update puma and add puma health check

Gemfile

@@ -167,7 +167,7 @@ gem 'sprockets', '~> 3.7.0'
 # also, better than thin since we can control worker concurrency.
 gem 'unicorn'
 
-gem 'puma', '~> 4.3.1' # used for development and optionally for production
+gem 'puma', '~> 4.3.5' # used for development and optionally for production
 
 gem 'nokogiri', '~> 1.10.8'
 

Gemfile.lock

@@ -1080,7 +1080,7 @@ DEPENDENCIES
   pry-rescue (~> 1.5.0)
   pry-stack_explorer (~> 0.4.9.2)
   puffing-billy (~> 2.3.1)
-  puma (~> 4.3.1)
+  puma (~> 4.3.5)
   rack-attack (~> 6.2.2)
   rack-mini-profiler
   rack-protection (~> 2.0.8)

config/initializers/health_checks.rb

@@ -19,6 +19,53 @@ class DelayedJobNeverRanCheck < OkComputer::Check
   end
 end
 
+class PumaCheck < OkComputer::Check
+  attr_reader :threshold
+
+  def initialize(backlog_threshold)
+    @threshold = backlog_threshold.to_i
+  end
+
+  def check
+    stats = self.stats
+
+    return mark_message "N/A as Puma is not used." if stats.nil?
+
+    if stats[:running] > 0
+      mark_message "Puma is running"
+    else
+      mark_failure
+      mark_message "Puma is not running"
+    end
+
+    if stats[:backlog] < threshold
+      mark_message "Backlog ok"
+    else
+      mark_failure
+      mark_message "Backlog congested"
+    end
+  end
+
+  def stats
+    return nil unless applicable?
+    server = Puma::Server.current
+    return nil if server.nil?
+
+    {
+      backlog: server.backlog || 0,
+      running: server.running || 0,
+      pool_capacity: server.pool_capacity || 0,
+      max_threads: server.max_threads || 0
+    }
+  end
+
+  def applicable?
+    return @applicable unless @applicable.nil?
+
+    @applicable = Object.const_defined?("Puma::Server") && !Puma::Server.current.nil?
+  end
+end
+
 # Register delayed_job backed up test
 dj_max = OpenProject::Configuration.health_checks_jobs_queue_count_threshold
 OkComputer::Registry.register "delayed_jobs_backed_up",
@@ -28,8 +75,11 @@ dj_never_ran_max = OpenProject::Configuration.health_checks_jobs_never_ran_minut
 OkComputer::Registry.register "delayed_jobs_never_ran",
                               DelayedJobNeverRanCheck.new(dj_never_ran_max)
 
+backlog_threshold = OpenProject::Configuration.health_checks_backlog_threshold
+OkComputer::Registry.register "puma", PumaCheck.new(backlog_threshold)
+
 # Make dj backed up optional due to bursts
-OkComputer.make_optional %w(delayed_jobs_backed_up)
+OkComputer.make_optional %w(delayed_jobs_backed_up puma)
 
 # Register web worker check for web + database
 OkComputer::CheckCollection.new('web').tap do |collection|
@@ -45,6 +95,7 @@ OkComputer::CheckCollection.new('full').tap do |collection|
   collection.register :mail, OkComputer::ActionMailerCheck.new
   collection.register :delayed_jobs_backed_up, OkComputer::Registry.fetch('delayed_jobs_backed_up')
   collection.register :delayed_jobs_never_ran, OkComputer::Registry.fetch('delayed_jobs_never_ran')
+  collection.register :puma, OkComputer::Registry.fetch('puma')
   OkComputer::Registry.default_collection.register 'full', collection
 end
 

lib/open_project/configuration.rb

@@ -124,6 +124,8 @@ module OpenProject
       'health_checks_jobs_queue_count_threshold' => 50,
       # Maximum number of minutes that jobs have not yet run after their designated 'run_at' time
       'health_checks_jobs_never_ran_minutes_ago' => 5,
+      # Maximum number of unprocessed requests in puma's backlog.
+      'health_checks_backlog_threshold' => 20,
 
       'after_login_default_redirect_url' => nil,
       'after_first_login_redirect_url' => nil,