retry-request

What is retry-request?

The retry-request npm package is designed to make it easier to handle network requests that might need to be retried due to failures or errors. It wraps around the standard request functionality, providing a way to automatically retry requests a specified number of times, with customizable intervals between retries. This is particularly useful in environments where network reliability can't always be guaranteed, or when dealing with services that might occasionally fail or be temporarily unavailable.

What are retry-request's main functionalities?

Basic retry functionality

This demonstrates how to use retry-request to make a simple HTTP request with retry functionality. If the request fails, retry-request will automatically retry the request based on its default configuration.

const retryRequest = require('retry-request');

const requestOptions = {
  url: 'http://example.com'
};

retryRequest(requestOptions, function(err, response, body) {
  if (!err) {
    console.log(body);
  }
});

Custom retry options

This example shows how to customize the retry behavior, including the number of retries, the delay between retries, and even specifying a custom request module to use for the actual HTTP requests.

const retryRequest = require('retry-request');

const requestOptions = {
  url: 'http://example.com'
};

const options = {
  retries: 5,
  request: require('request'),
  retryDelay: 1000
};

retryRequest(requestOptions, options, function(err, response, body) {
  if (!err) {
    console.log(body);
  }
});

Other packages similar to retry-request

axios-retry

axios-retry is a package that adds retry functionality to Axios requests. It is similar to retry-request but is specifically designed for use with Axios, a promise-based HTTP client, offering more modern syntax and promise support compared to the callback-based retry-request.

got

got is a more comprehensive HTTP request library that includes built-in retry functionality among many other features. Unlike retry-request, which is a wrapper around the request library, got is a standalone library offering a wide range of HTTP capabilities, including retries, which makes it a more versatile choice for complex applications.

superagent-retry

superagent-retry extends the superagent library with retry capabilities. It is similar to retry-request in that it adds retry functionality to an existing HTTP request library, but it is tailored for superagent users. This package is a good choice for those already using superagent and looking to add simple retry mechanisms.

README

Retry a request with built-in exponential backoff.

$ npm install --save request
$ npm install --save retry-request

var request = require('retry-request', {
  request: require('request')
});

It should work the same as request in both callback mode and stream mode.

Note: This module only works when used as a readable stream, i.e. POST requests aren't supported (#3).

Do I need to install request?

Yes! You must independently install request and provide it to this library:

var request = require('retry-request', {
  request: require('request')
});

The code will actually look for the request module automatically to save you this step. But, being explicit like in the example is also welcome.

Callback

urlThatReturns503 will be requested 3 total times before giving up and executing the callback.

request(urlThatReturns503, function (err, resp, body) {});

Stream

urlThatReturns503 will be requested 3 total times before giving up and emitting the response and complete event as usual.

request(urlThatReturns503)
  .on('error', function () {})
  .on('response', function () {})
  .on('complete', function () {});

Can I monitor what retry-request is doing internally?

Yes! This project uses debug to provide the current retry attempt, each response status, and the delay computed until the next retry attempt is made. To enable the debug mode, set the environment variable DEBUG to retry-request.

(Thanks for the implementation, @yihaozhadan!)

request(requestOptions, [opts], [cb])

requestOptions

Passed directly to request. See the list of options supported: https://github.com/request/request/#requestoptions-callback.

opts (optional)

opts.noResponseRetries

Type: Number

Default: 2

The number of times to retry after a response fails to come through, such as a DNS resolution error or a socket hangup.

var opts = {
  noResponseRetries: 0
};

request(url, opts, function (err, resp, body) {
  // url was requested 1 time before giving up and
  // executing this callback.
});

opts.objectMode

Type: Boolean

Default: false

Set to true if your custom opts.request function returns a stream in object mode.

opts.retries

Type: Number

Default: 2

var opts = {
  retries: 4
};

request(urlThatReturns503, opts, function (err, resp, body) {
  // urlThatReturns503 was requested a total of 5 times
  // before giving up and executing this callback.
});

opts.currentRetryAttempt

Type: Number

Default: 0

var opts = {
  currentRetryAttempt: 1
};

request(urlThatReturns503, opts, function (err, resp, body) {
  // urlThatReturns503 was requested as if it already failed once.
});

opts.shouldRetryFn

Type: Function

Default: Returns true if http.incomingMessage.statusCode is < 200 or >= 400.

var opts = {
  shouldRetryFn: function (incomingHttpMessage) {
    return incomingHttpMessage.statusMessage !== 'OK';
  }
};

request(urlThatReturnsNonOKStatusMessage, opts, function (err, resp, body) {
  // urlThatReturnsNonOKStatusMessage was requested a
  // total of 3 times, each time using `opts.shouldRetryFn`
  // to decide if it should continue before giving up and
  // executing this callback.
});

opts.request

Type: Function

Default: try { require('request') }

If we cannot locate request, we will throw an error advising you to provide it explicitly.

NOTE: If you override the request function, and it returns a stream in object mode, be sure to set opts.objectMode to true.

var originalRequest = require('request').defaults({
  pool: {
    maxSockets: Infinity
  }
});

var opts = {
  request: originalRequest
};

request(urlThatReturns503, opts, function (err, resp, body) {
  // Your provided `originalRequest` instance was used.
});

cb (optional)

Passed directly to request. See the callback section: https://github.com/request/request/#requestoptions-callback.