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MXS-1503: Split get_target_backend into smaller pieces

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Split the code into separate functions. This should make it easier to
comprehend.
This commit is contained in:
Markus Mäkelä
2018-03-28 12:32:17 +03:00
parent 9c7578272c
commit 3d63d18bdd
1 changed files with 101 additions and 87 deletions
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188
server/modules/routing/readwritesplit/rwsplit_route_stmt.cc
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@ -353,6 +353,96 @@ static inline bool rpl_lag_is_ok(SRWBackend& backend, int max_rlag)
backend->server()->rlag <= max_rlag); backend->server()->rlag <= max_rlag);
} }
SRWBackend get_hinted_backend(RWSplitSession *rses, char *name)
{
SRWBackend rval;
for (auto it = rses->backends.begin(); it != rses->backends.end(); it++)
{
auto& backend = *it;
/** The server must be a valid slave, relay server, or master */
if (backend->in_use() && strcasecmp(name, backend->name()) == 0 &&
(backend->is_slave() || backend->is_relay() || backend->is_master()))
{
rval = backend;
break;
}
}
return rval;
}
SRWBackend get_slave_backend(RWSplitSession *rses, int max_rlag)
{
SRWBackend rval;
for (auto it = rses->backends.begin(); it != rses->backends.end(); it++)
{
auto& backend = *it;
if (backend->in_use() && // Backend is in use
(backend->is_master() || backend->is_slave()) && // Either a master or a slave
rpl_lag_is_ok(backend, max_rlag)) // Not lagging too much
{
if (!rval)
{
// No previous candidate, accept any valid server (includes master)
if ((backend->is_master() && backend == rses->current_master) ||
backend->is_slave())
{
rval = backend;
}
}
else
{
if (!rses->rses_config.master_accept_reads && rval->is_master())
{
// Pick slaves over masters with master_accept_reads=false
rval = backend;
}
else
{
// Compare the two servers and pick the best one
rval = compare_backends(rval, backend, rses->rses_config.slave_selection_criteria);
}
}
}
}
return rval;
}
SRWBackend get_master_backend(RWSplitSession *rses)
{
SRWBackend rval;
/** get root master from available servers */
SRWBackend master = get_root_master(rses->backends);
if (master)
{
if (master->in_use() || master->can_connect())
{
if (master->is_master())
{
rval = master;
}
else
{
MXS_ERROR("Server '%s' does not have the master state and "
"can't be chosen as the master.", master->name());
}
}
else
{
MXS_ERROR("Server '%s' is not in use and can't be chosen as the master.",
master->name());
}
}
return rval;
}
/** /**
* Provide the router with a reference to a suitable backend * Provide the router with a reference to a suitable backend
* *
@ -372,102 +462,26 @@ SRWBackend get_target_backend(RWSplitSession *rses, backend_type_t btype,
/** Check whether using rses->target_node as target SLAVE */ /** Check whether using rses->target_node as target SLAVE */
if (rses->target_node && session_trx_is_read_only(rses->client_dcb->session)) if (rses->target_node && session_trx_is_read_only(rses->client_dcb->session))
{ {
MXS_DEBUG("In READ ONLY transaction, using server '%s'", MXS_DEBUG("In READ ONLY transaction, using server '%s'", rses->target_node->name());
rses->target_node->name());
return rses->target_node; return rses->target_node;
} }
if (name) /*< Choose backend by name from a hint */
{
ss_dassert(btype != BE_MASTER); /*< Master dominates and no name should be passed with it */
for (SRWBackendList::iterator it = rses->backends.begin();
it != rses->backends.end(); it++)
{
SRWBackend& backend = *it;
/** The server must be a valid slave, relay server, or master */
if (backend->in_use() &&
(strcasecmp(name, backend->name()) == 0) &&
(backend->is_slave() ||
backend->is_relay() ||
backend->is_master()))
{
return backend;
}
}
/** No server found, use a normal slave for it */
btype = BE_SLAVE;
}
SRWBackend rval; SRWBackend rval;
if (btype == BE_SLAVE) if (name) /*< Choose backend by name from a hint */
{ {
for (auto it = rses->backends.begin(); it != rses->backends.end(); it++) ss_dassert(btype != BE_MASTER);
{ btype = BE_SLAVE;
auto& backend = *it; rval = get_hinted_backend(rses, name);
}
if (backend->in_use() && // Backend is in use
(backend->is_master() || backend->is_slave()) && // Either a master or a slave else if (btype == BE_SLAVE)
rpl_lag_is_ok(backend, max_rlag)) // Not lagging too much {
{ rval = get_slave_backend(rses, max_rlag);
if (!rval)
{
// No previous candidate, accept any valid server (includes master)
if ((backend->is_master() && backend == rses->current_master) ||
backend->is_slave())
{
rval = backend;
}
}
else
{
if (!rses->rses_config.master_accept_reads && rval->is_master())
{
// Pick slaves over masters with master_accept_reads=false
rval = backend;
}
else
{
// Compare the two servers and pick the best one
rval = compare_backends(rval, backend, rses->rses_config.slave_selection_criteria);
}
}
}
}
} }
/**
* If target was originally master only then the execution jumps
* directly here.
*/
else if (btype == BE_MASTER) else if (btype == BE_MASTER)
{ {
/** get root master from available servers */ rval = get_master_backend(rses);
SRWBackend master = get_root_master(rses->backends);
if (master)
{
if (master->in_use() || master->can_connect())
{
if (master->is_master())
{
rval = master;
}
else
{
MXS_ERROR("Server '%s' does not have the master state and "
"can't be chosen as the master.", master->name());
}
}
else
{
MXS_ERROR("Server '%s' is not in use and can't be chosen as the master.",
master->name());
}
}
} }
return rval; return rval;