These activities enable asynchronous programming. send() broadcasts a
signal or a list of signals. Arrivals can subscribe to signals and (optionally)
assign a handler with trap(). Note that, while inside a batch, all the
signals subscribed before entering the batch are ignored. Upon a signal
reception, the arrival stops the current activity and executes the handler
(if provided). Then, the execution returns to the activity following the
point of the interruption. untrap() can be used to unsubscribe from
signals. wait() blocks until a signal is received.
Usage
send(.trj, signals, delay = 0, ..., tag)
trap(.trj, signals, handler = NULL, interruptible = TRUE, ..., tag)
untrap(.trj, signals, ..., tag)
wait(.trj, ..., tag)Arguments
- .trj
the trajectory object.
- signals
signal or list of signals, accepts either a string, a list of strings or a callable object (a function) which must return a string or a list of strings.
- delay
optional timeout to trigger the signals, accepts either a numeric or a callable object (a function) which must return a numeric.
- ...
unused.
- tag
activity tag name to perform named rollbacks (see
rollback) or just to better identify your activities.- handler
optional trajectory object to handle a signal received.
- interruptible
whether the handler can be interrupted by signals.
Examples
## block, signal and continue with a handler
signal <- "you shall pass"
t_blocked <- trajectory() %>%
trap(
signal,
trajectory() %>%
log_("executing the handler")) %>%
log_("waiting...") %>%
wait() %>%
log_("continuing!")
t_signaler <- trajectory() %>%
log_(signal) %>%
send(signal)
simmer() %>%
add_generator("blocked", t_blocked, at(0)) %>%
add_generator("signaler", t_signaler, at(5)) %>%
run() %>% invisible
#> 0: blocked0: waiting...
#> 5: signaler0: you shall pass
#> 5: blocked0: executing the handler
#> 5: blocked0: continuing!
## handlers can be interrupted, unless interruptible=FALSE
t_worker <- trajectory() %>%
trap(
signal,
handler = trajectory() %>%
log_("ok, I'm packing...") %>%
timeout(1)) %>%
log_("performing a looong task...") %>%
timeout(100) %>%
log_("and I'm leaving!")
simmer() %>%
add_generator("worker", t_worker, at(0)) %>%
add_generator("signaler", t_signaler, at(5, 5.5)) %>%
run() %>% invisible
#> 0: worker0: performing a looong task...
#> 5: signaler0: you shall pass
#> 5: worker0: ok, I'm packing...
#> 5.5: signaler1: you shall pass
#> 5.5: worker0: ok, I'm packing...
#> 6.5: worker0: and I'm leaving!