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MXS-1375: Fix double response to COM_CHANGE_USER

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When a persistent connection is reused, a COM_CHANGE_USER command is
executed to reset the session state. If the reused connection was closed
before the response to the COM_CHANGE_USER was received and taken into use
by another connection, another COM_CHANGE_USER would be sent to, again,
reset the session state. Due to the fact that the first response is still
on its way, it will appear as if two responses are generated for a single
COM_CHANGE_USER.

The way to fix this is to avoid putting connections that haven't been
successfully reset into the connection pool.
This commit is contained in:
Markus Mäkelä
2017-08-24 09:30:08 +03:00
parent bc1e2a844c
commit bc889b1b41
1 changed files with 19 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

25
server/modules/protocol/MySQL/MySQLBackend/mysql_backend.c
View File

@ -728,10 +728,12 @@ gw_read_and_write(DCB *dcb)
/** The reply to a COM_CHANGE_USER is in packet */
GWBUF *query = proto->stored_query;
uint8_t result = *((uint8_t*)GWBUF_DATA(read_buffer) + 4);
proto->stored_query = NULL;
proto->ignore_reply = false;
gwbuf_free(read_buffer);
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 rval = 0;
@ -739,14 +741,23 @@ gw_read_and_write(DCB *dcb)
{
rval = query ? dcb->func.write(dcb, query) : 1;
}
else if (query)
else
{
/** The COM_CHANGE USER failed, generate a fake hangup event to
* close the DCB and send an error to the client. */
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);
}
gwbuf_free(query);
poll_fake_hangup_event(dcb);
}
gwbuf_free(reply);
return rval;
}
@ -889,6 +900,7 @@ static int gw_MySQLWrite_backend(DCB *dcb, GWBUF *queue)
backend_protocol->protocol_auth_state == MXS_AUTH_STATE_COMPLETE)
{
ss_dassert(dcb->persistentstart == 0);
ss_dassert(!MYSQL_IS_COM_QUIT(GWBUF_DATA(queue)));
/**
* This is a DCB that was just taken out of the persistent connection pool.
* We need to sent a COM_CHANGE_USER query to the backend to reset the
@ -1956,5 +1968,6 @@ gw_send_change_user_to_backend(char *dbname,
static bool gw_connection_established(DCB* dcb)
{
MySQLProtocol *proto = (MySQLProtocol*)dcb->protocol;
return proto->protocol_auth_state == MXS_AUTH_STATE_COMPLETE;
return proto->protocol_auth_state == MXS_AUTH_STATE_COMPLETE &&
!proto->ignore_reply && !proto->stored_query;
}