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diff --git a/deps/npm/node_modules/npm-registry-client/node_modules/retry/README.md b/deps/npm/node_modules/npm-registry-client/node_modules/retry/README.md new file mode 100644 index 0000000000..eee05f7bb6 --- /dev/null +++ b/deps/npm/node_modules/npm-registry-client/node_modules/retry/README.md @@ -0,0 +1,215 @@ +# 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`: Wether to [unref](https://nodejs.org/api/timers.html#timers_unref) the setTimeout's, defaults to `false`. + +### 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`. +* `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. + +#### 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.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(). |