🚀 Feature Proposal

Fastify Request object is bound to the HTTP request lifecycle.

As a developer, I would expect that fastify creates a new Request object for every new request. While this is the case, fastify keeps object references across requests. This is due to the nature of prototype inheritance here.
This makes the code vulnerable to memory leaks: fastify/fastify-multipart#158 (comment)

We need to ensure that all properties are reset.

Motivation

As in other HTTP frameworks, the Request object is a new instance on every request. The developer shouldn't need to care about it. I propose to rethink that strategy because it's confusing and error-prone.

Example

fastify.decorateRequest('array', [])

fastify.post('/', async function (req, reply) {
    req.array.push(1)
    reply.code(200).send()
})

http.request(...) // array = [1]
http.request(...) // array = [1, 1]
.....

[ 1 ]
[ 1, 1 ]
[ 1, 1, 1 ]
[ 1, 1, 1, 1 ]
[ 1, 1, 1, 1, 1 ]
[ 1, 1, 1, 1, 1, 1 ]