From 41ad594229bdcc149740e0307bac9e0a15ed57f6 Mon Sep 17 00:00:00 2001
From: Etienne Donneger <etienne@pinax.network>
Date: Mon, 26 Aug 2024 14:06:10 +0000
Subject: [PATCH] Change Prometheus `/metrics` response from JSON to text (#68)

---
 index.ts                                          |  4 ++--
 src/types/zod.gen.ts                              |  9 +++++++--
 src/typespec/openapi3.tsp                         |  2 +-
 static/@openapi-to-graphql/graphql/schema.graphql |  2 +-
 static/@typespec/openapi3/openapi.json            | 13 +++++++++++--
 5 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/index.ts b/index.ts
index 1824214..91979d8 100644
--- a/index.ts
+++ b/index.ts
@@ -72,7 +72,7 @@ async function AntelopeTokenAPI() {
 
     app.get(
         "/metrics",
-        async (ctx: Context) => ctx.json<EndpointReturnTypes<"/metrics">, 200>(await prometheus.registry.getMetricsAsJSON())
+        async (ctx: Context) => new Response(await prometheus.registry.metrics())
     );
 
     // --------------------------
@@ -133,7 +133,7 @@ async function AntelopeTokenAPI() {
                         return response.success ? "OK" : `[500] bad_database_response: ${response.error.message}`;
                     },
                     openapi: () => openapi,
-                    metrics: async () => await prometheus.registry.getMetricsAsJSON(),
+                    metrics: async () => await prometheus.registry.metrics(),
                     version: () => APP_VERSION
                 }
             );
diff --git a/src/types/zod.gen.ts b/src/types/zod.gen.ts
index 8a52176..985f833 100644
--- a/src/types/zod.gen.ts
+++ b/src/types/zod.gen.ts
@@ -78,12 +78,17 @@ export type MonitoringHealthQueryResponseSchema = z.infer<typeof monitoringHealt
  /**
  * @description Metrics as text.
  */
-export const monitoringMetrics200Schema = z.object({});
+export const monitoringMetrics200Schema = z.coerce.string();
 export type MonitoringMetrics200Schema = z.infer<typeof monitoringMetrics200Schema>;
+/**
+ * @description An unexpected error response.
+ */
+export const monitoringMetricsErrorSchema = z.lazy(() => apiErrorSchema);
+export type MonitoringMetricsErrorSchema = z.infer<typeof monitoringMetricsErrorSchema>;
 /**
  * @description Metrics as text.
  */
-export const monitoringMetricsQueryResponseSchema = z.object({});
+export const monitoringMetricsQueryResponseSchema = z.coerce.string();
 export type MonitoringMetricsQueryResponseSchema = z.infer<typeof monitoringMetricsQueryResponseSchema>;
 
  /**
diff --git a/src/typespec/openapi3.tsp b/src/typespec/openapi3.tsp
index 9133b53..2c7a88c 100644
--- a/src/typespec/openapi3.tsp
+++ b/src/typespec/openapi3.tsp
@@ -242,5 +242,5 @@ interface Monitoring {
     @summary("Prometheus metrics")
     @route("/metrics")
     @get
-    metrics(): Record<unknown>;
+    metrics(): APIResponse<string>;
 }
diff --git a/static/@openapi-to-graphql/graphql/schema.graphql b/static/@openapi-to-graphql/graphql/schema.graphql
index d544624..3add36c 100644
--- a/static/@openapi-to-graphql/graphql/schema.graphql
+++ b/static/@openapi-to-graphql/graphql/schema.graphql
@@ -32,7 +32,7 @@ type Query {
   
   Equivalent to GET /metrics
   """
-  metrics: JSON
+  metrics: String
 
   """
   Reflection endpoint to return OpenAPI JSON spec. Also used by Swagger to generate the frontpage.
diff --git a/static/@typespec/openapi3/openapi.json b/static/@typespec/openapi3/openapi.json
index 93d72ab..a931736 100644
--- a/static/@typespec/openapi3/openapi.json
+++ b/static/@typespec/openapi3/openapi.json
@@ -151,8 +151,17 @@
             "content": {
               "application/json": {
                 "schema": {
-                  "type": "object",
-                  "additionalProperties": {}
+                  "type": "string"
+                }
+              }
+            }
+          },
+          "default": {
+            "description": "An unexpected error response.",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/APIError"
                 }
               }
             }