@Override
    public int getCallStackFrameId() {
        final SpanEvent spanEvent = callStack.peek();
        if (spanEvent == null) {
            return ROOT_STACKID;
        } else {
            return spanEvent.getStackId();
        }
    }
Get current TraceID. If it was not set this will return null.

@return
agent-module/profiler/src/main/java/com/navercorp/pinpoint/profiler/context/DefaultTrace.java