retry

A simple retry/wait tool for deno. Can re-call a function until a sucess, or execute a function with a timeout Ex:

const result = await retryAsync(
  async ()=> {/* get some data if those data are ready, throw an expection otherwise */}, 
  { delay: 100, maxTry: 5 }
)

This will try 5 times to get the data. If data is not ready after the 5 attempts, an exception is thrown. If data are obtained, retryAsync stop immediatly and returns the data.

const result = await waitUntil(fn, 10000);

This wait fn to complete withint 10 seconds. If fn complete on a sucess, return fn return value. If fn complete on an error, throw fn's error. If fn does not complete within 10 seconds, throws a TimeoutError.

How to:

to retry something:

const result = await retry(()=> {/* do something */}, {delay:100,maxTry:5})

to retry something async :
```
const result = await retryAsync(async ()=> {/* do something */}, {delay:100,maxTry:5})
```
Above examples make up to 5 attempts, waiting 100ms between each try.

to set a timeout on something async :

try {
  const result = await waitUntil(async ()=> {/* do something */}, 10000);
} catch (err) {
  if (error instanceof TimeoutError) {
    // fn does not complete
  } else {
    // fn throws an exception
  }
}

In the Above example fn has 10 seconds to complete, otherwhise an exception is thrown.

API

retry(fn, retryOptions): call repeteadly fn until fn does not throw and exception. Stop after retryOptions.maxTry count. Between each call wait retryOptions.delay milliseconds. if stop to call fn after retryOptions.maxTry, throws fn execption, otherwise returns fn return value.
retryAsync(fn, retryOptions): same as retry, except fn is an asynchronous function.
retryOptions:
- maxTry maximum calls to fn.
- delay: delay between each call (in milliseconds).
waitUntil(fn, delay, error?): waitUntil call asynchronously fn once. If fn complete within the delay (express in miliseconds), waitUntil returns the fn result. Otherwhise it thows the given error (if any) or a TimeoutError exception.
waitUntilAsync(fn, delay, error?): same as waitUntil, except fn is an asynchronous function.
TimeoutError: an error thrown by waitUntil. It has a property isTimeout set to true: therefore there's two means to check os fn timeout:
```
error instanceof TimeoutError
or
(error as any).isTimeout
```
In case of timeout fn is still executing. It is advise to add a mean to abort it. Note: retry, retryAsync and waitUntil return type is the return type of the given fn.

Compatilibity

Use std 0.81.0 (deno 1.6.1) but is is aslo tested with lates deno 1.3.x, deno 1.4.x and deno 1.5.x.