My self and another developer are working on an API using node.js and we are not advanced coders yet. We ran into problem. I will try and explain the problem here with sample references.
We have an API route that would be called on the frontend, please this is just a sample and not the real code. client said the codes should be private. We want to stop the function when an error is detected in another function we called. I am sure that we are not doing it rightly. Here is the API route for this post request and we called another function that we exported and imported here.
We simply want the httpCreateHarsh function to end if there is an error in the anotherFunction. With what we have, the error is seen in console.log when the user is not an admin for example but the httpCreateHarshfunction keeps running until it reaches the last line. Is this possible? Or is there another way we can structure the code to achieve this?
Shared sample of my code
const callAnotherFunction = require("../anotherfunction")
const httpCreateHarsh = async(req, res) => {
await callAnotherFunction(req, res);
return res.status(200).json('created')
}
//This is the second function we called:
const obj = {
status: 'success',
code: '244'
}
const anotherFunction = async(req, res) => {
if (req.body.user !== 'admin') {
return res.status(401).json('Unauthorized')
}
return obj
}
export default = anotherFunction
//The route here:
const express = require('express');
const router = express.Router();
const httpCreateHarsh = require('../httpCreateHarsh');
router.post("/harsh", httpCreateHarsh)
You couldn't return the res object in your second function.
To solve this problem you could throw exceptions and catch them in your handler function.
// request handler function
const httpCreateHarsh = async (req, res) => {
try {
await callAnotherFunction(req, res);
} catch (e) {
return res.status(401).json('Unauthorized')
}
return res.status(200).json('created')
}
const anotherFunction = asyn(req, res) => {
if (req.body.user !== 'admin') {
throw new Error('Unauthorized')
}
return obj
}
What you can do is you can wrap the code in httpCreateHarsh in an try...catch so whenever there is error inside it it will trigger the catch block and u exit the api.
const httpCreateHarsh = async(req, res)=>{
try{
await callAnotherFunction(req, res);
return res.status(200).json('created')
} catch(err){
return res.status(401).json('Unauthorized')
}
}
As an addition to this code you can return a promise from anotherFunction so that the catch block will be triggered once the promise is rejected.
For Exmaple:
const anotherFunction = async(req, res) => {
return new Promise(function(myResolve, myReject) {
if (req.body.user !== 'admin') {
myReject();
}
myResolve(obj);
});
}
If the code runs as you want it, it will generate the "cannot set headers after they are sent to the client" error, because you will be returning 2 responses
the first will be "unauthorized" by "anotherFunction" function and then the other response which is "created" of the current function "httpCreateHarsh".
what you should do instead is to call the "anotherFunction" as a middleware before moving to the "httpCreateHarsh" function.
it can be done this way:
// anotherfunction.js file containing the function you want to import
module.exports = {
async anotherFunction(req, res) {
if (req.body.user !== 'admin') {
return res.status(401).json('Unauthorized')
}
// this way, you can access this object from the "httpCreateHarsh" function by using req.body.obj
req.body.obj = {
status: 'success',
code: '244'
}
// this next indicates that there were no errors, and the next function will be called
next();
}
}
const httpCreateHarsh = async(req, res) => {
// do wathever you want here
return res.status(200).json('created')
}
//The route here:
const express = require('express');
const router = express.Router();
const httpCreateHarsh = require('../httpCreateHarsh');
const callAnotherFunction = require("../anotherfunction")
router.post("/harsh", (req, res, next) => callAnotherFunction(req, res, next), httpCreateHarsh)
We are overriding console.log in our productive ExpressJS application to add certain fields (e.g. timestamp, sessionid, requestid) as well as send logs to a syslog server.
We are doing this by adding console.requestId and console.sessionId properties to the global console object and then overriding console.log() to output these values as well as send logs to syslog. This works fine:
let originalConsoleLog = console.log;
console.log = function() {
let args = Array.from(arguments);
args.unshift(this.sessionId);
args.unshift(this.requestId);
originalConsoleLog.log.apply(console, args);
syslog.log(arguments);
}
app.get('/some-endpoint', async (req, res) => {
console.requestId = req.header('X-Request-Id');
console.sessionId = req.session = req.cookies['SESSIONID'];
let response = await someAsyncProcess();
console.log('foo');
req.json(response);
});
The problem comes when 2 requests are processed concurrently:
Request 1 sets requestId/sessionId REQ1/SESSA
Request 1 waits for someAsyncProcess()
Request 2 sets requestId/sessionId REQ2/SESSB
Request 1 logs REQ2/SESSB foo when it should log REQ1/SESSA foo
So globals (like console) are out.
