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Handle unexpected responses to COM_CHANGE_USER

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When an unexpected response to a COM_CHANGE_USER is received, it is now
processes and discarded instead of treated as an error. This will allow
further analysis of the situation in addition to possibly solving some of
the problems that the persistent connections have.

Added extra info level logging to relevant parts of the code that deal
with the COM_CHANGE_USER reply processing. This information should allow
tracking of the response state for debugging purposes.
This commit is contained in:
Markus Mäkelä
2017-08-29 15:31:51 +03:00
parent 63c803a818
commit 7cef722282
3 changed files with 95 additions and 23 deletions
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114
server/modules/protocol/MySQL/MySQLBackend/mysql_backend.c
View File

@ -616,6 +616,27 @@ static inline bool expecting_resultset(MySQLProtocol *proto)
proto->current_command == MYSQL_COM_STMT_FETCH;
}
/**
* Helpers for checking OK and ERR packets specific to COM_CHANGE_USER
*/
static inline bool not_ok_packet(const GWBUF* buffer)
{
uint8_t* data = GWBUF_DATA(buffer);
return data[4] != MYSQL_REPLY_OK ||
// Should be more than 7 bytes of payload
gw_mysql_get_byte3(data) < MYSQL_OK_PACKET_MIN_LEN - MYSQL_HEADER_LEN ||
// Should have no affected rows
data[5] != 0 ||
// Should not generate an insert ID
data[6] != 0;
}
static inline bool not_err_packet(const GWBUF* buffer)
{
return GWBUF_DATA(buffer)[4] != MYSQL_REPLY_ERR;
}
/**
* @brief With authentication completed, read new data and write to backend
*
@ -729,27 +750,44 @@ gw_read_and_write(DCB *dcb)
GWBUF* reply = modutil_get_next_MySQL_packet(&read_buffer);
ss_dassert(reply);
ss_dassert(read_buffer == NULL);
uint8_t result = GWBUF_DATA(reply)[4];
int n_unknown = 0;
while (reply && not_ok_packet(reply) && not_err_packet(reply))
{
gwbuf_free(reply);
reply = modutil_get_next_MySQL_packet(&read_buffer);
n_unknown++;
}
if (reply == NULL)
{
ss_dassert(n_unknown > 0);
MXS_WARNING("Ignored %d unknown responses to COM_CHANGE_USER but no OK packet was found.", n_unknown);
return 1;
}
uint8_t result = MYSQL_GET_COMMAND(GWBUF_DATA(reply));
int rval = 0;
if (result == MYSQL_REPLY_OK)
{
MXS_INFO("Response to COM_CHANGE_USER is OK, writing stored query");
rval = query ? dcb->func.write(dcb, query) : 1;
}
else
{
if (result == MYSQL_REPLY_ERR)
{
/** The COM_CHANGE USER failed, generate a fake hangup event to
* close the DCB and send an error to the client. */
log_error_response(dcb, reply);
}
else
{
MXS_ERROR("Unknown response to COM_CHANGE_USER: 0x%02hhx", result);
ss_dassert(false);
}
if (result == MYSQL_REPLY_ERR)
{
/** The COM_CHANGE USER failed, generate a fake hangup event to
* close the DCB and send an error to the client. */
log_error_response(dcb, reply);
}
else
{
/** This should never happen */
MXS_ERROR("Unknown response to COM_CHANGE_USER: 0x%02hhx", result);
ss_dassert(false);
}
gwbuf_free(query);
poll_fake_hangup_event(dcb);
}
@ -893,8 +931,7 @@ static int gw_MySQLWrite_backend(DCB *dcb, GWBUF *queue)
CHK_DCB(dcb);
if (dcb->was_persistent && dcb->state == DCB_STATE_POLLING &&
backend_protocol->protocol_auth_state == MXS_AUTH_STATE_COMPLETE)
