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

add_servers all_connections allocated available_connections disconnect hold new remove_servers servers size

### Public Class methods

new(opts = {}, &block)

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

add_servers(servers)

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

all_connections() {|conn if t == thread| ...}

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

allocated(server=:default)

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

available_connections(server=:default)

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

disconnect(opts={}, &block)

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

hold(server=:default) {|conn| ...}

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(servers)

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

servers()

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

size(server=:default)

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]