I have the following code:
"use strict";
const Raven = require("raven");
Raven.config(
"test"
).install();
module.exports = function(Reservation) {
function dateValidator(err) {
if (this.startDate >= this.endDate) {
err();
}
}
function sendEmail(campground) {
return new Promise((resolve, reject) => {
Reservation.app.models.Email.send(formEmailObject(campground),
function(
err,
mail
) {
if (err) {
console.log(err);
Raven.captureException(err);
reject(err);
} else {
console.log(mail);
console.log("email sent!");
resolve(mail);
}
});
});
}
function formEmailObject(campground) {
return {
to: "loopbackintern#yopmail.com",
from: "noreply#optis.be",
subject: "Thank you for your reservation at " + campground.name,
html:
"<p>We confirm your reservation for <strong>" +
campground.name +
"</strong></p>"
};
}
Reservation.validate("startDate", dateValidator, {
message: "endDate should be after startDate"
});
Reservation.observe("after save", async function(ctx, next) {
try {
const campground = await Reservation.app.models.Campground.findById(
ctx.instance.campgroundId
);
const mail = await sendEmail(campground);
next();
} catch (e) {
Raven.captureException(e);
next(e);
}
});
};
Sorry for the poor formatting. When the flow is done I get this error:
(node:3907) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: Callback was already called.
I am calling the next() callback in two places, one in the try code and one in the catch code. I assume that when it all goes right, next callback is called only once, and the same when it goes wrong. But it seems that it is called twice and I don't know why.
I also tried to call next outside the try/catch code but it results in the same error. If I left only the next that is called inside the catch code it doesn't throw the error.
Any idea? Thanks!
if you are using async function you shouldn't explicitly call next, it gets automatically called.
check out this github issue for loopback async/await
so your hook can be like the following.
Reservation.observe("after save", async ctx => {
try {
const campground = await Reservation.app.models.Campground.findById(
ctx.instance.campgroundId
);
const mail = await sendEmail(campground);
} catch (e) {
Raven.captureException(e);
throw e;
}
});
NB: you don't need to wrap it in try catch unless you want to modify/work with the error.
You should declare your sendEmail method as async as it returns a promise.
async function sendEmail(campground) {
...
}
After reading this article, I created a await-handler.js file which include following code.
module.exports = (promise) =>
promise
.then(data => ({
ok: true,
data
}))
.catch(error =>
Promise.resolve({
ok: false,
error
})
);
Then in MyModel.js file, I created a async function to get a value from database as follow.
const awaitHandler = require("./../await-handler.js")
const getMaxNumber = async (MyModel) => {
let result = await awaitHandler(MyModel.find());
if (result.ok) {
if (result.data.length) {
return result.data.reduce((max, b) => Math.max(max, b.propertyName), result.data[0] && result.data[0].propertyName);
} else {
return 0;
}
} else {
return result.error;
}
}
As per #Mehari's answer, I've commented call to next() method as follow:-
module.exports = function(MyModel) {
MyModel.observe('before save', async(ctx, next) => {
const maxNumber = await getMaxNumber (MyModel);
if(ctx.instance) {
...
set the required property using ctx.instance.*
like createdAt, createdBy properties
...
// return next();
} else {
...
code for patch
...
// return next();
}
})
}
This solves the warning issue whenever saving endpoint is triggered.
But the warning issue still appear when I run the endpoint to load the resource.Like
http://localhost:3000/api/MyModel
Previously, the issue appear only when the before save operation hook gets triggered.
After encountering this issue, I checked adding access and loaded operation hooks and I found that the the warnings are issued after loaded operation hook.
MyModel.observe('access', (ctx, next) => {
return next();
})
MyModel.observe('loaded', (ctx, next) => {
return next();
})
What could have caused this issue and how can it gets resolved?
Related
I am part of a project which uses nodeJS + ExpressJS for the backend application, and We have a middleware function to log accesses on routes in the database.
When an User tries to access the /user route with a post method, a middleware receives the Request, get information like the URL, ip address, origin, a description of the event and record it in the database.
