A connection pool allowing multi-threaded access to a pool of connections. This is the default connection pool used by Sequel.
The following additional options are respected:
:connection_handling - Set how to handle available connections. By default, uses a a stack for performance. Can be set to :queue to use a queue, which reduces the chances of connections becoming stale.
:max_connections - The maximum number of connections the connection pool will open (default 4)
:pool_sleep_time - The amount of time to sleep before attempting to acquire a connection again (default 0.001)
:pool_timeout - The amount of seconds to wait to acquire a connection before raising a PoolTimeoutError (default 5)
# File lib/sequel/connection_pool/threaded.rb, line 25 25: def initialize(opts = {}, &block) 26: super 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: @queue = opts[:connection_handling] == :queue 31: @available_connections = [] 32: @allocated = {} 33: @timeout = Integer(opts[:pool_timeout] || 5) 34: @sleep_time = Float(opts[:pool_sleep_time] || 0.001) 35: end
Yield all of the available connections, and the one 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 available connections, which means that until the method’s block returns, the pool is locked.
# File lib/sequel/connection_pool/threaded.rb, line 48 48: def all_connections 49: hold do |c| 50: sync do 51: yield c 52: @available_connections.each{|c| yield c} 53: end 54: end 55: end
Removes all connections currently available, 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 you want to be able to disconnect connections that are currently in use, use the ShardedThreadedConnectionPool, which can do that. This connection pool does not, for performance reasons. To use the sharded pool, pass the :servers=>{} option when connecting to the database.
Once a connection is requested using #, the connection pool creates new connections to the database.
# File lib/sequel/connection_pool/threaded.rb, line 67 67: def disconnect(opts={}, &block) 68: block ||= @disconnection_proc 69: sync do 70: @available_connections.each{|conn| block.call(conn)} if block 71: @available_connections.clear 72: end 73: end
Chooses the first available connection, 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/threaded.rb, line 89 89: def hold(server=nil) 90: t = Thread.current 91: if conn = owned_connection(t) 92: return yield(conn) 93: end 94: begin 95: unless conn = acquire(t) 96: time = Time.now 97: timeout = time + @timeout 98: sleep_time = @sleep_time 99: sleep sleep_time 100: until conn = acquire(t) 101: raise(::Sequel::PoolTimeout) if Time.now > timeout 102: sleep sleep_time 103: end 104: end 105: yield conn 106: rescue Sequel::DatabaseDisconnectError 107: oconn = conn 108: conn = nil 109: @disconnection_proc.call(oconn) if @disconnection_proc && oconn 110: @allocated.delete(t) 111: raise 112: ensure 113: sync{release(t)} if conn 114: end 115: end
The total number of connections opened, either available or allocated. This may not be completely accurate as it isn’t protected by the mutex.
# File lib/sequel/connection_pool/threaded.rb, line 39 39: def size 40: @allocated.length + @available_connections.length 41: end
Assigns a connection to the supplied thread, if one is available. The calling code should NOT already have the mutex when calling this.
# File lib/sequel/connection_pool/threaded.rb, line 122 122: def acquire(thread) 123: sync do 124: if conn = available 125: @allocated[thread] = conn 126: end 127: end 128: end
Returns an available connection. 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/threaded.rb, line 133 133: def available 134: @available_connections.pop || make_new(DEFAULT_SERVER) 135: end
Alias the default make_new method, so subclasses can call it directly.
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/threaded.rb, line 143 143: def make_new(server) 144: if (n = size) >= @max_size 145: @allocated.keys.each{|t| release(t) unless t.alive?} 146: n = nil 147: end 148: super if (n || size) < @max_size 149: end
Returns the connection owned by the supplied thread, if any. The calling code should NOT already have the mutex before calling this.
# File lib/sequel/connection_pool/threaded.rb, line 153 153: def owned_connection(thread) 154: sync{@allocated[thread]} 155: end
Releases the connection assigned to the supplied thread back to the pool. The calling code should already have the mutex before calling this.
# File lib/sequel/connection_pool/threaded.rb, line 159 159: def release(thread) 160: if @queue 161: @available_connections.unshift(@allocated.delete(thread)) 162: else 163: @available_connections << @allocated.delete(thread) 164: end 165: end
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