From aea148d771dca0e10ca1a2f5505446fbc689dad2 Mon Sep 17 00:00:00 2001
From: Saku Ytti <saku@ytti.fi>
Date: Sun, 22 Feb 2015 13:05:37 +0200
Subject: refactor HOLB prevention

Still not sure we want this. But previous one might have caused infinite
loop in #work.
Consider we have just 1 node all together, and our rotation interval is
more than our MAX_INTER_JOB_GAP, then we'd add @want to 2, instead of 1.
Now we want more threads than we have nodes, and 'while @jobs.size <
@jobs.want' will never be true
---
 lib/oxidized/jobs.rb   | 24 +++++++++++++++++++++---
 lib/oxidized/worker.rb |  6 +-----
 2 files changed, 22 insertions(+), 8 deletions(-)

(limited to 'lib/oxidized')

diff --git a/lib/oxidized/jobs.rb b/lib/oxidized/jobs.rb
index 3342679..ff7f92b 100644
--- a/lib/oxidized/jobs.rb
+++ b/lib/oxidized/jobs.rb
@@ -1,28 +1,46 @@
 module Oxidized
   class Jobs < Array
-    AVERAGE_DURATION = 5 # initially presume nodes take 5s to complete
+    AVERAGE_DURATION  = 5   # initially presume nodes take 5s to complete
+    MAX_INTER_JOB_GAP = 300 # add job if more than X from last job started
     attr_accessor :interval, :max, :want
+
     def initialize max, interval, nodes
       @max       = max
       @interval  = interval
       @nodes     = nodes
+      @last      = Time.now.utc
       @durations = Array.new @nodes.size, AVERAGE_DURATION
       duration AVERAGE_DURATION
       super()
     end
+
+    def push arg
+      @last = Time.now.utc
+      super
+    end
+
     def duration last
       @durations.push(last).shift
       @duration = @durations.inject(:+).to_f / @nodes.size #rolling average
       new_count
     end
+
     def new_count
       @want = ((@nodes.size * @duration) / @interval).to_i
       @want = 1 if @want < 1
       @want = @nodes.size if @want > @nodes.size
       @want = @max if @want > @max
     end
-    def add_job
-      @want += 1
+
+    def work
+      # if   a) we want less or same amount of threads as we now running
+      # and  b) we want less threads running than the total amount of nodes
+      # and  c) there is more than MAX_INTER_JOB_GAP since last one was started
+      # then we want one more thread (rationale is to fix hanging thread causing HOLB)
+      if @want <= size and @want < @nodes.size
+        @want +=1 if (Time.now.utc - @last) > MAX_INTER_JOB_GAP
+      end
     end
+
   end
 end
diff --git a/lib/oxidized/worker.rb b/lib/oxidized/worker.rb
index 99fc8b8..7ed70ac 100644
--- a/lib/oxidized/worker.rb
+++ b/lib/oxidized/worker.rb
@@ -2,12 +2,9 @@ module Oxidized
   require 'oxidized/job'
   require 'oxidized/jobs'
   class Worker
-    MAX_INTER_JOB_GAP = 300
-
     def initialize nodes
       @nodes   = nodes
       @jobs    = Jobs.new CFG.threads, CFG.interval, @nodes
-      @last    = Time.now.utc
       Thread.abort_on_exception = true
     end
 
@@ -15,7 +12,7 @@ module Oxidized
       ended = []
       @jobs.delete_if { |job| ended << job if not job.alive? }
       ended.each      { |job| process job }
-      @jobs.add_job if Time.now.utc - @last > MAX_INTER_JOB_GAP
+      @jobs.work
       while @jobs.size < @jobs.want
         Log.debug "Jobs #{@jobs.size}, Want: #{@jobs.want}"
         # ask for next node in queue non destructive way
@@ -26,7 +23,6 @@ module Oxidized
         # shift nodes and get the next node
         node = @nodes.get
         node.running? ? next : node.running = true
-        @last = Time.now.utc
         @jobs.push Job.new node
       end
     end
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