85b3d7c465
The section name of a filter in the MaxScale configuration file is unique for each filter. Hence, by providing that name to the filter instance creation function, it is possible to act differently depending on which particular instance is being created. Case in point. There can be multiple cache filters defined in the MaxScale configuration file, each with a different set of rules, ttl and even backing store. Each cache will be backed by a separate storage that e.g. in the case of RocksDB will correspond to a particular path. In other words, for each cache instance corresponding to a particular cache definition in the MaxScale configuration file, we need to be able to create a unique path. If the filter section name (in the MaxScale configuration file) that anyways needs to be unique, is provided to the filter, then that name can be used when forming the unique path. The alternative is to require the DBA to provide some unique parameter for each cache definition, which adds configuration overhead and is errorprone. Furthermore, by providing the name to filters, also error messages can be customized for a particular section when appropriate.
120 lines
4.2 KiB
C
120 lines
4.2 KiB
C
#ifndef _FILTER_H
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#define _FILTER_H
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/*
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* Copyright (c) 2016 MariaDB Corporation Ab
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*
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* Use of this software is governed by the Business Source License included
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* in the LICENSE.TXT file and at www.mariadb.com/bsl.
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*
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* Change Date: 2019-07-01
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*
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* On the date above, in accordance with the Business Source License, use
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* of this software will be governed by version 2 or later of the General
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* Public License.
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*/
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/**
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* @file filter.h - The filter interface mechanisms
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*
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* Revision History
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*
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* Date Who Description
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* 27/05/2014 Mark Riddoch Initial implementation
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*
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*/
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#include <dcb.h>
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#include <session.h>
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#include <buffer.h>
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#include <stdint.h>
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/**
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* The FILTER handle points to module specific data, so the best we can do
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* is to make it a void * externally.
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*/
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typedef void *FILTER;
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/**
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* The structure used to pass name, value pairs to the filter instances
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*/
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typedef struct
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{
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char *name; /**< Name of the parameter */
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char *value; /**< Value of the parameter */
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} FILTER_PARAMETER;
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/**
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* @verbatim
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* The "module object" structure for a query router module
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*
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* The entry points are:
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* createInstance Called by the service to create a new
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* instance of the filter
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* newSession Called to create a new user session
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* within the filter
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* closeSession Called when a session is closed
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* freeSession Called when a session is freed
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* setDownstream Sets the downstream component of the
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* filter pipline
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* routeQuery Called on each query that requires
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* routing
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* clientReply Called for each reply packet
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* diagnostics Called to force the filter to print
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* diagnostic output
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*
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* @endverbatim
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*
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* @see load_module
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*/
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typedef struct filter_object
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{
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FILTER *(*createInstance)(const char *name,
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char **options,
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FILTER_PARAMETER **params);
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void *(*newSession)(FILTER *instance, SESSION *session);
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void (*closeSession)(FILTER *instance, void *fsession);
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void (*freeSession)(FILTER *instance, void *fsession);
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void (*setDownstream)(FILTER *instance, void *fsession, DOWNSTREAM *downstream);
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void (*setUpstream)(FILTER *instance, void *fsession, UPSTREAM *downstream);
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int (*routeQuery)(FILTER *instance, void *fsession, GWBUF *queue);
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int (*clientReply)(FILTER *instance, void *fsession, GWBUF *queue);
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void (*diagnostics)(FILTER *instance, void *fsession, DCB *dcb);
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} FILTER_OBJECT;
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/**
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* The filter API version. If the FILTER_OBJECT structure or the filter API
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* is changed these values must be updated in line with the rules in the
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* file modinfo.h.
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*/
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#define FILTER_VERSION {2, 1, 0}
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/**
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* The definition of a filter from the configuration file.
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* This is basically the link between a plugin to load and the
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* optons to pass to that plugin.
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*/
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typedef struct filter_def
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{
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char *name; /**< The Filter name */
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char *module; /**< The module to load */
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char **options; /**< The options set for this filter */
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FILTER_PARAMETER **parameters; /**< The filter parameters */
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FILTER filter; /**< The runtime filter */
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FILTER_OBJECT *obj; /**< The "MODULE_OBJECT" for the filter */
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SPINLOCK spin; /**< Spinlock to protect the filter definition */
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struct filter_def *next; /**< Next filter in the chain of all filters */
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} FILTER_DEF;
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FILTER_DEF *filter_alloc(char *, char *);
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void filter_free(FILTER_DEF *);
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bool filter_load(FILTER_DEF* filter);
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FILTER_DEF *filter_find(char *);
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void filterAddOption(FILTER_DEF *, char *);
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void filterAddParameter(FILTER_DEF *, char *, char *);
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DOWNSTREAM *filterApply(FILTER_DEF *, SESSION *, DOWNSTREAM *);
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UPSTREAM *filterUpstream(FILTER_DEF *, void *, UPSTREAM *);
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int filter_standard_parameter(char *);
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void dprintAllFilters(DCB *);
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void dprintFilter(DCB *, FILTER_DEF *);
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void dListFilters(DCB *);
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#endif
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