WL#11040: X Protocol installed by default

Affects: Server-8.0   —   Status: Complete   —   Priority: Medium

Summary
=======

MySQL Server must be available through X Protocol in default MySQL 8
installation.

In case the user wants to lock down the MySQL Server, it should stay
possible to:

* disable building the mysqlx plugin
* disable loading the mysqlx plugin

Current Behaviour in 5.7
========================

To build the mysqlx plugin, the user must:

* get an version of MySQL Server that has X Plugin 
* build the MySQL Server without specifying -DWITH_RAPID=no or -DWITH_MYSQLX=no or -DMYSQLX_DISABLE=ON

To use the X Protocol, user must:

* install X Plugin permanently by executing one of commands below:

        INSTALL PLUGIN 'mysqlx' SONAME "mysqlx.so";
        INSTALL PLUGIN 'mysqlx' SONAME "mysqlx.dll";

* or start mysql-server with:

        mysqld --plugin-load-add="mysqlx=mysqlx.so"
        mysqld --plugin-load-add="mysqlx=mysqlx.dll"

Goal
====

The user should not have to explicitly install the mysqlx plugin to
use the X Protocol. Instead it must be available by default.

To achieve that the plugin MUST not be removed from the sources when
rapid sources are removed. 


Notes
=====

In WL#10992 a X Protocol password cache plugin was introduced. The new plugin is placed inside the same binary as mysqlx plugin. This means that "mysqlx.so" contains mysqlx and mysqlx_cache_cleaner plugins. The command to install new plugin is almost the same as of the old one:

    INSTALL PLUGIN mysqlx_cache_cleaner SONAME 'mysqlx.so';

Merging of "mysqlx.so" adds two plugins into mysqld. The worklog focuses on "mysqlx" still the same rules apply to "mysqlx_cache_cleaner". For example it can be disabled by adding to cnf:

    mysqlx_cache_cleaner=0

or cmd line:

    --mysqlx_cache_cleaner=0
# Functional Requirements 

## Source Level Requirements

SRC1
:  mysqlx plugin MUST not be a rapid plugin

SRC2
:  a user MUST be able to disable building mysqlx plugin

## Startup Time Requirements

RUN1
:  a user MUST be able to disable loading mysqlx plugin at startup time

RUN2
:  user MUST be able to connect to MySQL Server by X Protocol after new database
   initialization with default values

## Upgrade Requirements

UP1
:  a user running MySQL 5.7 that wasn't using mysqlx plugin MUST have mysqlx plugin enabled in 8.0 after upgrade

UP2
:  a user running MySQL 5.7 that was using mysqlx plugin MUST have mysqlx plugin
enabled in 8.0 after upgrade

UP3
:  a user running MySQL 5.7 that had INSTALLed the mysqlx plugin, but disabled
   loading it with skip-mysqlx in the configuration, it MUST be disabled in 8.0
   too

# Implementation of Runtime Requirements

Multiple way exist to load the plugin by default:

* install it at --initialize time and handle upgrade cases manually
* linking the plugin into the mysqld binaries statically

## Install plugin at --initialize

Cons:

* changing setup/update scripts, which must install the plugin
* requires two INSTALL PLUGINs calls load other mysql-plugins from the same .so 
(WL#10992)

## Link plugin statically into the mysqld

Pros:

* always enabled, with no changes to the setup scripts
* simpler installation and upgrade handling

## Decision

Linking X Plugin into mysqld is the easiest way of integration which is going to be implemented.

# Implementation of Source Requirements

For SRC1, User must not be able to turn off the compilation of X Plugin by specifying "-DWITH_RAPID=OFF" 

For SRC2, 

1. User must be able to turn off the compilation and installation of X Plugin by
   specifying "-DWITH_MYSQLX=OFF". Both cmake variables
   are auto-generated for every plugin by MySQL Servers cmake files.
2. User must able to initialize new database when X Plugin isn't compiled
3. User must able to start MySQL Server when X Plugin isn't compiled

# Implementation of Startup Time Requirements

For RUN1, current plugin infrastructure allows user to disable a plugin using:

1. From config file by adding mysqlx=0
2. From command line by adding --mysqlx=0
3. From command line by adding --skip-mysqlx
MTR tests
=========

New component is going to be introduced to reset X Plugin status variables between MTR tests. To do the reset, the script needs to execute following SQL sequence:

    INSTALL COMPONENT "file://component_mysqlx_global_reset";
    SELECT mysqlx_reset_global_status_variables() != 1

It should be used only by tests.