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MXS-852: Handle one-way session commands

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Session commands that will not return a response can be completed
immediately. This requires some special code in the readwritesplit Backend
class implementation as well as a small addition to the Backend class
itself.

Since not all commands expect a response from the server, the queued query
routing function needs some adjustment. The routing of queued queries
should be attempted until a command which expects a response is found or
the queue is empty.

By properly handling these types of session commands, the router can
enable the execution of COM_STMT_CLOSE and COM_STMT_RESET on all
servers. This will prevent resource leakages in the server and allow
proper handling of COM_STMT type command.
This commit is contained in:
Markus Mäkelä 2017-06-22 13:16:12 +03:00
parent 5fc30740b7
commit 52b7fb9340
8 changed files with 46 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
include/maxscale/protocol/mysql.h
View File

@ -547,4 +547,13 @@ bool mxs_mysql_extract_ps_response(GWBUF* buffer, MXS_PS_RESPONSE* out);
*/
uint32_t mxs_mysql_extract_ps_id(GWBUF* buffer);
/**
* @brief Determine if a packet contains a one way message
*
* @param cmd Command to inspect
*
* @return True if a response is expected from the server
*/
bool mxs_mysql_command_will_respond(uint8_t cmd);
MXS_END_DECLS

2
server/core/backend.cc
View File

@ -93,7 +93,9 @@ bool Backend::execute_session_command()
{
case MYSQL_COM_QUIT:
case MYSQL_COM_STMT_CLOSE:
/** These commands do not generate responses */
rval = write(buffer, NO_RESPONSE);
complete_session_command();
break;
case MYSQL_COM_CHANGE_USER:

7
server/modules/protocol/MySQL/mysql_common.c
View File

@ -1649,3 +1649,10 @@ uint32_t mxs_mysql_extract_ps_id(GWBUF* buffer)
return rval;
}
bool mxs_mysql_command_will_respond(uint8_t cmd)
{
return cmd != MYSQL_COM_STMT_SEND_LONG_DATA &&
cmd != MYSQL_COM_QUIT &&
cmd != MYSQL_COM_STMT_CLOSE;
}

18
server/modules/routing/readwritesplit/readwritesplit.cc
View File

@ -547,7 +547,10 @@ bool route_stored_query(ROUTER_CLIENT_SES *rses)
{
bool rval = true;
if (rses->query_queue)
/** Loop over the stored statements as long as the routeQuery call doesn't
* append more data to the queue. If it appends data to the queue, we need
* to wait for a response before attempting another reroute */
while (rses->query_queue)
{
GWBUF* query_queue = modutil_get_next_MySQL_packet(&rses->query_queue);
query_queue = gwbuf_make_contiguous(query_queue);
@ -574,8 +577,17 @@ bool route_stored_query(ROUTER_CLIENT_SES *rses)
gwbuf_free(query_queue);
}
ss_dassert(rses->query_queue == NULL);
rses->query_queue = temp_storage;
if (rses->query_queue == NULL)
{
/** Query successfully routed and no responses are expected */
rses->query_queue = temp_storage;
}
else
{
/** Routing was stopped, we need to wait for a response before retrying */
rses->query_queue = gwbuf_append(temp_storage, rses->query_queue);
break;
}
}
return rval;

3
server/modules/routing/readwritesplit/readwritesplit.hh
View File

@ -195,9 +195,10 @@ public:
bool execute_session_command()
{
bool expect_response = mxs_mysql_command_will_respond(next_session_command()->get_command());
bool rval = mxs::Backend::execute_session_command();
if (rval)
if (rval && expect_response)
{
set_reply_state(REPLY_STATE_START);
}

1
server/modules/routing/readwritesplit/rwsplit_internal.hh
View File

@ -45,7 +45,6 @@ bool handle_target_is_all(route_target_t route_target,
GWBUF *querybuf, int packet_type, uint32_t qtype);
uint8_t determine_packet_type(GWBUF *querybuf, bool *non_empty_packet);
void log_transaction_status(ROUTER_CLIENT_SES *rses, GWBUF *querybuf, uint32_t qtype);
bool command_will_respond(uint8_t packet_type);
bool is_packet_a_query(int packet_type);
bool send_readonly_error(DCB *dcb);

21
server/modules/routing/readwritesplit/rwsplit_mysql.cc
View File

@ -104,27 +104,6 @@ is_packet_a_query(int packet_type)
return (packet_type == MYSQL_COM_QUERY);
}
/*
* This looks MySQL specific
*/
/**
* @brief Determine if a packet contains a one way message
*
* Packet type tells us this, but in a DB specific way. This function is
* provided so that code that is not DB specific can find out whether a packet
* contains a one way messsage. Clearly, to be effective different functions must be
* called for different DB types.
*
* @param packet_type Type of packet (integer)
* @return bool indicating whether packet contains a one way message
*/
bool command_will_respond(uint8_t packet_type)
{
return packet_type != MYSQL_COM_STMT_SEND_LONG_DATA &&
packet_type != MYSQL_COM_QUIT &&
packet_type != MYSQL_COM_STMT_CLOSE;
}
/*
* This one is problematic because it is MySQL specific, but also router
* specific.

13
server/modules/routing/readwritesplit/rwsplit_route_stmt.cc
View File

@ -270,7 +270,7 @@ bool route_session_write(ROUTER_CLIENT_SES *rses, GWBUF *querybuf,
/** The SessionCommand takes ownership of the buffer */
uint64_t id = rses->sescmd_count++;
mxs::SSessionCommand sescmd(new mxs::SessionCommand(querybuf, id));
bool expecting_response = command_will_respond(command);
bool expecting_response = mxs_mysql_command_will_respond(command);
int nsucc = 0;
uint64_t lowest_pos = id;
@ -349,6 +349,13 @@ bool route_session_write(ROUTER_CLIENT_SES *rses, GWBUF *querybuf,
if (nsucc)
{
rses->sent_sescmd = id;
if (!expecting_response)
{
/** The command doesn't generate a response so we increment the
* completed session command count */
rses->recv_sescmd++;
}
}
return nsucc;
@ -552,7 +559,9 @@ route_target_t get_route_target(ROUTER_CLIENT_SES *rses, uint8_t command,
target = TARGET_MASTER;
}
else if (qc_query_is_type(qtype, QUERY_TYPE_PREPARE_STMT) ||
qc_query_is_type(qtype, QUERY_TYPE_PREPARE_NAMED_STMT))
qc_query_is_type(qtype, QUERY_TYPE_PREPARE_NAMED_STMT) ||
command == MYSQL_COM_STMT_CLOSE ||
command == MYSQL_COM_STMT_RESET)
{
target = TARGET_ALL;
}