fix: send keep-alive timeout

Provide a hint for the server to keep connection alive until it is
considered no longer re-usable by client. This reduces the risk of
a race where the client sends a request and the server closes it
before receiving it.

Author: ronag

lib/client.js

@@ -412,6 +412,7 @@ class Parser extends HTTPParser {
     const request = client[kQueue][client[kRunningIdx]]
 
     // TODO: Check for content-length mismatch?
+    // TODO: keep-alive timeout & max?
 
     assert(this.statusCode < 200)
 
@@ -797,6 +798,14 @@ function write (client, request) {
     socket.write(`content-length: ${contentLength}\r\n`, 'ascii')
   }
 
+  if (client[kSocketTimeout]) {
+    // Provide a hint for the server to keep connection alive until it is
+    // considered no longer re-usable by client. This reduces the risk of
+    // a race where the client sends a request and the server closes it
+    // before receiving it.
+    socket.write(`keep-alive: timeout=${Math.ceil(client[kSocketTimeout] * 2) / 1000}\r\n`)
+  }
+
   if (method === 'HEAD') {
     // https://github.com/mcollina/undici/issues/258
 

lib/request.js

@@ -122,6 +122,11 @@ class Request extends AsyncResource {
             key.toLowerCase() === 'connection'
           ) {
             throw new InvalidArgumentError('invalid connection header')
+          } else if (
+            key.length === 10 &&
+            key.toLowerCase() === 'keep-alive'
+          ) {
+            throw new InvalidArgumentError('invalid keep-alive header')
           } else {
             header += `${key}: ${val}\r\n`
           }

test/invalid-headers.js

@@ -4,7 +4,7 @@ const { test } = require('tap')
 const { Client, errors } = require('..')
 
 test('invalid headers', (t) => {
-  t.plan(5)
+  t.plan(6)
 
   const client = new Client('http://localhost:3000')
   t.teardown(client.destroy.bind(client))
@@ -38,6 +38,16 @@ test('invalid headers', (t) => {
     t.ok(err instanceof errors.InvalidArgumentError)
   })
 
+  client.request({
+    path: '/',
+    method: 'GET',
+    headers: {
+      'keep-alive': 'timeout=5'
+    }
+  }, (err, data) => {
+    t.ok(err instanceof errors.InvalidArgumentError)
+  })
+
   client.request({
     path: '/',
     method: 'GET',