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MXS-1310: Add deterministic conflict resolution

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The schemarouter can now resolve database mapping conflicts in a
deterministic manner. This will fix the problem of central databases which
are replicated shards being assigned in a non-deterministic manner.
This commit is contained in:
Markus Mäkelä
2017-07-05 19:19:49 +03:00
parent a23e81c438
commit 9618e63b5f
3 changed files with 28 additions and 3 deletions
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13
server/modules/routing/schemarouter/schemarouter.c
View File

@ -357,6 +357,17 @@ showdb_response_t parse_showdb_response(ROUTER_CLIENT_SES* rses, backend_ref_t*
rses->rses_client_dcb->user,
rses->rses_client_dcb->remote);
}
else if (rses->router->preferred_server &&
strcmp(target, rses->router->preferred_server->unique_name) == 0)
{
/** In conflict situations, use the preferred server */
MXS_INFO("Forcing location of '%s' from '%s' to ''%s",
data, (char*)hashtable_fetch(rses->shardmap->hash,
data), target);
hashtable_delete(rses->shardmap->hash, data);
hashtable_add(rses->shardmap->hash, data, target);
}
}
MXS_FREE(data);
}
@ -651,6 +662,7 @@ MXS_MODULE* MXS_CREATE_MODULE()
{"refresh_databases", MXS_MODULE_PARAM_BOOL, "true"},
{"refresh_interval", MXS_MODULE_PARAM_COUNT, DEFAULT_REFRESH_INTERVAL},
{"debug", MXS_MODULE_PARAM_BOOL, "false"},
{"preferred_server", MXS_MODULE_PARAM_SERVER},
{MXS_END_MODULE_PARAMS}
}
};
@ -719,6 +731,7 @@ static MXS_ROUTER* createInstance(SERVICE *service, char **options)
router->schemarouter_config.max_sescmd_hist = config_get_integer(conf, "max_sescmd_history");
router->schemarouter_config.disable_sescmd_hist = config_get_bool(conf, "disable_sescmd_history");
router->schemarouter_config.debug = config_get_bool(conf, "debug");
router->preferred_server = config_get_server(conf, "preferred_server");
if ((config_get_param(conf, "auth_all_servers")) == NULL)
{

7
server/modules/routing/schemarouter/schemarouter.h
View File

@ -365,14 +365,15 @@ typedef struct router_instance
unsigned int bitvalue; /*< Required value of server->status */
ROUTER_STATS stats; /*< Statistics for this router */
struct router_instance* next; /*< Next router on the list */
bool available_slaves; /*< The router has some slaves available */
bool available_slaves; /*< The router has some slaves available */
HASHTABLE* ignored_dbs; /*< List of databases to ignore when the
* database mapping finds multiple servers
* with the same database */
pcre2_code* ignore_regex; /*< Databases matching this regex will
pcre2_code* ignore_regex; /*< Databases matching this regex will
* not cause the session to be terminated
* if they are found on more than one server. */
pcre2_match_data* ignore_match_data;
pcre2_match_data* ignore_match_data;
SERVER* preferred_server; /**< Server to prefer in conflict situations */
} ROUTER_INSTANCE;