Added the lagfilter which is used to route queries to a master after executing queries that modify data.
This commit is contained in:
Markus Makela
@ -34,6 +34,10 @@ add_library(namedserverfilter SHARED namedserverfilter.c)
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target_link_libraries(namedserverfilter log_manager utils)
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target_link_libraries(namedserverfilter log_manager utils)
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install(TARGETS namedserverfilter DESTINATION modules)
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install(TARGETS namedserverfilter DESTINATION modules)
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add_library(lagfilter SHARED lagfilter.c)
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target_link_libraries(lagfilter log_manager utils query_classifier)
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install(TARGETS lagfilter DESTINATION modules)
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add_subdirectory(hint)
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add_subdirectory(hint)
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335
server/modules/filter/lagfilter.c
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335
server/modules/filter/lagfilter.c
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@ -0,0 +1,335 @@
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/*
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* This file is distributed as part of MaxScale by MariaDB Corporation. It is free
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* software: you can redistribute it and/or modify it under the terms of the
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* GNU General Public License as published by the Free Software Foundation,
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* version 2.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 51
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* Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Copyright MariaDB Corporation Ab 2014
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*/
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#include <stdio.h>
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#include <filter.h>
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#include <modinfo.h>
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#include <modutil.h>
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#include <skygw_utils.h>
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#include <log_manager.h>
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#include <string.h>
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#include <hint.h>
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#include <query_classifier.h>
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/** Defined in log_manager.cc */
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extern int lm_enabled_logfiles_bitmask;
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extern size_t log_ses_count[];
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extern __thread log_info_t tls_log_info;
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/**
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* @file lagfilter.c - a very simple filter designed to send queries to the
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* master server after data modification has occurred. This is done to prevent
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* replication lag affecting the outcome of a select query.
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*
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* @verbatim
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*
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* Two optional parameters that define the behavior after a data modifying query
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* is executed:
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*
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* count=<number of queries> Queries to route to master after data modification.
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* time=<time period> Seconds to wait before queries are routed to slaves.
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*
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* Date Who Description
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* 03/03/2015 Markus Mäkelä Written for demonstrative purposes
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* @endverbatim
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*/
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MODULE_INFO info = {
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MODULE_API_FILTER,
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MODULE_GA,
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FILTER_VERSION,
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"A routing hint filter that send queries to the master after data modification"
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};
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static char *version_str = "V1.1.0";
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static FILTER *createInstance(char **options, FILTER_PARAMETER **params);
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static void *newSession(FILTER *instance, SESSION *session);
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static void closeSession(FILTER *instance, void *session);
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static void freeSession(FILTER *instance, void *session);
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static void setDownstream(FILTER *instance, void *fsession, DOWNSTREAM *downstream);
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static int routeQuery(FILTER *instance, void *fsession, GWBUF *queue);
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static void diagnostic(FILTER *instance, void *fsession, DCB *dcb);
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static FILTER_OBJECT MyObject = {
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createInstance,
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newSession,
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closeSession,
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freeSession,
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setDownstream,
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NULL, // No Upstream requirement
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routeQuery,
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NULL,
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diagnostic,
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};
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struct LAGSTATS{
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int n_add_count; /*< No. of statements diverted based on count */
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int n_add_time; /*< No. of statements diverted based on time */
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int n_modified; /*< No. of statements not diverted */
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};
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/**
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* Instance structure
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*/
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typedef struct {
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int time; /*< The number of seconds to wait before routing queries
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* to slave servers after a data modification operation
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* is done. */
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int count; /*< Number of hints to add after each operation
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* that modifies data. */
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struct LAGSTATS stats;
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} LAG_INSTANCE;
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/**
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* The session structure for this filter
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*/
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typedef struct {
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DOWNSTREAM down; /*< The downstream filter */
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int hints_left; /*< Number of hints left to add to queries*/
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time_t last_modification; /*< Time of the last modifying operation */
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int active; /*< Is filter active */
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} LAG_SESSION;
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/**
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* Implementation of the mandatory version entry point
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*
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* @return version string of the module
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*/
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char *
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version()
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{
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return version_str;
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}
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/**
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* The module initialization routine, called when the module
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* is first loaded.
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*/
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void
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ModuleInit()
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{
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}
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/**
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* The module entry point routine. It is this routine that
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* must populate the structure that is referred to as the
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* "module object", this is a structure with the set of
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* external entry points for this module.
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*
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* @return The module object
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*/
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FILTER_OBJECT *
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GetModuleObject()
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{
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return &MyObject;
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}
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/**
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* Create an instance of the filter for a particular service
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* within MaxScale.
