public final void rollbackAll() {
        graphs.entrySet().forEach(e -> {
            final Graph graph = e.getValue();
            if (graph.features().graph().supportsTransactions() && graph.tx().isOpen())
                graph.tx().rollback();
        });
    }
Rollback transactions across all {@link Graph} objects.
gremlin-server/src/main/java/org/apache/tinkerpop/gremlin/server/util/DefaultGraphManager.java