From 9f65041bda08adc01edc8836b8a63249dd053cd0 Mon Sep 17 00:00:00 2001
From: Scott Hawker <shawker@commercehub.com>
Date: Thu, 2 Apr 2026 09:24:59 -0600
Subject: [PATCH 1/2] fix(stream): handle S3 upload errors without crashing the
 process

When an S3 upload fails (e.g., RequestTimeout), the error flows through
toS3()'s .catch() handler which calls toS3Stream.emit("error", err).
If no error listener is attached to that stream, emit("error") throws,
and since the throw happens inside a .catch() handler, it creates a new
unhandled promise rejection that crashes the Lambda runtime.

Three changes:

1. toS3() .catch(): Stop calling emit("error") on the stream. Just
   store the error and set the emittedError flag. The error propagates
   through the _final callback when the stream is ended.

2. leos3.js newStream(): Add an error listener on the internal s3
   upload stream so any error events have a listener and don't throw.

3. leos3.js submitStream(): Listen for both "error" and "finish"
   events with a callback guard. Previously only "finish" was handled,
   but _final(callback) with a truthy error emits "error" not "finish".

Task: ES-2976
Made-with: Cursor
---
 lib/stream/helper/leos3.js | 19 ++++++++++++++-----
 lib/stream/leo-stream.js   |  5 +----
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/lib/stream/helper/leos3.js b/lib/stream/helper/leos3.js
index cae5380..8304336 100644
--- a/lib/stream/helper/leos3.js
+++ b/lib/stream/helper/leos3.js
@@ -23,13 +23,19 @@ module.exports = function(ls, queue, configure, opts, onFlush) {
 
 	function submitStream(callback) {
 		if (count > 0) {
-			s3.on("finish", (err) => {
-				if (err) {
-					logger.error(err);
-				} else {
+			let called = false;
+			s3.on("error", (err) => {
+				if (!called) {
+					called = true;
+					callback(err);
+				}
+			});
+			s3.on("finish", () => {
+				if (!called) {
+					called = true;
 					logger.debug("UPLOADED FILE");
+					callback();
 				}
-				callback(err);
 			});
 			s3.end();
 		} else {
@@ -72,6 +78,9 @@ module.exports = function(ls, queue, configure, opts, onFlush) {
 
 		logger.info("S3 Location:", newFile);
 		s3 = ls.toS3(configure.resources.LeoS3 || configure.s3, newFile);
+		s3.on('error', (err) => {
+			logger.error("S3 upload error for queue '" + queue + "':", err);
+		});
 		e = {
 			event: queue,
 			start: null,
diff --git a/lib/stream/leo-stream.js b/lib/stream/leo-stream.js
index d06e02d..591c4a8 100644
--- a/lib/stream/leo-stream.js
+++ b/lib/stream/leo-stream.js
@@ -174,10 +174,7 @@ module.exports = function(configure) {
 				}
 			}).done().catch(err => {
 				uploadDonePromiseError = err;
-				if (toS3Stream) {
-					emittedError = true;
-					toS3Stream.emit("error", uploadDonePromiseError);
-				}
+				emittedError = true;
 			});
 
 			toS3Stream = write((s, enc, done) => {

From 9f45a09b60c208324b3415ea4c0ffac38d3754e6 Mon Sep 17 00:00:00 2001
From: Scott Hawker <shawker@commercehub.com>
Date: Thu, 2 Apr 2026 10:17:48 -0600
Subject: [PATCH 2/2] revert: restore toS3() error emission in leo-stream.js
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Revert the leo-stream.js change from 9f65041. The original behavior of
emitting the error on toS3Stream is correct — the fix in leos3.js adds
the missing error listener that catches it.

Task: ES-2976
---
 lib/stream/leo-stream.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/stream/leo-stream.js b/lib/stream/leo-stream.js
index 591c4a8..d06e02d 100644
--- a/lib/stream/leo-stream.js
+++ b/lib/stream/leo-stream.js
@@ -174,7 +174,10 @@ module.exports = function(configure) {
 				}
 			}).done().catch(err => {
 				uploadDonePromiseError = err;
-				emittedError = true;
+				if (toS3Stream) {
+					emittedError = true;
+					toS3Stream.emit("error", uploadDonePromiseError);
+				}
 			});
 
 			toS3Stream = write((s, enc, done) => {