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*
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* @param options The options for this filter
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* @param params The array of name/value pair parameters for the filter
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*
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* @return The instance data for this new instance
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*/
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static FILTER *
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createInstance(char **options, FILTER_PARAMETER **params)
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{
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LAG_INSTANCE *my_instance;
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int i;
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if ((my_instance = calloc(1, sizeof(LAG_INSTANCE))) != NULL)
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{
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my_instance->count = 0;
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my_instance->time = 0;
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my_instance->stats.n_add_count = 0;
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my_instance->stats.n_add_time = 0;
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my_instance->stats.n_modified = 0;
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for (i = 0; params && params[i]; i++)
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{
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if (!strcmp(params[i]->name, "count"))
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my_instance->count = atoi(params[i]->value);
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else if (!strcmp(params[i]->name, "time"))
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my_instance->time = atoi(params[i]->value);
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else
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{
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LOGIF(LE, (skygw_log_write_flush(
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LOGFILE_ERROR,
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"lagfilter: Unexpected parameter '%s'.\n",
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params[i]->name)));
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}
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}
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}
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return (FILTER *)my_instance;
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}
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/**
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* Associate a new session with this instance of the filter.
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*
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* @param instance The filter instance data
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* @param session The session itself
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* @return Session specific data for this session
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*/
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static void *
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newSession(FILTER *instance, SESSION *session)
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{
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LAG_INSTANCE *my_instance = (LAG_INSTANCE *)instance;
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LAG_SESSION *my_session;
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if ((my_session = malloc(sizeof(LAG_SESSION))) != NULL)
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{
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my_session->active = 1;
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my_session->hints_left = 0;
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my_session->last_modification = 0;
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}
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return my_session;
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}
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/**
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* Close a session with the filter, this is the mechanism
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* by which a filter may cleanup data structure etc.
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*
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* @param instance The filter instance data
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* @param session The session being closed
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*/
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static void
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closeSession(FILTER *instance, void *session)
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{
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}
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/**
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* Free the memory associated with this filter session.
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*
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* @param instance The filter instance data
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* @param session The session being closed
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*/
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static void
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freeSession(FILTER *instance, void *session)
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{
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free(session);
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return;
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}
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/**
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* Set the downstream component for this filter.
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*
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* @param instance The filter instance data
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* @param session The session being closed
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* @param downstream The downstream filter or router
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*/
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static void
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setDownstream(FILTER *instance, void *session, DOWNSTREAM *downstream)
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{
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LAG_SESSION *my_session = (LAG_SESSION *)session;
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my_session->down = *downstream;
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}
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/**
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* The routeQuery entry point. This is passed the query buffer
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* to which the filter should be applied. Once applied the
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* query should normally be passed to the downstream component
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* (filter or router) in the filter chain.
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*
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* If the regular expressed configured in the match parameter of the
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* filter definition matches the SQL text then add the hint
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* "Route to named server" with the name defined in the server parameter
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*
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* @param instance The filter instance data
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* @param session The filter session
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* @param queue The query data
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*/
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static int
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routeQuery(FILTER *instance, void *session, GWBUF *queue)
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{
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LAG_INSTANCE *my_instance = (LAG_INSTANCE *)instance;
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LAG_SESSION *my_session = (LAG_SESSION *)session;
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char *sql;
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time_t now = time(NULL);
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if (modutil_is_SQL(queue))
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{
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if (queue->next != NULL)
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{
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queue = gwbuf_make_contiguous(queue);
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}
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if(!query_is_parsed(queue))
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{
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parse_query(queue);
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}
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if(query_classifier_get_operation(queue) & (QUERY_OP_DELETE|QUERY_OP_INSERT|QUERY_OP_UPDATE))
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{
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my_session->hints_left = my_instance->count;
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my_session->last_modification = now;
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my_instance->stats.n_modified++;
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}
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else if(my_session->hints_left > 0)
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{
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queue->hint = hint_create_route(queue->hint,
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HINT_ROUTE_TO_MASTER,
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NULL);
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my_session->hints_left--;
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my_instance->stats.n_add_count++;
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}
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else if(difftime(now,my_session->last_modification) < my_instance->time)
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{
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queue->hint = hint_create_route(queue->hint,
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HINT_ROUTE_TO_MASTER,
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NULL);
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my_instance->stats.n_add_time++;
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}
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}
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return my_session->down.routeQuery(my_session->down.instance,
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my_session->down.session, queue);
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}
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/**
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* Diagnostics routine
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*
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* If fsession is NULL then print diagnostics on the filter
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* instance as a whole, otherwise print diagnostics for the
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* particular session.
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*
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* @param instance The filter instance
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* @param fsession Filter session, may be NULL
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* @param dcb The DCB for diagnostic output
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*/
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static void
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diagnostic(FILTER *instance, void *fsession, DCB *dcb)
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{
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LAG_INSTANCE *my_instance = (LAG_INSTANCE *)instance;
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LAG_SESSION *my_session = (LAG_SESSION *)fsession;
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dcb_printf(dcb, "Configuration:\n\tCount: %d\n",
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my_instance->count);
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dcb_printf(dcb, "\tTime: %d seconds\n\n",
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my_instance->time);
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dcb_printf(dcb, "Statistics:\n");
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dcb_printf(dcb, "\tNo. of data modifications: %d\n",
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my_instance->stats.n_modified);
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dcb_printf(dcb, "\tNo. of hints added based on count: %d\n",
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my_instance->stats.n_add_count);
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dcb_printf(dcb, "\tNo. of hints added based on time: %d\n",
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my_instance->stats.n_add_time);
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}
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Reference in New Issue
Block a user