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cluster - worker shutdown - use WNOHANG with nil return tests #1741

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merged 2 commits into from
Mar 19, 2019
Merged

cluster - worker shutdown - use WNOHANG with nil return tests #1741

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b94c3e3
Puma::Cluster#stop_workers - use WNOHANG with nil return tests
MSP-Greg Mar 15, 2019
d1ac2bf
travis.yml - update to 2.5.5 & 2.6.2, remove 2.6.2 from allow failure
MSP-Greg Mar 19, 2019
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7 changes: 3 additions & 4 deletions .travis.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -24,8 +24,8 @@ rvm:
- 2.2.10
- 2.3.8
- 2.4.5
- 2.5.3
- 2.6
- 2.5.5
- 2.6.2
- ruby-head

matrix:
Expand All @@ -35,13 +35,12 @@ matrix:
env: RUBYOPT="--jit"
- rvm: 2.3.8
os: osx
- rvm: 2.5.3
- rvm: 2.5.5
os: osx
- rvm: jruby-9.2.6.0
- rvm: jruby-head

allow_failures:
- rvm: 2.6
- rvm: ruby-head
- rvm: ruby-head
env: RUBYOPT="--jit"
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20 changes: 19 additions & 1 deletion lib/puma/cluster.rb
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Expand Up @@ -37,7 +37,25 @@ def stop_workers
@workers.each { |x| x.term }

begin
@workers.each { |w| Process.waitpid(w.pid) }
if RUBY_VERSION < '2.6'
@workers.each { |w| Process.waitpid(w.pid) }
else
# below code is for a bug in Ruby 2.6+, above waitpid call hangs
t_st = Process.clock_gettime(Process::CLOCK_MONOTONIC)
pids = @workers.map(&:pid)
loop do
pids.reject! do |w_pid|
if Process.waitpid(w_pid, Process::WNOHANG)
log " worker status: #{$?}"
true
end
end
break if pids.empty?
sleep 0.5
end
t_end = Process.clock_gettime(Process::CLOCK_MONOTONIC)
log format(" worker shutdown time: %6.2f", t_end - t_st)
end
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There are two cycles instead of one.

You can use redo.

See #1738 (comment)

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@AlexWayfer

Thanks. As mentioned, I did it this way so it would loop thru all the workers on first pass, then go back for the nil returns. I'd rather use Process.waitpid(-1, Process::WNOHANG), as that's a bit cleaner, but it seems to repeatedly fail on trunk JIT, I never tried with 2.6.x JIT...

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As mentioned, I did it this way so it would loop thru all the workers on first pass, then go back for the nil returns.

It's strange algorithm.

Option 1, with redo:

  1. Go through all workers
  2. Sleep and redo on the first fail (wait every first fail)

Option 2:

  1. Go through all workers and attempt to stop them
  2. Delete from array in success, wait after all if any failed
  3. Retry if there are any remained

Option 3, your choice, as I see:

  1. Go through all workers
  2. Delete in success, and retry (go further)
  3. Don't do anything in fail, just sleep in the end
  4. Retry until there are any

I think, the first option is simplest (but may be longest), the second is most optimal, and the third is strange.

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I changed the logic to use reject!

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I changed the logic to use reject!

You can use loop do instead of while true do. 😉

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I often look here:
https://msp-greg.github.io/ruby_trunk/file.control_expressions.html

loop do isn't mentioned there. Time to review kernel methods again...

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Also, about two cycles (and map): do we need for @workers after successful run of this code?

If no — we can use @workers.reject!.

rescue Interrupt
log "! Cancelled waiting for workers"
end
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