presto-main/src/main/java/io/prestosql/connector/ConnectorManager.java/ConnectorManager/stop
class ConnectorManager:    @PreDestroy
    public synchronized void stop()
    {
        if (stopped.getAndSet(true)) {
            return;
        }

        for (Map.Entry<CatalogName, MaterializedConnector> entry : connectors.entrySet()) {
            Connector connector = entry.getValue().getConnector();
            try (ThreadContextClassLoader ignored = new ThreadContextClassLoader(connector.getClass().getClassLoader())) {
                connector.shutdown();
            }
            catch (Throwable t) {
                log.error(t, "Error shutting down connector: %s", entry.getKey());
            }
        }
    }