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Minor refactoring of error handling

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Refactored common code into a reusable function. Now all of the backend
error handling uses the same function.

Moved responsibility of the DCB error handling tracking to the backend
protocol. The routers no longer need to manage the
`dcb->dcb_errhandle_called` variable of the failed DCB.

Removed calls to handleError with client DCBs as parameters. All of the
routers close the DCB given to handleError if it is a client DCB. The only
time the error handler would be called is when the routeQuery function
fails. The handleError call is redundant as the router already knows that
the session should be closed when it returns from routeQuery.
This commit is contained in:
Markus Mäkelä
2017-03-05 10:28:07 +02:00
parent a3cae79fdf
commit 29ece502f5
2 changed files with 58 additions and 221 deletions
Download Patch File Download Diff File Expand all files Collapse all files

248
server/modules/protocol/MySQL/MySQLBackend/mysql_backend.c
View File

@ -602,6 +602,34 @@ gw_read_backend_event(DCB *dcb)
return rc;
}
static void do_handle_error(DCB *dcb, mxs_error_action_t action, const char *errmsg)
{
bool succp = false;
MXS_SESSION *session = dcb->session;
if (!dcb->dcb_errhandle_called)
{
GWBUF *errbuf = mysql_create_custom_error(1, 0, errmsg);
void *rsession = session->router_session;
MXS_ROUTER_OBJECT *router = session->service->router;
MXS_ROUTER *router_instance = session->service->router_instance;
router->handleError(router_instance, rsession, errbuf,
dcb, action, &succp);
gwbuf_free(errbuf);
dcb->dcb_errhandle_called = true;
}
/**
* If error handler fails it means that routing session can't continue
* and it must be closed. In success, only this DCB is closed.
*/
if (!succp)
{
session->state = SESSION_STATE_STOPPING;
}
}
/**
* @brief Authentication of backend - read the reply, or handle an error
*
@ -609,43 +637,21 @@ gw_read_backend_event(DCB *dcb)
* @param local_session The current MySQL session data structure
* @return
*/
static void
gw_reply_on_error(DCB *dcb, mxs_auth_state_t state)
static void gw_reply_on_error(DCB *dcb, mxs_auth_state_t state)
{
MXS_SESSION *session = dcb->session;
CHK_SESSION(session);
/* Only reload the users table if authentication failed and the
* client session is not stopping. It is possible that authentication
* fails because the client has closed the connection before all
* backends have done authentication. */
if (state == MXS_AUTH_STATE_FAILED && session->state != SESSION_STATE_STOPPING)
{
service_refresh_users(session->service);
}
GWBUF* errbuf = mysql_create_custom_error(1, 0, "Authentication with backend "
"failed. Session will be closed.");
if (session->router_session)
{
bool succp = false;
session->service->router->handleError(session->service->router_instance,
session->router_session,
errbuf, dcb, ERRACT_REPLY_CLIENT, &succp);
do_handle_error(dcb, ERRACT_REPLY_CLIENT,
"Authentication with backend failed. Session will be closed.");
session->state = SESSION_STATE_STOPPING;
ss_dassert(dcb->dcb_errhandle_called);
}
else
{
/** A NULL router_session is valid if a router declares the
* RCAP_TYPE_NO_RSESSION capability flag */
dcb->dcb_errhandle_called = true;
}
gwbuf_free(errbuf);
}
/**
@ -712,28 +718,7 @@ gw_read_and_write(DCB *dcb)
if (return_code < 0)
{
