I want to keep a log during my integration test suite. I'm testing that every 'item' is being compiled and logging how much time it took. I'm using node 4.3.
First of all I create the log file:
before(function() {
if (!fs.existsSync("./log.csv")) {
fs.writeFile("./log.csv", "Name; Time");
}
});
Then within each it block I would do this:
for (const item of items) {
it('compiles', function() {
return item.testCompile();
});
}
And item class has these methods:
testCompile() {
return this
.buildItem()
.then(result => {
// whatever testing stuff
});
}
buildItem() {
return this
.internalLogicForCompiling()
.then(result => {
// This is not appending anything
fs.appendFile("./log.csv", `${item.name}; ${result.compileTime}`);
return result;
});
}
So far the file is created but never updated... Any clue what I'm doing wrong?
PS: I assume if the file doesn't exists, fs should throw an error, however it doesn't.
Your code is generally ignoring the fact that your fs calls are asynchronous. Promises are not magic. If you use code that is asynchronous but does not use promises, you need to do more than plop that code in a promise can call it done.
The easiest way to deal with the issue would be to use fs.writeFileSync and fs.appendFileSync instead of the calls you make. Otherwise, you should write your before like this:
before(function(done) {
if (!fs.existsSync("./log.csv")) {
fs.writeFile("./log.csv", "Name; Time", done);
}
});
I've just added the done callback.
And buildItem could be something like this so that the promise it returns won't resolve before appendFile is done doing its work:
buildItem() {
return this
.internalLogicForCompiling()
.then(result => {
return new Promise((resolve, reject) => {
fs.appendFile("./log.csv", `${item.name}; ${result.compileTime}`, (err) => {
if (err) {
reject(err);
return;
}
resolve(result);
});
});
});
}
Related
I have the following code that I cannot figure out what I need to do to make this entire process finish before sending a response back to the client. Basically I am looking for the client to receive a response once everything in the method completes or errors out, not before.
I have tried several things, moving things around and adding some .then() and .catch() blocks that may not even be needed. I'm still fairly new to NodeJs so while I understand how things kind of work, I still have not got used to asynchronous coding.
let markStepsComplete = async function() {
let stepsToProcess = new Multimap();//multimap JS npm
let results = await dbUtils.getCompletedSteps();
results.forEach(result => {
stepsToProcess.set(result.ticket_id, result.step_id);
});
return new Promise((resolve,reject)=>{
stepsToProcess.forEachEntry(async function(entry, key) {
let payload = {
ticketId: key,
stepIds: entry
}
let response = await updateStep(payload)//returns promise
if (response.statusCode === 200) {
await Promise.all(payload.stepIds.map(async (stepId) => {
try {
await dbUtils.markStepsCompleted(stepId, payload.ticketId);
} catch(err) {
reject(err);
}
}));
}
else {
await Promise.all(payload.stepIds.map(async (stepId) => {
try {
await dbUtils.markStepsProcessed(stepId, payload.ticketId, response.statusCode);
} catch(err) {
console.log(err);
reject(err);
}
}));
}
});
resolve('Steps Marked Complete');
});//promise end
}
This is the path that i am testing right now that's making the call to the above method.
The updateStep() method is the method that actually calls a HTTP request to an outside REST API. That seems to be working returning a promise.
app.use('/api/posts',async (req,res,next)=>{
let data = await markStepsComplete.markStepsComplete()
.then((data)=>{
res.status(200).json({message: data})
})
.catch((e)=>{
console.log('error from catch:',e);
})
})
The code above runs and does run some stuff in our database as part of this process, but I get back the "Steps Marked Complete" resolve message before the process finishes.
Since the resolve is hit before the process ends, I can never get any of the reject() errors to come back to the client since resolve is called already.
Thanks in advance.
I noticed this snippet and wanted to call it out because it wont work:
payload.stepIds.forEach(async (stepId) => {
try {
await dbUtils.markStepsProcessed(stepId, payload.ticketId, response.statusCode);
} catch(err) {
console.log(err);
reject(err);
}
});
when looping through an array of items that require an async fetch, you can do something like:
await Promise.all(payload.stepIds.map(async (stepId) => {
try {
await dbUtils.markStepsProcessed(stepId, payload.ticketId, response.statusCode);
} catch(err) {
console.log(err);
reject(err);
}
}));
I want to write some instance / static methods for a model, which uses the mongoose's API and do something before and after using the mongoose's API.
For example, I write my own Article.createArticle method, it checks the data before Article.create, and return article.toObject() after creation.
this is how I want my createArticle works:
Article.createArticle({someKeys: 'SomeData', ...})
.then(obj => {
// get plain object here
});
I tried to write something like this:
Article.Schema.static({
createArticle: function(data) {
return new Promise(function(resolve, reject){
checkDataKeys(data);
resolve(mongoose.model('Article').create(data)
.then(article => resolve(article.toObject()));
);
});
},
});
with this createArticle, I only get undefined in then,
I must get something wrong.
Also, in addition to make the createArticle work, is there any way to make the code more elegant?
Thanks.
I myself found a methods that works for me. Though I'm not very understand the mechanism, maybe I'll try to work on it later...
