RedisScheduler is a chronological scheduler for Redis. It allows you to schedule
items to be processed at arbitrary points in time (via RedisScheduler#schedule!)
and easily retrieve only those items that are due to be processed (via
RedisScheduler#each).
It does everything you'd expect from a production scheduler:
* You can schedule items at arbitrary times.
* You can iterate over ready items in either blocking or non-blocking mode.
* It supports multiple simultaneous readers and writers.
* A Ruby exception causes the item to be rescheduled at the original time.
* Work items lost as part of a Ruby crash or segfault are recoverable.
In non-blocking mode (the default), RedisScheduler#each will iterate only over
those work items whose scheduled time is less than or equal to the current time,
and then stop. In blocking mode, RedisScheduler#each will iterate over the same
items, but will also block until items are available. In this mode, #each will
never return.
For debugging purposes, you can use RedisScheduler#items to iterate over all
items in the queue, but note that this method is not guaranteed to be
consistent.
For error recovery purposes, you can use RedisScheduler#processing_set_items
to iterate over all the items in the processing set to determine whether any
of them are the result of a process crash.
== Synopsis
r = Redis.new
s = RedisScheduler.new r, blocking: true
startt = Time.now
s.schedule! "a", startt + 10
s.schedule! "b", startt + 15
s.schedule! "c", startt + 20
s.each { |item, at| puts "#{Time.now - startt}: #{item}" }
prints:
10.03481788: a
15.05255288: b
20.06058172: c
... waits forever ...
== Implementation
See http://masanjin.net/blog/using-redis-for-scheduling for some details.
== Bug reports
Please file bugs here: https://github.com/wmorgan/redis-scheduler/issues
Please send comments to: wmorgan-redis-scheduler-readme@masanjin.net.