Add option to adjust restart randomizer

* Add option to adjust the rolling restart randomization.
* Increase the default random factor from 10 seconds to 300 seconds.
* Make sure rand() gets a float to avoid producing integer second.
* Adjust tests to use shortened restart splay.

Signed-off-by: Ben Kochie <superq@gmail.com>

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## Master
 
+- Add option to adjust restart randomizer (#78)
 - Simplify workers memory calculation in PumaMemory‘s `get_total` method #81
 - Add rubocop in gemspec and CI, with offenses corrected and unnecessary cops disabled.
 - Add `pre_term`-like `rolling_pre_term` config for terminations caused by rolling restart (#86)

lib/puma_worker_killer.rb

@@ -6,12 +6,14 @@ module PumaWorkerKiller
   extend self
 
   attr_accessor :ram, :frequency, :percent_usage, :rolling_restart_frequency,
+                :rolling_restart_splay_seconds,
                 :reaper_status_logs, :pre_term, :rolling_pre_term, :on_calculation
 
   self.ram           = 512  # mb
   self.frequency     = 10   # seconds
   self.percent_usage = 0.99 # percent of RAM to use
   self.rolling_restart_frequency = 6 * 3600 # 6 hours in seconds
+  self.rolling_restart_splay_seconds = 0.0..300.0 # 0 to 5 minutes in seconds
   self.reaper_status_logs = true
   self.pre_term = nil
   self.rolling_pre_term = nil
@@ -30,8 +32,10 @@ def start(frequency = self.frequency, reaper = self.reaper)
     enable_rolling_restart(rolling_restart_frequency) if rolling_restart_frequency
   end
 
-  def enable_rolling_restart(frequency = rolling_restart_frequency)
-    frequency += rand(0..10.0) # so all workers don't restart at the exact same time across multiple machines
+  def enable_rolling_restart(frequency = rolling_restart_frequency,
+                             splay_seconds = rolling_restart_splay_seconds)
+    # Randomize so all workers don't restart at the exact same time across multiple machines.
+    frequency += rand(splay_seconds)
     AutoReap.new(frequency, RollingRestart.new(nil, rolling_pre_term)).start
   end
 end

test/fixtures/rolling_pre_term.ru

@@ -5,6 +5,6 @@ load File.expand_path('fixture_helper.rb', __dir__)
 PumaWorkerKiller.config do |config|
   config.rolling_pre_term = ->(worker) { puts("About to terminate (rolling) worker: #{worker.pid}") }
 end
-PumaWorkerKiller.enable_rolling_restart(1) # 1 second
+PumaWorkerKiller.enable_rolling_restart(1, 0..5.0) # 1 second, short 1-5s splay.
 
 run HelloWorldApp

test/fixtures/rolling_restart.ru

@@ -2,6 +2,6 @@
 
 load File.expand_path('fixture_helper.rb', __dir__)
 
-PumaWorkerKiller.enable_rolling_restart(1) # 1 second
+PumaWorkerKiller.enable_rolling_restart(1, 0..5.0) # 1 second, short 1-5s splay.
 
 run HelloWorldApp