From d6653c9b0bc718c7e941f263b79ed50ae69dec88 Mon Sep 17 00:00:00 2001
From: Daniel Jackins <djackins@twilio.com>
Date: Mon, 1 Jul 2024 20:35:57 -0600
Subject: [PATCH 1/3] flush keepalive batches earlier

---
 .../__tests__/batched-dispatcher.test.ts      | 25 +++++++++++++++++++
 .../plugins/segmentio/batched-dispatcher.ts   | 16 ++++++++++--
 2 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/packages/browser/src/plugins/segmentio/__tests__/batched-dispatcher.test.ts b/packages/browser/src/plugins/segmentio/__tests__/batched-dispatcher.test.ts
index d45ddd32a..869c9fc86 100644
--- a/packages/browser/src/plugins/segmentio/__tests__/batched-dispatcher.test.ts
+++ b/packages/browser/src/plugins/segmentio/__tests__/batched-dispatcher.test.ts
@@ -130,6 +130,31 @@ describe('Batching', () => {
     expect(fetch).toHaveBeenCalledTimes(1)
   })
 
+  it('sends requests if the size of events exceeds keepalive limits', async () => {
+    const { dispatch } = batch(`https://api.segment.io`, {
+      size: 600,
+      keepalive: true,
+    })
+
+    // fatEvent is about ~1kb in size
+    for (let i = 0; i < 250; i++) {
+      await dispatch(`https://api.segment.io/v1/t`, {
+        event: 'small event',
+      })
+    }
+    expect(fetch).not.toHaveBeenCalled()
+
+    for (let i = 0; i < 65; i++) {
+      await dispatch(`https://api.segment.io/v1/t`, {
+        event: 'fat event',
+        properties: fatEvent,
+      })
+    }
+
+    // still called, even though our batch limit is 600 events
+    expect(fetch).toHaveBeenCalledTimes(1)
+  })
+
   it('sends requests when the timeout expires', async () => {
     const { dispatch } = batch(`https://api.segment.io`, {
       size: 100,
diff --git a/packages/browser/src/plugins/segmentio/batched-dispatcher.ts b/packages/browser/src/plugins/segmentio/batched-dispatcher.ts
index 1fb172d6a..91d7575c5 100644
--- a/packages/browser/src/plugins/segmentio/batched-dispatcher.ts
+++ b/packages/browser/src/plugins/segmentio/batched-dispatcher.ts
@@ -5,6 +5,7 @@ import { onPageChange } from '../../lib/on-page-change'
 export type BatchingDispatchConfig = {
   size?: number
   timeout?: number
+  keepalive?: boolean
 }
 
 const MAX_PAYLOAD_SIZE = 500
@@ -23,6 +24,15 @@ function approachingTrackingAPILimit(buffer: unknown): boolean {
   return kilobytes(buffer) >= MAX_PAYLOAD_SIZE - 50
 }
 
+/**
+ * Checks if payload is over the limit for keepalive
+ * requests. If keepalive is enabled we want to avoid
+ * going over this to prevent data loss.
+ */
+function passedKeepaliveLimit(buffer: unknown): boolean {
+  return kilobytes(buffer) >= 64
+}
+
 function chunks(batch: object[]): Array<object[]> {
   const result: object[][] = []
   let index = 0
@@ -67,7 +77,7 @@ export default function batch(
     })
 
     return fetch(`https://${apiHost}/b`, {
-      keepalive: pageUnloaded,
+      keepalive: config?.keepalive || pageUnloaded,
       headers: {
         'Content-Type': 'text/plain',
       },
@@ -114,7 +124,9 @@ export default function batch(
     buffer.push(body)
 
     const bufferOverflow =
-      buffer.length >= limit || approachingTrackingAPILimit(buffer)
+      buffer.length >= limit ||
+      approachingTrackingAPILimit(buffer) ||
+      (config?.keepalive && passedKeepaliveLimit(buffer))
 
     return bufferOverflow || pageUnloaded ? flush() : scheduleFlush()
   }

From fd295d5e531aa5adc003ca759038bee220e3be7b Mon Sep 17 00:00:00 2001
From: Daniel Jackins <djackins@twilio.com>
Date: Tue, 2 Jul 2024 10:29:07 -0600
Subject: [PATCH 2/3] changeset

---
 .changeset/shaggy-dryers-press.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/shaggy-dryers-press.md

diff --git a/.changeset/shaggy-dryers-press.md b/.changeset/shaggy-dryers-press.md
new file mode 100644
index 000000000..efc9755a5
--- /dev/null
+++ b/.changeset/shaggy-dryers-press.md
@@ -0,0 +1,5 @@
+---
+'@segment/analytics-next': minor
+---
+
+Flush large keepalive requests

From e6cba113184d4575a0d55fbe7fcd986939f0d30e Mon Sep 17 00:00:00 2001
From: Daniel Jackins <djackins@twilio.com>
Date: Tue, 2 Jul 2024 10:57:41 -0600
Subject: [PATCH 3/3] add small buffer

---
 packages/browser/src/plugins/segmentio/batched-dispatcher.ts | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/packages/browser/src/plugins/segmentio/batched-dispatcher.ts b/packages/browser/src/plugins/segmentio/batched-dispatcher.ts
index 91d7575c5..bfc123c80 100644
--- a/packages/browser/src/plugins/segmentio/batched-dispatcher.ts
+++ b/packages/browser/src/plugins/segmentio/batched-dispatcher.ts
@@ -9,6 +9,7 @@ export type BatchingDispatchConfig = {
 }
 
 const MAX_PAYLOAD_SIZE = 500
+const MAX_KEEPALIVE_SIZE = 64
 
 function kilobytes(buffer: unknown): number {
   const size = encodeURI(JSON.stringify(buffer)).split(/%..|./).length - 1
@@ -25,12 +26,12 @@ function approachingTrackingAPILimit(buffer: unknown): boolean {
 }
 
 /**
- * Checks if payload is over the limit for keepalive
+ * Checks if payload is over or approaching the limit for keepalive
  * requests. If keepalive is enabled we want to avoid
  * going over this to prevent data loss.
  */
 function passedKeepaliveLimit(buffer: unknown): boolean {
-  return kilobytes(buffer) >= 64
+  return kilobytes(buffer) >= MAX_KEEPALIVE_SIZE - 10
 }
 
 function chunks(batch: object[]): Array<object[]> {