Everything works just fine, but some of my teammates were discussing about how to log the erros also in the database.
I will put bellow a code example
const create = (request, response) => {
try {
const user = request.body;
const userExists = await usersRepository.findOne({ where: { email } });
if(userExists) {
return response.status.json({ error: 'E-mail already in use' });
}
const creadtedUser = await usersRepository.create(user);
return response.status(200).json({ user: creadtedUser });
} catch (error) {
response.status(500).json({ error });
}
};
When we were discussing about how to implement it, we realized we'd have to call a log error function in a lot of places since we have many flows which leads to an error response.
So the code would be just like:
const create = (request, response) => {
try {
const user = request.body;
const userExists = await usersRepository.findOne({ where: { email } });
if(userExists) {
function() // here we would log the error
return response.status.json({ error: 'E-mail already in use' });
}
const creadtedUser = await usersRepository.create(user);
return response.status(200).json({ user: creadtedUser });
} catch (error) {
function() // here we would log the error
response.status(500).json({ error });
}
};
is it a properly way of dealing with error logging or is there any better way of doing it? Thank you for reading!
You can use the built-in error handler provided by Express.JS for this kind of logic, of course it requires a bit of setup. Like most things in Express.JS, the error handler it's just a middleware function with four parameters err, req, res and next, which MUST be placed after all your other middlewares. It comes to play when, inside a router handle (for example), your call next(err) (where err it's an Error) or by simply throwing err. Check out the documentation for more.
app.use(...)
app.use(...)
app.use((req, res, next) => {
if (req.params.id === undefined) {
let error = new Error("ID required.")
error.statusCode = 400
error.statusMessage = "Request not valid, ID not found."
throw error;
} else {
// Do some stuff...
}
})
// NOTE: After ALL your other middlewares
app.use((err, req, res, next) => {
console.error(err)
res
.status(err.statusCode)
.json(err.statusMessage)
})
Ideally you should log the errors only inside the catch block. Whenever you encounter an error just throw a new error by calling throw new Error("Type your error message here"). Then your function inside catch block will log and handle the error appropriately.
I would change your code to this:
const create = (request, response) => {
try {
const user = request.body;
const userExists = await usersRepository.findOne({ where: { email } });
if(userExists) {
throw new Error("E-mail already in use")
}
const creadtedUser = await usersRepository.create(user);
return response.status(200).json({ user: creadtedUser });
} catch (error) {
function() // log your error
response.status(500).json({ error.message });
}
};
Read more about Errors here.
I'm curious whether you can write if statements in an Express app to conditionally execute your code without providing else statements.
if(pred) {
doSomething()
}
return foo;
calcBar(); // doesn't run.
Above is the synchronous code that stops execution after the return statement.
My Express function looks like this:
app.get('/matches', async function(req, res) {
try {
const data = await someGraphQLCall();
if(data.length === 0) {
res.json({ message: "No data." });
}
const someOtherData = await someOtherGraphQLCall(data.foo);
res.json({ someOtherData });
} catch (err) {
res.json({err})
}
}
I know because of this question that code after the first res.json might still be executed. Is there a way to stop that? I don't want the second GraphQL call to execute if the first if condition is met. Is that possible without using else ?
Edit:
As the question I linked above mentioned, using a return statement is a bad option because:
it also makes it less meaningful and vague, cause it uses incorrect semantics. If you are not using the value from the function, then you shouldn't return one.
You can use return keyword on the first response to immediately return from the function.
app.get('/matches', async function(req, res) {
try {
const data = await someGraphQLCall();
if(data.length === 0) {
return res.json({ message: "No data." });
}
const someOtherData = await someOtherGraphQLCall(data.foo);
res.json({ someOtherData });
} catch (err) {
res.json({err})
}
}
Edit:
As an alternative, you can split the logic of the data and building up response. This way you can use return and it's easier to read:
app.get('/matches', async function (req, res) {
try {
const data = await getDataFromGraphQLCall();
res.json(data);
} catch (err) {
res.json({ err })
}
});
async function getDataFromGraphQLCall() {
const data = await someGraphQLCall();
if (data.length === 0) {
return { message: "No data." };
}
const someOtherData = await someOtherGraphQLCall(data.foo);
return { someOtherData };
}
If you are wondering if there is a way to achieve that without the else, yes it is.
