The 'backoff' npm package provides a mechanism to handle retry logic with exponential backoff and other backoff strategies. It is useful for scenarios where you need to retry operations that may fail intermittently, such as network requests or database queries.
Exponential Backoff
This feature allows you to implement an exponential backoff strategy using the Fibonacci sequence. The code sample demonstrates how to set up a Fibonacci backoff with a randomisation factor, initial delay, and maximum delay. It also shows how to handle the 'ready' and 'fail' events.
const backoff = require('backoff');
const fibonacciBackoff = backoff.fibonacci({ randomisationFactor: 0.2, initialDelay: 10, maxDelay: 1000 });
fibonacciBackoff.on('ready', function(number, delay) {
console.log(`Retrying after ${delay} ms`);
// Perform the operation that needs to be retried
});
fibonacciBackoff.on('fail', function() {
console.log('Operation failed after maximum retries');
});
// Start the backoff process
fibonacciBackoff.backoff();Retry with Custom Strategy
This feature allows you to implement a custom retry strategy using exponential backoff. The code sample demonstrates how to set up an exponential backoff with an initial delay and maximum delay. It also shows how to handle the 'ready' and 'fail' events.
const backoff = require('backoff');
const customStrategy = backoff.exponential({ initialDelay: 100, maxDelay: 10000 });
customStrategy.on('ready', function(number, delay) {
console.log(`Retry attempt #${number} after ${delay} ms`);
// Perform the operation that needs to be retried
});
customStrategy.on('fail', function() {
console.log('Operation failed after maximum retries');
});
// Start the backoff process
customStrategy.backoff();Handling Errors
This feature demonstrates how to handle errors during the retry process. The code sample shows how to simulate an operation that may fail and how to retry the operation using exponential backoff until it succeeds or reaches the maximum number of retries.
const backoff = require('backoff');
const exponentialBackoff = backoff.exponential({ initialDelay: 100, maxDelay: 10000 });
exponentialBackoff.on('ready', function(number, delay) {
console.log(`Retry attempt #${number} after ${delay} ms`);
// Simulate an operation that may fail
const success = Math.random() > 0.5;
if (!success) {
exponentialBackoff.backoff();
} else {
console.log('Operation succeeded');
}
});
exponentialBackoff.on('fail', function() {
console.log('Operation failed after maximum retries');
});
// Start the backoff process
exponentialBackoff.backoff();The 'retry' package provides a similar functionality to 'backoff' by allowing you to retry operations with configurable strategies. It supports exponential backoff, custom retry strategies, and error handling. Compared to 'backoff', 'retry' offers a more flexible API for defining custom retry logic.
The 'promise-retry' package is designed for retrying operations that return promises. It provides a simple API for retrying promise-based operations with configurable retry strategies, including exponential backoff. Compared to 'backoff', 'promise-retry' is more focused on promise-based workflows.
The 'async-retry' package is another alternative that supports retrying asynchronous operations with configurable strategies. It works well with both promises and async/await syntax. Compared to 'backoff', 'async-retry' offers a more modern API that integrates seamlessly with async/await.
Fibonacci and exponential backoffs for Node.js.
npm install backoff
npm test
The usual way to instantiate a new Backoff object is to use one predefined
factory method: backoff.fibonacci([options]), backoff.exponential([options]).
Backoff inherits from EventEmitter. When a backoff starts, a backoff
event is emitted and, when a backoff ends, a ready event is emitted.
Handlers for these two events are called with the current backoff number and
delay.
var backoff = require('backoff');
var fibonacciBackoff = backoff.fibonacci({
randomisationFactor: 0,
initialDelay: 10,
maxDelay: 300
});
fibonacciBackoff.failAfter(10);
fibonacciBackoff.on('backoff', function(number, delay) {
// Do something when backoff starts, e.g. show to the
// user the delay before next reconnection attempt.
console.log(number + ' ' + delay + 'ms');
});
fibonacciBackoff.on('ready', function(number, delay) {
// Do something when backoff ends, e.g. retry a failed
// operation (DNS lookup, API call, etc.). If it fails
// again then backoff, otherwise reset the backoff
// instance.
fibonacciBackoff.backoff();
});
fibonacciBackoff.on('fail', function() {
// Do something when the maximum number of backoffs is
// reached, e.g. ask the user to check its connection.
console.log('fail');
});
fibonacciBackoff.backoff();
The previous example would print the following.
0 10ms
1 10ms
2 20ms
3 30ms
4 50ms
5 80ms
6 130ms
7 210ms
8 300ms
9 300ms
fail
Note that Backoff objects are meant to be instantiated once and reused
several times by calling reset after a successful "retry".
It's also possible to avoid some boilerplate code when invoking an asynchronous
function in a backoff loop by using backoff.call(fn, [args, ...], callback).
