From 8312615574ab9b0d72b94bf6fe9dba13eabc0b6f Mon Sep 17 00:00:00 2001
From: Steve Kemp <steve@steve.org.uk>
Date: Wed, 18 Feb 2015 04:10:36 +0000
Subject: Updated the way we wait for jobs.

The new approach uses the redis gems timeout functionality
and ensures we never return a null-job.  Instead we timeout
and repeat with a stalling-sleep in the way.

This closes #9553.
---
 lib/custodian/queue.rb | 22 +++++++---------------
 1 file changed, 7 insertions(+), 15 deletions(-)

(limited to 'lib')

diff --git a/lib/custodian/queue.rb b/lib/custodian/queue.rb
index 9a7d90f..c48bba3 100644
--- a/lib/custodian/queue.rb
+++ b/lib/custodian/queue.rb
@@ -87,27 +87,19 @@ end
     #
     #  Fetch a job from the queue.
     #
-    #  The timeout is used to specify the period we wait for a new job.
+    #  The timeout is used to specify the period we wait for a new job, and
+    # we pause that same period between fetches.
     #
-    def fetch(timeout)
+    def fetch(timeout = 1)
       job = nil
-      timeout ||= 0
 
-      # 
-      # Don't melt the CPU.
-      #
-      sleep_interval = 0.5
+      while( 1 )
 
-      loop do
-        job = @redis.lpop( "queue" )
-        break if job or timeout < 0
+        foo, job = @redis.blpop( "queue", :timeout => timeout )
+        return job if ( job )
 
-        sleep( sleep_interval )
-
-        timeout -= sleep_interval
+        sleep( timeout )
       end
-
-      return( job )
     end
 
     #
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