From 3b28862407fbe4c4c8ad10d358ab443220411339 Mon Sep 17 00:00:00 2001
From: Sebastian Wessel <sebastianwessel@users.noreply.github.com>
Date: Mon, 27 Feb 2023 16:38:57 +0000
Subject: [PATCH] feat: add /healthz endpoint to httpServer resolve #69

---
 .../httpserver/src/HttpServerService.impl.ts  | 15 ++++++++
 .../httpserver/src/config/getDefaultConfig.ts |  1 +
 .../src/routes/openapi/getOpenApiJson.impl.ts | 38 ++++++++++++++++++-
 .../httpserver/src/types/HttpServerConfig.ts  |  1 +
 4 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/packages/httpserver/src/HttpServerService.impl.ts b/packages/httpserver/src/HttpServerService.impl.ts
index 9124a1fa0..a5c438fed 100644
--- a/packages/httpserver/src/HttpServerService.impl.ts
+++ b/packages/httpserver/src/HttpServerService.impl.ts
@@ -161,6 +161,21 @@ export class HttpServerService extends Service<HttpServerConfig> {
         reply.send(new UnhandledError().getErrorResponse())
       }
     })
+
+    if (this.config.enableHealthz) {
+      this.server.get('/healthz', async (_request, reply) => {
+        const isEventBridgeReady = await this.eventBridge.isReady()
+
+        reply.header('content-type', 'application/json; charset=utf-8')
+        if (isEventBridgeReady) {
+          reply.status(StatusCode.OK)
+          reply.send(new HandledError(StatusCode.OK).getErrorResponse())
+          return
+        }
+        reply.status(StatusCode.InternalServerError)
+        reply.send(new HandledError(StatusCode.InternalServerError).getErrorResponse())
+      })
+    }
   }
 
   addBeforeResponse(method: HTTPMethods, pattern: string, handler: BeforeResponseHook) {
diff --git a/packages/httpserver/src/config/getDefaultConfig.ts b/packages/httpserver/src/config/getDefaultConfig.ts
index 0fb4f3dce..31e508fe2 100644
--- a/packages/httpserver/src/config/getDefaultConfig.ts
+++ b/packages/httpserver/src/config/getDefaultConfig.ts
@@ -10,6 +10,7 @@ export const getDefaultConfig = (): HttpServerConfig => {
     domain: 'localhost',
     enableHelmet: true,
     enableCompress: true,
+    enableHealthz: true,
     enableCors: false,
     host: '',
     logLevel: 'warn',
diff --git a/packages/httpserver/src/routes/openapi/getOpenApiJson.impl.ts b/packages/httpserver/src/routes/openapi/getOpenApiJson.impl.ts
index 3df623099..e051bc48b 100644
--- a/packages/httpserver/src/routes/openapi/getOpenApiJson.impl.ts
+++ b/packages/httpserver/src/routes/openapi/getOpenApiJson.impl.ts
@@ -26,6 +26,7 @@ export const getOpenApiJson = function (this: HttpServerService) {
   const security = this.config.openApi?.security
   const externalDocs = this.config.openApi?.externalDocs
   const tags = this.config.openApi?.tags
+  const isHealthzEnabled = this.config.enableHealthz
 
   const logger = this.logger.getChildLogger({
     serviceName: this.info.serviceName,
@@ -51,6 +52,15 @@ export const getOpenApiJson = function (this: HttpServerService) {
       securitySchema = Object.keys(components.securitySchemes).map((name) => ({ [name]: [] }))
     }
 
+    const getErrorName = (code: StatusCode) =>
+      StatusCode[code]
+        .replace(/[A-Z]/g, (letter) => ` ${letter}`)
+        .replace(/^./, (str) => {
+          return str.toUpperCase()
+        })
+        .trim()
+        .replace(/^O K$/g, 'OK')
+
     const getErrorResponseSchema = (code: StatusCode, message: string, schema?: SchemaObject) => {
       return {
         type: 'object',
@@ -225,8 +235,6 @@ export const getOpenApiJson = function (this: HttpServerService) {
 
       const errorResponses: Record<number, unknown> = {}
 
-      const getErrorName = (code: StatusCode) => StatusCode[code].replace(/[A-Z]/g, (letter) => ` ${letter}`)
-
       if (definition.openApi?.inputPayload) {
         errorResponses[400] = {
           description: getErrorName(400),
@@ -306,6 +314,32 @@ export const getOpenApiJson = function (this: HttpServerService) {
       }
     })
 
+    if (isHealthzEnabled) {
+      json.paths['/healthz'] = {
+        get: {
+          description: 'indicates if the http server service is healthy',
+          responses: {
+            200: {
+              description: 'http server service is up and running and successfully connected to event bridge',
+              content: {
+                'application/json': {
+                  schema: getErrorResponseSchema(200, getErrorName(200)),
+                },
+              },
+            },
+            500: {
+              description: 'http server service is not up and running or not successfully connected to event bridge',
+              content: {
+                'application/json': {
+                  schema: getErrorResponseSchema(500, getErrorName(500)),
+                },
+              },
+            },
+          },
+        },
+      }
+    }
+
     reply.header('content-type', 'application/json; charset=utf-8')
     return json
   }
diff --git a/packages/httpserver/src/types/HttpServerConfig.ts b/packages/httpserver/src/types/HttpServerConfig.ts
index a3c09707b..52c3e460f 100644
--- a/packages/httpserver/src/types/HttpServerConfig.ts
+++ b/packages/httpserver/src/types/HttpServerConfig.ts
@@ -23,6 +23,7 @@ export type HttpServerConfig = {
   cookieSecret?: string
   apiMountPath?: string
   enableHelmet?: boolean
+  enableHealthz?: boolean
   helmetOptions?: FastifyHelmetOptions
   enableCompress?: boolean
   compressOptions?: FastifyCompressOptions