[asterisk-bugs] [Asterisk 0013220]: [patch] Calls in high-weighted queue block low-weighted

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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http://bugs.digium.com/view.php?id=13220 
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Reported By:                garychen
Assigned To:                mmichelson
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Project:                    Asterisk
Issue ID:                   13220
Category:                   Applications/app_queue
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     ready for review
Asterisk Version:           1.4.19 
Regression:                 No 
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2008-08-01 08:28 CDT
Last Modified:              2009-03-30 11:17 CDT
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Summary:                    [patch] Calls in high-weighted queue block
low-weighted
Description: 
I have two queues, weighted 4 and 5. High priority calls are placed in
Q6002, while low priority ones in Q6001.

All agents are member of both queues.

The problem is whenever there's a high priority call ringing on an agent
(the agent not answer the call), low priority calls not routed to any idle
agents. They are blocked.
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---------------------------------------------------------------------- 
 (0102397) svnbot (reporter) - 2009-03-30 11:17
 http://bugs.digium.com/view.php?id=13220#c102397 
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Repository: asterisk
Revision: 185031

U   branches/1.4/apps/app_queue.c

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r185031 | mmichelson | 2009-03-30 11:17:35 -0500 (Mon, 30 Mar 2009) | 39
lines

Fix queue weight behavior so that calls in low-weight queues are not
inappropriately blocked.

(This is copied and pasted from the review request I made for this patch)

Asterisk has some odd behavior when queue weights are used. The current
logic used when
potentially calling a queue member is:

If the member we are going to call is part of another queue and _that
other queue has any 
callers in it_ and has a higher weight than the queue we are calling from,
then don't try 
to contact that member. The issue here is what I have marked with
underscores. If the 
higher-weighted queue has any callers in it at all, then the queue member
will be unreachable 
from the lower-weighted queue. This has the potential to be really really
bad if using a 
queue strategy, such as leastrecent or fewestcalls, with the potential to
call the same 
member repeatedly.

The fix proposed by garychen on issue 13220 is very simple and, as far as
I can see, works 
well for this situation. With this set of changes, the logic used becomes:

If the member we are going to call is part of another queue, the other
queue has a higher 
weight than the queue we are calling from, and the higher weight queue has
at least as many 
callers as available members, then do not try to contact the queue member.
If the higher 
weighted queue has fewer callers than available members, then there is no
reason to deny 
the call to this member since the other queue can afford to spare a
member.

Since the fix involved writing a generic function for determining the
number of available 
members in the queue, I also modified the is_our_turn function to make use
of the new 
num_available_members function to determine if it is our turn to try
calling a member. There 
is one small behavior change. Before writing this patch, if you had
autofill disabled, then 
if you were the head caller in a queue, you would automatically be told
that it was your 
turn to try calling a member. This did not take into account whether there
were actually any 
queue members available to take the call. Now we actually make sure there
is at least one 
member available to take the call if autofill is disabled.

(closes issue http://bugs.digium.com/view.php?id=13220)
Reported by: garychen

Review: http://reviewboard.digium.com/r/202/


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http://svn.digium.com/view/asterisk?view=rev&revision=185031 

Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2009-03-30 11:17 svnbot         Checkin                                      
2009-03-30 11:17 svnbot         Note Added: 0102397                          
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