Truncate stack when application_error stack trace exceeds 8kb (close #1327)

PR #1328 
* add truncate function to application error event

Author: Jack-Keene

common/changes/@snowplow/browser-plugin-error-tracking/issue-1327_truncate-stack-trace_2024-07-16-10-59.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@snowplow/browser-plugin-error-tracking",
+      "comment": "Truncate error stack trace if it's size is greater than 8kb",
+      "type": "none"
+    }
+  ],
+  "packageName": "@snowplow/browser-plugin-error-tracking"
+}

plugins/browser-plugin-error-tracking/src/index.ts

@@ -36,6 +36,7 @@ import {
   dispatchToTrackersInCollection,
 } from '@snowplow/browser-tracker-core';
 import { buildSelfDescribingEvent, CommonEventProperties, SelfDescribingJson } from '@snowplow/tracker-core';
+import { truncateString } from './util';
 
 let _trackers: Record<string, BrowserTracker> = {};
 
@@ -74,7 +75,8 @@ export function trackError(
   trackers: Array<string> = Object.keys(_trackers)
 ) {
   const { message, filename, lineno, colno, error, context, timestamp } = event,
-    stack = error && error.stack ? error.stack : null;
+    stack = error && truncateString(error.stack, 8192),
+    truncatedMessage = message && truncateString(message, 2048);
 
   dispatchToTrackersInCollection(trackers, _trackers, (t) => {
     t.core.track(
@@ -83,7 +85,7 @@ export function trackError(
           schema: 'iglu:com.snowplowanalytics.snowplow/application_error/jsonschema/1-0-1',
           data: {
             programmingLanguage: 'JAVASCRIPT',
-            message: message ?? "JS Exception. Browser doesn't support ErrorEvent API",
+            message: truncatedMessage ?? "JS Exception. Browser doesn't support ErrorEvent API",
             stackTrace: stack,
             lineNumber: lineno,
             lineColumn: colno,

plugins/browser-plugin-error-tracking/src/util.ts

@@ -0,0 +1,15 @@
+/**
+ * Truncate string if it's longer than 8192 chars
+ *
+ * @param string - The stack trace to truncate
+ * @param maxLength - The maximum length of the truncated string. Default = 8192
+ * @returns The truncated string
+ */
+export function truncateString(string?: string, maxLength: number = 8192): string | undefined {
+  if (string && string.length > maxLength) {
+    const truncatedString = string.substring(0, maxLength);
+    return truncatedString;
+  }
+
+  return string;
+}

plugins/browser-plugin-error-tracking/test/events.test.ts

@@ -60,10 +60,18 @@ describe('AdTrackingPlugin', () => {
     encodeBase64: false,
     plugins: [ErrorTrackingPlugin()],
   });
+  addTracker('sp4', 'sp4', 'js-3.0.0', '', state, {
+    encodeBase64: false,
+    plugins: [ErrorTrackingPlugin()],
+  });
 
   const error = new Error('this is an error');
   error.stack = 'stacktrace-1';
 
+  const oversizedError = new Error('this is a longer error');
+  oversizedError.stack = 'x'.repeat(10000);
+  const oversizedMessage = 'y'.repeat(10000);
+
   trackError(
     {
       message: 'message-1',
@@ -89,6 +97,14 @@ describe('AdTrackingPlugin', () => {
     ['sp3']
   );
 
+  trackError(
+    {
+      message: oversizedMessage,
+      error: oversizedError,
+    },
+    ['sp4']
+  );
+
   it('trackError adds the expected application error event to the queue', () => {
     expect(
       extractUeEvent('iglu:com.snowplowanalytics.snowplow/application_error/jsonschema/1-0-1').from(state.outQueues[0])
@@ -126,4 +142,16 @@ describe('AdTrackingPlugin', () => {
       },
     });
   });
+
+  it('trackError replaces undefined messages with placeholder', () => {
+    expect(
+      extractUeEvent('iglu:com.snowplowanalytics.snowplow/application_error/jsonschema/1-0-1').from(state.outQueues[3])
+    ).toMatchObject({
+      schema: 'iglu:com.snowplowanalytics.snowplow/application_error/jsonschema/1-0-1',
+      data: {
+        message: 'y'.repeat(2048),
+        stackTrace: 'x'.repeat(8192),
+      },
+    });
+  });
 });