feat: Add warning for large payloads (#620)

src/common/harvest/harvest.js

@@ -16,6 +16,9 @@ import { applyFnToProps } from '../util/traverse'
 import { SharedContext } from '../context/shared-context'
 import { VERSION } from '../constants/env'
 import { isWorkerScope, isIE } from '../constants/runtime'
+import { warn } from '../util/console'
+
+const warnings = {}
 
 /**
  * @typedef {import('./types.js').NetworkSendSpec} NetworkSendSpec
@@ -24,7 +27,6 @@ import { isWorkerScope, isIE } from '../constants/runtime'
  * @typedef {import('./types.js').FeatureHarvestCallback} FeatureHarvestCallback
  * @typedef {import('./types.js').FeatureHarvestCallbackOptions} FeatureHarvestCallbackOptions
  */
-
 export class Harvest extends SharedContext {
   constructor (parent) {
     super(parent) // gets any allowed properties from the parent and stores them in `sharedContext`
@@ -115,6 +117,8 @@ export class Harvest extends SharedContext {
       } else {
         body = stringify(body)
       }
+      /** Warn --once per endpoint-- if the agent tries to send large payloads */
+      if (body.length > 750000 && (warnings[endpoint] = (warnings?.[endpoint] || 0) + 1) === 1) warn(`The Browser Agent is attempting to send a very large payload to /${endpoint}. This is usually tied to large amounts of custom attributes. Please check your configurations.`)
     }
 
     if (!body || body.length === 0 || body === '{}' || body === '[]') {

src/common/harvest/harvest.test.js

@@ -3,6 +3,7 @@ import { faker } from '@faker-js/faker'
 import * as encodeModule from '../url/encode'
 import * as submitDataModule from '../util/submit-data'
 import * as configModule from '../config/config'
+import { warn } from '../util/console'
 import { applyFnToProps } from '../util/traverse'
 
 import { Harvest } from './harvest'
@@ -288,6 +289,20 @@ describe('_send', () => {
     })
   })
 
+  test('should warn (once) if payload is large', () => {
+    spec.payload.body = 'x'.repeat(1024 * 1024) // ~1mb string
+
+    const result = harvestInstance._send(spec)
+
+    expect(result).toEqual(true)
+    expect(warn).toHaveBeenCalledWith(expect.stringContaining('The Browser Agent is attempting to send a very large payload'))
+    expect(warn).toHaveBeenCalledTimes(1)
+
+    const result2 = harvestInstance._send(spec)
+    expect(result2).toEqual(true)
+    expect(warn).toHaveBeenCalledTimes(1)
+  })
+
   test('should set body to events when endpoint is events', () => {
     spec.endpoint = 'events'
     spec.payload.body.e = faker.lorem.sentence()