ArticleSchema.static({
createArticle: function(data) {
checkDataKeys(data); // pre works
return mongoose.model('Article').create(data)
.then(obj => {
return obj.toObject(); // afterworks
// here, just get the plain obj from doc
// and *return* it
});
},
});
update: after I searched something about Promise, maybe this could be better.
ArticleSchema.static({
createArticle: function(data) {
checkDataKeys(data); // pre works
return mongoose.model('Article').create(data)
.then(obj => {
return Promise.resolve(obj.toObject());
// Some say that this is totally same as directly return
})
.catch(err => {
return Promise.reject(err);
// if error, this will ensure the err will be caught
// for some async cases
});
},
});
I'm new to Express framework and learning, I'm having a problem using .then. The problem is I have 2 functions and I want the first one to complete before the second to start executing. I'm exporting the modules.
var ubm = require('./userBasic');
There are 2 functions setUserData and showUserId, the showUserId must execute only after setUserData has performed its operation.
var userId = ubm.setUserData(userName,userEmail,userDOB,moment);
userId.then(ubm.showUserId(userId));
Below are the 2 functions:
module.exports = {
setUserData: function (userName,userEmail,userDOB,moment){
//Performing database activities
return userId;
}
showUserId: function (userId){
console.log(userId);
}
}
When i run it says TypeError: Cannot read property 'then' of undefined.
Like I said I'm very new and learning and was unable to figure out the solution. I did some google search and got a brief about promise, but I don't know how to implement here.
Try using promises
module.exports = {
setUserData: function(userName, userEmail, userDOB, moment) {
return new Promise(function(resolve, reject) {
//db stuff
reject(error);
resolve(userId);
});
},
showUserId: function(userId) {
console.log(userId);
};
};
So in your execution you would write
ubm.setUserData(username, usereEmail, userDOB, moment)
.then((data) => {
showUserId(data);
})
.catch((err) => {
console.log(err);
});
A couple of things to note is that in this instance you could just log data without the need for another function like
ubm.setUserData(username, usereEmail, userDOB, moment)
.then((data) => {
console.log(data);
})
.catch((err) => {
console.log(err);
});
Whatever value you pass into resolve() will be returned as well as you pass errors into reject().
The node mongodb docs specify to use next/each for large number of documents so as to not have everything loaded onto memory if we were to use toArray.
So, i thought my sample code should work as is. But it just returns one document.
What should be the correct way to deal with this problem?
This is my code sample :
var findAsync = function (collection,query) {
return mongodb.MongoClient.connectAsync(mongodbServerString)
.then(function (db) {
return [db.collection(collection).find(query), db];
});
};
findAsync("UserProfile",{})
.spread(function (cursor,db) {
return [cursor.project({Email:true}),db];
})
.spread(function (cursor, db) {
return cursor.eachAsync().then(function (doc) {
console.log(doc);
}).catch(function () {
db.close();
});
});
Promises represent singular values. Promises are basically like function returns, since a function cannot return multiple values - it wouldn't make sense to convert each to a promise returning function.
What you can do is either convert it to an Observable returning function and then use .forEach on that to get a promise back for the completion of the sequence or you can implement something similar manually:
function each(cursor, fn) {
return new Promise((resolve, reject) => {
cursor.forEach((err, data) => {
if(err) {
cursor.close();
return reject(err);
}
try { fn(data); } catch(e) { cursor.close(); reject(e); }
}, err => { { // finished callback
if(err) reject(err);
else resolve();
});
});
}
Which would let you write:
each(cursor, doc => console.log(doc)).then(...).catch(...)
Also note that Mongo connections are persistent, you're supposed to connect once when the server starts and then keep the connection open for as long as the server is run.
I'm trying to using the Mongoose Promises to have a cleaner code (see nested functions).
Specifically, I'm trying to build something like this:
Model.findOne({_id: req.params.id, client: req.credentials.clientId}).exec()
.then(function(resource){
if (!resource) {
throw new restify.ResourceNotFoundError();
}
return resource;
})
.then(function(resource) {
resource.name = req.body.name;
return resource.save; <-- not correct!
})
.then(null, function(err) {
//handle errors here
});
So, in one of the promises I would need to save my model. As of the latest stable release, Model.save() does not return a promise (bug is here).
To use the classical save method, I could use this:
//..before as above
.then(function(resource) {
resource.name = req.body.name;
resource.save(function(err) {
if (err)
throw new Error();
//how do I return OK to the parent promise?
});
})
But as also commented in the code, how do I return to the holding promise the return value of the save callback (which runs async)?
Is there a better way?
(btw, findOneAndUpdate is a no-go solution for my case)
One way of doing it would be to wrap the .save code in your own method which returns a promise. You'll need a promise library, like RSVP or Q. I'll write it in RSVP, but you should get the idea.
var save = function(resource) {
return new RSVP.Promise(function(resolve, reject) {
resource.save(function(err, resource) {
if (err) return reject(err);
resolve(resource);
});
});
}
Then in your calling code:
// ...
.then(function(resource) {
resource.name = req.body.name;
return save(resource);
})
.then(function(resource) {
// Whatever
})
.catch(function(err) {
// handle errors here
});
The other way of doing it would be to nodeify the save method, but I'd do it they way I've detailed above.