fetchover v1.0.0

fetchover

A fetch implementation with extensible failover strategies.

Supports node and browsers.

Usage

import { fetchOver, SimpleStrategy } from 'fetchover'

// define your failover servers
const servers = [
  'https://fallback1.server',
  'https://fallback2.server'
]
// choose a failover implemention (or create your own)
const failover = new SimpleFailover({ servers, timeout: 5e3 })
const fetch = fetchOver({ failover, strategy: 'sequential' })

// just fetch as always (with optional timeout)
const res = await fetch('https://target.server', { timeout: 10e3 })

Different strategies are available.

• strategy='sequential' (default) the "fallback" servers are called one after another in sequence.
• strategy='random' is similar but the order of "fallback" servers being called is random.
• strategy='parallel' all servers are called in parallel. The response of the first to succeed is returned, the other requests are aborted.
  ⚠️ Note: Take care to cope with multiple writes, e.g. using optimistic-locking in your DB.

Failover

For customizing the behavior of the failover scenarios different failover adapters are offered.

SimpleFailover

The SimpleFailover mechanism will issue the request (using the same pathname but different hostname) to different "fallback" servers in case that the "target" server of the initial request is unavailable.

With timeout you can control when the next request after a failure can be issued, effectively acting as circuit breaker here. Default is 5 seconds.

In case that only the circuit breaker functionality is needed, don't name any fallback servers.

type declaration

interface SimpleFailoverOptions {
  /** list of failover servers */
  servers?: string[]
  /**
   * timeout of consecutive request after failure (circuit breaker)
   * @default 5e3
   */
  timeout?: number
}

class SimpleFailover implements Failover {
    constructor(param: SimpleFailoverOptions);
}

License

MIT Licensed