Message queues for R. Built on top of 'SQLite' databases.
liteq works with multiple producer and/or consumer processes accessing
the same queue, via the locking mechanism of 'SQLite'. If a queue is
locked by 'SQLite', the process that tries to access it, must wait until
it is unlocked. The maximum amount of waiting time is by default 10
seconds, and it can be changed via the R_LITEQ_BUSY_TIMEOUT
environment variable, in milliseconds. If you have many concurrent
processes using the same liteq database, and see database locked
errors, then you can try to increase the timeout value.
# We don't run this, because it writes to the cache directory
db <- tempfile()
q <- ensure_queue("jobs", db = db)
q
list_queues(db)# Publish two messages
publish(q, title = "First message", message = "Hello world!")
publish(q, title = "Second message", message = "Hello again!")
is_empty(q)
message_count(q)
list_messages(q)
# Consume one
msg <- try_consume(q)
msg
ack(msg)
list_messages(q)
msg2 <- try_consume(q)
nack(msg2)
list_messages(q)
# No more messages
is_empty(q)
try_consume(q)
# NOT RUN {
## See the manual page
# }
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