mirror of
https://github.com/idanoo/GoScrobble.git
synced 2024-11-22 16:35:14 +00:00
228 lines
8.8 KiB
Markdown
228 lines
8.8 KiB
Markdown
<!-- badges/ -->
|
|
[](http://travis-ci.org/tim-kos/node-retry "Check this project's build status on TravisCI")
|
|
[](https://codecov.io/gh/tim-kos/node-retry)
|
|
<!-- /badges -->
|
|
|
|
# retry
|
|
|
|
Abstraction for exponential and custom retry strategies for failed operations.
|
|
|
|
## Installation
|
|
|
|
npm install retry
|
|
|
|
## Current Status
|
|
|
|
This module has been tested and is ready to be used.
|
|
|
|
## Tutorial
|
|
|
|
The example below will retry a potentially failing `dns.resolve` operation
|
|
`10` times using an exponential backoff strategy. With the default settings, this
|
|
means the last attempt is made after `17 minutes and 3 seconds`.
|
|
|
|
``` javascript
|
|
var dns = require('dns');
|
|
var retry = require('retry');
|
|
|
|
function faultTolerantResolve(address, cb) {
|
|
var operation = retry.operation();
|
|
|
|
operation.attempt(function(currentAttempt) {
|
|
dns.resolve(address, function(err, addresses) {
|
|
if (operation.retry(err)) {
|
|
return;
|
|
}
|
|
|
|
cb(err ? operation.mainError() : null, addresses);
|
|
});
|
|
});
|
|
}
|
|
|
|
faultTolerantResolve('nodejs.org', function(err, addresses) {
|
|
console.log(err, addresses);
|
|
});
|
|
```
|
|
|
|
Of course you can also configure the factors that go into the exponential
|
|
backoff. See the API documentation below for all available settings.
|
|
currentAttempt is an int representing the number of attempts so far.
|
|
|
|
``` javascript
|
|
var operation = retry.operation({
|
|
retries: 5,
|
|
factor: 3,
|
|
minTimeout: 1 * 1000,
|
|
maxTimeout: 60 * 1000,
|
|
randomize: true,
|
|
});
|
|
```
|
|
|
|
## API
|
|
|
|
### retry.operation([options])
|
|
|
|
Creates a new `RetryOperation` object. `options` is the same as `retry.timeouts()`'s `options`, with two additions:
|
|
|
|
* `forever`: Whether to retry forever, defaults to `false`.
|
|
* `unref`: Whether to [unref](https://nodejs.org/api/timers.html#timers_unref) the setTimeout's, defaults to `false`.
|
|
* `maxRetryTime`: The maximum time (in milliseconds) that the retried operation is allowed to run. Default is `Infinity`.
|
|
|
|
### retry.timeouts([options])
|
|
|
|
Returns an array of timeouts. All time `options` and return values are in
|
|
milliseconds. If `options` is an array, a copy of that array is returned.
|
|
|
|
`options` is a JS object that can contain any of the following keys:
|
|
|
|
* `retries`: The maximum amount of times to retry the operation. Default is `10`. Seting this to `1` means `do it once, then retry it once`.
|
|
* `factor`: The exponential factor to use. Default is `2`.
|
|
* `minTimeout`: The number of milliseconds before starting the first retry. Default is `1000`.
|
|
* `maxTimeout`: The maximum number of milliseconds between two retries. Default is `Infinity`.
|
|
* `randomize`: Randomizes the timeouts by multiplying with a factor between `1` to `2`. Default is `false`.
|
|
|
|
The formula used to calculate the individual timeouts is:
|
|
|
|
```
|
|
Math.min(random * minTimeout * Math.pow(factor, attempt), maxTimeout)
|
|
```
|
|
|
|
Have a look at [this article][article] for a better explanation of approach.
|
|
|
|
If you want to tune your `factor` / `times` settings to attempt the last retry
|
|
after a certain amount of time, you can use wolfram alpha. For example in order
|
|
to tune for `10` attempts in `5 minutes`, you can use this equation:
|
|
|
|
|
|
|
|
Explaining the various values from left to right:
|
|
|
|
* `k = 0 ... 9`: The `retries` value (10)
|
|
* `1000`: The `minTimeout` value in ms (1000)
|
|
* `x^k`: No need to change this, `x` will be your resulting factor
|
|
* `5 * 60 * 1000`: The desired total amount of time for retrying in ms (5 minutes)
|
|
|
|
To make this a little easier for you, use wolfram alpha to do the calculations:
|
|
|
|
<http://www.wolframalpha.com/input/?i=Sum%5B1000*x^k%2C+{k%2C+0%2C+9}%5D+%3D+5+*+60+*+1000>
|
|
|
|
[article]: http://dthain.blogspot.com/2009/02/exponential-backoff-in-distributed.html
|
|
|
|
### retry.createTimeout(attempt, opts)
|
|
|
|
Returns a new `timeout` (integer in milliseconds) based on the given parameters.
|
|
|
|
`attempt` is an integer representing for which retry the timeout should be calculated. If your retry operation was executed 4 times you had one attempt and 3 retries. If you then want to calculate a new timeout, you should set `attempt` to 4 (attempts are zero-indexed).
|
|
|
|
`opts` can include `factor`, `minTimeout`, `randomize` (boolean) and `maxTimeout`. They are documented above.
