across a connection we've already seen, we stop the loop. 69 conns = {} 70 conns.compare_by_identity 71 while true 72 conn = nil 73 begin 74 break unless (conn = queue.pop(timeout: 0)) && !conns[conn] 75 conns[conn] = true 76 yield conn 77 ensure 78 queue.push(conn) if conn 79 end 80 end 81 end 82 83 nil 84 end
Removes all connections currently in the pool’s queue. This method has the effect of disconnecting from the database, assuming that no connections are currently being used.
Once a connection is requested using hold, the connection pool creates new connections to the database.
If the :server option is provided, it should be a symbol or array of symbols, and then the method will only disconnect connectsion from those specified shards.
# File lib/sequel/connection_pool/sharded_timed_queue.rb 95 def disconnect(opts=OPTS) 96 (opts[:server] ? Array(opts[:server]) : sync{@servers.keys}).each do |server| 97 raise Sequel::Error, "invalid server" unless queue = sync{@queues[server]} 98 while conn = queue.pop(timeout: 0) 99 disconnect_pool_connection(conn, server) 100 end 101 fill_queue(server) 102 end 103 nil 104 end
Chooses the first available connection for the given server, or if none are available, creates a new connection. Passes the connection to the supplied block:
pool.hold(:server1) {|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_timed_queue.rb 119 def hold(server=:default) 120 server = pick_server(server) 121 t = Sequel.current 122 if conn = owned_connection(t, server) 123 return yield(conn) 124 end 125 126 begin 127 conn = acquire(t, server) 128 yield conn 129 rescue Sequel::DatabaseDisconnectError, *@error_classes => e 130 if disconnect_error?(e) 131 oconn = conn 132 conn = nil 133 disconnect_pool_connection(oconn, server) if oconn 134 sync{@allocated[server].delete(t)} 135 fill_queue(server) 136 end 137 raise 138 ensure 139 release(t, conn, server) if conn 140 end 141 end
The number of threads waiting to check out a connection for the given server.
# File lib/sequel/connection_pool/sharded_timed_queue.rb 145 def num_waiting(server=:default) 146 @queues[pick_server(server)].num_waiting 147 end
# File lib/sequel/connection_pool/sharded_timed_queue.rb 196 def pool_type 197 :sharded_timed_queue 198 end
Remove servers from the connection pool. Similar to disconnecting from all given servers, except that after it is used, future requests for the servers will use the :default server instead.
Note that an error will be raised if there are any connections currently checked out for the given servers.
# File lib/sequel/connection_pool/sharded_timed_queue.rb 160 def remove_servers(servers) 161 conns = [] 162 raise(Sequel::Error, "cannot remove default server") if servers.include?(:default) 163 164 sync do 165 servers.each do |server| 166 next unless @servers.has_key?(server) 167 168 queue = @queues[server] 169 170 while conn = queue.pop(timeout: 0) 171 @sizes[server] -= 1 172 conns << conn 173 end 174 175 unless @sizes[server] == 0 176 raise Sequel::Error, "cannot remove server #{server} as it has allocated connections" 177 end 178 179 @servers.delete(server) 180 @sizes.delete(server) 181 @queues.delete(server) 182 @allocated.delete(server) 183 end 184 end 185 186 nil 187 ensure 188 disconnect_connections(conns) 189 end
Return an array of symbols for servers in the connection pool.
# File lib/sequel/connection_pool/sharded_timed_queue.rb 192 def servers 193 sync{@servers.keys} 194 end
The total number of connections in the pool. Using a non-existant server will return nil.
# File lib/sequel/connection_pool/sharded_timed_queue.rb 150 def size(server=:default) 151 sync{@sizes[server]} 152 end