How to get http headers from event listener spi code

Getting advice
1

I’m writing an event listener spi that records some custom content of httprequest header, e.g. traceid, etc when some event occurred. Yet while referring to code in JBossLoggingEventListenerProvider as below, I found the value of http headers are always null when I did some operation whether in postman or in keycloak admin console page, e.g. calling token endpoint in postman or login/logout in admin page.
Is there configuration that control the http headers from KeycloakContext? Anyone would help this? thanks in advance.

-----sample snippet in JBossLoggingEventListenerProvider------

private void setKeycloakContext(StringBuilder sb) {
        KeycloakContext context = session.getContext();
        UriInfo uriInfo = context.getUri();
        **HttpHeaders headers = context.getRequestHeaders();**
        if (uriInfo != null) {
            sb.append(", requestUri=");
            sb.append(uriInfo.getRequestUri().toString());
        }

        if (headers != null) {
            sb.append(", cookies=[");
            boolean f = true;
            for (Map.Entry<String, Cookie> e : headers.getCookies().entrySet()) {
                if (f) {
                    f = false;
                } else {
                    sb.append(", ");
                }
                sb.append(e.getValue().toString());
            }
            sb.append("]");
        }

-------here is my code-----------

final KeycloakContext context = session.getContext();
        logger.info("CCC-----" + context);

        final HttpHeaders requestHeaders = context.getRequestHeaders();
        logger.info("AAA-----" + requestHeaders);


        String traceId = null;
        String callerContextId = null;

        if(requestHeaders != null){
            logger.info("000-----");
            final MultivaluedMap<String, String> reqHeader = requestHeaders.getRequestHeaders();
            logger.info("111-----" + reqHeader.toString());

            final List<String> reqList = requestHeaders.getRequestHeader(Constants.RequestHeader.TRACE_ID);
            logger.info("222-----"+reqList);

            traceId = requestHeaders.getHeaderString(Constants.RequestHeader.TRACE_ID);
            callerContextId = requestHeaders.getHeaderString(Constants.RequestHeader.CONTEXT_ID);
        }

        if (traceId==null || traceId.isEmpty()){
            traceId = generateRandomString(10);
            logger.warn("request header trace_id is empty. Generated random trace_id :" + traceId);
        }