retry-request

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.
});

opts.maxRetryDelay

Type: Number

Default: 64

The maximum time to delay in seconds. If retryDelayMultiplier results in a delay greater than maxRetryDelay, retries should delay by maxRetryDelay seconds instead.

opts.retryDelayMultiplier

Type: Number

Default: 2

The multiplier by which to increase the delay time between the completion of failed requests, and the initiation of the subsequent retrying request.

opts.totalTimeout

Type: Number

Default: 600

The length of time to keep retrying in seconds. The last sleep period will be shortened as necessary, so that the last retry runs at deadline (and not considerably beyond it). The total time starting from when the initial request is sent, after which an error will be returned, regardless of the retrying attempts made meanwhile.

cb (optional)

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