feat(server): custom header support (#198)

* Added support for writing headers

* Updated ReadMe

* Made headers apart of options

* Removed res.status

* Added test coverage

Author: LuigiZaccagnini

README.md

@@ -105,6 +105,40 @@ createTerminus(server, {
 });
 ```
 
+### With custom headers
+```js
+const http = require("http");
+const express = require("express");
+const { createTerminus, HealthCheckError } = require('@godaddy/terminus');
+const app = express();
+
+app.get("/", (req, res) => {
+  res.send("ok");
+});
+
+const server = http.createServer(app);
+
+function healthCheck({ state }) {
+  return Promise.resolve();
+}
+
+const options = {
+  healthChecks: {
+    "/healthcheck": healthCheck,
+    verbatim: true,
+    __unsafeExposeStackTraces: true,
+  },
+  headers: {
+    "Access-Control-Allow-Origin": "*",
+    "Access-Control-Allow-Methods": "OPTIONS, POST, GET",
+  },
+};
+
+terminus.createTerminus(server, options);
+
+server.listen(3000);
+```
+
 ### With express
 
 ```javascript

lib/terminus.js

@@ -15,9 +15,9 @@ function noopResolves () {
   return Promise.resolve()
 }
 
-async function sendSuccess (res, { info, verbatim, statusOk }) {
-  res.statusCode = statusOk
+async function sendSuccess (res, { info, verbatim, statusOk, headers }) {
   res.setHeader('Content-Type', 'application/json')
+  res.writeHead(statusOk, headers)
   if (info) {
     return res.end(
       JSON.stringify(
@@ -34,7 +34,7 @@ async function sendSuccess (res, { info, verbatim, statusOk }) {
 }
 
 async function sendFailure (res, options) {
-  const { error, onSendFailureDuringShutdown, exposeStackTraces, statusCode, statusError } = options
+  const { error, headers, onSendFailureDuringShutdown, exposeStackTraces, statusCode, statusError } = options
 
   function replaceErrors (_, value) {
     if (value instanceof Error) {
@@ -54,8 +54,8 @@ async function sendFailure (res, options) {
   if (onSendFailureDuringShutdown) {
     await onSendFailureDuringShutdown()
   }
-  res.statusCode = statusCode || statusError
   res.setHeader('Content-Type', 'application/json')
+  res.writeHead(statusCode || statusError, headers)
   if (error) {
     return res.end(JSON.stringify({
       status: 'error',
@@ -73,7 +73,7 @@ const intialState = {
 function noop () {}
 
 function decorateWithHealthCheck (server, state, options) {
-  const { healthChecks, logger, onSendFailureDuringShutdown, sendFailuresDuringShutdown, caseInsensitive, statusOk, statusError } = options
+  const { healthChecks, logger, headers, onSendFailureDuringShutdown, sendFailuresDuringShutdown, caseInsensitive, statusOk, statusError } = options
 
   let hasSetHandler = false
   const createHandler = (listener) => {
@@ -88,16 +88,29 @@ function decorateWithHealthCheck (server, state, options) {
           info = await healthCheck({ state })
         } catch (error) {
           logger('healthcheck failed', error)
-          return sendFailure(res, { error: error.causes, exposeStackTraces: healthChecks.__unsafeExposeStackTraces, statusCode: error.statusCode, statusError })
+          return sendFailure(
+            res,
+            {
+              error: error.causes,
+              headers,
+              exposeStackTraces: healthChecks.__unsafeExposeStackTraces,
+              statusCode: error.statusCode,
+              statusError
+            }
+          )
         }
-        return sendSuccess(res, { info, verbatim: healthChecks.verbatim, statusOk })
+        return sendSuccess(
+          res,
+          { info, verbatim: healthChecks.verbatim, statusOk, headers }
+        )
       }
 
     hasSetHandler = true
 
     return async (req, res) => {
       const url = caseInsensitive ? req.url.toLowerCase() : req.url
       const healthCheck = healthChecks[url]
+
       if (healthCheck) {
         return check(healthCheck, res)
       } else {
@@ -164,7 +177,8 @@ function terminus (server, options = {}) {
     logger = noop,
     caseInsensitive = false,
     statusOk = 200,
-    statusError = 503
+    statusError = 503,
+    headers = options.headers || {}
   } = options
   const onSignal = options.onSignal || options.onSigterm || noopResolves
   const state = Object.assign({}, intialState)
@@ -177,7 +191,8 @@ function terminus (server, options = {}) {
       onSendFailureDuringShutdown,
       caseInsensitive,
       statusOk,
-      statusError
+      statusError,
+      headers
     })
   }
 
@@ -190,7 +205,8 @@ function terminus (server, options = {}) {
     beforeShutdown,
     onShutdown,
     timeout,
-    logger
+    logger,
+    headers
   })
 
   return server

lib/terminus.spec.js

@@ -656,4 +656,27 @@ describe('Terminus', () => {
       'server3:onSignal'
     ].join('\n'))
   })
-})
+
+  it('accepts custom headers', async () => {
+  
+  createTerminus(server, {
+    healthChecks: {
+      '/health': () => {
+        return Promise.resolve()
+      }
+    },
+    headers: {
+      "Access-Control-Allow-Origin": "*",
+      "Access-Control-Allow-Methods": "OPTIONS, POST, GET",
+    },
+  })
+  server.listen(8000)
+
+  const res = await fetch('http://localhost:8000/health')
+  expect(res.status).to.eql(200)
+  expect(res.headers.has('Access-Control-Allow-Methods')).to.eql(true)
+  expect(res.headers.get('Access-Control-Allow-Methods')).to.eql('OPTIONS, POST, GET')
+  expect(res.headers.has('Access-Control-Allow-Origin')).to.eql(true)
+  expect(res.headers.get('Access-Control-Allow-Origin')).to.eql('*')
+  })
+})