Locals are also out since we do not want to pass some logger instance to each and every module.
What we need is a "pseudo global" variable which is scoped to a single request in ExpressJS. Something like closure but to external modules as well:
let logger = new Logger(sessionId, requestId);
function() {
// I can see logger
logger.log('hello');
// This module can't
let foo = require('foo');
}
The idea is that we can set a request and session id on this logger variable and all functions/modules/methods called from here on will console.log with this session/request id. The variable "belongs" to all code called from the request responder.
We don't want to inject this logger instance into every submodule we use but we want to capure console.log requests dynamically and inject the relevant local sessionId and requestId.
You'll probably need to use async hooks for this, something like
const asyncHooks = require('async_hooks');
const store = new Map();
const asyncHook = asyncHooks.createHook({
init: (asyncId, _, triggerAsyncId) => {
if (store.has(triggerAsyncId)) {
store.set(asyncId, store.get(triggerAsyncId))
}
},
destroy: (asyncId) => {
if (store.has(asyncId)) {
store.delete(asyncId);
}
}
});
asyncHook.enable();
const createRequestContext = (sessionId, requestId) => {
const context = { sessionId, requestId };
store.set(asyncHooks.executionAsyncId(), context);
return context;
};
const getRequestContext = () => {
return store.get(asyncHooks.executionAsyncId());
};
let originalConsoleLog = console.log;
console.log = function() {
let args = Array.from(arguments);
const { sessionId, requestId } = getRequestContext();
args.unshift(sessionId);
args.unshift(requestId);
originalConsoleLog.log.apply(console, args);
syslog.log(arguments);
}
app.get('/some-endpoint', async (req, res) => {
const requestId = req.header('X-Request-Id');
const sessionId = req.session = req.cookies['SESSIONID'];
createRequestContext(requestId, sesscionId);
let response = await someAsyncProcess();
console.log('foo');
req.json(response);
});
I am trying to implement a singleton pattern for the fastify instance. My code is as follows :-
const { createFastifyServer: server } = require("../app");
const getFastifyInstance = (() => {
let fastify;
return {
fastifyInstance: async () => {
if (!fastify) {
console.log("Called")
fastify = server();
await fastify.ready();
}
return fastify
}
}
})();
const { fastifyInstance } = getFastifyInstance
module.exports = fastifyInstance
Now wherever I am importing the code in a different file, the console prints "Called" each time it's imported in a new file, but shouldn't that be only once if singleton pattern was correctly implemented. Any idea what am I doing wrong?
I have the vanilla probot event function from the docs that comments on new issues:
const probotApp = app => {
app.on("issues.opened", async context => {
const params = context.issue({ body: "Hello World!" });
return context.github.issues.createComment(params);
});
}
This works fine.
I refactor the code into a separate file:
index.js
const { createComment } = require("./src/event/probot.event");
const probotApp = app => {
app.on("issues.opened", createComment);
}
probot.event.js
module.exports.createComment = async context => {
const params = context.issue({ body: "Hello World!" });
return context.github.issues.createComment(params);
};
But I receive this error:
ERROR (event): handler is not a function
TypeError: handler is not a function
at C:\Users\User\probot\node_modules\#octokit\webhooks\dist-node\index.js:103:14
at processTicksAndRejections (internal/process/task_queues.js:97:5)
at async Promise.all (index 0)
When I create a test as recommended in the docs with a fixture and mock the event webhook call with nock this works fine. But when I create a real issue on GitHub this error is thrown.
How can I refactor the code into a separate file without causing the error?
This was my mistake.
This is the whole probot.event.js file:
module.exports.createComment = async context => {
const params = context.issue({ body: "Hello World!" });
return context.github.issues.createComment(params);
};
module.exports = app => {
// some other event definitions
}
By defining module.exports = app I overwrote the previous module.export. The createComment function was therefore never exported.
Removing module.exports = app = { ... } fixed it!
I am new to mock concept and javascript programming either. I want to to mock pg (postgres module) in the javascript program. I can imitate very simple scenario, but in actual I don't.
