Motivation

For integration with external tools for

• healthcheck
• monitoring
• management
• ...

MySQL Router needs interface that is:

• easy to interface with for applications
• easy to use for users

In principle the MySQL Protocol could be used for this task, but the HTTP protocol fits the needs of this task better.

HTTP

Using HTTP as underlying protocol allows to:

• encrypt the traffic with TLS
• authorize the users

• allow to use existing tools and frameworks tested and validated by the web community to

  • easily interface with browsers for user-interfaces
  • easily expose REST endpoints to applications (document with tools like https://swagger.io/)

Goal

Add a tiny HTTP server library to MySQL Router to allow to expose REST endpoints and a web-interface.

Requirements

FR1

communication MUST be encrypted by default

FR2

it MUST be possible to limit access to authenticated users

FR3

it MUST be possible to deliver data for humans

FR4

it MUST be possible to deliver machine parsable data

Protocol Evaluation

There are several option on how to expose monitoring information:

• a SQL based interface over MySQL classic or xprotocol
• a REST based interface based on HTTP and JSON

Both allow to:

• provide secure access (authentication)
• encrypted transportation (TLS)
• compression if needed

Implementations

The HTTP protocol server implementation can be taken from

• libevent's HTTP library

which is already part of the Routers dependencies.

Session State

One of the differentiators between HTTP and MySQL protocols is statefulness:

• HTTP is stateless
• MySQL protocols are stateful

Conclusion

As state isn't needed, going with HTTP opens many interesting options down the road:

• a integrated, browser based internal live reporting interface
• simple administration via HTTP CRUD operations
• simple integration the typical user, web-environment

Implementation

http_server module

http_server module provides:

• APIs for other plugins to register and unregister URL routes
• HTTP handling

Configuration

config-section: http_server

options

bind_address

IPv4 address to bind to for "port". Default: 0.0.0.0

port

TCP port to listen for HTTP requests on. Default: 8081

static_folder

base directory for static file requests. Default: empty. If empty, no static files will served.

libevent

Using libevent's HTTP component

• http://www.wangafu.net/~nickm/libevent-2.0/doxygen/html/http_8h.html
• https://github.com/libevent/libevent/blob/master/sample/http-server.c

removes the need to write a HTTP server library. libevent is already a dependency of the MySQL Router.