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MXS-2427 Check all hints when routing

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Now considers other routing hints if first one fails. The order is inverted compared
to e.g. namedserver filter settings because of how routing hints are stored. If all hints
are unsuccessful, route to any slave.
This commit is contained in:
Esa Korhonen 2019-04-25 10:30:29 +03:00
parent 08bd7c99be
commit dd188962cd
2 changed files with 62 additions and 74 deletions
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132
server/modules/routing/readwritesplit/rwsplit_route_stmt.cc
View File

@ -597,7 +597,7 @@ static inline bool rpl_lag_is_ok(SRWBackend& backend, int max_rlag)
return max_rlag == MXS_RLAG_UNDEFINED || backend->server()->rlag <= max_rlag;
}
SRWBackend RWSplitSession::get_hinted_backend(char* name)
SRWBackend RWSplitSession::get_hinted_backend(const char* name)
{
SRWBackend rval;
@ -735,15 +735,15 @@ SRWBackend RWSplitSession::get_last_used_backend()
*
* @param rses Pointer to router client session
* @param btype Backend type
* @param name Name of the backend which is primarily searched. May be NULL.
* @param name Name of the requested backend. May be NULL if any name is accepted.
* @param max_rlag Maximum replication lag
* @param target The target backend
*
* @return True if a backend was found
*/
SRWBackend RWSplitSession::get_target_backend(backend_type_t btype,
char* name,
int max_rlag)
const char* name,
int max_rlag)
{
/** Check whether using target_node as target SLAVE */
if (m_target_node && session_trx_is_read_only(m_client->session))
@ -752,13 +752,11 @@ SRWBackend RWSplitSession::get_target_backend(backend_type_t btype,
}
SRWBackend rval;
if (name) /*< Choose backend by name from a hint */
if (name)
{
btype = BE_SLAVE;
// Choose backend by name from a hint
rval = get_hinted_backend(name);
}
else if (btype == BE_SLAVE)
{
rval = get_slave_backend(max_rlag);
@ -767,7 +765,6 @@ SRWBackend RWSplitSession::get_target_backend(backend_type_t btype,
{
rval = get_master_backend();
}
return rval;
}
@ -808,82 +805,73 @@ int RWSplitSession::get_max_replication_lag()
*/
SRWBackend RWSplitSession::handle_hinted_target(GWBUF* querybuf, route_target_t route_target)
{
char* named_server = NULL;
int rlag_max = MXS_RLAG_UNDEFINED;
const char rlag_hint_tag[] = "max_slave_replication_lag";
const int comparelen = sizeof(rlag_hint_tag);
int config_max_rlag = get_max_replication_lag(); // From router configuration.
SRWBackend target;
HINT* hint = querybuf->hint;
while (hint != NULL)
for (HINT* hint = querybuf->hint; !target && hint; hint = hint->next)
{
if (hint->type == HINT_ROUTE_TO_NAMED_SERVER)
{
/**
* Set the name of searched
* backend server.
*/
named_server = (char*)hint->data;
MXS_INFO("Hint: route to server '%s'", named_server);
}
else if (hint->type == HINT_PARAMETER
&& (strncasecmp((char*)hint->data,
"max_slave_replication_lag",
strlen("max_slave_replication_lag")) == 0))
{
int val = (int)strtol((char*)hint->value, (char**)NULL, 10);
if (val != 0 || errno == 0)
// Set the name of searched backend server.
const char* named_server = (char*)hint->data;
MXS_INFO("Hint: route to server '%s'.", named_server);
target = get_target_backend(BE_UNDEFINED, named_server, config_max_rlag);
if (!target)
{
/** Set max. acceptable replication lag value for backend srv */
rlag_max = val;
MXS_INFO("Hint: max_slave_replication_lag=%d", rlag_max);
// Target may differ from the requested name if the routing target is locked, e.g. by a trx.
// Target is null only if not locked and named server was not found or was invalid.
if (mxb_log_is_priority_enabled(LOG_INFO))
{
char* status = nullptr;
for (const auto& a : m_backends)
{
if (strcmp(a->server()->name, named_server) == 0)
{
status = server_status(a->server());
break;
}
}
MXS_INFO("Was supposed to route to named server %s but couldn't find the server in a "
"suitable state. Server state: %s",
named_server, status ? status : "Could not find server");
MXS_FREE(status);
}
}
}
else if (hint->type == HINT_PARAMETER
&& (strncasecmp((char*)hint->data, rlag_hint_tag, comparelen) == 0))
{
const char* str_val = (char*)hint->value;
int hint_max_rlag = (int)strtol(str_val, (char**)NULL, 10);
if (hint_max_rlag != 0 || errno == 0)
{
MXS_INFO("Hint: %s=%d", rlag_hint_tag, hint_max_rlag);
target = get_target_backend(BE_SLAVE, nullptr, hint_max_rlag);
if (!target)
{
MXS_INFO("Was supposed to route to server with replication lag "
"at most %d but couldn't find such a slave.", hint_max_rlag);
}
}
else
{
MXS_ERROR("Hint: Could not parse value of %s: '%s' is not a valid number.",
rlag_hint_tag, str_val);
}
}
hint = hint->next;
} /*< while */
if (rlag_max == MXS_RLAG_UNDEFINED) /*< no rlag max hint, use config */
{
rlag_max = get_max_replication_lag();
}
/** target may be master or slave */
backend_type_t btype = route_target & TARGET_SLAVE ? BE_SLAVE : BE_MASTER;
/**
* Search backend server by name or replication lag.
* If it fails, then try to find valid slave or master.
*/
SRWBackend target = get_target_backend(btype, named_server, rlag_max);
if (!target)
{
if (TARGET_IS_NAMED_SERVER(route_target))
{
char* status = nullptr;
// If no target so far, pick any available. TODO: should this be error instead?
// Erroring here is more appropriate when namedserverfilter allows setting multiple target types
// e.g. target=server1,->slave
for (const auto& a : m_backends)
{
if (strcmp(a->server()->name, named_server) == 0)
{
status = server_status(a->server());
break;
}
}
MXS_INFO("Was supposed to route to named server %s but couldn't find the server in a "
"suitable state. Server state: %s", named_server,
status ? status : "Could not find server");
MXS_FREE(status);
}
else if (TARGET_IS_RLAG_MAX(route_target))
{
MXS_INFO("Was supposed to route to server with "
"replication lag at most %d but couldn't "
"find such a slave.",
rlag_max);
}
backend_type_t btype = route_target & TARGET_SLAVE ? BE_SLAVE : BE_MASTER;
target = get_target_backend(btype, NULL, config_max_rlag);
}
return target;
}

4
server/modules/routing/readwritesplit/rwsplitsession.hh
View File

@ -189,11 +189,11 @@ private:
bool route_stored_query();
void close_stale_connections();
mxs::SRWBackend get_hinted_backend(char* name);
mxs::SRWBackend get_hinted_backend(const char* name);
mxs::SRWBackend get_slave_backend(int max_rlag);
mxs::SRWBackend get_master_backend();
mxs::SRWBackend get_last_used_backend();
mxs::SRWBackend get_target_backend(backend_type_t btype, char* name, int max_rlag);
mxs::SRWBackend get_target_backend(backend_type_t btype, const char* name, int max_rlag);
bool handle_target_is_all(route_target_t route_target,
GWBUF* querybuf,