commit a48f2c813dc40ce02005a67bf503383d0482669e (HEAD -> v1.9.1-pcp)
Author: Frank Ch. Eigler <fche@redhat.com>
Date:   Thu Jan 7 15:21:38 2016 -0500

    png graphing: add &bust=XXXX url parameter to prevent browser-side img caching
    
    Despite pcp pmwebd's varying 302 redirection and anti-caching
    directives, web browser still sometimes cache img src content.
    Defeat this with an extra graphite-png cache-busting url parameter.

diff --git a/src/app/panels/graph/graph.js b/src/app/panels/graph/graph.js
index 485d64d76ae1..bf4468cf580c 100755
--- a/src/app/panels/graph/graph.js
+++ b/src/app/panels/graph/graph.js
@@ -426,6 +426,7 @@ function (angular, $, kbn, moment, _, GraphTooltip) {
           }
 
           url += scope.panel.steppedLine ? '&lineMode=staircase' : '';
+          url += '&bust='+Date.now(); /* preclude image caching */
 
           elem.html('<img src="' + url + '"></img>');
         }
