From: Corey Kosak <kosak@google.com>
Date: Fri, 22 Jan 2016 21:56:37 +0000 (-0500)
Subject: Don't divide by 0 when doing percentages (e.g. with the swap plugin).
X-Git-Tag: collectd-5.5.2~69
X-Git-Url: https://git.verplant.org/?a=commitdiff_plain;h=f1552fdc8b98860f22e69d162db295bfb9b49180;p=collectd.git

Don't divide by 0 when doing percentages (e.g. with the swap plugin).

Prior to this change, if all the values being sent sum to zero, then the
calculated percentage is a division by 0 which is either Inf or NaN
depending on the numerator.

This is not a theoretical concern: it can easily happen if all the input
gauges are 0.

This change forces the output to be zero if the denominator is zero.
---

diff --git a/src/daemon/plugin.c b/src/daemon/plugin.c
index e7d4e8df..29716185 100644
--- a/src/daemon/plugin.c
+++ b/src/daemon/plugin.c
@@ -2272,7 +2272,7 @@ int plugin_dispatch_multivalue (value_list_t const *template, /* {{{ */
 		case DS_TYPE_GAUGE:
 			vl->values[0].gauge = va_arg (ap, gauge_t);
 			if (store_percentage)
-				vl->values[0].gauge *= 100.0 / sum;
+				vl->values[0].gauge *= sum ? (100.0 / sum) : 0;
 			break;
 		case DS_TYPE_ABSOLUTE:
 			vl->values[0].absolute = va_arg (ap, absolute_t);