But, It might not be THE cleanest way. IMO, using return is the best way to stop the execution of the controller.
Anyways, You can split the chunk of code into middlewares and use ternary operator to conditionally send responses.
In your example, separate out data = await someGraphQLCall(); as follows:
const middlewareOne = async function(req, res, next) {
let data = [];
let response = { message: "No data." };
try {
data = await someGraphQLCall();
req.locals.data = data; // <- attach the data to req.locals
} catch (err) {
response = { err };
}
data.length === 0 ? res.json(response) : next();
};
And then, mount the middlewareOne BEFORE your controller:
app.get("/matches", middlewareOne, async function controller(req, res) {
try {
const someOtherData = await someOtherGraphQLCall(req.locals.data.foo);
res.json({ someOtherData });
} catch (err) {
res.json({ err });
}
});
How this works is, the controller function would only be executed by express if the next() is called from the previous middleware -- middlewareOne in the example.
And as middlewareOne only calls next() if the data.length is not 0, it would work as you expected.
For more information on passing data from one middleware to other, read this
The return statement terminates the function execution in this context. In my opinion, you should handle the success case then the error case since the code will be read top to bottom.
In if statement, data could be undefined or null.
You can read more here: MDN - return
app.get('/matches', async function(req, res) {
try {
const data = await someGraphQLCall();
// alternative, if (data && data[0]) {
if (data && data.length) {
const someOtherData = await someOtherGraphQLCall(data.foo);
return res.json({ someOtherData });
}
return res.json({ message: "No data." });
} catch (err) {
console.log(err); // log error with logger and drain to loggly.
res.json({ err })
}
}
With Void operator:
Void operator allows you to return undefined but evaluate the given expression.
You can read more here: MDN - Void
app.get('/matches', async function(req, res) {
try {
const data = await someGraphQLCall();
// alternative, if (data && data[0]) {
if (data && data.length) {
const someOtherData = await someOtherGraphQLCall(data.foo);
return void res.json({ someOtherData });
}
return void res.json({ message: "No data." });
} catch (err) {
console.log(err); // log error with logger and drain to loggly.
res.json({ err })
}
}
I have the following Express endpoint:
const all = require('promise-all');
router.post('/verify', upload.single('photo'), async (req, res) => {
...
await all({'p1': p1, 'p2': p2}).then((response) => {
...
console.log("Response:",
ruleCtrl.manageRule(detection, res);
});
});
ruleCtrl.manageRuleis as follows:
export async function manageRule(identifierDetected, res) {
let rule = db.getRule(identifierDetected);
await all([rule]).then((ruleExtracted) => {
...
res.json(ruleExtracted);
}).catch((err) => {
res.status(418).send("DOCUMENT_NOT_RECOGNIZED");
});
}
and db.getRule:
export async function getRule(idRule) {
return new Promise((resolve, reject) => {
Rule.findOne({ruleID: idRule}, (err, rule) => {
if (err) {
reject("MongoDB Rule error: " + err);
} else {
resolve(rule);
}
});
})
}
My response is into manageRule and this function depends of the values extracted into the await all. So, right now, Express is returning a response before get the information from mongoose database (db).
Which is the way to handle this issue?
Thanks everyone!
I would refactor your code a bit to make it easier to read, and also return the result from ruleCtrl.manageRule(detection, res);.
The request might simply be timing out since your original code is missing a return there or an await (to make sure it finishes executing)
Express endpoint:
const all = require('promise-all');
router.post('/verify', upload.single('photo'), async (req, res) => {
...
