Retry

A npm package for easily adding retry to fetch calls.

Getting Started

Install the npm package:

npm install @dataforsyningen/retry

Import the options and functions you need, for instance:

import { retryOptions, fetchWithRetry } from '@dataforsyningen/retry/index.js'

You can set global options like this:

// Set the default retry timeout.
retryOptions.timeout = 200
// disable dynamically updating timeout.
retryOptions.dynamicTimeout = false

And you can use the retry with fetch like the usual fetch calls:

fetchWithRetry(resource, options)

You can pass custom parameters in the options object in additional to fetch's usual options (see https://developer.mozilla.org/en-US/docs/Web/API/RequestInit).

Here are the possible options:

Name	Default	Description
retries	4	The number of times the application should attempt to retry API calls.
timeout	500	The time the application should wait before attempting a retry.
growthFactor	2	The exponential growth factor which the timeout is multiplied by after each failed attempt.
statusCodes	[408, 500, 502, 503, 504, 506, 507, 508, 510]	The response status codes where a retry should be attempted.

Here is an example of how to use it with an OpenLayers WMTS source:

import WMTS from 'ol/source/WMTS'
import TileState from 'ol/TileState.js'

// create an options object to use in a WMTS source constructor. 
const options = {
    ...
}

// Add retry to the tileLoadFunction.
options.tileLoadFunction = function (tile, src) {
fetchWithRetry(src)
    .then(response => {
        if (!response.ok) {
            tile.setState(TileState.ERROR)
        }
        return response.blob()
    })
    .then(blob => {
        tile.getImage().src = URL.createObjectURL(blob)
    })
    .catch((e) => {
        tile.setState(TileState.ERROR)
    })
}

// Create the WMTS Source.
const wmtsSource = new WMTS(options)