[Ingest Manager] Do not use @kbn/config-schema to validate Fleet request

[nchaulet]

Description

When enrolling 1000 agents, Performing HTTP request validation is accounting for approximately 8% of the total CPU time.

@kbn/config-schema rely on Joi that is the most performance oriented library, we should probably use something else for validating Fleet request (enroll, ack, and checkin)

@kobelb @jfsiii both io-ts and ajv are already dependencies in Kibana, do you have any experiences or recommendation of using one or the other?

[elasticmachine]

Pinging @elastic/ingest-management (Team:Ingest Management)

[kobelb]

do you have any experiences or recommendation of using one or the other?

I do not, unfortunately.

[jfsiii]

@nchaulet TL;DR: 👍 for Ajv

I haven't used io-ts myself but there an issue where a few teams talk about their usage #45074

I used Ajv quite a bit while trying different OpenAPI / TS experiments. I like it and it's also used by Fastify, fwiw https://github.com/fastify/fastify/blob/master/docs/Validation-and-Serialization.md

One drawback is that we can't currently[1] send the schema we have in the OpenAPI spec. However, I think even the current differences between the two might not matter for our simple case (iiuc).

[1]: OpenAPI 3.1 and JSON Schema 2019-09 (coming in Ajv 7) will make it so we can share the schema https://apisyouwonthate.com/blog/openapi-v31-and-json-schema-2019-09