@Override
    public Response process(Request request, Execution execution) {
        if (execution.trace().getTraceLevel()<4) return execution.process(request);

        StringBuilder b = new StringBuilder("{");
        for (Map.Entry<String,Object> property : request.properties().listProperties().entrySet())
            b.append(property.getKey()).append(": '").append(property.getValue()).append("',");
        b.setLength(b.length()-1); // remove last comma
        b.append("}");
        execution.trace().trace(b.toString(),4);
        return execution.process(request);
    }
A processor which adds the current content of the Request.properties() to
the trace before calling the next processor, if traceLevel is 4 or more.

@author bratseth
container-core/src/main/java/com/yahoo/processing/processors/RequestPropertyTracer.java