static ObjectNode startTimeAndDuration(ObjectMapper objectMapper, long durationNanos,
                                             long startTimeMicros) {
        final ObjectNode objectNode = objectMapper.createObjectNode();
        objectNode.put("durationNanos", durationNanos);
        objectNode.put("startTimeMicros", startTimeMicros);
        return objectNode;
    }
A formatter that converts a {@link RequestOnlyLog} or {@link RequestLog} into a JSON format message.
core/src/main/java/com/linecorp/armeria/common/logging/JsonLogFormatter.java