I am using the Spring Boot Open Telemetry Starter as mentioned here to trace calls between APIs.

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A sample code looks like this:

    @GetMapping("/trace/svc1")
    public ResponseEntity<String> service1(@RequestHeader Map<String, String> headers) {
        System.out.println(String.format("Service 1 Traceparent: "+headers.get("traceparent")));
        ResponseEntity<String> response
                = restTemplate.getForEntity("http://localhost:8081/trace/svc2", String.class);
        return new ResponseEntity<String>("Completed Service 1", HttpStatus.OK);
    }

    @GetMapping("/trace/svc2")
    public ResponseEntity<String> service2(@RequestHeader Map<String, String> headers) {
        System.out.println(String.format("Service 2 Traceparent: "+headers.get("traceparent")));
        ResponseEntity<String> response
                = restTemplate.getForEntity("http://localhost:8081/trace/svc3", String.class);
        return new ResponseEntity<String>("Completed Service 2", HttpStatus.OK);
    }

    @GetMapping("/trace/svc3")
    public ResponseEntity<String> service3(@RequestHeader Map<String, String> headers) {
        System.out.println(String.format("Service 3 Traceparent: "+headers.get("traceparent")));
        return new ResponseEntity<String>("Completed Service 3", HttpStatus.OK);
    }

This is printing the trace parent in Service 2 and Service 3 as expected: Service 2 Traceparent: 00-62995a5f4f5759db12af1f4efb20221e-5bdc0cd84b66ecdc-01 Service 3 Traceparent: 00-62995a5f4f5759db12af1f4efb20221e-cc1b7c935d711554-01

Now I plan to log the trace parent in our log aggregation solution and use the trace id to query the traces later. So I have the following questions:

1. Can the trace parent be printed in service 1 itself? which is the first place where the trace is generated. In some cases if service 1 is the only API in question, we do not get to see the trace id in the logs at all.

2. Can a custom trace id be injected in the trace parent? For example if a transaction id or a correlation id needs to be injected as a trace parent, can that be done?

For example, I have tried to create a span like this to ensure that mytraceid and myspanid are propagated, but I can see brand new trace id and span ids are generated,

        Context context =
                Context.current()
                        .with(
                                Span.wrap(
                                        SpanContext.create(
                                                Hex.encodeHexString("mytraceid".getBytes()),
                                                Hex.encodeHexString("myspanid".getBytes()),
                                                TraceFlags.getDefault(),
                                                TraceState.getDefault())));