BC-5586 Investigate possibilities to detect OutOfMemory errors on production

- Fix heap size calculation, at is was off a few percentage. Now use process API and only use gc-stats for knowing when a full GC was done

Author: paulrutter

CHANGELOG.md

@@ -1,3 +1,6 @@
+03-10-2017 - Paul Rütter
+- 1.0.5 - Change heap calculation.
+
 03-10-2017 - Paul Rütter
 - 1.0.4 - Add error handler in case the calling process is not running anymore. Also, block execution a while to allow heapdump to be created.
 

README.md

@@ -29,7 +29,7 @@ Just add the following snippet to your node process.
 
 ```javascript
 require("node-oom-heapdump")({
-    threshold: 75,
+    threshold: 90,
     path: "./my_heapdump"
 });
 ```
@@ -46,7 +46,7 @@ These might impact performance though.
 
 # Options
 * heapdumpOnOOM - boolean whether to create a heapdump when an out of memory occurs. Default true.
-* threshold - integer between 0 and 100 (%) which determines when to make the heapdump. When the used heapSize exceeds the threshold, a heapdump is made. 
+* threshold - integer between 0 and 100 (%) which determines when to make the heapdump. When the used heapSize exceeds the threshold, a heapdump is made. This value can be tuned depending on your configuration; if memory usage is very volatile, a lower value might make more sense. Default is 90.
 * path - the path where the heapdump ends up when an out of memory error occurs.
 * port - optionally, the alternative DevTools protocol port. Defaults to 9229. Should map on the port given to the --inspect arg.
 

lib/index.js

@@ -18,11 +18,11 @@ class NodeOomHeapDumpImpl {
     gcStats.on('stats', (stats) => {
       // gctype 2 is a Full GC (Mark/Sweep/Compact)
       if (stats.gctype === 2 && !this._busy) {
-        let heapSizeUsedPercentage = (parseInt(stats.after.totalHeapSize) / parseInt(stats.after.heapSizeLimit)) * 100;
-        if (heapSizeUsedPercentage > this._opts.threshold) {
-
-          // this is a full GC and the used heap size is using more than 80% of the assigned heap space limit
-          console.warn('OoM is imminent: Full GC (Mark/Sweep/Compact) complete and still more than %s% (%s%) of the heap is used. Creating heapdump now. GC stats: ', this._opts.threshold, Math.round(heapSizeUsedPercentage), stats);
+        let memoryUsage = process.memoryUsage();
+        var memoryUsagePercentage = Math.round((memoryUsage.heapUsed / memoryUsage.heapTotal) * 100);
+        if (memoryUsagePercentage > this._opts.threshold) {
+          // this is a full GC and the used heap size is using more than x% of the assigned heap space limit
+          console.warn('OoM is imminent: Full GC (Mark/Sweep/Compact) complete and still more than %s% (%s%) of the heap is used. Creating heapdump now. GC stats: ', this._opts.threshold, Math.round(memoryUsagePercentage), stats);
 
           this.createHeapSnapshot(path.resolve('./' + this._opts.path + '.heapsnapshot'), "OoM");
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "node-oom-heapdump",
-  "version": "1.0.4",
+  "version": "1.0.5",
   "description": "Create a V8 heap snapshot right before an \"Out of Memory\" error occurs, or create a heap snapshot on request.",
   "main": "index.js",
   "scripts": {

tests/oom_app.js

@@ -1,5 +1,5 @@
 let oom = require("../index.js")({
-    threshold: 75,
+    threshold: 90,
     path: "../my_heapdump",
     heapdumpOnOOM: true
 });