|
|
|
|
`retry.createTimeout()` is used internally by `retry.timeouts()` and is public for you to be able to create your own timeouts for reinserting an item, see [issue #13](https://github.com/tim-kos/node-retry/issues/13).
|
|
|
|
### retry.wrap(obj, [options], [methodNames])
|
|
|
|
Wrap all functions of the `obj` with retry. Optionally you can pass operation options and
|
|
an array of method names which need to be wrapped.
|
|
|
|
```
|
|
retry.wrap(obj)
|
|
|
|
retry.wrap(obj, ['method1', 'method2'])
|
|
|
|
retry.wrap(obj, {retries: 3})
|
|
|
|
retry.wrap(obj, {retries: 3}, ['method1', 'method2'])
|
|
```
|
|
The `options` object can take any options that the usual call to `retry.operation` can take.
|
|
|
|
### new RetryOperation(timeouts, [options])
|
|
|
|
Creates a new `RetryOperation` where `timeouts` is an array where each value is
|
|
a timeout given in milliseconds.
|
|
|
|
Available options:
|
|
* `forever`: Whether to retry forever, defaults to `false`.
|
|
* `unref`: Wether to [unref](https://nodejs.org/api/timers.html#timers_unref) the setTimeout's, defaults to `false`.
|
|
|
|
If `forever` is true, the following changes happen:
|
|
* `RetryOperation.errors()` will only output an array of one item: the last error.
|
|
* `RetryOperation` will repeatedly use the `timeouts` array. Once all of its timeouts have been used up, it restarts with the first timeout, then uses the second and so on.
|
|
|
|
#### retryOperation.errors()
|
|
|
|
Returns an array of all errors that have been passed to `retryOperation.retry()` so far. The
|
|
returning array has the errors ordered chronologically based on when they were passed to
|
|
`retryOperation.retry()`, which means the first passed error is at index zero and the last is
|
|
at the last index.
|
|
|
|
#### retryOperation.mainError()
|
|
|
|
A reference to the error object that occured most frequently. Errors are
|
|
compared using the `error.message` property.
|
|
|
|
If multiple error messages occured the same amount of time, the last error
|
|
object with that message is returned.
|
|
|
|
If no errors occured so far, the value is `null`.
|
|
|
|
#### retryOperation.attempt(fn, timeoutOps)
|
|
|
|
Defines the function `fn` that is to be retried and executes it for the first
|
|
time right away. The `fn` function can receive an optional `currentAttempt` callback that represents the number of attempts to execute `fn` so far.
|
|
|
|
Optionally defines `timeoutOps` which is an object having a property `timeout` in miliseconds and a property `cb` callback function.
|
|
Whenever your retry operation takes longer than `timeout` to execute, the timeout callback function `cb` is called.
|
|
|
|
|
|
#### retryOperation.try(fn)
|
|
|
|
This is an alias for `retryOperation.attempt(fn)`. This is deprecated. Please use `retryOperation.attempt(fn)` instead.
|
|
|
|
#### retryOperation.start(fn)
|
|
|
|
This is an alias for `retryOperation.attempt(fn)`. This is deprecated. Please use `retryOperation.attempt(fn)` instead.
|
|
|
|
#### retryOperation.retry(error)
|
|
|
|
Returns `false` when no `error` value is given, or the maximum amount of retries
|
|
has been reached.
|
|
|
|
Otherwise it returns `true`, and retries the operation after the timeout for
|
|
the current attempt number.
|
|
|
|
#### retryOperation.stop()
|
|
|
|
Allows you to stop the operation being retried. Useful for aborting the operation on a fatal error etc.
|
|
|
|
#### retryOperation.reset()
|
|
|
|
Resets the internal state of the operation object, so that you can call `attempt()` again as if this was a new operation object.
|
|
|
|
#### retryOperation.attempts()
|
|
|
|
Returns an int representing the number of attempts it took to call `fn` before it was successful.
|
|
|
|
## License
|
|
|
|
retry is licensed under the MIT license.
|
|
|
|
|
|
# Changelog
|
|
|
|
0.10.0 Adding `stop` functionality, thanks to @maxnachlinger.
|
|
|
|
0.9.0 Adding `unref` functionality, thanks to @satazor.
|
|
|
|
0.8.0 Implementing retry.wrap.
|
|
|
|
0.7.0 Some bug fixes and made retry.createTimeout() public. Fixed issues [#10](https://github.com/tim-kos/node-retry/issues/10), [#12](https://github.com/tim-kos/node-retry/issues/12), and [#13](https://github.com/tim-kos/node-retry/issues/13).
|
|
|
|
0.6.0 Introduced optional timeOps parameter for the attempt() function which is an object having a property timeout in milliseconds and a property cb callback function. Whenever your retry operation takes longer than timeout to execute, the timeout callback function cb is called.
|
|
|
|
0.5.0 Some minor refactoring.
|
|
|
|
0.4.0 Changed retryOperation.try() to retryOperation.attempt(). Deprecated the aliases start() and try() for it.
|
|
|
|
0.3.0 Added retryOperation.start() which is an alias for retryOperation.try().
|
|
|
|
0.2.0 Added attempts() function and parameter to retryOperation.try() representing the number of attempts it took to call fn().
|