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Fix to #478, http://bugs.skysql.com/show_bug.cgi?id=478

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Execution of session commands failed because session commands and normal sql statements were executed in a wrong order if backend was executing previous session command while new sql stmt was routed to that backend. There was a window where ordering went wrong.
It is possible that one normal sql stmt arrives while previous sescmds are still being executed.

Introduced a new member in backend_ref_t structure, bref_pending_cmd where new sql stmt pointer is stored in that case. When sescmds are executed completely, that command is automatically executed next.
This commit is contained in:
VilhoRaatikka
2014-09-26 15:40:32 +03:00
parent 2183dbcc28
commit 5ec1a83f3b
4 changed files with 60 additions and 2 deletions
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57
server/modules/routing/readwritesplit/readwritesplit.c
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@ -1957,6 +1957,26 @@ static int routeQuery(
if (succp) /*< Have DCB of the target backend */
{
backend_ref_t* bref;
sescmd_cursor_t* scur;
bref = get_bref_from_dcb(router_cli_ses, target_dcb);
scur = &bref->bref_sescmd_cur;
/**
* Store current stmt if execution of previous session command
* haven't completed yet. Note that according to MySQL protocol
* there can only be one such non-sescmd stmt at the time.
*/
if (sescmd_cursor_is_active(scur))
{
ss_dassert(bref->bref_pending_cmd == NULL);
bref->bref_pending_cmd = gwbuf_clone(querybuf);
rses_end_locked_router_action(router_cli_ses);
ret = 1;
goto retblock;
}
if ((ret = target_dcb->func.write(target_dcb, gwbuf_clone(querybuf))) == 1)
{
backend_ref_t* bref;
@ -2295,7 +2315,34 @@ static void clientReply (
ss_dassert(succp);
}
/** Unlock router session */
else if (bref->bref_pending_cmd != NULL) /*< non-sescmd is waiting to be routed */
{
int ret;
CHK_GWBUF(bref->bref_pending_cmd);
if ((ret = bref->bref_dcb->func.write(bref->bref_dcb,
gwbuf_clone(bref->bref_pending_cmd))) == 1)
{
ROUTER_INSTANCE* inst = (ROUTER_INSTANCE *)instance;
atomic_add(&inst->stats.n_queries, 1);
/**
* Add one query response waiter to backend reference
*/
bref_set_state(bref, BREF_QUERY_ACTIVE);
bref_set_state(bref, BREF_WAITING_RESULT);
}
else
{
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Routing query \"%s\" failed.",
bref->bref_pending_cmd)));
}
gwbuf_free(bref->bref_pending_cmd);
bref->bref_pending_cmd = NULL;
}
/** Unlock router session */
rses_end_locked_router_action(router_cli_ses);
lock_failed:
@ -3656,6 +3703,14 @@ static bool route_session_write(
{
succp = false;
}
else if (LOG_IS_ENABLED(LOGFILE_TRACE))
{
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Wrote to %s:%d",
backend_ref[i].bref_backend->backend_server->name,
backend_ref[i].bref_backend->backend_server->port)));
}
}
}
rses_end_locked_router_action(router_cli_ses);