From 4eeec0b773e03c11742e63e06e3c0021c1e829a0 Mon Sep 17 00:00:00 2001
From: Dmitrii Fedorov <dmitrii.fedorov@sentry.io>
Date: Wed, 7 May 2025 17:44:05 -0700
Subject: [PATCH] feat(envoy): Allow to pass arbitrary http headers to upstream
 calls

---
 relay-config/src/config.rs            | 11 +++++++++++
 relay-server/src/services/upstream.rs |  4 ++++
 2 files changed, 15 insertions(+)

diff --git a/relay-config/src/config.rs b/relay-config/src/config.rs
index 2637f591ba..fef39aec5f 100644
--- a/relay-config/src/config.rs
+++ b/relay-config/src/config.rs
@@ -854,6 +854,11 @@ pub struct Http {
     ///
     /// This option does not have any effect on processing mode.
     pub global_metrics: bool,
+    /// Additional HTTP headers to send with every request to the upstream.
+    ///
+    /// These headers are added to every request made to the upstream. They can be used to
+    /// configure custom authentication, routing, or other HTTP headers required by the upstream.
+    additional_headers: HashMap<String, String>,
 }
 
 impl Default for Http {
@@ -869,6 +874,7 @@ impl Default for Http {
             project_failure_interval: default_project_failure_interval(),
             encoding: HttpEncoding::Zstd,
             global_metrics: false,
+            additional_headers: HashMap::new(),
         }
     }
 }
@@ -1898,6 +1904,11 @@ impl Config {
         self.values.http.host_header.as_deref()
     }
 
+    /// Returns additional HTTP headers to send with every request to the upstream.
+    pub fn http_additional_headers(&self) -> &HashMap<String, String> {
+        &self.values.http.additional_headers
+    }
+
     /// Returns the listen address.
     pub fn listen_addr(&self) -> SocketAddr {
         (self.values.relay.host, self.values.relay.port).into()
diff --git a/relay-server/src/services/upstream.rs b/relay-server/src/services/upstream.rs
index dce270d6eb..47b9770845 100644
--- a/relay-server/src/services/upstream.rs
+++ b/relay-server/src/services/upstream.rs
@@ -771,9 +771,13 @@ impl SharedClient {
                 .config
                 .http_host_header()
                 .unwrap_or_else(|| self.config.upstream_descriptor().host());
+            let additional_headers = self.config.http_additional_headers();
 
             let mut builder = RequestBuilder::reqwest(self.reqwest.request(request.method(), url));
             builder.header("Host", host_header.as_bytes());
+            for (key, value) in additional_headers {
+                builder.header(key, value);
+            }
 
             if request.set_relay_id() {
                 if let Some(credentials) = self.config.credentials() {