With replication enabled, RecoveryManager spins uselessly on primary instead of waiting for events.

[lmwnshn]

Feature Request

Summary

With replication enabled, RecoveryManager spins uselessly on primary instead of waiting for events.

Solution

Look at RecoveryManager::RunTask() and get rid of the while loop hack.
ReplicationLogProvider::WaitForEvent() was added much later and might be helpful here if you can modify it accordingly.
And/or, look at AbstractLogProvider.

In general, the RecoveryManager needs to be able to distinguish between "this log provider will never get more logs" (wal.log) and "this log provider may get more logs" (replication).

[jkosh44]

Why does the primary node even need an instance of the recovery manager? Could we just check in DB main if it's the primary instance and if so not start the recovery manager?

[jkosh44]

We could change

      if (use_replication_) {
        auto log_provider = replication_manager->IsPrimary()
                                ? nullptr
                                : replication_manager->GetAsReplica()
                                      ->GetReplicationLogProvider()
                                      .CastManagedPointerTo<storage::AbstractLogProvider>();
        recovery_manager = std::make_unique<storage::RecoveryManager>(
            log_provider, catalog_layer->GetCatalog(), txn_layer->GetTransactionManager(),
            txn_layer->GetDeferredActionManager(), common::ManagedPointer(replication_manager),
            common::ManagedPointer(thread_registry), common::ManagedPointer(storage_layer->GetBlockStore()));
        recovery_manager->StartRecovery();
      }

to

      if (use_replication_ && replication_manager->IsReplica()) {
        auto log_provider = replication_manager->GetAsReplica()
                                      ->GetReplicationLogProvider()
                                      .CastManagedPointerTo<storage::AbstractLogProvider>();
        recovery_manager = std::make_unique<storage::RecoveryManager>(
            log_provider, catalog_layer->GetCatalog(), txn_layer->GetTransactionManager(),
            txn_layer->GetDeferredActionManager(), common::ManagedPointer(replication_manager),
            common::ManagedPointer(thread_registry), common::ManagedPointer(storage_layer->GetBlockStore()));
        recovery_manager->StartRecovery();
      }