From f4bb56fe328f7055faaa10cf69d96c5e1d643e3b Mon Sep 17 00:00:00 2001
From: Dominik Broj <dominik.broj@grafana.com>
Date: Mon, 11 Mar 2024 10:23:16 +0100
Subject: [PATCH] Fix passing additional headers to custom fetch (#4038)

# What this PR does

Fix passing additional headers to custom fetch

## Which issue(s) this PR closes

Closes https://github.com/grafana/support-escalations/issues/9630

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## Checklist

- [ ] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required)
- [x] Added the relevant release notes label (see labels prefixed w/
`release:`). These labels dictate how your PR will
    show up in the autogenerated release notes.
---
 .../network/oncall-api/http-client.test.ts    |  6 ++--
 .../src/network/oncall-api/http-client.ts     | 28 ++++++++-----------
 2 files changed, 15 insertions(+), 19 deletions(-)

diff --git a/grafana-plugin/src/network/oncall-api/http-client.test.ts b/grafana-plugin/src/network/oncall-api/http-client.test.ts
index d7e315a7..a3acc789 100644
--- a/grafana-plugin/src/network/oncall-api/http-client.test.ts
+++ b/grafana-plugin/src/network/oncall-api/http-client.test.ts
@@ -21,10 +21,10 @@ jest.mock('openapi-fetch', () => ({
 
 const fetchMock = jest.fn().mockResolvedValue(true);
 
+const HEADERS = new Headers();
+HEADERS.set('Content-Type', 'application/json');
 const REQUEST_CONFIG = {
-  headers: {
-    'Content-Type': 'application/json',
-  },
+  headers: HEADERS,
 };
 const URL = 'https://someurl.com';
 const SUCCESSFUL_RESPONSE_MOCK = { ok: true };
diff --git a/grafana-plugin/src/network/oncall-api/http-client.ts b/grafana-plugin/src/network/oncall-api/http-client.ts
index 4d5b4a20..ef0d630e 100644
--- a/grafana-plugin/src/network/oncall-api/http-client.ts
+++ b/grafana-plugin/src/network/oncall-api/http-client.ts
@@ -20,24 +20,20 @@ const showApiError = (errorResponse: Response) => {
 
 export const getCustomFetchFn =
   ({ withGlobalErrorHandler }: { withGlobalErrorHandler: boolean }) =>
-  async (url: string, reqConfig: Parameters<typeof fetch>[1] = {}): Promise<Response> => {
+  async (url: string, requestConfig: Parameters<typeof fetch>[1] & { headers?: Headers } = {}): Promise<Response> => {
     const { faro } = FaroHelper;
     const otel = faro?.api?.getOTEL();
-    const requestConfig = {
-      ...reqConfig,
-      headers: {
-        ...reqConfig.headers,
-        'Content-Type': 'application/json',
-        /**
-         * In short, this header will tell the Grafana plugin proxy, a Go service which use Go's HTTP Transport,
-         * to retry POST requests (and other non-idempotent requests). This doesn't necessarily make these requests
-         * idempotent, but it will make them retry-able from Go's (read: net/http) perspective.
-         *
-         * https://stackoverflow.com/questions/42847294/how-to-catch-http-server-closed-idle-connection-error/62292758#62292758
-         * https://raintank-corp.slack.com/archives/C01C4K8DETW/p1692280544382739?thread_ts=1692279329.797149&cid=C01C4K8DETW
-         */ 'X-Idempotency-Key': `${Date.now()}-${Math.random()}`,
-      },
-    };
+
+    /**
+     * In short, this header will tell the Grafana plugin proxy, a Go service which use Go's HTTP Transport,
+     * to retry POST requests (and other non-idempotent requests). This doesn't necessarily make these requests
+     * idempotent, but it will make them retry-able from Go's (read: net/http) perspective.
+     *
+     * https://stackoverflow.com/questions/42847294/how-to-catch-http-server-closed-idle-connection-error/62292758#62292758
+     * https://raintank-corp.slack.com/archives/C01C4K8DETW/p1692280544382739?thread_ts=1692279329.797149&cid=C01C4K8DETW
+     */
+    requestConfig.headers.set('X-Idempotency-Key', `${Date.now()}-${Math.random()}`);
+    requestConfig.headers.set('Content-Type', 'application/json');
 
     if (faro && otel) {
       const tracer = otel.trace.getTracer('default');