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Support for prepared statement, namely support for following comands : COM_STMT_PREPARE, COM_STMT_EXECUTE, COM_STMT_SEND_LONG_DATA, COM_STMT_RESET, COM_STMT_CLOSE, SQLCOM_PREPARE, SQLCOM_EXECUTE, SQLCOM_DEALLOCATE_PREPARE (DEALLOCATE/DROP PREPARE stmt).

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All prepare commands are executed in every backend server currently connected.

All executes are routed to master. If stmt type was recorded in prepare phase in rwsplit router, read-only stmts could be routed to slaves.

COM_STMT_PREPARE gets arbitrary number of response packets from backend database. Since statements are prepared in every backend server and only one multi-packet response can be replied to client, redundant multi-packet responses are discarded. This is done in router. Mechanisms from session command handling are utilized with little changes: router must identify when response consists of multiple packets so that it knows to calculate the number of packets in response and that it is able to discard correct number of packets.

Information to the reply-handling router is provided by backend protocol, which includes a ordered list of commands of commands sent to protocol-owning backend server. A command is stored to protocol struct in mysql_backend.c:gw_MySQLWrite_backend if the statement buffer's type has GWBUF_TYPE_SINGLE_STMT set in mysql_client.c:route_by_statement. GWBUF_TYPE_SINGLE_STATEMENT indicates that there is single statement in the buffer, as opposite to Read Connection router, which accepts streaming input from client.
This commit is contained in:
VilhoRaatikka
2014-06-25 17:15:46 +03:00
parent 2d128de85f
commit 7ff14e23a5
6 changed files with 791 additions and 326 deletions
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46
server/modules/protocol/mysql_client.c
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@ -495,7 +495,7 @@ static int gw_mysql_do_authentication(DCB *dcb, GWBUF *queue) {
int
gw_MySQLWrite_client(DCB *dcb, GWBUF *queue)
{
return dcb_write(dcb, queue);
return dcb_write(dcb, queue);
}
/**
@ -582,7 +582,7 @@ int gw_read_client_event(
/**
* Now there should be at least one complete mysql packet in read_buffer.
*/
switch (protocol->state) {
switch (protocol->protocol_auth_state) {
case MYSQL_AUTH_SENT:
{
@ -595,7 +595,7 @@ int gw_read_client_event(
if (auth_val == 0)
{
SESSION *session = NULL;
protocol->state = MYSQL_AUTH_RECV;
protocol->protocol_auth_state = MYSQL_AUTH_RECV;
/**
* Create session, and a router session for it.
* If successful, there will be backend connection(s)
@ -607,7 +607,8 @@ int gw_read_client_event(
{
CHK_SESSION(session);
ss_dassert(session->state != SESSION_STATE_ALLOC);
protocol->state = MYSQL_IDLE;
protocol->protocol_auth_state = MYSQL_IDLE;
/**
* Send an AUTH_OK packet to the client,
* packet sequence is # 2
@ -616,7 +617,7 @@ int gw_read_client_event(
}
else
{
protocol->state = MYSQL_AUTH_FAILED;
protocol->protocol_auth_state = MYSQL_AUTH_FAILED;
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [gw_read_client_event] session "
@ -637,7 +638,7 @@ int gw_read_client_event(
}
else
{
protocol->state = MYSQL_AUTH_FAILED;
protocol->protocol_auth_state = MYSQL_AUTH_FAILED;
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [gw_read_client_event] after "
@ -888,8 +889,8 @@ int gw_write_client_event(DCB *dcb)
}
protocol = (MySQLProtocol *)dcb->protocol;
CHK_PROTOCOL(protocol);
if (protocol->state == MYSQL_IDLE)
if (protocol->protocol_auth_state == MYSQL_IDLE)
{
dcb_drain_writeq(dcb);
goto return_1;
@ -1231,7 +1232,7 @@ int gw_MySQLAccept(DCB *listener)
MySQLSendHandshake(client_dcb);
// client protocol state change
protocol->state = MYSQL_AUTH_SENT;
protocol->protocol_auth_state = MYSQL_AUTH_SENT;
/**
* Set new descriptor to event set. At the same time,
@ -1289,8 +1290,15 @@ static int gw_error_client_event(
SESSION* session;
CHK_DCB(dcb);
session = dcb->session;
CHK_SESSION(session);
LOGIF(LD, (skygw_log_write(
LOGFILE_DEBUG,
"%lu [gw_error_client_event] Error event handling for DCB %p "
"in state %s, session %p.",
pthread_self(),
dcb,
STRDCBSTATE(dcb->state),
(session != NULL ? session : NULL))));
#if defined(SS_DEBUG)
LOGIF(LE, (skygw_log_write_flush(
@ -1368,7 +1376,7 @@ gw_client_hangup_event(DCB *dcb)
/**
* Detect if buffer includes partial mysql packet or multiple packets.
* Store partial packet to pendingqueue. Send complete packets one by one
* Store partial packet to dcb_readqueue. Send complete packets one by one
* to router.
*
* It is assumed readbuf includes at least one complete packet.
@ -1387,6 +1395,20 @@ static int route_by_statement(SESSION *session, GWBUF *readbuf)
if (packetbuf != NULL)
{
CHK_GWBUF(packetbuf);
/**
* This means that buffer includes exactly one MySQL
* statement.
* backend func.write uses the information. MySQL backend
* protocol, for example, stores the command identifier
* to protocol structure. When some other thread reads
* the corresponding response the command tells how to
* handle response.
*
* Set it here instead of gw_read_client_event to make
* sure it is set to each (MySQL) packet.
*/
gwbuf_set_type(packetbuf, GWBUF_TYPE_SINGLE_STMT);
/** Route query */
rc = SESSION_ROUTE_QUERY(session, packetbuf);
}
else