The enqueue . . . to statement

The enqueue...to statement sends an event to a context you identify.

The enqueue...to statement is superseded by the send...to statement. The enqueue...to statement will be deprecated in a future release. Use the send...to statement instead. See The send . . . to statement.

You must enqueue an expression of type event, and the destination must be one of the following:

context — The enqueue...to statement sends an event to the back of the input queue of the specified context. The expression is evaluated and the resulting event is sent to the input queue of only the specified context.

sequence<context> — The enqueue...to statement sends a copy of the event to the back of the input queue of each context in the specified sequence. The expression is evaluated and the resulting event is sent to the input queue of all the contexts in the sequence.

sequence <context> ctxs := [ c1, c2, c3 ];
Ping ping = Ping();
enqueue ping to ctxs;

You cannot enqueue an event to a com.apama.Channel object that contains a context. You cannot enqueue an event to a dictionary of contexts. However, it is a common pattern to enqueue to a sequence generated by dictionary.values(). For example:

If the target context's input queue is full the sending context blocks and waits for space on the queue unless doing so would cause a deadlock. See Deadlock avoidance when parallel processing.

Note that enqueued events are processed in the order they are enqueued. Enqueued events are put on the back of the input queue, behind any externally sourced events already queued.

You must create the context before you enqueue an event to the context. You cannot enqueue an event to a context that you have declared but not created. For example, the following code causes the correlator to terminate the monitor instance:

monitor m {
   context c;
   action onload()
   {
      enqueue A() to c;
   }
}

If you enqueue an event to a sequence of contexts and one of the contexts has not been created first then the correlator terminates the monitor instance. For details, see Sending an event to a particular context.

Enqueueing an event to a sequence of contexts is non-deterministic. For details, see Sending an event to a sequence of contexts.

The enqueue...to statement can operate on any values as well as events, provided that the any value is of a routable event type.

You cannot enqueue an event that has a field of type action, chunk, listener, or stream. There is a runtime check if the event (or one of its members) can contain an any field; an exception is thrown if the any field contains an object of type action, chunk, listener, or stream.