GWBUF* errbuf;
bool succp;
#if defined(SS_DEBUG)
MXS_ERROR("Backend read error handling #2.");
#endif
errbuf = mysql_create_custom_error(1,
0,
"Read from backend failed");
session->service->router->handleError(
session->service->router_instance,
session->router_session,
errbuf,
dcb,
ERRACT_NEW_CONNECTION,
&succp);
gwbuf_free(errbuf);
if (!succp)
{
session->state = SESSION_STATE_STOPPING;
}
do_handle_error(dcb, ERRACT_NEW_CONNECTION, "Read from backend failed");
return 0;
}
@ -1113,18 +1098,11 @@ static int gw_MySQLWrite_backend(DCB *dcb, GWBUF *queue)
*/
static int gw_error_backend_event(DCB *dcb)
{
MXS_SESSION* session;
void* rsession;
MXS_ROUTER_OBJECT* router;
MXS_ROUTER* router_instance;
GWBUF* errbuf;
bool succp;
mxs_session_state_t ses_state;
CHK_DCB(dcb);
session = dcb->session;
MXS_SESSION *session = dcb->session;
CHK_SESSION(session);
if (SESSION_STATE_DUMMY == session->state)
if (session->state == SESSION_STATE_DUMMY)
{
if (dcb->persistentstart == 0)
{
@ -1133,81 +1111,32 @@ static int gw_error_backend_event(DCB *dcb)
"Closing connection.");
}
dcb_close(dcb);
return 1;
}
rsession = session->router_session;
router = session->service->router;
router_instance = session->service->router_instance;
/**
* Avoid running redundant error handling procedure.
* dcb_close is already called for the DCB. Thus, either connection is
* closed by router and COM_QUIT sent or there was an error which
* have already been handled.
*/
if (dcb->state != DCB_STATE_POLLING)
else if (dcb->state != DCB_STATE_POLLING || session->state != SESSION_STATE_ROUTER_READY)
{
int error, len;
int error;
int len = sizeof(error);
len = sizeof(error);
if (getsockopt(dcb->fd, SOL_SOCKET, SO_ERROR, &error, (socklen_t *) & len) == 0)
if (getsockopt(dcb->fd, SOL_SOCKET, SO_ERROR, &error, (socklen_t *) & len) == 0 && error != 0)
{
if (error != 0)
char errstring[MXS_STRERROR_BUFLEN];
if (dcb->state != DCB_STATE_POLLING)
{
char errstring[MXS_STRERROR_BUFLEN];
MXS_ERROR("DCB in state %s got error '%s'.",
STRDCBSTATE(dcb->state),
MXS_ERROR("DCB in state %s got error '%s'.", STRDCBSTATE(dcb->state),
strerror_r(error, errstring, sizeof(errstring)));
}
}
return 1;
}
errbuf = mysql_create_custom_error(1,
0,
"Lost connection to backend server.");
ses_state = session->state;
if (ses_state != SESSION_STATE_ROUTER_READY)
{
int error, len;
len = sizeof(error);
if (getsockopt(dcb->fd, SOL_SOCKET, SO_ERROR, &error, (socklen_t *) & len) == 0)
{
if (error != 0)
else
{
char errstring[MXS_STRERROR_BUFLEN];
MXS_ERROR("Error '%s' in session that is not ready for routing.",
strerror_r(error, errstring, sizeof(errstring)));
}
}
gwbuf_free(errbuf);
goto retblock;
}
#if defined(SS_DEBUG)
MXS_INFO("Backend error event handling.");
#endif
router->handleError(router_instance,
rsession,
errbuf,
dcb,
ERRACT_NEW_CONNECTION,
&succp);
gwbuf_free(errbuf);
/**
* If error handler fails it means that routing session can't continue
* and it must be closed. In success, only this DCB is closed.
*/
if (!succp)
else
{
session->state = SESSION_STATE_STOPPING;
do_handle_error(dcb, ERRACT_NEW_CONNECTION, "Lost connection to backend server.");
}
retblock:
return 1;
}
@ -1223,47 +1152,21 @@ retblock:
*/
static int gw_backend_hangup(DCB *dcb)
{
MXS_SESSION* session;
void* rsession;
MXS_ROUTER_OBJECT* router;
MXS_ROUTER* router_instance;
bool succp;
GWBUF* errbuf;
mxs_session_state_t ses_state;
CHK_DCB(dcb);
