Add rate() function resistant to counter reset

src/datasource-zabbix/dataProcessor.js

@@ -7,6 +7,7 @@ let groupBy = ts.groupBy_perf;
 let groupBy_exported = (interval, groupFunc, datapoints) => groupBy(datapoints, interval, groupFunc);
 let sumSeries = ts.sumSeries;
 let delta = ts.delta;
+let rate = ts.rate;
 let scale = (factor, datapoints) => ts.scale(datapoints, factor);
 
 let SUM = ts.SUM;
@@ -100,6 +101,7 @@ let metricFunctions = {
   groupBy: groupByWrapper,
   scale: scale,
   delta: delta,
+  rate: rate,
   aggregateBy: aggregateByWrapper,
   average: _.partial(aggregateWrapper, AVERAGE),
   min: _.partial(aggregateWrapper, MIN),

src/datasource-zabbix/metricFunctions.js

@@ -50,6 +50,13 @@ addFuncDef({
   defaultParams: [],
 });
 
+addFuncDef({
+  name: 'rate',
+  category: 'Transform',
+  params: [],
+  defaultParams: [],
+});
+
 // Aggregate
 
 addFuncDef({

src/datasource-zabbix/timeseries.js

@@ -4,7 +4,8 @@
  * This module contains functions for working with time series.
  *
  * datapoints - array of points where point is [value, timestamp]. In almost all cases (if other wasn't
- * explicitly said) we assume datapoints are sorted by timestamp.
+ * explicitly said) we assume datapoints are sorted by timestamp. Timestamp is the number of milliseconds
+ * since 1 January 1970 00:00:00 UTC.
  *
  */
 
@@ -168,6 +169,10 @@ function scale(datapoints, factor) {
   });
 }
 
+/**
+ * Simple delta. Calculate value delta between points.
+ * @param {*} datapoints
+ */
 function delta(datapoints) {
   let newSeries = [];
   let deltaValue;
@@ -178,6 +183,32 @@ function delta(datapoints) {
   return newSeries;
 }
 
+/**
+ * Calculates rate per second. Resistant to counter reset.
+ * @param {*} datapoints
+ */
+function rate(datapoints) {
+  let newSeries = [];
+  let point, point_prev;
+  let valueDelta = 0;
+  let timeDelta = 0;
+  for (let i = 1; i < datapoints.length; i++) {
+    point = datapoints[i];
+    point_prev = datapoints[i - 1];
+
+    // Convert ms to seconds
+    timeDelta = (point[POINT_TIMESTAMP] - point_prev[POINT_TIMESTAMP]) / 1000;
+
+    // Handle counter reset - use previous value
+    if (point[POINT_VALUE] >= point_prev[POINT_VALUE]) {
+      valueDelta = (point[POINT_VALUE] - point_prev[POINT_VALUE]) / timeDelta;
+    }
+
+    newSeries.push([valueDelta, point[POINT_TIMESTAMP]]);
+  }
+  return newSeries;
+}
+
 function SUM(values) {
   var sum = 0;
   _.each(values, function (value) {
@@ -297,6 +328,7 @@ const exportedFunctions = {
   sumSeries,
   scale,
   delta,
+  rate,
   SUM,
   COUNT,
   AVERAGE,