Fastify Instrumentation does not Capture Request Body

[astorm]

Unsure if this is an enhancement request or a bug report, but it looks like our fastify instrumentation does not collect the request bodies as captured by the standard fastify-formbody middlware. Fastify populates it's own Request object's body property (request.body) with these values, but [we read our request bodies in from the native node IncomeingMessage/Request object, which is different from fastify's.

You can observe this behavior by running the following small sample program

const fastify = require('fastify')()

fastify.register(require('fastify-formbody'))

fastify.post('/test', (req, reply) => {
  console.log(req.body)
  reply.send("Hello World")
})

const server = fastify.listen(0, '0.0.0.0',(err, address) => {
  if (err) throw err

  console.log(address)
})

and posting some form variables.

$ curl -i http://localhost:3000 -d foo=bar

Fastify captures the request body, but if you examine the generated transactions, no request body is captured.

Ideally our Fastify instrumentation should match our express instrumentation's functionality and capture these values.