public static LogMessage of(
            Instant time, String host, long processId, long threadId,
            String service, String component, Level level, String payload) {
        return new LogMessage(time, host, processId, threadId, service, component, level, payload);
    }
Private constructor.  Log messages should never be instantiated
directly; only as the result of a static factory method.
vespalog/src/main/java/com/yahoo/log/LogMessage.java