@Override
    public void handle(final ConsumerRecord<String, Bytes> record) {
        try (HistogramMetrics.Timer ignored = histogram.createTimer()) {
            SegmentObject segment = SegmentObject.parseFrom(record.value().get());
            if (log.isDebugEnabled()) {
                log.debug(
                    "Fetched a tracing segment[{}] from service instance[{}].",
                    segment.getTraceSegmentId(),
                    segment.getServiceInstance()
                );
            }
            segmentParserService.send(segment);
        } catch (InvalidProtocolBufferException e) {
            errorCounter.inc();
            log.error("handle record failed", e);
        }
    }
A handler deserializes the message of the trace segment data and pushes it to downstream.
oap-server/server-fetcher-plugin/kafka-fetcher-plugin/src/main/java/org/apache/skywalking/oap/server/analyzer/agent/kafka/provider/handler/TraceSegmentHandler.java