I am using fetch in a NodeJS application. Technically, I have a ReactJS front-end calling the NodeJS backend (as a proxy), and then the proxy calls out to backend services on a different domain.
However, from logging errors from consumers (I haven't been able to reproduce this issue myself) I see that a lot of these proxy calls (using fetch) throw an error that just says Network Request Failed, which is of no help. Some context:
This only occurs on a subset of all total calls (lets say 5% of traffic)
Users that encounter this error can often make the same call again some time later (next couple minutes/hours/days) and it will go through
From Application Insights, I can see no correlation between browsers, locations, etc
Calls often return fast, like < 100 ms
All calls are HTTPS, non are HTTP
We have a fetch polyfill from fetch-ponyfill that will take over if fetch is not available (Internet Explorer). I did test this package itself and the calls went through fine. I also mentioned that this error does occur on browsers that do support fetch, so I don't think this is the error.
Fetch settings for all requests
Method is set per request, but I've seen it fail on different types (GET, POST, etc)
Mode is set to 'same-origin'. I thought this was odd, since we were sending a request from one domain to another, but I tried to set it differently and it didn't affect anything. Also, why would some requests work for some, but not for others?
Body is set per request, based on the data being sent.
Headers is usually just Accept and Content-Type, both set to JSON.
I have tried researching this topic before, but most posts I found referenced React native applications running on iOS, where you have to set some security permissions in the plist file to allow HTTP requests or something to do with transport security.
I have implement logging specific points for the data in Application Insights, and I can see that fetch() was called, but then() was never reached; it went straight to the .catch(). So it's not even reaching code that parses the request, because apparently no request came back (we then parse the JSON response and call other functions, but like I said, it doesn't even reach this point).
Which is also odd, since the request never comes back, but it fails (often) within 100 ms.
My suspicions:
Some consumers have some sort of add-on for there browser that is messing with the request. Although, I run with uBlock Origin and HTTPS Everywhere and I have not seen this error. I'm not sure what else could be modifying requests that would cause it to immediately fail.
The call goes through, which then reaches an Azure Application Gateway, which might fail for some reason (too many connected clients, not enough ports, etc) and returns a response that immediately fails the fetch call without running the .then() on the response.
For #2, I remember I had traced a network call that failed and returned Network Request Failed: Made it through the proxy -> made it through the Application Gateway -> hit the backend services -> backend services sent a response. I am currently requesting access to backend service logs in order to verify this on some more recent calls (last time I did this, I did it through a screenshare with a backend developer), and hopefully clear up the path back to the client (the ReactJS application). I do remember though that it made it to the backend services successfully.
So I'm honestly not sure what's going on here. Does anyone have any insight?
Based on your excellent description and detective work, it's clear that the problem is between your Node app and the other domain. The other domain is throwing an error and your proxy has no choice but to say that there's an error on the server. That's why it's always throwing a 500-series error, the Network Request Failed error that you're seeing.
It's an intermittent problem, so the error is inconsistent. It's a waste of your time to continue to look at the browser because the problem will have been created beyond that, either in your proxy translating that request or on the remote server. You have to find that error.
Here's what I'd do...
Implement brute-force logging in your Node app. You can use Bunyan, or Winston or just require(fs) and write out to some file when an error occurs. Then look at the results. Only log it out when the response code from the other server is in the 400 or 500 ranges. Log the request object and the response object.
Something like this with Bunyan:
fetch(urlToRemoteServer)
.then(res => res.json())
.then(res => whateverElseYoureDoing(res))
.catch(err => {
// Get the request & response to the remote server
log.info({request: req, response: res, err: err});
});
where the res in this case is the response we just got from the other domain and req is our request to them.
The logs on your Azure server will then have the entire request and response. From this you can find commonalities. and (🤞) the cause of the problem.
My tech stack includes react on UI and spring boot on server.
All the other api requests made to server work just fine but one request that has response of an array with a million records has this issue.
The response size is about 15mb and the request shows 200 as status code.
But the timing tab of the request shows this flag - Caution: request is not finished yet.
As long as this flag stays, the application becomes unresponsive.
On doing my research on this issue, I found that this means that chrome is expecting some more data as response.
Is there something to be mentioned in the response header to resolve this issue?
As the application becomes unresponsive, how can this be terminated by a button click? I added axios cancel token but that cancels the request only if its pending and not when 200 comes as status.
I'm using Ionic platform for my mobile application. Using angular
$http for sending requests to server.
Intermittently when Mobile app tries to access server $http goes to it's errorCallback with response status -1 only no other
data.
When I check log on server, not able to see any hit.
I've changed timeout of application to 2 minutes using interceptors.
I have used chrome debugger but it won't show anything apart from
request it forms, shows nothing in response and preview columns.
I got that in Ionic we use pre-flight to check if server is alive
before sending actual request. But it's for CORS; we have enabled
CORS on server and thats why app is working good since last 15 days.
Thought of using network packet tracer tool but if call not logged on
server no use of it. as Status -1 says $http aborted the request.
My Question is why it's aborting when I click once and do send
when I click same button again.
Please me help to figure out an issue.
After lots of debugging and surfing over internet for issue.
I guess that an issue was like mobile app sending pre-flight messages and so $http aborting the request and even some time Server played a culprit here how will tell you;
We have server hosted on AWS in where we had Load balancer in different zone and actual API server is in different zone. After changing them to same zone ask, production people to test now they are not getting this issue.
The another reason was we were using unstable mobile networks to test.
If any one have any thing else on this please let me know.
In the last two days my GAE App sometimes response quickly and most of the times loading so slow or loading forever.
Same application version in another domain works just fine.
I checked my logs to see any errors and I surprised with a lots of HTTP(503) from Unknown Origin:
The error details:
.
Any Idea?
Thanks
Your app seems to be configured for warmup requests. Unfortunately, your app is responding to the requests for /_ah/start with a 503, which is causing the process to be terminated (and an new process started, which will make your app seem very slow).
The relevant message is:
Process terminated because it failed to respond to the start request with an HTTP status code of 200-299 or 404.
You probably want to remove the -warmup from the inbound_services: section of your app.yaml, or configure a warmup handler on /_ah/start.
https://cloud.google.com/appengine/docs/php/warmup-requests/configuring
I cleared the Memcache and the problem gone away. ^_^
I have integrated siteminder with my spring application which runs on Tomcat and the front end is developed on AngularJS.
The problem is that after 20 minutes of logging in I am getting error in webagent.log saying 'Unable to process SMSESSION cookie'.
Interesting point is that it is happening only for GET requests and apache is throwing 302 for these requests, trying to redirect to SSO login page.
However, for POST requests, I am getting 200 with proper response.
When user is redirected to SSO login page, SSO again redirects to the application without asking to enter login credentials again. And again application works fine for next 20 minutes until GET requests starts failing again.
Does anyone know root-cause/solution of this issue?
Thanks.
Do you have different rules created for GET and POST requests.. What is the idle and maximum timeout value set for the rules.
If you are in a position to enable debug on the webagent, that will tell you exactly why the request is being rejected although from the sound of it, it seems to be an obvious case of session timing out.