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MXS-1644 Do not refresh users if max connections is reached

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According to MXS-1644 the refreshing of users may cause a crash.
In that particular case, the refreshing is triggered by the
authentication failing due to the user having hit the
'max_user_connection' limit of the server.

That is, refreshing the users in the situation is never going to
change the end-result. With this change, the users will not be
refreshed in that case and hopefully the crash will be avoided.

Note that this is something of a workaround as the crash could not
be repeated and the refreshing of the users should obviously not
ever cause MaxScale to crash.
This commit is contained in:
Johan Wikman 2018-02-14 13:42:42 +02:00
parent 9b03cf46d1
commit 558fdc1875
1 changed files with 17 additions and 6 deletions
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23
server/modules/protocol/mysql_backend.c
View File

@ -19,6 +19,7 @@
#include <utils.h>
#include <netinet/tcp.h>
#include <gw.h>
#include <mysqld_error.h>
/* The following can be compared using memcmp to detect a null password */
uint8_t null_client_sha1[MYSQL_SCRAMBLE_LEN]="";
@ -86,7 +87,7 @@ static int gw_read_reply_or_error(DCB *dcb, MYSQL_session local_session);
static int gw_read_and_write(DCB *dcb, MYSQL_session local_session);
static int gw_read_backend_handshake(MySQLProtocol *conn);
static int gw_decode_mysql_server_handshake(MySQLProtocol *conn, uint8_t *payload);
static int gw_receive_backend_auth(MySQLProtocol *protocol);
static int gw_receive_backend_auth(MySQLProtocol *protocol, uint16_t *code);
static mysql_auth_state_t gw_send_authentication_to_backend(char *dbname,
char *user,
uint8_t *passwd,
@ -883,12 +884,13 @@ gw_read_reply_or_error(DCB *dcb, MYSQL_session local_session)
}
CHK_SESSION(session);
uint16_t code = 0;
if (backend_protocol->protocol_auth_state == MYSQL_AUTH_RECV)
{
/**
* Read backend's reply to authentication message
*/
int receive_rc = gw_receive_backend_auth(backend_protocol);
int receive_rc = gw_receive_backend_auth(backend_protocol, &code);
switch (receive_rc)
{
@ -945,7 +947,12 @@ gw_read_reply_or_error(DCB *dcb, MYSQL_session local_session)
if (backend_protocol->protocol_auth_state == MYSQL_AUTH_FAILED &&
dcb->session->state != SESSION_STATE_STOPPING)
{
service_refresh_users(dcb->session->service);
// If the authentication failed due to too many connections,
// we do not refresh the users as it would not change anything.
if (code != ER_TOO_MANY_USER_CONNECTIONS)
{
service_refresh_users(dcb->session->service);
}
}
#if defined(SS_DEBUG)
MXS_DEBUG("%lu [gw_read_backend_event] "
@ -2224,11 +2231,14 @@ gw_decode_mysql_server_handshake(MySQLProtocol *conn, uint8_t *payload)
* Receive the MySQL authentication packet from backend, packet # is 2
*
* @param protocol The MySQL protocol structure
* @return -1 in case of failure, 0 if there was nothing to read, 1 if read
* was successful.
* @param code [out] The protocol error code, if -1 is returned.
* @return -1 in case of failure,
* 0 if there was nothing to read,
* 1 if read was successful.
*/
static int
gw_receive_backend_auth(MySQLProtocol *protocol)
gw_receive_backend_auth(MySQLProtocol *protocol, uint16_t *code)
{
int n = -1;
GWBUF *head = NULL;
@ -2258,6 +2268,7 @@ gw_receive_backend_auth(MySQLProtocol *protocol)
else if (ptr[4] == 0xff)
{
size_t len = MYSQL_GET_PACKET_LEN(ptr);
*code = MYSQL_GET_ERRCODE(ptr);
char* err = strndup(&((char *)ptr)[8], 5);
char* bufstr = strndup(&((char *)ptr)[13], len - 4 - 5);