threadedPort

type:

queue(port, Sys.CongestionPolicy policy, int32 queueSize)

Where queueSize must be >= 1.

example:

config threadedPort : queue(P1, Sys.Wait, 10), queue(P2, Sys.DropFirst);

description:

Process tuples that arrive on each named input port in a separate thread, even if this operator is fused. That means that a fused upstream operator, instead of directly calling this port, merely deposits the tuple in a queue that is associated with the port. The queue keeps tuples in arrival order. A dedicated thread for this port then picks up the tuple from the queue when it is ready. That allows for more concurrent execution of operators, especially in the same partition. A maximum size for the queue can be specified. A congestion mode is also specified as part of a threaded port. There are three valid values for the congestion policy:

• Wait
• DropFirst
• DropLast

If Wait is specified, then any thread that deposits into a full queue blocks until there is free space in the queue. If DropLast is specified, then any thread that tries to deposit a tuple into a full queue instead drops that tuple. DropFirst is similar, but drops the oldest tuple in the queue when the queue is full.

Important: Punctuation is never dropped. Thus the blocking behavior can manifest even when DropLast or DropFirst policies are specified.

default:

If the config is omitted, then under fusion, tuples that arrive on this port directly trigger the process function of the operator in the caller's thread. If the config is present but the optional queue size is omitted, the compiler or the middleware decides the queue size.

where:

Any operator invocation of a non-composite operator.

For information about controlling the mechanism that is used when the threaded port is waiting on a full queue, see the --avoid-runtime-yield compiler option in the sc command.