Presented by, MySQL AB® & O’Reilly Media, Inc. Developing INFORMATION_SCHEMA Plugins Mark Leith Support Manager, Americas

Overview  INFORMATION_SCHEMA overview  Plugin Overview  Developing a simple Hello World I_S table  Building and installing  Interacting with another program  Interacting with another library

INFORMATION_SCHEMA  Specified within the SQL Standard  (ISO/IEC :2003)‏  Virtual tables which give database metadata  MySQL implements a subset of the Standard   ORMATION_SCHEMA.html ORMATION_SCHEMA.html

Plugins  A means to load shared libraries in to a running MySQL instance  Developed in C/C++  api.html api.html  User Defined Functions  Storage Engines  Fulltext parsers  Daemons  INFORMATION_SCHEMA Tables!

 Located in include/mysql/plugin.h The Plugin Interface struct st_mysql_plugin { int type; /* the plugin type (a MYSQL_XXX_PLUGIN value) */ void *info; /* pointer to type-specific plugin descriptor */ const char *name; /* plugin name */ const char *author; /* plugin author (for SHOW PLUGINS) */ const char *descr; /* general descriptive text (for SHOW PLUGINS ) */ int license; /* the plugin license (PLUGIN_LICENSE_XXX) */ int (*init)(void *); /* the function to invoke when plugin is loaded */ int (*deinit)(void *)/* the function to invoke when plugin is unloaded */ unsigned int version; /* plugin version (for SHOW PLUGINS) */ struct st_mysql_show_var *status_vars; struct st_mysql_sys_var **system_vars; void * __reserved1; /* reserved for dependency checking */ };

Plugin Types  Define the plugin type (types listed below)  Used within plugin functions such as plugin_foreach() MYSQL_UDF_PLUGIN 0 /* User-defined function */ MYSQL_STORAGE_ENGINE_PLUGIN 1 /* Storage Engine */ MYSQL_FTPARSER_PLUGIN 2 /* Full-text parser plugin */ MYSQL_DAEMON_PLUGIN 3 /* The daemon/raw plugin type */ MYSQL_INFORMATION_SCHEMA_PLUGIN 4 /* The I_S plugin type */  I_S plugins loaded within sql/sql_show.cc int schema_tables_add(THD *thd, List *files, const char *wild) { … if (plugin_foreach(thd, add_schema_table, MYSQL_INFORMATION_SCHEMA_PLUGIN, &add_data)) DBUG_RETURN(1);

Starting a HELLO_WORLD Table  Must have MySQL source tree  Create a new plugin/hello_world/hello_world.cc file  plugin.h and mysql_priv.h includes required  Add a prototype for schema_table_store_record() /* Required for schema_table_store_record() * /#include "mysql_priv.h" #include bool schema_table_store_record(THD *thd, TABLE *table);

Define the Table Structure  Uses an array of ST_FIELD_INFO structs  field_nameColumn name  field_lengthColumn length or display length  field_typeColumn datatype  valueNot used within I_S plugins  field_flagsSet NULL / UNSIGNED attributes  old_nameInternal mapping for I_S tables to SHOW output  open_methodOpen table using supplied method  Last entry in the array is an end marker ST_FIELD_INFO hello_world_fields[]= { {"HELLO", 10, MYSQL_TYPE_STRING, 0, 0, "Hello", 0}, {"WORLD", 10, MYSQL_TYPE_STRING, 0, 0, "World", 0}, {0, 0, MYSQL_TYPE_NULL, 0, 0, 0, 0} };

A Closer Look MYSQL_TYPE_STRING MYSQL_TYPE_LONG MYSQL_TYPE_LONGLONG MYSQL_TYPE_DECIMAL MYSQL_TYPE_DATETIME VARCHAR INT BIGINT DECIMAL DATETIME  Field_type  Field_flags MY_I_S_MAYBE_NULL MY_I_S_UNSIGNED  Open_method SKIP_OPEN_TABLE OPEN_FRM_ONLY OPEN_FULL_TABLE

Define Function to Fill Table  Called every time the table is accessed  Fills the virtual table with data int fill_hello_world(THD *thd, TABLE_LIST *tables, COND *cond) { DBUG_ENTER("fill_hello_world_is_plugin"); CHARSET_INFO *scs= system_charset_info; TABLE *table= tables->table; int rc= 0; table->field[0]->store("Hello", strlen("Hello"), scs); table->field[1]->store("World", strlen("World"), scs); if (schema_table_store_record(thd, table)) rc= 1; DBUG_RETURN(rc); }

