job_queue: add logging of long build queue

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

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?