feat(node): support http agent with keepAlive (#22)

README.md

@@ -39,7 +39,7 @@ const { $fetch } = require('ohmyfetch')
 We use [conditional exports](https://nodejs.org/api/packages.html#packages_conditional_exports) to detect Node.js
  and automatically use [node-fetch](https://github.com/node-fetch/node-fetch). If `globalThis.fetch` is available, will be used instead.
 
-### undici support
+### `undici` support
 
 In order to use experimental fetch implementation from [nodejs/undici](https://github.com/nodejs/undici), You can import from `ohmyfetch/undici`.
 
@@ -49,6 +49,12 @@ import { $fetch } from 'ohmyfetch/undici'
 
 On Node.js versions older than `16.5`, node-fetch will be used as the fallback.
 
+### `keepAlive` support
+
+By setting `FETCH_KEEP_ALIVE` environment variable to `true`, A http/https agent will be registred that keeps sockets around even when there are no outstanding requests, so they can be used for future requests without having to reestablish a TCP connection.
+
+**Note:** This option can potentially introduce memory leaks. Please check [node-fetch/node-fetch#1325](https://github.com/unjs/ohmyfetch/pull/22).
+
 ## ✔️ Parsing Response
 
 `$fetch` Smartly parses JSON and native values using [destr](https://github.com/unjs/destr) and fallback to text if it fails to parse.

src/node.ts

@@ -1,8 +1,32 @@
+import http from 'http'
+import https, { AgentOptions } from 'https'
 import nodeFetch from 'node-fetch'
+
 import { createFetch } from './base'
 
 export * from './base'
 
-export const fetch = globalThis.fetch || nodeFetch as any as typeof globalThis.fetch
+export function createNodeFetch () {
+  const useKeepAlive = JSON.parse(process.env.FETCH_KEEP_ALIVE || 'false')
+  if (!useKeepAlive) {
+    return nodeFetch
+  }
+
+  // https://github.com/node-fetch/node-fetch#custom-agent
+  const agentOpts: AgentOptions = { keepAlive: true }
+  const httpAgent = new http.Agent(agentOpts)
+  const httpsAgent = new https.Agent(agentOpts)
+  const nodeFetchOptions = {
+    agent (parsedURL: any) {
+      return parsedURL.protocol === 'http:' ? httpAgent : httpsAgent
+    }
+  }
+
+  return function nodeFetchWithKeepAlive (input: RequestInfo, init?: RequestInit) {
+    return (nodeFetch as any)(input, { ...nodeFetchOptions, ...init })
+  }
+}
+
+export const fetch = globalThis.fetch || createNodeFetch()
 
 export const $fetch = createFetch({ fetch })

src/undici.ts

@@ -1,9 +1,9 @@
 import { fetch as undiciFetch } from 'undici'
-import nodeFetch from 'node-fetch'
+import { createNodeFetch } from './node'
 import { createFetch } from './base'
 
 export * from './base'
 
-export const fetch = globalThis.fetch || undiciFetch || nodeFetch
+export const fetch = globalThis.fetch || undiciFetch || createNodeFetch()
 
 export const $fetch = createFetch({ fetch })