This document provides an overview of MySQL plugin development, highlighting the various types of plugins supported by the MySQL server, such as daemon, authentication, and storage engine plugins. It discusses the lifecycle of server plugins, their linking types, and the availability of sample plugins and further reading resources for developers. The content is positioned for advanced developers and includes a safe harbor statement regarding product direction.

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MySQL Plugin
Development
Getting started
Georgi “Joro” Kodinov
Team Lead, MySQL Server General Team

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• Background in banking IT
• Veteran software developer
• Leading the MySQL Server General development team
• With MySQL since 2006
• Working out of Plovdiv, Bulgaria
• NOT a professional speaker
• @gkodinov, georgi.kodinov@oracle.com
About Me

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MySQL 5.7
Just Released !
“New version of the world’s most
popular open source database is up
to 3x faster than MySQL 5.6 in
benchmark tests”
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Technical level: advanced developer !
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What will I cover ?
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• The lifecycle of a server plugin
• What plugin types does the server support
• What plugin linkage does the server support
• What are plugin services
• Where to find examples to copy from
• Further reading

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What will not be covered ?
• A complete start-to-finish plugin development cycle
• Adding plugin services to the server code
• Complex plugin API details
• UDF functions
• Non-server plugins
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Due to lack of time and complexity

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Plugins: The Big Picture
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MySQL server binary
Server Code
Type A
Plugins
Type B
Plugins
…
Plugin B API
Plugin binary 1
Type A
Plugins
…
Plugin A API
Services
Clients

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A lifecycle of a plugin
Phase What triggers it ?
Initialization • INSTALL PLUGIN
• Server startup
• --plugin-load[-add] options
• mysql.plugin table
OPTIONAL: API call(s) Server events, mostly query execution
De-initialization • UNINSTALL PLUGIN
• Server shutdown
• User session end
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What plugin types
does the server support ?
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Daemon plugins
• The simplest: No plugin API !
• When is the API called
– No API to call
• Good for
– Doing stuff on server startup/shutdown
– Spawning a daemon thread that can call plugin services
• Limitations
– No APIs to call
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INFORMATION_SCHEMA plugins
• Used to return read-only data in tabular format
• When is the API called ?
– When somebody selects from the table
• Good for
– Returning plugin data to the server as ephemeral tables
• Limitations
– Fills in a temporary table
– Not a lot of query condition pushdown
– One table per plugin definition
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Authentication plugins
• Verify user account credentials
• When is the API called
– Whenever credentials need to be checked (login time, sudo)
• Good for
– Hooking up into enterprise directories
– Limiting user access
• Limitations
– No session yet (not all plugin services work)
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Audit plugins
• Process various auditing events
• When is the API called
– In a LOT of occasions: server start, query start/end, session start/end, events logged,
etc.
• Good for
– Logging, preventing or reacting to various server events
– Can handle high volume of calls through event pre-filtering
• Limitations
– Can go into infinite recursion (plugin services can trigger audit events too)
– References are cached, so unloading a plugin is not immediate
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Password validation plugins
• Enforce password strength policies
• When is the API called
– When a new user password hash is set for a user account
– Explicitly (through a SQL function)
• Good for
– Enforcing custom password strength policies
• Limitations
– No backing store provided. Password reuse can’t be controlled.
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Storage engine plugins
• Implement table backing storage
• When is the API called
– When the server needs to open, read data, write data or close a table.
– Explicitly (through the HANDLER SQL interface)
• Good for
– Implementing different types of backing storage for MySQL tables
• Limitations
– VERY complex !
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Miscellaneous other plugins
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Plugin type What is it ?
Full text parser plugin Parse full text syntax and convert to full text filters
Replication Support for single master replication engines
Group replication Support for group replication engines
UDF plugin Not implemented

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What plugin linkage
does the server support ?
As in MySQL 5.7
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Internal plugins
• Examples
– MyISAM storage engine, InnoDB storage engine, native authentication plugin, etc. …
• The server can’t operate properly without these
• Statically linked into the server
• Part of the server’s code repository
• ABI compatibility not needed
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Static plugins
• Examples:
– sha256 authentication plugin
• Required only when used.
• Statically linked into the server binary for availability
• Can be dynamically added in the plugin/ source directory
• Require the server’s source code to compile
• ABI compatibility is optional
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Dynamic plugins
• Examples:
– windows authentication plugin, enterprise audit plugin
• Required only when used.
• Separate binaries, dynamically loaded into the server
• Can be dynamically added in the plugin/ source directory
• Do not require the server’s source code to compile
– a binary installation is enough
• ABI compatibility is highly recommended
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Plugin services at a glance
• Plugins use services to call the server
– Vs. server calling the plugins in all other cases
• Can be added only as part of the server
• A plugin based C structure with function pointers filled in by the server
when the plugin is loaded
• A constantly growing number of services provided
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Where to find examples to copy from ?
• Not easy to code plugins from scratch
– Nontrivial amount of boilerplate code needed
• Where are the sample plugins ?
– Subdirectories of the plugin/ and storage/ source directories
• Usage patterns in the documentation and mysql-test/
• Notable examples:
– Audit_null, Daemon_example, example storage engine, federated
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Further reading
• http://dev.mysql.com/doc/refman/5.7/en/extending-mysql.html
– The best reference there is !
• The “MySQL 5.1 Plugin Development” book
– ISBN-13: 978-1849510608
• http://forums.mysql.com
– User discussions on various MySQL related topics
• Your favorite search engine
– With MySQL being so popular a lot of people have tried developing plugins
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Questions ?
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Safe Harbor Statement
The preceding is intended to outline our general product direction. It is intended for
information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.
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