// Catch any exceptions from the promises. This is the same as using .catch
try {
// Lets assign the returned responses to variable
let [p1Result, p2Result] = await all({'p1': p1, 'p2': p2});
...
console.log("Responses:", p1Result, p2Result);
// return the response from manageRule method
return ruleCtrl.manageRule(detection, res);
} catch(err) {
// Handle err here
}
});
One of the great benefits with async await is moving away from chained promises, so simply return the result from the await to a variable instead of using .then()
ruleCtrl.manageRule
export async function manageRule(identifierDetected, res) {
// Use try catch here to catch error from db.getRule. Assign to variable and return
// res.json
try {
let ruleExtracted = await db.getRule(identifierDetected);
...
return res.json(ruleExtracted);
} catch(err) {
return res.status(418).send("DOCUMENT_NOT_RECOGNIZED");
}
}
You dont have to return res.json or res.status here, I just like to keep track of when I want to end function execution.
You could refactor the ruleCtrl.manageRule method even further by not sending in res as a parameter but by returning the result from db.getRule instead. Let router.post('/verify) handle req and res, so to make it even easier to read.
To overcome callback hell in javascript, I'm trying to use async await from legacy code written in SQLServer procedure.
But I'm not sure my code might be write properly.
My first confusing point is when async function returns, should it return resolve() as boolean, or just return reject and handle with try-catch?
Here is my code snippets.
Please correct me to right direction.
apiRoutes.js
app.route('/api/dansok/cancelDansok')
.post(dansokCancelHandler.cancelDansok);
dansokCancelController.js
const sequelize = models.Sequelize;
const jwt = require('jsonwebtoken');
async function jwtAccessAuthCheck(accessToken) {
if (!accessToken) {
return Promise.reject('Empty access token');
}
jwt.verify(accessToken,"dipa",function(err){
if(err) {
return Promise.reject('TokenExpiredError.');
} else {
return Promise.resolve();
}
});
}
async function checkFeeHist(dansokSeqNo) {
let feeHist = await models.FeeHist.findOne({
where: { DansokSeqNo: dansokSeqNo}
});
return !!feeHist;
}
async function getNextDansokHistSerialNo(dansokSeqNo) {
....
}
async function getDansokFee(dansokSeqNo) {
....
}
async function doCancel(dansokSeqNo) {
try {
if (await !checkFeeHist(dansokSeqNo)) {
log.error("doCancel() invalid dansokSeqNo for cancel, ", dansokSeqNo);
return;
}
let nextDansokSerialNo = await getNextDansokHistSerialNo(dansokSeqNo);
await insertNewDansokHist(dansokSeqNo, nextDansokSerialNo);
await updateDansokHist(dansokSeqNo);
await updateVBankList(dansokSeqNo, danokFee.VBankSeqNo);
await getVBankList(dansokSeqNo);
} catch (e) {
log.error("doCancel() exception:", e);
}
}
exports.cancelDansok = function (req, res) {
res.setHeader("Content-Type", "application/json; charset=utf-8");
const dansokSeqNo = req.body.DANSOKSEQNO;
const discKindCode = req.body.HISTKIND;
const worker = req.body.PROCWORKER;
const workerIp = req.body.CREATEIP;
const accessToken = req.headers.accesstoken;
//check input parameter
if (!dansokSeqNo || !discKindCode || !worker || !workerIp) {
let e = {status:400, message:'params are empty.'};
return res.status(e.status).json(e);
}
try {
jwtAccessAuthCheck(accessToken)
.then(() => {
log.info("jwt success");
doCancel(dansokSeqNo).then(() => {
log.info("cancelDansok() finish");
res.status(200).json({ message: 'cancelDansok success.' });
});
});
} catch(e) {
return res.status(e.status).json(e);
}
};
You'll need to rewrite jwtAccessAuthCheck(accessToken) so that it keeps track of the outcome of its nested tasks. In the code you've written:
// Code that needs fixes!
async function jwtAccessAuthCheck(accessToken) {
// This part is fine. We are in the main async flow.