Create the Init Function  Runs when the plugin is installed/loaded  ST_SCHEMA_TABLE is an internal table representation  Points to the ST_FIELD_INFO struct / table definition  Points to the function to fill the table  Manages any other init needed for the plugin int hello_world_plugin_init(void *p) { DBUG_ENTER("init_hello_world_is_plugin"); ST_SCHEMA_TABLE *schema= (ST_SCHEMA_TABLE*) p; schema->fields_info= hello_world_fields; schema->fill_table= fill_hello_world; DBUG_RETURN(0); }

Create the Deinit Function  Run when the plugin is unloaded  Does nothing for HELLO_WORLD  Use this function to do any clean up in your plugin int hello_world_plugin_deinit(void *p) { DBUG_ENTER("deinit_info_schema_example_plugin"); DBUG_RETURN(0); }

Create the Plugin Definition  Info struct points to the interface version built against struct st_mysql_information_schema hello_world_plugin_info= { MYSQL_INFORMATION_SCHEMA_INTERFACE_VERSION }; mysql_declare_plugin(hello_world_plugin) { MYSQL_INFORMATION_SCHEMA_PLUGIN, &hello_world_plugin_info, /* Pointer to info struct */ "HELLO_WORLD", /* Plugin Name (used in INSTALL PLUGIN) */ "Mark Leith, MySQL AB", /* Plugin Author */ "HELLO_WORLD example plugin",/* Plugin Description */ PLUGIN_LICENSE_GPL, /* _GPL, _BSD or _PROPRIETARY */ hello_world_plugin_init, /* Pointer to plugin init function */ hello_world_plugin_deinit, /* Pointer to plugin deinit function */ 0x0100, /* 1.0 */ NULL, /* status variables */ NULL, /* system variables */ NULL /* config options */ } mysql_declare_plugin_end;

Build the Plugin  Define MYSQL_DYNAMIC_PLUGIN  Make shared  Include the sql and include source directories g++ -DMYSQL_DYNAMIC_PLUGIN -shared \ > -I/home/leithal/mysql/mysql-5.1/include \ > -I/home/leithal/mysql/mysql-5.1/sql \ > -o is_hello_world.so hello_world.cc ls -l total 16 -rw-r--r-- 1 leithal leithal :20 hello_world.cc -rwxr-xr-x 1 leithal leithal :27 is_hello_world.so cp is_hello_world.so /usr/local/mysql/lib/mysql/plugin

Install and Use! mysql> INSTALL PLUGIN HELLO_WORLD SONAME 'is_hello_world.so'; Query OK, 0 rows affected (0.01 sec) mysql> USE INFORMATION_SCHEMA; Database changed mysql> SHOW TABLES LIKE 'HELL%'; | Tables_in_information_schema (HELL%) | | HELLO_WORLD | row in set (0.00 sec) mysql> SELECT * FROM HELLO_WORLD; | HELLO | WORLD | | Hello | World | row in set (0.00 sec)

So We'll Do Something Interesting  How's the disk space doing on my db server? df -h Filesystem Size Used Avail Use% Mounted on /dev/hda1 4.6G 3.5G 886M 81% / varrun 126M 84K 125M 1% /var/run varlock 126M 0 126M 0% /var/lock procbususb 10M 76K 10M 1% /proc/bus/usb udev 10M 76K 10M 1% /dev devshm 126M 0 126M 0% /dev/shm lrm 126M 18M 108M 14% /lib/modules/ generic/volatile  If I can get this in a table I can track it over time  I can also report on it easily  How about an I_S table with events to catalog?

Create Template & Table Structure  Add stdio.h,string.h and stdlib.h includes  Mirror init, deinit and info functions  Fill in the plugin declaration scruct appropriately  Define the new table: ST_FIELD_INFO fs_info_schema_fields[]= { {"FILESYSTEM", 120, MYSQL_TYPE_STRING, 0, 0, "Filesystem", 0}, {"SIZE", 8, MYSQL_TYPE_LONGLONG, 0, 0, "Mountpoint Size", 0}, {"USED", 8, MYSQL_TYPE_LONGLONG, 0, 0, "Used Space", 0}, {"AVAILABLE", 8, MYSQL_TYPE_LONGLONG, 0, 0, "Available Space", 0}, {"CAPACITY", 4, MYSQL_TYPE_STRING, 0, 0, "Percent Used", 0}, {"MOUNTED_ON", 120, MYSQL_TYPE_STRING, 0, 0, "Filesystem Mounted On", 0}, {0, 0, MYSQL_TYPE_STRING, 0, 0, 0, 0} };

