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MXS-199: Support Causal Read in Read Write Splitting (#164)

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* MXS-199: Support Causal Read in Read Write Splitting

* move most causal read logic into rwsplit router and get server type from monitor

* misc fix: remove new line

* refactor, move config to right place, replace ltrim with gwbuf_consume

* refacter a little for previous commit

* fix code style
This commit is contained in:
dapeng
2018-02-05 15:09:18 +08:00
committed by Johan Wikman
parent 0696f3f60a
commit 8a0c8e63f2
9 changed files with 222 additions and 3 deletions
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81
server/modules/routing/readwritesplit/readwritesplit.cc
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@ -744,6 +744,7 @@ RWSplitSession::RWSplitSession(RWSplit* instance, MXS_SESSION* session,
router(instance),
sent_sescmd(0),
recv_sescmd(0),
gtid_pos(""),
rses_chk_tail(CHK_NUM_ROUTER_SES)
{
if (rses_config.rw_max_slave_conn_percent)
@ -1142,6 +1143,62 @@ static void log_unexpected_response(DCB* dcb, GWBUF* buffer)
}
}
/**
* @bref discard the result of wait gtid statment, the result will be an error
* packet or an error packet.
* @param buffer origin reply buffer
* @param proto MySQLProtocol
* @return reset buffer
*/
GWBUF *discard_master_wait_gtid_result(GWBUF *buffer, RWSplitSession *rses)
{
uint8_t header_and_command[MYSQL_HEADER_LEN + 1];
uint8_t packet_len = 0;
uint8_t offset = 0;
mxs_mysql_cmd_t com;
gwbuf_copy_data(buffer, 0, MYSQL_HEADER_LEN + 1, header_and_command);
/* ignore error packet */
if (MYSQL_GET_COMMAND(header_and_command) == MYSQL_REPLY_ERR)
{
rses->wait_gtid_state = EXPECTING_NOTHING;
return buffer;
}
/* this packet must be an ok packet now */
ss_dassert(MYSQL_GET_COMMAND(header_and_command) == MYSQL_REPLY_OK);
packet_len = MYSQL_GET_PAYLOAD_LEN(header_and_command) + MYSQL_HEADER_LEN;
rses->wait_gtid_state = EXPECTING_REAL_RESULT;
rses->next_seq = 1;
return gwbuf_consume(buffer, packet_len);
}
/**
* @bref After discarded the wait result, we need correct the seqence number of every packet
*
* @param buffer origin reply buffer
* @param proto MySQLProtocol
*
*/
void correct_packet_sequence(GWBUF *buffer, RWSplitSession *rses)
{
uint8_t header[3];
uint32_t offset = 0;
uint32_t packet_len = 0;
if (rses->wait_gtid_state == EXPECTING_REAL_RESULT)
{
while (gwbuf_copy_data(buffer, offset, 3, header) == 3)
{
packet_len = MYSQL_GET_PAYLOAD_LEN(header) + MYSQL_HEADER_LEN;
uint8_t *seq = gwbuf_byte_pointer(buffer, offset + MYSQL_SEQ_OFFSET);
*seq = rses->next_seq;
rses->next_seq++;
offset += packet_len;
}
}
}
/**
* @brief Client Reply routine
*
@ -1156,12 +1213,34 @@ static void clientReply(MXS_ROUTER *instance,
DCB *backend_dcb)
{
RWSplitSession *rses = (RWSplitSession *)router_session;
RWSplit *inst = (RWSplit *)instance;
DCB *client_dcb = backend_dcb->session->client_dcb;
CHK_CLIENT_RSES(rses);
ss_dassert(!rses->rses_closed);
SRWBackend& backend = get_backend_from_dcb(rses, backend_dcb);
if (inst->config().enable_causal_read &&
GWBUF_IS_REPLY_OK(writebuf) &&
backend == rses->current_master)
{
/** Save gtid position */
char *tmp = gwbuf_get_property(writebuf, (char *)"gtid");
if (tmp)
{
rses->gtid_pos = std::string(tmp);
}
}
if (rses->wait_gtid_state == EXPECTING_WAIT_GTID_RESULT)
{
writebuf = discard_master_wait_gtid_result(writebuf, rses);
}
if (rses->wait_gtid_state == EXPECTING_REAL_RESULT)
{
correct_packet_sequence(writebuf, rses);
}
if (backend->get_reply_state() == REPLY_STATE_DONE)
{
/** If we receive an unexpected response from the server, the internal
@ -1437,6 +1516,8 @@ MXS_MODULE *MXS_CREATE_MODULE()
{"strict_sp_calls", MXS_MODULE_PARAM_BOOL, "false"},
{"master_accept_reads", MXS_MODULE_PARAM_BOOL, "false"},
{"connection_keepalive", MXS_MODULE_PARAM_COUNT, "0"},
{"enable_causal_read", MXS_MODULE_PARAM_BOOL, "false"},
{"causal_read_timeout", MXS_MODULE_PARAM_STRING, "0"},
{MXS_END_MODULE_PARAMS}
}
};