if (!accessToken) {
return Promise.reject('Empty access token');
}
// This needs to be rewritten, as the async function itself doesn't know anything about
// the outcome of `jwt.verify`...
jwt.verify(accessToken,"dipa",function(err){
if(err) {
// This is wrapped in a `function(err)` callback, so the return value is irrelevant
// to the async function itself
return Promise.reject('TokenExpiredError.');
} else {
// Same problem here.
return Promise.resolve();
}
});
// Since the main async scope didn't handle anything related to `jwt.verify`, the content
// below will print even before `jwt.verify()` completes! And the async call will be
// considered complete right away.
console.log('Completed before jwt.verify() outcome');
}
A better rewrite would be:
// Fixed code. The outcome of `jwt.verify` is explicitly delegated back to a new Promise's
// `resolve` and `reject` handlers, Promise which we await for.
async function jwtAccessAuthCheck(accessToken) {
await new Promise((resolve, reject) => {
if (!accessToken) {
reject('Empty access token');
return;
}
jwt.verify(accessToken,"dipa",function(err){
if(err) {
reject('TokenExpiredError.');
} else {
resolve();
}
});
});
// We won't consider this async call done until the Promise above completes.
console.log('Completed');
}
An alternate signature that would also work in this specific use case:
// Also works this way without the `async` type:
function jwtAccessAuthCheck(accessToken) {
return new Promise((resolve, reject) => {
...
});
}
Regarding your cancelDansok(req, res) middleware, since jwtAccessAuthCheck is guaranteed to return a Promise (you made it an async function), you'll also need to handle its returned Promise directly. No try / catch can handle the outcome of this asynchronous task.
exports.cancelDansok = function (req, res) {
...
jwtAccessAuthCheck(accessToken)
.then(() => {
log.info("jwt success");
return doCancel(dansokSeqNo);
})
.then(() => {
log.info("cancelDansok() finish");
res.status(200).json({ message: 'cancelDansok success.' });
})
.catch(e => {
res.status(e.status).json(e);
});
};
I strongly suggest reading a few Promise-related articles to get the hang of it. They're very handy and powerful, but also bring a little pain when mixed with other JS patterns (async callbacks, try / catch...).
https://www.promisejs.org/
Node.js util.promisify
Given the following Node.js express route:
router.route('/user')
.post(async function(req, res) {
if(req.body.password === req.body.passwordConfirm) {
try {
var response = await userManager.addUser(req.body);
res.status(201).send();
} catch(err) {
logger.error('POST /user failed with error: '+err);
res.status(500).send({err:"something went wrong.."});
}
} else {
res.status(400).send({err:'passwords do not match'});
}
})
and the corresponding function in userManager:
var userManager = function() {
this.addUser = async function(userobject) {
userobject.password_hash = await genHash(userobject.password_hash);
var user = new User(userobject);
return await user.save();
};
};
module.exports = userManager;
Can I safely assume that if the code in the catch block does not run, there were no errors? Since the userManager.addUser and everything inside it return promises, which if rejected, should be caught by the catch block.
Or did I miss something and should I still check the response for validity?
Yes, you can safely assume all errors from await userManager.addUser(req.body) are caught.
If the promise returned is rejected with value x, then the await keyword ensures it'll throw x.
But that doesn't ensure there are no errors outside that function call, like in your catch.
Best practice:
post() doesn't expect an async callback function, so it'll ignore your implicitly returned promise.
So when you pass it one, wrap try/catch around everything, since there's no-one to pass up to:
router.route('/user').post(async function(req, res) {
try {
if (req.body.password === req.body.passwordConfirm) {
try {
var response = await userManager.addUser(req.body);
res.status(201).send();
} catch (err) {
logger.error('POST /user failed with error: '+err);
res.status(500).send({err:"something went wrong.."});
}
} else {
res.status(400).send({err:'passwords do not match'});
}
} catch (err) {
logger.error('POST /user fatal error: '+err);
}
})
This way all programming errors are caught and never end up silenced or as unhandled rejections.
Or better, if it's an option, write a post that expects an async function.