Node-fetch-plus NPM

Node Fetch Plus

An extension of node-fetch that provides retries, timing and logging.

Installation

$ npm install node-fetch-plus --save

Configuration

A node-fetch-plus client can be created using the NodeFetchPlus constructor.

const NodeFetchPlus = require('node-fetch-plus');

const client = new NodeFetchPlus();

By default this creates a client with a fetch method that is identical to node-fetch. For example, the following are identical:

const fetch = require('node-fetch');

const NodeFetchPlus = require('node-fetch-plus');
const client = new NodeFetchPlus();

fetch('http://test.com');
client.fetch('http://test.com');

The fetch method of a node-fetch-plus instance supports all the options that node-fetch supports. Read the documentation for a full list of options.

Retries

node-fetch-plus supports retrying failed HTTP requests. It will retry on any error (e.g. network connection timeouts):

const NodeFetchPlus = require('node-fetch-plus')
const client = new NodeFetchPlus({
  retry: {
    retries: 2,
    minTimeout: 300
  }
});

await client.fetch('http://test.com');

This will try to make a request to http://test.com upto 3 times. If the request fails after the maximum number of retries an error will be thrown. Retries are handled by the retry, below is a list of supported options.

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.

Read the documentation to see a list of all supported options.

By default node-fetch-plus will retry successful HTTP requests with the following status codes:

408 Request timeout
500 Internal server error
502 Bad gateway
503 Service unavailable
504 Gateway timeout

To configure this behaviour you can specify a list of status codes which should be retried:

const NodeFetchPlus = require('node-fetch-plus')
const client = new NodeFetchPlus({
  retry: {
    retries: 2,
    minTimeout: 300,
    retryOnStatusCodes: [408, 500, 502, 503, 504]
  }
});

await client.fetch('http://test.com');

This will retry the request if it receives any of the status codes listed in retryOnStatusCodes. After all retries the last response is returned from the client.

Events

node-fetch-plus is an EventEmitter and will emit events at certain times within the request/response lifecycle.

Request

A request event is emitted just before the HTTP request is made.

const NodeFetchPlus = require('node-fetch-plus')
const client = new NodeFetchPlus();

client.on('request', (data) => {
  console.log(`Making ${data.method} request to ${data.url}. Attempt ${data.attempt} of ${data.maxAttempts}`);
});

The following information is available:

url - the full URL being requested.
method - the HTTP method of the request.
attempt - the attempt being made, starts at 1.
maxAttempts - the maximum number of attempts that will be made.

Response

A response event is emitted just after the HTTP response is received.

const NodeFetchPlus = require('node-fetch-plus')
const client = new NodeFetchPlus();

client.on('response', (data) => {
  console.log(`Received ${data.statusCode} from ${data.url} in ${data.responseTime}ms. Attempt ${data.attempt} of ${data.maxAttempts}`);
});

The following information is available:

url - the full URL being requested.
method - the HTTP method of the request.
statusCode - the HTTP status code of the response.
responseTime - the time it took to execute the request, in milliseconds.
attempt - the attempt being made, starts at 1.
maxAttempts - the maximum number of attempts that will be made.

Error

An error event is emitted when a request fails to execute.

const NodeFetchPlus = require('node-fetch-plus')
const client = new NodeFetchPlus();

client.on('error', (data) => {
  console.log(`Error received while making ${data.method} request to ${data.url} because ${data.message}. Attempt ${data.attempt} of ${data.maxAttempts}`);
});

The following information is available:

url - the full URL being requested.
method - the HTTP method of the request.
message - the error message that was received.
responseTime - the time it took to execute the request, in milliseconds.
attempt - the attempt being made, starts at 1.
maxAttempts - the maximum number of attempts that will be made.

NOTE By default if an EventEmitter emits an error event and there are no bound listeners it will terminate the node process. The events in node-fetch-plus are considered optional and so we bind an empty listener on the error event when you call createClient. This prevents the process being terminated should you decide not to listen to the error event.

Testing node-fetch-plus

When integrating with node-fetch-plus it can be useful to test certain responses without the retries taking effect. You can easily stub the fetch method using sinon.

const NodeFetchPlus = require('node-fetch-plus');
const { mockResponse } = require('node-fetch-plus/test');

const sinon = require('sinon');
const sandbox = sinon.createSandbox();

const response = mockResponse(500);
sandbox.stub(NodeFetchPlus.prototype, 'fetch').resolves(response);

const client = new NodeFetchPlus();

await client.fetch('http://any-url.com');

The mockResponse function returns a valid node-fetch Response. It takes a status and an optional body. So if you want to test the response body too:

const NodeFetchPlus = require('node-fetch-plus');
const { mockResponse } = require('node-fetch-plus/test');

const sinon = require('sinon');
const sandbox = sinon.createSandbox();

const response = mockResponse(200, JSON.stringify({
  id: 1234
}));
sandbox.stub(NodeFetchPlus.prototype, 'fetch').resolves(response);

const client = new NodeFetchPlus();

const res = await client.fetch('http://any-url.com');
const body = await res.json();