> For the complete documentation index, see [llms.txt](https://mariadb.com/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mariadb.com/docs/server/reference/plugins/api-plugin/page-make_a_plugin.md). # How to make a plugin Plugin API reference: How to make a plugin . Generated from the MariaDB server headers by doxygen and moxygen. This is a tutorial and a walk-through on how to bootstrap, implement, compile, test and distribute a MariaDB [Plugin Library](/docs/server/reference/plugins/api-plugin/page-concepts.md#plugin-library). ## Architecture and Design Decisions. The most important architectural decision is to decide what [Plugin API](/docs/server/reference/plugins/api-plugin/page-concepts.md#plugin-api) to implement. To make that determination you need to understand when your plugin needs to be called by the server and with what parameters. Sometimes just the base [st\_maria\_plugin](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration.md#st_maria_plugin) API is good enough. [st\_maria\_plugin::init](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration.md#init-1) is called when the plugin is loaded and [st\_maria\_plugin::deinit](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration.md#deinit-1) is called when the plugin is unloaded. This will suffice if you are after implementing e.g. a network listener: you can start a background thread that listens for connections and processes connects, disconnects and commands in [st\_maria\_plugin::init](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration.md#init-1). And then signal to it to shut down gracefully from [st\_maria\_plugin::deinit](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration.md#deinit-1). In this case you implement the so called [Daemon Plugin](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_types/daemon_plugin_data.md). This has no API whatsoever. Just a version. But, in general, you need to understand the available [Plugin Types](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_types.md) and decide on implementing the one that suits your needs best. Do you want to provide a better password validation method? Look into [Password Validation Plugin](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_types/password_validation_plugin_data.md). Need to expose data in tabular format to server? Do a [Information Schema Plugin](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_types/information_schema_plugin_data.md). The good part is that you can actually combine multiple [Plugin](/docs/server/reference/plugins/api-plugin/page-concepts.md#plugin) into a single [Plugin Library](/docs/server/reference/plugins/api-plugin/page-concepts.md#plugin-library). So, back to the example above, if you need to implement a network listener, but also return the current connection table as an INFORMATION\_SCHEMA table you can define the two [Plugin](/docs/server/reference/plugins/api-plugin/page-concepts.md#plugin) implementations into your single [Plugin Library](/docs/server/reference/plugins/api-plugin/page-concepts.md#plugin-library). ## Code your plugin library It's easiest to just take one of the existing plugins and copy its code. But, in case you want to start afresh, here's a very minimal boilerplate to copy from ```cpp #include /* TODO: if needed: #include */ static int plugin_one_init(void *) { /* TODO: code here */ return 0; /* success */ } static int plugin_one_deinit(void *) { /* TODO: code here */ return 0; /* success */ } static struct st_mysql_daemon plugin_one = { MYSQL_DAEMON_INTERFACE_VERSION }; maria_declare_plugin(plugin_one) { MYSQL_DAEMON_PLUGIN, &plugin_one, "plugin example", "You", "A boilerplate plugin code", PLUGIN_LICENSE_GPL, plugin_one_init, /* Plugin Init */ plugin_one_deinit, /* Plugin Deinit */ 0x0100, /* 1.0 */ NULL, /* status variables */ NULL, /* system variables */ "1.0", /* string version */ MariaDB_PLUGIN_MATURITY_EXPERIMENTAL /* maturity */ } maria_declare_plugin_end; ``` **See also**: [maria\_declare\_plugin](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration.md#maria_declare_plugin), [maria\_declare\_plugin\_end](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration.md#maria_declare_plugin_end), [MYSQL\_DAEMON\_PLUGIN](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_types.md#mysql_daemon_plugin), [MYSQL\_DAEMON\_INTERFACE\_VERSION](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_types/daemon_plugin_data.md#mysql_daemon_interface_version), [PLUGIN\_LICENSE\_GPL](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration/plugin_license.md#plugin_license_gpl), [MariaDB\_PLUGIN\_MATURITY\_EXPERIMENTAL](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration/plugin_maturity.md#mariadb_plugin_maturity_experimental) If you need to add system variables, you can add the following to the above: ```cpp static unsigned int v1; static int v1_check_function(MYSQL_THD thd, struct st_mysql_sys_var *var, void *save, struct st_mysql_value *value) { /* TODO: code here, enhance the below */ long long v; if (value->val_int(value, &v)) return 1; /* FAILURE */ *(unsigned int*) save= (unsigned int) v; return 0; /* OK */ } static void v1_update_function(MYSQL_THD thd, struct st_mysql_sys_var *var, void *var_ptr, const void *save) { /* TODO: code here */ } static MYSQL_SYSVAR_UINT( v1, /* SQL variable name */ v1, /* local C variable reference */ PLUGIN_VAR_RQCMDARG, /* flags: An argument is required */ "gizmo variable", /* SQL visible description */ v1_check_function, v1_update_function, 0, /* default value */ 0, /* minimal value */ 365*100, /* maximum value */ 1 /* increase step */ ); static struct st_mysql_sys_var* sysvars[]= { MYSQL_SYSVAR(v1), /* variable reference */ NULL /* terminator. keep */ }; ``` And then pass on the `sysvars` to the [maria\_declare\_plugin](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration.md#maria_declare_plugin) 's system variable placeholder. **See also**: [MYSQL\_SYSVAR\_UINT](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration/plugin_sys_vars/plugin_sysvar_macros.md#mysql_sysvar_uint), [mysql\_var\_check\_func](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration/plugin_sys_vars.md#mysql_var_check_func), [mysql\_var\_update\_func](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration/plugin_sys_vars.md#mysql_var_update_func), [MYSQL\_SYSVAR](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration/plugin_sys_vars/implementation_only_plugin_vars.md#mysql_sysvar) Similarly, if you need status variables, you can add the following: ```cpp static volatile int var_s1; static struct st_mysql_show_var status_vars[]= { { "s1", /* status variable SQL name */ (char *) &var_s1, /* reference to the C variable */ SHOW_INT /* type */ }, { 0, 0, SHOW_UNDEF} /* terminator. keep */ }; ``` And then pass on the `status_vars` to the [maria\_declare\_plugin](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration.md#maria_declare_plugin) 's status variable placeholder. **See also**: [st\_mysql\_show\_var](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration/plugin_status_vars.md#st_mysql_show_var), [SHOW\_INT](/docs/server/reference/plugins/api-plugin/plugin_api/plugin_declaration/plugin_status_vars.md#show_int)