Merge pull request #21 from nhsuk/healthcheck

Healthcheck

README.md

@@ -75,6 +75,14 @@ Free-text user comments.
 }
 ```
 
+### Healthcheck
+
+Test the health of the function. Useful for monitoring.
+
+Returns a 503 response if database is unreachable. 200 OK otherwise.
+
+`GET /healthcheck/`
+
 ## Contributing
 
 ### Tests

comments/index.js

@@ -1,3 +1,3 @@
-const { handleRequest, requestTypes } = require('../lib/index.js');
+const { handleComments } = require('../lib/index.js');
 
-module.exports = (context, req) => handleRequest(context, req, requestTypes.COMMENTS);
+module.exports = (context, req) => handleComments(context, req);

healthcheck/function.json

@@ -0,0 +1,18 @@
+{
+    "bindings": [
+      {
+        "authLevel": "anonymous",
+        "type": "httpTrigger",
+        "direction": "in",
+        "name": "req",
+        "methods": [
+          "get"
+        ]
+      },
+      {
+        "type": "http",
+        "direction": "out",
+        "name": "$return"
+      }
+    ]
+}

healthcheck/index.js

@@ -0,0 +1,3 @@
+const { handleHealthcheck } = require('../lib/index.js');
+
+module.exports = async (context, req) => handleHealthcheck(context, req);

lib/database.js

@@ -11,6 +11,21 @@ const COLLECTION_NAME = 'feedback';
 
 const { validateInitialResponse, validateTextComments } = require('./validation.js');
 
+/**
+ * @returns {Promise} - A promise which returns true for healthy connection, false for unhealthy.
+ */
+module.exports.healthcheck = async () => {
+  try {
+    const client = await mongoClient.connect(CONNECTION_STRING);
+    const db = client.db(DB_NAME);
+    const result = await db.admin().ping();
+    return result.ok === 1;
+  } catch (err) {
+    console.error(err); // eslint-disable-line no-console
+    return false;
+  }
+};
+
 /**
  * @param {Object} data - Data object to be saved into the database
  * @returns {Promise} - A promise which resolves to a unique token

lib/index.js

@@ -2,48 +2,53 @@ const database = require('./database.js');
 const { HttpError } = require('./validation.js');
 const responses = require('./responses.js');
 
-const requestTypes = {
-  COMMENTS: 'COMMENTS',
-  SATISFIED: 'SATISFIED',
+const handleError = (err) => {
+  // only return error message in response if it is a HttpError
+  if (err instanceof HttpError) {
+    return responses.httpError(err.statusCode, err.message);
+  }
+  console.error('500 ERROR:', err.message); // eslint-disable-line no-console
+  return responses.error500();
 };
 
-module.exports.requestTypes = requestTypes;
+module.exports.handleHealthcheck = async () => {
+  const healthy = await database.healthcheck();
+  if (!healthy) {
+    return responses.httpError(503, 'Service unavailable');
+  }
+
+  return responses.healthcheckOk();
+};
 
-/**
- * @param {Object} context - See azure function context documentation
- * @param {Object} req - See azure function request documentation
- * @param {string} requestType - requestTypes enum value representing which type of request this is
- * @returns {Object} response object
- */
-module.exports.handleRequest = async (context, req, requestType) => {
+module.exports.handleSatisfied = async (context, req) => {
   if (!req.body) {
     return responses.nodata();
   }
-
   let token = req.body.token || null;
-
   try {
-    if (requestType === requestTypes.SATISFIED) {
-      token = await database.saveInitialResponse({
-        isSatisfied: req.body.isSatisfied,
-        token,
-        url: req.body.url,
-      });
-    }
-    if (requestType === requestTypes.COMMENTS) {
-      token = await database.saveTextComments({
-        comments: req.body.comments,
-        token,
-      });
-    }
+    token = await database.saveInitialResponse({
+      isSatisfied: req.body.isSatisfied,
+      token,
+      url: req.body.url,
+    });
   } catch (err) {
-    // only return error message in response if it is a HttpError
-    if (err instanceof HttpError) {
-      return responses.httpError(err.statusCode, err.message);
-    }
-    context.log('500 ERROR:', err.message);
-    return responses.error500();
+    return handleError(err);
   }
+  return responses.ok(token);
+};
 
+module.exports.handleComments = async (context, req) => {
+  if (!req.body) {
+    return responses.nodata();
+  }
+  let token = req.body.token || null;
+  try {
+    token = await database.saveTextComments({
+      comments: req.body.comments,
+      token,
+    });
+  } catch (err) {
+    return handleError(err);
+  }
   return responses.ok(token);
 };

lib/index.test.js

@@ -1,6 +1,6 @@
 /* global expect jest */
 
-const { handleRequest, requestTypes } = require('./index.js');
+const { handleComments, handleSatisfied, handleHealthcheck } = require('./index.js');
 const { ValidationError } = require('./validation.js');
 const context = require('../tests/unit/defaultContext.js');
 
@@ -16,8 +16,8 @@ describe('http handler for /satisfied/', () => {
     const request = {
