I want to release the resources associated with a node js request without sending any kind of response to the client.
This might sound weird but my goal is very simple, the last few days my servers have been targeted by hackers... i'm trying to improve the defenses and if i identify a malicious request i could just DROP IT without sending any response i would make the attacker wait for connection timeout and it would give a little more advantage.
i tried:
exports.test = (req, res) => {
res.end();
};
but this case the server sends an empty response which isn't my goal since i want make client wait forever
also tried:
exports.test = (req, res) => {
res.socket.destroy();
};
which on google cloud functions throws an exception
does anyone know if on GCF if i simple return the function it will be released or the connection will be hang on?
exports.test = (req, res) => {
return; //will google release all resources or connection and socket will be kept until timeout?
};
Cloud Functions does not enable what you're trying to do. The only way it will keep the connection open is if your function times out with no response. You can't instruct it to keep the connection open while also terminating the function. Or, to put it another way, you're going to have to pay the usual Cloud Functions rate for execution-seconds in order to keep that connection open.
Related
How to prevent new requests before sending the response to the last request. on On the other hand just process one request at the same time.
app.get('/get', function (req, res) {
//Stop enter new request
someAsyncFunction(function(result){
res.send(result);
//New Request can enter now
}
}
Even tho I agree with jfriend00 that this might not be the optimal way to do this, if you see that it's the way to go, I would just use some kind of state management to check if it's allowed to access that /get request and return a different response if it's not.
You can use your database to do this. I strongly recommend using Redis for this because it's in-memory and really quick. So it's super convenient. You can use mongodb or mysql if you prefer so, but Redis would be the best. This is how it would look, abstractly -
Let's say you have an entry in your database called isLoading, and it's set to false by default.
app.get('/get', function (req, res) {
//get isloading from your state management of choice and check it's value
if(isLoading == true) {
// If the app is loading, notify the client that he should wait
// You can check for the status code in your client and react accordingly
return res.status(226).json({message: "I'm currently being used, hold on"})
}
// Code below executes if isLoading is not true
//Set your isLoading DB variable to true, and proceed to do what you have
isLoading = true
someAsyncFunction(function(result){
// Only after this is done, isLoading is set to false and someAsyncFunction can be ran again
isLoading = false
return res.send(result)
}
}
Hope this helps
Uhhhh, servers are designed to handle multiple requests from multiple users so while one request is being processed with asynchronous operations, other requests can be processed. Without that, they don't scale beyond a few users. That is the design of any server framework for node.js, including Express.
So, whatever problem you're actually trying to solve, that is NOT how you should solve it.
If you have some sort of concurrency issue that is pushing you to ask for this, then please share the ACTUAL concurrency problem you need to solve because it's much better to solve it a different way than to handicap your server into one request at a time.
I have an express service where a lot of my endpoints look like the following.
var express = require('express');
var router = express.Router();
router.get('/updateThisValue', (req, res) => {
let value = req['query'].value
try {
database.update(value, function() { // callback function on update
console.log(undefinedValue.undefined) // crash the server
})
} catch (err) {
// Log the error and other stuff
}
})
Looking at this code, if a database update is called, something will crash in the callback function and since there is no try-catch, the whole server should crash as well.
Right now, I am okay with the server crashing. The problem is that I would like to be able to log some debugging information in the callback before it crashes, namely the express endpoint hit and the parameters passed to it.
One solution is that I could just log every single endpoint hit, but the only problem with that is that the server starts to have very large logs. So we don't log endpoints hit by default. The frustration however is that recently an endpoint hit the server that did cause it crash and I'm still unsure what the actual endpoint hit and parameters passed to it where.
Basically, I want the server to still crash but at least I would be able to trace the endpoint hit and its parameters
Could this help: https://expressjs.com/en/guide/error-handling.html
Normally you would see the exception in the console or in the logs of your process manager (like pm2).
I am using this (contentful-export) library in my express app like so
const app = require('express');
...
app.get('/export', (req, rex, next) => {
const contentfulExport = require('contentful-export');
const options = {
...
}
contentfulExport(options).then((result) => {
res.send(result);
});
})
now this does work, but the method takes a bit of time and sends status / progress messages to the node console, but I would like to keep the user updated also.. is there a way I can send the node console progress messages to the client??
This is my first time using node / express any help would be appreciated, I'm not sure if this already has an answer since im not entirely sure what to call it?
Looking of the documentation for contentful-export I don't think this is possible. The way this usually works in Node is that you have an object (contentfulExport in this case), you call a method on this object and the same object is also an EventEmitter. This way you'd get a hook to react to fired events.
// pseudo code
someLibrary.on('someEvent', (event) => { /* do something */ })
someLibrary.doLongRunningTask()
.then(/* ... */)
This is not documented for contentful-export so I assume that there is no way to hook into the log messages that are sent to the console.
Your question has another tricky angle though. In the code you shared you include a single endpoint (/export). If you would like to display updates or show some progress you'd probably need a second endpoint giving information about the progress of your long running task (which you can not access with contentful-export though).
The way this is usually handled is that you kick of a long running task via a certain HTTP endpoint and then use another endpoint that serves infos via polling or or a web socket connection.
Sorry that I can't give a proper solution but due to the limitation of contentful-export I don't think there is a clean/easy way to show progress of the exported data.
Hope that helps. :)
Sorry if this is a basic question. I'm just starting my 3rd week of doing Node.js programming! I looked around and didn't see an answer to this, specifically. Maybe it's just assumed when answering questions about child_process.spawn/fork by those who know this stuff better than I do.
I have a Node/Express app where I want to take in an HTTP request, save a bit of data to Mongo, return success/error, but...at the same time kick off a process to take some of the data and do a lookup against a web API. I want to save that data back to Mongo, but there's no need to have that communicated back to the HTTP client. (I'll probably log the success/error of that call somewhere.)
How do I kick off that 2nd task to run independent of the main request and not cause the response to wait for it to complete?
The 2nd task will also be written in Node.js. I'd like it to just be another function in the same file, if possible.
Thanks in advance!
I don't see why you would need spawning another process just for that. In node you are not limited to the http request lifecycle to run stuff like other frameworks. This should do it:
function yourHandler(req, res, next) {
dataAccess.writeToMongo(someData, function(err, res) {
var status = err ? 500 : 200;
// write back to response already!
res.status(status);
res.end();
// do not completely terminate yet
// kick off web api call
apiClient.doSomething();
});
}
Full disclosure: I'm very new to the totally asynchronous model.
In my application there are a number of instances where information needs to be committed to the db, but the application can continue on without knowing the result. Is it acceptable to render a page before waiting for a db write to complete?
Yes. For example:
app.get('/', function(req, res, next) {
res.jsonp({
message: 'Hello World!'
});
var i = 0;
while (true) {
i++;
}
});
When a user visits '/', he will see the result immediately. But if there is only one node instance is running, when the other user visits '/', he won't receive any response as the only instance is under a infinite loop.
If you have a lot of heavy work to do(for example, CPU-bound works), it's much better to use a message queue such as MSMQ and AMQP instead of having all the works done in the node instance.
Sure. But how would you notify the user of an error if something did go wrong? Unless you're doing sockets or ajax or something, requests are the standard way.