Here is my userHandler.js:
var pg = require('pg');
var connectionString = process.env.DATABASE_URL || 'postgres://admin:admin#localhost:5432/mydb';
exports.handlePost = function(req,res){
var results = [];
// Grab data from http request
var adata = [req.body.Username, ..., req.body.FaxNum]; //Ignore for short.
// Get a Postgres client from the connection pool
pg.connect(connectionString, function(err, client, done) {
// SQL Query > Insert Data
var func_ = 'SELECT Dugong.Users_Add($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16,$17,$18,$19)';
var addUser_ = client.query(func_, adata);
addUser_.on('error', function(error){
var data = {success : false,
username : req.body.Username,
reason : {errmsg : error.detail,
errid : 'addUser_' }};
return res.json(data);
});
addUser_.on('end',function(result){
var data = {success : true, username : req.body.Username};
console.log('Insert record completed');
return res.json(data);
});
// Handle Errors
if(err) {
console.log(err);
return ;
}
return;
});
};
And here is my unit test file. m_users_page.js:
var express = require('express');
var router = express.Router();
var test = require('unit.js');
var mock = require('mock');
var httpMocks = require('node-mocks-http');
var real_users_page = require('../routes/users_page.js');
var b = mock("../routes/userHandler.js", {
pg: {
connect: function (connectionString,callback) {
if(connectionString === 'postgres://admin:admin#localhost:5432/skorplusdb'){
console.log('333');
//pseudo object
var client = {query : function(func_, adata, cb){
cb(null,adata);
}};
client.on('error', 'test emit the error in my mock unit.');
//pseudo done object
var done = function(){};
callback(null, client, done);
return ;
}
}
}
}, require);
describe('Test with static login', function(){
it('Test simple login', function(done){
var request = httpMocks.createRequest({
method: 'POST',
url: '/users',
body: { Username:"Je", ..., FaxAreaCode:'232'} //Ignore for short
});
var response = httpMocks.createResponse();
b.handlePost(request,response, function(){
var data = response._getData();
console.log("7777777777" + data);
done();
});
});
});
Here is the error :
$ mocha testing/m_users_page.js
Test with static login
333
1) Test simple login
0 passing (7ms)
1 failing
1) Test with static login Test simple login:
TypeError: Object #<Object> has no method 'on'
at Object.mock.pg.connect (testing/m_users_page.js:22:14)
at Object.exports.handlePost (routes/userHandler.js:30:6)
at Context.<anonymous> (testing/m_users_page.js:63:5)
My questions are:
What is a proper way to do a unit test in Node + Express + Mock + node-mocks-http?
How to find good framework with well document I must read. After several days, I started to circling around the result from search engines. They are too simple, I can't adapt it to my problem.
First, make sure you understand the difference between unit tests and integration tests. If you want to test against the actual db, even if it has a dummy data set, that's an integration test and it doesn't need a mock: just connect to the database with the dummy data.
But suppose you want to test your webserver module, and you want to mock the db. First, pass the database module as a parameter rather than requiring pg directly. Also, wrap the postgres interface with your own class:
const { Pool } = require('pg');
module.exports = class DatabaseInterop {
// Connection parameters can be passed to the constructor or the connect method, parameters to
// DatabaseInterop::connect will override the initial constructor parameters.
constructor ({
user,
password,
database,
host,
logger={log: console.log, err: console.error},
}) {
this.logger = logger;
this._params = {
user,
password,
database,
host,
};
}
connect (params) {
const {
user,
password,
database,
host,
} = Object.assign({}, this._params, params);
this._pool = new Pool({
user,
password,
database,
host,
});
['SIGHUP', 'SIGINT', 'SIGQUIT', 'SIGILL', 'SIGTRAP', 'SIGABRT',
'SIGBUS', 'SIGFPE', 'SIGUSR1', 'SIGSEGV', 'SIGUSR2', 'SIGTERM'
].forEach(function (sig) {
process.on(sig, async () => {
logger.log(`Exiting for ${sig}...`);
process.exit(0);
});
});
return this;
}
async stop () {
return this._pool.end();
}
runQuery (queryString, params=[]) {
return params.length ? this._pool.query(queryString, params) : this._pool.query(queryString);
}
};
Now to mock it out, you can simply extend your custom class in your test file:
const DatabaseInterop = require('/path/to/database_interop.js');
class MockDB extends DatabaseInterop {
connect () {
// no-op
}
runQuery (qs, ...params) {
// return whatever
}
stop () {
// noop
}
}
Now for your tests you can inject the mock and your actual system inject the actual interface.