From 769fc90818c5c6334ecf07460efda557bcea71f9 Mon Sep 17 00:00:00 2001
From: Richard <richard.spenceley@zappistore.com>
Date: Fri, 9 Oct 2026 18:50:46 +0100
Subject: [PATCH] [STO-928] Return X-Trace-ID on every response and pin the
 OTel module

add_header without 'always' only applies to 200, 201, 204, 206 and 3xx
responses, so 202s and every error response went out without a trace ID.

nginx-module-otel was installed unpinned from the nginx mainline repo. Its
latest build depends on nginx 1.31.6, which upgraded nginx past the 1.31.3
source the headers-more module is compiled against, so a fresh build of
master fails to start.
---
 CHANGELOG.md     | 5 +++++
 Dockerfile       | 3 ++-
 config/http.conf | 2 +-
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index d82b5f4..e037735 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changelog
 
+## 1.31.3-1
+
+* Return `X-Trace-ID` on every response, including `202` and `4xx`/`5xx`.
+* Pin `nginx-module-otel` to the base image's nginx version.
+
 ## 1.31.3
 
 * Update base image to `zappi/nginx:1.31.3` (Debian Trixie).
diff --git a/Dockerfile b/Dockerfile
index 7b20c36..68f84ec 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -56,9 +56,10 @@ RUN apt-get update -y && \
         wget
 
 # Module: OpenTelemetry (OTel)
+ARG NGINX_OTEL_VERSION="0.1.2-1~trixie"
 RUN apt-get update -y && \
     apt-get install --no-install-recommends -y \
-      nginx-module-otel && \
+      "nginx-module-otel=${NGINX_VERSION}+${NGINX_OTEL_VERSION}" && \
     rm -rf /var/lib/apt/lists/* /tmp/*
 
 # Copy compiled module
diff --git a/config/http.conf b/config/http.conf
index c31b2e1..99de6b2 100644
--- a/config/http.conf
+++ b/config/http.conf
@@ -114,7 +114,7 @@ http {
   add_header    X-Proxy-Request-Time            $request_time;
 
   # Observability headers
-  add_header    X-Trace-ID    $otel_trace_id;
+  add_header    X-Trace-ID    $otel_trace_id always;
 
   gzip on;
   gzip_comp_level 5;