Delayed job processing loop uses wall time to calculate remaining sleep seconds
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Verseth commented
Looking through the codebase, I noticed that Time.now
is used to calculate the remaining time to sleep between the iterations of the delayed job processing loop.
This could result in undefined behaviour, as Time.now
reports wall time, which could change and get updated at any point.
This is the code I'm talking about: https://github.com/resque/resque-scheduler/blob/master/lib/resque/scheduler.rb#L416
def poll_sleep_loop
@sleeping = true
if poll_sleep_amount > 0
start = Time.now
loop do
elapsed_sleep = (Time.now - start)
remaining_sleep = poll_sleep_amount - elapsed_sleep
# etc (...)
If the system's time was updated and moved backward one hour between the two calls to Time.now
, the scheduler would sleep for one hour.
One way to mitigate this issue would be to use monotonic time to measure the remaining seconds to sleep like so:
def poll_sleep_loop
@sleeping = true
if poll_sleep_amount > 0
start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
loop do
elapsed_sleep = (Process.clock_gettime(Process::CLOCK_MONOTONIC) - start)
remaining_sleep = poll_sleep_amount - elapsed_sleep
# etc (...)