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MXS-3892: Handle multiple pending queries

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If the client sends another query before reading the previous result, it
was possible that another session finished the shard update and the
following query would reuse this result. This would cause the assertion in
the delayed call to fail as it assumes the shard would always be empty
when it was being called. To correctly handle this case, the delayed call
must be the one that moves the session into the normal routing state.
This commit is contained in:
Markus Mäkelä
2021-12-31 15:33:15 +02:00
parent 5724338959
commit 3a05c22269
1 changed files with 12 additions and 8 deletions
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20
server/modules/routing/schemarouter/schemaroutersession.cc
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@ -294,6 +294,13 @@ int32_t SchemaRouterSession::routeQuery(GWBUF* pPacket)
if (m_shard.empty() && (m_state & INIT_MAPPING) == 0)
{
if (m_dcid)
{
// The delayed call is already in place, let it take care of the shard update
m_queue.push_back(pPacket);
return 1;
}
// Check if another session has managed to update the shard cache
m_shard = m_router->m_shard_manager.get_shard(m_key, m_config->refresh_min_interval);
@ -307,16 +314,13 @@ int32_t SchemaRouterSession::routeQuery(GWBUF* pPacket)
}
else
{
// Too many concurrent updates
// Wait for the other session to finish its update and reuse that result
mxb_assert(m_dcid == 0);
m_queue.push_back(pPacket);
if (m_dcid == 0)
{
// Wait for the other session to finish its update
auto worker = mxs::RoutingWorker::get_current();
m_dcid = worker->delayed_call(1000, &SchemaRouterSession::delay_routing, this);
MXS_INFO("Waiting for the database mapping to be completed by another session");
}
auto worker = mxs::RoutingWorker::get_current();
m_dcid = worker->delayed_call(1000, &SchemaRouterSession::delay_routing, this);
MXS_INFO("Waiting for the database mapping to be completed by another session");
return 1;
}