From 9ee6907009c024d647f558ec0c6d866712ef3ab7 Mon Sep 17 00:00:00 2001
From: Petr Heinz <petr@betterstack.com>
Date: Wed, 2 Sep 2026 17:47:14 +0200
Subject: [PATCH] T-16672 Throw on ingesting errors so AWS retries the
 invocation

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 index.js           |  3 ++-
 test/index.test.js | 52 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/index.js b/index.js
index 04826eb..f0d2484 100644
--- a/index.js
+++ b/index.js
@@ -5,7 +5,8 @@ import { parseRecords } from "./src/parser.js"
 if (!process.env.BETTER_STACK_SOURCE_TOKEN) {
   throw new Error("Better Stack source token has not been set in ENV variable BETTER_STACK_SOURCE_TOKEN.")
 }
-const options = {}
+// Fail the Lambda invocation when logs can't be delivered, so AWS retries it
+const options = { throwExceptions: true }
 if (process.env.BETTER_STACK_ENTRYPOINT) {
   options.endpoint = process.env.BETTER_STACK_ENTRYPOINT
 }
diff --git a/test/index.test.js b/test/index.test.js
index 57c784a..b54ba43 100644
--- a/test/index.test.js
+++ b/test/index.test.js
@@ -125,3 +125,55 @@ test("handler sends gzip-compressed MessagePack logs", async t => {
     request_id: requestId,
   })
 })
+
+test("handler rejects when ingesting fails, so AWS retries the invocation", async t => {
+  let requestCount = 0
+  const server = createServer((request, response) => {
+    request.on("data", () => {})
+    request.on("end", () => {
+      requestCount++
+      response.writeHead(500)
+      response.end()
+    })
+  })
+
+  server.listen(0, "127.0.0.1")
+  await once(server, "listening")
+
+  const previousToken = process.env.BETTER_STACK_SOURCE_TOKEN
+  const previousEntrypoint = process.env.BETTER_STACK_ENTRYPOINT
+  const { port } = server.address()
+
+  process.env.BETTER_STACK_SOURCE_TOKEN = "source-token"
+  process.env.BETTER_STACK_ENTRYPOINT = `http://127.0.0.1:${port}`
+
+  t.after(async () => {
+    if (previousToken === undefined) {
+      delete process.env.BETTER_STACK_SOURCE_TOKEN
+    } else {
+      process.env.BETTER_STACK_SOURCE_TOKEN = previousToken
+    }
+
+    if (previousEntrypoint === undefined) {
+      delete process.env.BETTER_STACK_ENTRYPOINT
+    } else {
+      process.env.BETTER_STACK_ENTRYPOINT = previousEntrypoint
+    }
+
+    await new Promise((resolve, reject) => {
+      server.close(error => error ? reject(error) : resolve())
+    })
+  })
+
+  const event = { source: "unknown" }
+  const context = {
+    functionName: "forward-cloudwatch-logs",
+    invokedFunctionArn: "arn:aws:lambda:eu-west-1:123456789012:function:forward-cloudwatch-logs",
+  }
+
+  // Query string busts the module cache so the logger is created with this test's entrypoint
+  const { handler } = await import("../index.js?failing-ingest")
+  await assert.rejects(handler(event, context))
+
+  assert.ok(requestCount >= 1)
+})