default void log(Logger logger, Level level, String format, Object first, Object... rest) {
        log(logger, level, () -> {
            var args = new Object[1 + rest.length];
            args[0] = first;
            System.arraycopy(rest, 0, args, 1, rest.length);
            return String.format(format, args);
        });
    }
Context for FleetController and all instances 1:1 with the FleetController.

@author hakon
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/FleetControllerContext.java