Typical usage looks like the following.
var call = backoff.call(get, 'https://duplika.ca/', function(err, res) {
console.log('Num retries: ' + call.getNumRetries());
if (err) {
console.log('Error: ' + err.message);
} else {
console.log('Status: ' + res.statusCode);
}
});
call.setStrategy(new backoff.ExponentialStrategy());
call.failAfter(10);
call.start();
Constructs a Fibonacci backoff (10, 10, 20, 30, 50, etc.).
The options are the following.
With these values, the backoff delay will increase from 100 ms to 10000 ms. The randomisation factor controls the range of randomness and must be between 0 and 1. By default, no randomisation is applied on the backoff delay.
Constructs an exponential backoff (10, 20, 40, 80, etc.).
The options are the following.
With these values, the backoff delay will increase from 100 ms to 10000 ms. The randomisation factor controls the range of randomness and must be between 0 and 1. By default, no randomisation is applied on the backoff delay.
Constructs a FunctionCall instance for the given function. The wrapped
function will get retried until it succeds or reaches the maximum number
of backoffs. In both cases, the callback function will be invoked with the
last result returned by the wrapped function.
It is the caller's responsability to initiate the call by invoking the
start method on the returned FunctionCall instance.
Constructs a new backoff object from a specific backoff strategy. The backoff
strategy must implement the BackoffStrategyinterface defined bellow.
Sets a limit on the maximum number of backoffs that can be performed before a fail event gets emitted and the backoff instance is reset. By default, there is no limit on the number of backoffs that can be performed.
Starts a backoff operation. If provided, the error parameter will be emitted
as the last argument of the backoff and fail events to let the listeners
know why the backoff operation was attempted.
An error will be thrown an error if a backoff operation is already in progress.
In practice, this method should be called after a failed attempt to perform a sensitive operation (connecting to a database, downloading a resource over the network, etc.).
Resets the backoff delay to the initial backoff delay and stop any backoff operation in progress. After reset, a backoff instance can and should be reused.
In practice, this method should be called after having successfully completed the sensitive operation guarded by the backoff instance or if the client code request to stop any reconnection attempt.
backoff.backoff([err])Emitted when a backoff operation is started. Signals to the client how long the next backoff delay will be.
Emitted when a backoff operation is done. Signals that the failing operation should be retried.
backoff.backoff([err])Emitted when the maximum number of backoffs is reached. This event will only
be emitted if the client has set a limit on the number of backoffs by calling
backoff.failAfter(numberOfBackoffs). The backoff instance is automatically
reset after this event is emitted.
A backoff strategy must provide the following methods.
Computes and returns the next backoff delay.
Resets the backoff delay to its initial value.
Exponential (10, 20, 40, 80, etc.) backoff strategy implementation.
The options are the following.
Fibonnaci (10, 10, 20, 30, 50, etc.) backoff strategy implementation.
The options are the following.
This class manages the calling of an asynchronous function within a backoff loop.
This class should rarely be instantiated directly since the factory method
backoff.call(fn, [args, ...], callback) offers a more convenient and safer
way to create FunctionCall instances.
Constructs a function handler for the given asynchronous function.
Returns whether the call is pending, i.e. hasn't been started.
Returns whether the call is in progress.
Returns whether the call is completed.
Returns whether the call is aborted.
FibonacciStrategy.Sets the backoff strategy to use. This method should be called before
call.start() otherwise an exception will be thrown.
Sets the maximum number of backoffs before the call is aborted. By default, there is no limit on the number of backoffs that can be performed.
This method should be called before call.start() otherwise an exception will
be thrown..
Retrieves the last intermediary result returned by the wrapped function. This method can be called at any point in time during the call life cycle, i.e. before, during and after the wrapped function invocation.
Returns an array containing the arguments passed to the completion callback of the wrapped function. For example, to get the error code returned by the last call, one would do the following.
var results = call.getLastResult();
// The error code is the first parameter of the callback.
var error = results[0];
Returns the number of times the wrapped function call was retried. For a wrapped function that succeeded immediately, this would return 0. This method can be called at any point in time during the call life cycle, i.e. before, during and after the wrapped function invocation.
Initiates the call the wrapped function. This method should only be called once otherwise an exception will be thrown.
Aborts the call.
The last result can be retrieved using call.getLastResult(). This method
can be called at any point in time during the call life cycle, i.e. before,
during and after the wrapped function invocation.
Emitted each time the wrapped function is called.
Emitted each time the wrapped function invokes its callback.
Emitted each time a backoff operation is started.
The annotated source code can be found at mathieuturcotte.github.io/node-backoff/docs.
This code is free to use under the terms of the MIT license.
2.4.1
ExponentialStrategy.FAQs
Fibonacci and exponential backoffs.
The npm package backoff receives a total of 545,367 weekly downloads. As such, backoff popularity was classified as popular.
We found that backoff demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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