Method monitorProtocolVersion

fdbclient/MultiVersionTransaction.actor.cpp:1893–1916

Watch the cluster protocol version for changes and update the database state when it does. Must be called from the main thread

// Watch the cluster protocol version for changes and update the database state when it does.
// Must be called from the main thread
ThreadFuture<Void> MultiVersionDatabase::DatabaseState::monitorProtocolVersion() {
	startLegacyVersionMonitors();

	Optional<ProtocolVersion> expected = dbProtocolVersion;
	ThreadFuture<ProtocolVersion> f = versionMonitorDb->getServerProtocol(dbProtocolVersion);

	Reference<DatabaseState> self = Reference<DatabaseState>::addRef(this);
	return mapThreadFuture<ProtocolVersion, Void>(f, [self, expected](ErrorOr<ProtocolVersion> cv) {
		if (cv.isError()) {
			if (cv.getError().code() == error_code_operation_cancelled) {
				return ErrorOr<Void>(cv.getError());
			}

			TraceEvent("ErrorGettingClusterProtocolVersion")
			    .error(cv.getError())
			    .detail("ExpectedProtocolVersion", expected);
		}

		ProtocolVersion clusterVersion =
		    !cv.isError() ? cv.get() : self->dbProtocolVersion.orDefault(currentProtocolVersion());
		onMainThreadVoid([self, clusterVersion]() { self->protocolVersionChanged(clusterVersion); });
		return ErrorOr<Void>(Void());
	});
}

// Called when a change to the protocol version of the cluster has been detected.
// Must be called from the main thread