How to retry a http request until a condition is met using rxjs - node.js

Question

I want to retry a http request until some data exists up to 10 times with a delay of 2 seconds between each retry.
const $metrics = from(axios(this.getMetrics(session._id, sessionRequest._id, side)));
const res = $metrics.pipe(
map((val: any) => {
console.log("VALUE:", val.data.metrics.length);
if (val.data.metrics.length === 0) {
throw val;
}
return val;
}),
retryWhen((errors) => errors.pipe(delay(2000), take(10))),
).subscribe();
I am trying to follow the example in the documentation. https://www.learnrxjs.io/operators/error_handling/retry.html
I create $metrics observable from an axios http promise.
I use the map operator to check if the response of the http request matches my condition to retry. val.data.metrics.length === 0. If it does it throws an error.
I retry the http requests up to 10 times with a 10 second delay.
I expect after 3-4 retries for this metrics array to have data, but in my console when i log the response i get the following.
VALUE: 0
Im not sure if this is even making multiple http requests because the console log only returns one output instead of 10.
UPDATE
Ive updated the code to use retryWhen instead of retry, it does a delay of 2 seconds and will only take 10 errors before stopping.
Now i believe the problem is that it only makes 1 http request because the console log only returns a single output.

Answer 1

try use defer()
const $metrics = defer(()=>from(axios(this.getMetrics(session._id, sessionRequest._id, side))))
one thing to point out, you should inspect your network tab and see if the request is made in retry. your console.log is in map() operator which will be skipped when error thrown, could be why u don't see console.log there. You can try out the example below.
import { timer, interval,from } from 'rxjs';
import { map, tap, retryWhen, delayWhen,delay,take } from 'rxjs/operators';
//emit value every 1s
const source = from(fetch('http://kaksfk')).pipe(tap(val => console.log(`fetcching you won't see`)))
const example = source.pipe(
retryWhen(errors =>
errors.pipe(
// log error message
tap(val => console.log(`retrying`)),
// restart in 5 seconds
delay(2000),
take(5),
),
),
)