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fix(docs-infra): fix the backoff example (#38896) 

Previously, the `backoff()` example did not work as intended. More
specifically, the `range(1, maxTries)` observable would complete
immediately after emitting the `maxTries`th value, causing the overall
observable to also complete. As a result, it would only make
`maxTries - 1` attempts to recover from an error. More importantly, the
outer observable would complete successfully instead of erroring.

This commit fixes the `backoff()` operator by ensuring it makes exactly
`maxTries` attempts to recover and it propagates the actual error to the
outer observable.

The test for this change is added in the next commit.

PR Close #38896
This commit is contained in:
Sonu Kapoor 2020-09-19 11:52:03 -04:00 committed by Alex Rickabaugh
parent 19d543f71e
commit 37297cfed7
1 changed files with 12 additions and 11 deletions
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23
aio/content/examples/practical-observable-usage/src/backoff.ts
View File

@ -1,17 +1,18 @@
// TODO: Add unit tests for this file.
import { pipe, range, timer, zip } from 'rxjs';
import { of, pipe, range, throwError, timer, zip } from 'rxjs';
import { ajax } from 'rxjs/ajax';
import { retryWhen, map, mergeMap } from 'rxjs/operators';
import { map, mergeMap, retryWhen } from 'rxjs/operators';
function backoff(maxTries, ms) {
return pipe(
retryWhen(attempts => zip(range(1, maxTries), attempts)
.pipe(
map(([i]) => i * i),
mergeMap(i => timer(i * ms))
)
)
);
function backoff(maxTries, delay) {
return pipe(
retryWhen(attempts =>
zip(range(1, maxTries + 1), attempts).pipe(
mergeMap(([i, err]) => (i > maxTries) ? throwError(err) : of(i)),
map(i => i * i),
mergeMap(v => timer(v * delay)),
),
),
);
}
ajax('/api/endpoint')