Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Fastify version

4.13.0

Plugin version

No response

Node.js version

v18.16.1

Operating system

macOS

Operating system version (i.e. 20.04, 11.3, 10)

13.0.1

Description

We are experiencing OOM errors in our tests, both locally (macOS) and in CI (linux).

After some analysis we found that the fastify instances are kept in memory even after .close() was called.

We were able to reproduce this in a minimal reproduction, where only the repeated invocation of Fastify().close() leads to the allocation of more and more memory.

What looks interesting is the connectionsCheckingInterval. This is new in Node.js v18.0.0: https://nodejs.org/api/http.html#httpcreateserveroptions-requestlistener. When running the script with Node.js v16.13.0, memory still increases, but not as much and there are no Router/Server instances in memory after the script has finished.

Steps to Reproduce

// memory-test.js
const Fastify = require('fastify')

const initialRss = process.memoryUsage().rss

async function main() {
  for (let i = 0; i < 2000; i += 1) {
    if (i % 100 === 0) {
      global.gc()
      console.log('server', i, process.memoryUsage().rss - initialRss)
    }
    const server = Fastify()
    // eslint-disable-next-line no-await-in-loop
    await server.close()
  }
  await new Promise(resolve => setTimeout(resolve, 1000))
  global.gc()
  debugger
}

main()

Run with node --expose-gc ./memory-test.js to see logs or node --inspect-brk --expose-gc ./memory-test.js to analyse memory allocation.

Expected Behavior

Fastify instances being freed after calling .close().