       body: { isSatisfied: true },
     };
-    const response = await handleRequest(context, request, requestTypes.SATISFIED);
-    expect(response).toEqual({ body: { status: 'ok' } });
+    const response = await handleSatisfied(context, request);
+    expect(response).toMatchObject({ body: { status: 'ok' } });
     expect(database.saveInitialResponse).toBeCalledWith({ isSatisfied: true, token: null });
   });
 
@@ -27,8 +27,8 @@ describe('http handler for /satisfied/', () => {
         isSatisfied: false,
       },
     };
-    const response = await handleRequest(context, request, requestTypes.SATISFIED);
-    expect(response).toEqual({ body: { status: 'ok' } });
+    const response = await handleSatisfied(context, request);
+    expect(response).toMatchObject({ body: { status: 'ok' } });
     expect(database.saveInitialResponse).toBeCalledWith({ isSatisfied: false, token: null });
   });
 
@@ -39,8 +39,8 @@ describe('http handler for /satisfied/', () => {
     const request = {
       body: { isSatisfied: true },
     };
-    const response = await handleRequest(context, request, requestTypes.SATISFIED);
-    expect(response).toEqual({ body: { error: 'Something went wrong' }, status: 500 });
+    const response = await handleSatisfied(context, request);
+    expect(response).toMatchObject({ body: { error: 'Something went wrong' }, status: 500 });
   });
 
   test('returns error when validation fails', async () => {
@@ -50,14 +50,14 @@ describe('http handler for /satisfied/', () => {
     const request = {
       body: { isSatisfied: true },
     };
-    const response = await handleRequest(context, request, requestTypes.SATISFIED);
-    expect(response).toEqual({ body: { error: 'some validation message' }, status: 400 });
+    const response = await handleSatisfied(context, request);
+    expect(response).toMatchObject({ body: { error: 'some validation message' }, status: 400 });
   });
 
   test('returns error when no body given', async () => {
     const request = {};
-    const response = await handleRequest(context, request, requestTypes.SATISFIED);
-    expect(response).toEqual({ body: { error: 'Please pass a JSON request body' }, status: 400 });
+    const response = await handleSatisfied(context, request);
+    expect(response).toMatchObject({ body: { error: 'Please pass a JSON request body' }, status: 400 });
   });
 });
 
@@ -73,8 +73,28 @@ describe('http handler for /comments/', () => {
         token: 'my-token',
       },
     };
-    const response = await handleRequest(context, request, requestTypes.COMMENTS);
-    expect(response).toEqual({ body: { status: 'ok' } });
+    const response = await handleComments(context, request);
+    expect(response).toMatchObject({ body: { status: 'ok' } });
     expect(database.saveTextComments).toBeCalledWith({ comments: 'Needs more cowbell.', token: 'my-token' });
   });
 });
+
+describe('http handler for /healthcheck/', () => {
+  beforeEach(() => {
+    database.healthcheck.mockClear();
+  });
+
+  test('returns ok when database is available', async () => {
+    database.healthcheck = jest.fn().mockImplementation(async () => true);
+    const request = {};
+    const response = await handleHealthcheck(context, request);
+    expect(response).toMatchObject({ body: { status: 'ok' } });
+  });
+
+  test('returns 503 when database is unavailable', async () => {
+    database.healthcheck = jest.fn().mockImplementation(async () => false);
+    const request = {};
+    const response = await handleHealthcheck(context, request);
+    expect(response).toMatchObject({ status: 503 });
+  });
+});

lib/responses.js

@@ -6,6 +6,10 @@
  *
  */
 
+const globalHeaders = {
+  'Content-Type': 'application/json',
+};
+
 /**
  * HTTP 200 ok response.
  * @param {string} token - UUIDv4 token
@@ -16,6 +20,9 @@ module.exports.ok = (token) => ({
     status: 'ok',
     token,
   },
+  headers: {
+    ...globalHeaders,
+  },
 });
 
 /**
@@ -26,6 +33,9 @@ module.exports.nodata = () => ({
   body: {
     error: 'Please pass a JSON request body',
   },
+  headers: {
+    ...globalHeaders,
+  },
   status: 400,
 });
 
@@ -37,6 +47,9 @@ module.exports.error500 = () => ({
   body: {
     error: 'Something went wrong',
   },
+  headers: {
+    ...globalHeaders,
+  },
   status: 500,
 });
 
@@ -48,5 +61,17 @@ module.exports.error500 = () => ({
  */
 module.exports.httpError = (statusCode, message) => ({
   body: { error: message },
+  headers: {
+    ...globalHeaders,
+  },
   status: statusCode,
 });
+
+module.exports.healthcheckOk = () => ({
+  body: {
+    status: 'ok',
+  },
+  headers: {
+    ...globalHeaders,
+  },
+});

satisfied/index.js

@@ -1,3 +1,3 @@
-const { handleRequest, requestTypes } = require('../lib/index.js');
+const { handleSatisfied } = require('../lib/index.js');
 
-module.exports = async (context, req) => handleRequest(context, req, requestTypes.SATISFIED);
+module.exports = async (context, req) => handleSatisfied(context, req);