if (dcb->was_persistent)
{
ss_dassert(!dcb->dcb_fakequeue);
ss_dassert(!dcb->dcb_readqueue);
@ -902,6 +939,18 @@ static int gw_MySQLWrite_backend(DCB *dcb, GWBUF *queue)
ss_dassert(!dcb->writeq);
ss_dassert(dcb->persistentstart == 0);
dcb->was_persistent = false;
backend_protocol->ignore_reply = false;
if (dcb->state != DCB_STATE_POLLING ||
backend_protocol->protocol_auth_state != MXS_AUTH_STATE_COMPLETE)
{
MXS_INFO("DCB and protocol state do not qualify for pooling: %s, %s",
STRDCBSTATE(dcb->state),
STRPROTOCOLSTATE(backend_protocol->protocol_auth_state));
gwbuf_free(queue);
return 0;
}
/**
* This is a DCB that was just taken out of the persistent connection pool.
@ -918,22 +967,41 @@ static int gw_MySQLWrite_backend(DCB *dcb, GWBUF *queue)
if (MYSQL_IS_COM_QUIT(GWBUF_DATA(queue)))
{
/** The connection is being closed before the first write to this
* backend was done. The COM_QUIT is ignored and the DCB is put
* into the pool once iẗ́'s closed. */
* backend was done. The COM_QUIT is ignored and the DCB will be put
* back into the pool once it's closed. */
MXS_INFO("COM_QUIT received as the first write, ignoring and "
"sending the DCB back to the pool.");
gwbuf_free(queue);
return 1;
}
backend_protocol->ignore_reply = true;
backend_protocol->stored_query = queue;
GWBUF *buf = gw_create_change_user_packet(dcb->session->client_dcb->data, dcb->protocol);
return dcb_write(dcb, buf) ? 1 : 0;
int rc = 0;
if (dcb_write(dcb, buf))
{
MXS_INFO("Sent COM_CHANGE_USER");
backend_protocol->ignore_reply = true;
backend_protocol->stored_query = queue;
rc = 1;
}
else
{
gwbuf_free(queue);
}
return rc;
}
else if (backend_protocol->ignore_reply)
{
if (MYSQL_IS_COM_QUIT((uint8_t*)GWBUF_DATA(queue)))
{
/** The COM_CHANGE_USER was already sent but the session is already
* closing. We ignore the COM_QUIT in the hopes that the response
* to the COM_CHANGE_USER comes before the DCB is closed. If the
* DCB is closed before the response arrives, the connection will
* not qualify the persistent connection pool. */
MXS_INFO("COM_QUIT received while COM_CHANGE_USER is in progress, ignoring");
gwbuf_free(queue);
}
else
@ -941,8 +1009,10 @@ static int gw_MySQLWrite_backend(DCB *dcb, GWBUF *queue)
/**
* We're still waiting on the reply to the COM_CHANGE_USER, append the
* buffer to the stored query. This is possible if the client sends
* BLOB data on the first command.
* BLOB data on the first command or is sending multiple COM_QUERY
* packets at one time.
*/
MXS_INFO("COM_CHANGE_USER in progress, appending query to queue");
backend_protocol->stored_query = gwbuf_append(backend_protocol->stored_query, queue);
}
return 1;
@ -1982,5 +2052,5 @@ static bool gw_connection_established(DCB* dcb)
{
MySQLProtocol *proto = (MySQLProtocol*)dcb->protocol;
return proto->protocol_auth_state == MXS_AUTH_STATE_COMPLETE &&
!proto->ignore_reply && !proto->stored_query;
!proto->ignore_reply && !proto->stored_query;
}

1
server/modules/protocol/MySQL/mysql_common.c
View File

@ -104,6 +104,7 @@ MySQLProtocol* mysql_protocol_init(DCB* dcb, int fd)
p->protocol_command.scom_nbytes_to_read = 0;
p->stored_query = NULL;
p->extra_capabilities = 0;
p->ignore_reply = false;
#if defined(SS_DEBUG)
p->protocol_chk_top = CHK_NUM_PROTOCOL;
p->protocol_chk_tail = CHK_NUM_PROTOCOL;