Running Other Programs  Open with popen() and read in the results /* get filesystem information from df on linux like systems */ FILE *f; char buf[128]; char *c, *s, *size; const char delim[]= " "; unsigned long long uli; double d; if (NULL != (f= popen("/bin/df -h", "r"))) { int ln= 0; while(!feof(f)) { fgets(buf, sizeof(buf), f); switch(ln++) {

Tokenize and Push Results  Can do this how you like /* skip the header line of df */ case 0: break; default: c= buf; /* hack to stop processing when falling off the end of output */ if (strchr(c, ' ') == NULL) break; /* Filesystem */ s= strtok(c, delim); table->field[0]->store(s, strlen(s), scs); /* Size */ s= strtok(NULL, delim); d= strtod(s, &size); uli= get_bytes(d, size); table->field[1]->store(uli, TRUE); ….

Store the Row and Finish up /* Use% */ s= strtok(NULL, delim); table->field[4]->store(s, strlen(s), scs); /* Mountpoint */ s= strtok(NULL, delim); stripnl(s); table->field[5]->store(s, strlen(s), scs); /* store the row */ if (schema_table_store_record(thd, table)) rc= 1; break; } pclose(f); } else rc= 1; DBUG_RETURN(rc); }

Build, Install, Try..  Build as before and try it out! mysql> select * from file_system_mountpoints; | FILESYSTEM | SIZE | USED | AVAILABLE | CAPACITY | MOUNTED_ON | | /dev/hda1 | | | | 81% | / | | varrun | | | | 1% | /var/run | | varlock | | 0 | | 0% | /var/lock | | procbususb | | | | 1% | /proc/bus/usb | | udev | | | | 1% | /dev | | devshm | | 0 | | 0% | /dev/shm | | lrm | | | | 14% | /lib/modules/ generic/volatile | rows in set (0.06 sec) mysql> desc file_system_mountpoints; | Field | Type | Null | Key | Default | Extra | | FILESYSTEM | varchar(120) | NO | | | | | SIZE | bigint(11) | NO | | 0 | | | USED | bigint(11) | NO | | 0 | | | AVAILABLE | bigint(11) | NO | | 0 | | | CAPACITY | varchar(4) | NO | | | | | MOUNTED_ON | varchar(120) | NO | | | | rows in set (0.01 sec)

Now Let's Use another Library  The SIGAR library from Hyperic  Lets us do cross platform OS stats monitoring  Released under GPL  Again, start with the same base functions etc. as before

Include Lib Header, Use Lib in Fill sigar_t *t; sigar_open(&t); sigar_file_system_list_t fslist; sigar_file_system_list_get(t, &fslist); for (uint i = 0; i < fslist.number; i++) { sigar_file_system_t fs = fslist.data[i]; sigar_file_system_usage_t fsusage; rc= sigar_file_system_usage_get(t, fs.dir_name, &fsusage); if (fs.type == 2 || fs.type == 3) { table->field[0]->store(fs.dir_name, strlen(fs.dir_name), scs); table->field[1]->store(fsusage.total, TRUE); table->field[2]->store(fsusage.used, TRUE); table->field[3]->store(fsusage.free, TRUE); table->field[4]->store(fsusage.files, TRUE); if (schema_table_store_record(thd, table)) rc= 1; } sigar_file_system_list_destroy(t, &fslist); sigar_close(t);

Building and Including the Library g++ -DMYSQL_DYNAMIC_PLUGIN -Wall -shared \ -lsigar -Wl,-rpath -Wl,/home/leithal/os_stats_info_schema/sigar/ \ -L/home/leithal/os_stats_info_schema/sigar/ \ -I/home/leithal/os_stats_info_schema/sigar/include/ \ -I/home/leithal/mysql/mysql-5.1/include \ -I/home/leithal/mysql/mysql-5.1/sql \ -o os_stats_info_schema.so os_stats_info_schema.cc  -lsigar links the library  Use -rpath to pass in library location  This is for runtime  Can also use LD_LIBRARY_PATH  -L (linker) and -I (include) paths  -L points to the directory with the built library

Try it out! mysql> INSTALL PLUGIN os_disk_usage SONAME 'os_stats_info_schema.so'; Query OK, 0 rows affected (0.00 sec) mysql> SHOW TABLES LIKE 'OS%'; | Tables_in_information_schema (OS%) | | OS_DISK_USAGE | row in set (0.00 sec) mysql> SELECT * FROM OS_DISK_USAGE; | FILESYSTEM | SIZE | USED | FREE | FILES | | / | | | | | row in set (0.00 sec)

Resources and Questions!   information-schema-plugins-best.html information-schema-plugins-best.html  -mysql-internals-with.html (Great resource for monitoring server internals) -mysql-internals-with.html  Questions?