MXS_SESSION *session = dcb->session;
CHK_SESSION(session);
if (dcb->persistentstart)
{
dcb->dcb_errhandle_called = true;
goto retblock;
}
session = dcb->session;
if (session == NULL)
else if (session->state != SESSION_STATE_ROUTER_READY)
{
goto retblock;
}
CHK_SESSION(session);
rsession = session->router_session;
router = session->service->router;
router_instance = session->service->router_instance;
errbuf = mysql_create_custom_error(1,
0,
"Lost connection to backend server.");
ses_state = session->state;
if (ses_state != SESSION_STATE_ROUTER_READY)
{
int error, len;
len = sizeof(error);
int error;
int len = sizeof(error);
if (getsockopt(dcb->fd, SOL_SOCKET, SO_ERROR, &error, (socklen_t *) & len) == 0)
{
if (error != 0 && ses_state != SESSION_STATE_STOPPING)
if (error != 0 && session->state != SESSION_STATE_STOPPING)
{
char errstring[MXS_STRERROR_BUFLEN];
MXS_ERROR("Hangup in session that is not ready for routing, "
@ -1271,31 +1174,12 @@ static int gw_backend_hangup(DCB *dcb)
strerror_r(error, errstring, sizeof(errstring)));
}
}
gwbuf_free(errbuf);
/*
* I'm pretty certain this is best removed and
* causes trouble if present, but have left it
* here just for now as a comment. Martin
*/
/* dcb_close(dcb); */
goto retblock;
}
router->handleError(router_instance,
rsession,
errbuf,
dcb,
ERRACT_NEW_CONNECTION,
&succp);
gwbuf_free(errbuf);
/** There are no required backends available, close session. */
if (!succp)
else
{
session->state = SESSION_STATE_STOPPING;
do_handle_error(dcb, ERRACT_NEW_CONNECTION, "Lost connection to backend server.");
}
retblock:
return 1;
}
@ -1400,29 +1284,7 @@ static int backend_write_delayqueue(DCB *dcb, GWBUF *buffer)
if (rc == 0)
{
MXS_SESSION *session = dcb->session;
CHK_SESSION(session);
MXS_ROUTER_OBJECT *router = session->service->router;
MXS_ROUTER *router_instance = session->service->router_instance;
void *rsession = session->router_session;
bool succp = false;
GWBUF* errbuf = mysql_create_custom_error(
1, 0, "Failed to write buffered data to back-end server. "
"Buffer was empty or back-end was disconnected during "
"operation. Attempting to find a new backend.");
router->handleError(router_instance,
rsession,
errbuf,
dcb,
ERRACT_NEW_CONNECTION,
&succp);
gwbuf_free(errbuf);
if (!succp)
{
session->state = SESSION_STATE_STOPPING;
}
do_handle_error(dcb, ERRACT_NEW_CONNECTION, "Lost connection to backend server.");
}
return rc;

31
server/modules/protocol/MySQL/MySQLClient/mysql_client.c
View File

@ -1019,36 +1019,11 @@ gw_read_finish_processing(DCB *dcb, GWBUF *read_buffer, uint64_t capabilities)
/* else return_code is still 0 from when it was originally set */
/* Note that read_buffer has been freed or transferred by this point */
/** Routing failed */
if (return_code != 0)
{
bool router_can_continue;
GWBUF* errbuf;
/**
* 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 for router to continue operation.
*/
session->service->router->handleError(session->service->router_instance,
session->router_session,
errbuf,
dcb,
ERRACT_NEW_CONNECTION,
&router_can_continue);
gwbuf_free(errbuf);
/**
* If the router cannot continue, close session
*/
if (!router_can_continue)
{
MXS_ERROR("Routing the query failed. "
"Session will be closed.");
}
/** Routing failed, close the client connection */
dcb_close(dcb);
MXS_ERROR("Routing the query failed. Session will be closed.");
}
if (proto->current_command == MYSQL_COM_QUIT)