From dc6106abd764cebf6f86f318f967492123fd009f Mon Sep 17 00:00:00 2001
From: Grzegorz Swatowski <grzegorz@sumologic.com>
Date: Wed, 13 Mar 2024 16:33:56 +0100
Subject: [PATCH] feat(exporter-trace-otlp-http): fallback to XHR if sendBeacon
 fails

---
 .../browser/OTLPExporterBrowserBase.ts        | 15 ++++-----
 .../src/platform/browser/util.ts              | 32 ++++++++++++++-----
 2 files changed, 30 insertions(+), 17 deletions(-)

diff --git a/experimental/packages/otlp-exporter-base/src/platform/browser/OTLPExporterBrowserBase.ts b/experimental/packages/otlp-exporter-base/src/platform/browser/OTLPExporterBrowserBase.ts
index 1c3715055a..66edb8f2a9 100644
--- a/experimental/packages/otlp-exporter-base/src/platform/browser/OTLPExporterBrowserBase.ts
+++ b/experimental/packages/otlp-exporter-base/src/platform/browser/OTLPExporterBrowserBase.ts
@@ -69,7 +69,12 @@ export abstract class OTLPExporterBrowserBase<
     const body = JSON.stringify(serviceRequest);
 
     const promise = new Promise<void>((resolve, reject) => {
-      if (this._useXHR) {
+      if (
+        !this._useXHR &&
+        sendWithBeacon(body, this.url, { type: 'application/json' })
+      ) {
+        resolve();
+      } else {
         sendWithXhr(
           body,
           this.url,
@@ -78,14 +83,6 @@ export abstract class OTLPExporterBrowserBase<
           resolve,
           reject
         );
-      } else {
-        sendWithBeacon(
-          body,
-          this.url,
-          { type: 'application/json' },
-          resolve,
-          reject
-        );
       }
     }).then(onSuccess, onError);
 
diff --git a/experimental/packages/otlp-exporter-base/src/platform/browser/util.ts b/experimental/packages/otlp-exporter-base/src/platform/browser/util.ts
index fade4afa88..f7d771f42a 100644
--- a/experimental/packages/otlp-exporter-base/src/platform/browser/util.ts
+++ b/experimental/packages/otlp-exporter-base/src/platform/browser/util.ts
@@ -24,6 +24,13 @@ import {
   parseRetryAfterToMills,
 } from '../../util';
 
+let minimumFailedSendBeaconPayloadSize = Infinity;
+
+// exported only for test files
+export const resetSendWithBeacon = () => {
+  minimumFailedSendBeaconPayloadSize = Infinity;
+};
+
 /**
  * Send metrics/spans using browser navigator.sendBeacon
  * @param body
@@ -36,16 +43,25 @@ export function sendWithBeacon(
   body: string,
   url: string,
   blobPropertyBag: BlobPropertyBag,
-  onSuccess: () => void,
-  onError: (error: OTLPExporterError) => void
-): void {
-  if (navigator.sendBeacon(url, new Blob([body], blobPropertyBag))) {
+): boolean {
+  // navigator.sendBeacon returns 'false' if the given payload exceeds the user agent limit.
+  // See https://w3c.github.io/beacon/#return-value for specification.
+  // Because we don't know what the limit is and to keep user's console clean, we only try to send payloads that may suceed.
+  const blob = new Blob([body], blobPropertyBag);
+  if (
+    blob.size < minimumFailedSendBeaconPayloadSize &&
+    navigator.sendBeacon(url, blob)
+  ) {
     diag.debug('sendBeacon - can send', body);
-    onSuccess();
-  } else {
-    const error = new OTLPExporterError(`sendBeacon - cannot send ${body}`);
-    onError(error);
+    return true;
   }
+
+  minimumFailedSendBeaconPayloadSize = blob.size;
+  diag.info(
+    'sendBeacon failed because the given payload was too big; try to lower your span processor limits',
+  );
+
+  return false;
 }
 
 /**