job_queue: add logging of long build queue

This will make it easier to monitor whether the new queueing system is
behaving as expected.

Author: carlocab

src/job_queue.rb

@@ -5,11 +5,12 @@
 
 # A variation of `Thread::Queue` that allows us to prioritise certain types of jobs.
 class JobQueue
-  def initialize(queue_type)
+  def initialize(queue_type, logger)
     @mutex = Mutex.new
     @queue = Hash.new { |h, k| h[k] = [] }
     @queue_type = queue_type
     @condvar = ConditionVariable.new
+    @logger = logger
   end
 
   def <<(job)
@@ -24,9 +25,12 @@ def pop
       loop do
         running_long_build_count = SharedState.instance.running_jobs(@queue_type).count(&:long_build?)
         long_build_slots = QueueTypes.slots(@queue_type) / 2
+        @logger.call("Long builds: #{running_long_build_count} running, #{long_build_slots} available")
 
         if running_long_build_count < long_build_slots && !@queue[:long].empty?
-          break @queue[:long].shift
+          job = @queue[:long].shift
+          @logger.call("Long build slot available. Scheduling #{job.runner_name} for deployment...")
+          break job
         elsif !@queue[:default].empty?
           break @queue[:default].shift
         else

src/orka_start_processor.rb

@@ -27,7 +27,7 @@ class OrkaStartProcessor < ThreadRunner
 
   def initialize(queue_type, name)
     super("#{self.class.name} (#{name})")
-    @queue = JobQueue.new(queue_type)
+    @queue = JobQueue.new(queue_type, method(:log))
   end
 
   def pausable?