What is the proper way of detecting network errors in stream downloads using Axios in Nest.js? - axios

Question

I'm working with the HttpService module from Nest.js to make the HTTP calls. I'm able to download an image from https://unsplash.com; when there is no network interruptions the code is working as expected.
This is the code I have for making the download call and start writing into the desired file
const urlDownload = 'https://unsplash.com/photos/xiie4XeSzTU/download?force=true';
let response = await this.httpService.get(urlDownload, {
responseType: 'stream'
}).toPromise();
response.data.pipe(writer);
And this is the code where I'm trying to handle the possible events of the writer and returning a response
let downloadFile = path.resolve(__dirname,'../../files/landscape.jpg');
let writer = fs.createWriteStream(downloadFile);
return new Promise((resolve, reject) => {
writer.on('finish', ()=>{
resolve('Image downloaded');
});
writer.on('error', ()=>{
reject('Image downloaded failed');
});
});
I'm deliberately turning off the wifi during the download to try the server response with Image downloaded failed (what I have in the writer error handler), but instead I'm getting an 500 statusCode, internal server error. When I go to the Nest console to whatch the error it appears
[Nest] 11220 - 2020-05-22 18:16:45 [ExceptionsHandler] getaddrinfo ENOTFOUND unsplash.com +439536ms
Error: getaddrinfo ENOTFOUND unsplash.com
at GetAddrInfoReqWrap.onlookup [as oncomplete] (dns.js:64:26)
How can I solve this and catch correcty the network error from Nest to return a friendly message?

Answer 1

I could solve it. I let it here with the hope of helping somebody in the future.
It is not firing the error handler function because that handler is attached to the writter, and there is not writting error, it just stops writing because the cut of the connection but that is not an error.
I re-writed the response variable to stop being a promise and better I started treating it like an observer.
let response = this.httpService.get(urlDownload, {
responseType: 'stream',
});
And then it is the response in previus Promise format
return new Promise((resolve, reject) => {
writer.on('error', () => {
resolve('error due to, possibly, an unexisting file path');
})
response.subscribe({
next(response) { response.data.pipe(writer) },
error(err) {
console.error('More details: ' + err);
resolve('Error in the download :/')
},
complete() { resolve('Completed'); }
})
});
I'm not using the reject function of the promise but it is perfectly doable