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Fix to bug #694, http://bugs.mariadb.com/show_bug.cgi?id=694

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query_classifier.cc: set_query_type lost previous query type if the new was more restrictive. Problem was that if query is both READ and SESSION_WRITE and configuration parameter use_sql_variables_in=all was set, routing target became ambiguous. Replaced call to set_query_type with simply adding new type to type (=bit field) and checking unsupported combinations in readwritesplit.c:get_route_target. If such a case is met, a detailed error is written to error log in readwritesplit.c. mysql_client.c sees the error code and sends an error to client. Then mysql_client.c calls router's handleError which ensures that there are enough backend servers so that the session can continue.
This commit is contained in:
VilhoRaatikka
2015-01-15 15:16:22 +02:00
parent b3824a1eaf
commit 39e4253c81
3 changed files with 95 additions and 37 deletions
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25
query_classifier/query_classifier.cc
View File

@ -391,29 +391,6 @@ return_here:
return failp;
}
/**
* Set new query type if new is more restrictive than old.
*
* Parameters:
* @param qtype Existing type
*
* @param new_type New query type
*
* @return Query type as an unsigned int value which must be casted to qtype.
*
*
* @details The implementation relies on that enumerated values correspond
* to the restrictiviness of the value. That is, smaller value means less
* restrictive, for example, QUERY_TYPE_READ is smaller than QUERY_TYPE_WRITE.
*
*/
static u_int32_t set_query_type(
u_int32_t* qtype,
u_int32_t new_type)
{
*qtype = MAX(*qtype, new_type);
return *qtype;
}
/**
* Detect query type by examining parsed representation of it.
@ -817,7 +794,7 @@ static skygw_query_type_t resolve_query_type(
break;
} /**< switch */
/**< Set new query type */
type |= set_query_type(&type, func_qtype);
type |= func_qtype;
}
#if defined(UPDATE_VAR_SUPPORT)
/**

42
server/modules/protocol/mysql_client.c
View File

@ -870,12 +870,45 @@ int gw_read_client_event(
}
else
{
modutil_send_mysql_err_packet(dcb,
bool succp;
GWBUF* errbuf;
/**
* Send error message indicating that routing
* failed
*/
mysql_send_custom_error(
dcb,
1,
0,
2003,
"HY000",
"Write to backend failed. Session closed.");
"Routing query to backend failed. See "
"the error log for further details.");
/**
* Create error to be sent to client if session
* can't be continued.
*/
errbuf = mysql_create_custom_error(
1,
0,
"Routing failed. Session is closed.");
/**
* Ensure that there are enough backends
* available.
*/
router->handleError(
router_instance,
session->router_session,
errbuf,
dcb,
ERRACT_NEW_CONNECTION,
&succp);
free(errbuf);
/**
* If there are not enough backends close
* session
*/
if (!succp)
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Routing the query failed. "
@ -884,6 +917,7 @@ int gw_read_client_event(
dcb_close(dcb);
}
}
}
goto return_rc;
} /* MYSQL_IDLE */
break;

51
server/modules/routing/readwritesplit/readwritesplit.c
View File

@ -1368,8 +1368,27 @@ static route_target_t get_route_target (
QUERY_IS_TYPE(qtype, QUERY_TYPE_ENABLE_AUTOCOMMIT) ||
QUERY_IS_TYPE(qtype, QUERY_TYPE_DISABLE_AUTOCOMMIT))
{
/** hints don't affect on routing */
target = TARGET_ALL;
/**
* This is problematic query because it would be routed to all
* backends but since this is SELECT that is not possible:
* 1. response set is not handled correctly in clientReply and
* 2. multiple results can degrade performance.
*/
if (QUERY_IS_TYPE(qtype, QUERY_TYPE_READ))
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Warning : The query can't be routed to all "
"backend servers because it includes SELECT and "
"SQL variable modifications which is not supported. "
"Set use_sql_variables_in=master or split the "
"query to two, where SQL variable modifications "
"are done in the first and the SELECT in the "
"second one.")));
target = TARGET_MASTER;
}
target |= TARGET_ALL;
}
/**
* Hints may affect on routing of the following queries
@ -2139,6 +2158,34 @@ static bool route_single_stmt(
if (TARGET_IS_ALL(route_target))
{
/** Multiple, conflicting routing target. Return error */
if (TARGET_IS_MASTER(route_target) ||
TARGET_IS_SLAVE(route_target))
{
char* query_str = modutil_get_query(querybuf);
char* qtype_str = skygw_get_qtype_str(qtype);
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error: Can't route %s:%s:\"%s\". SELECT with "
"session data modification is not supported "
"if configuration parameter "
"use_sql_variables_in=all .",
STRPACKETTYPE(packet_type),
qtype_str,
(query_str == NULL ? "(empty)" : query_str))));
LOGIF(LT, (skygw_log_write(LOGFILE_TRACE,
"Unable to route the query "
"without losing session data "
"modification from other "
"servers. <")));
if (query_str) free (query_str);
if (qtype_str) free(qtype_str);
succp = false;
goto retblock;
}
/**
* It is not sure if the session command in question requires
* response. Statement is examined in route_session_write.