public void trace(Object message, int traceLevel) {
            if (this.traceLevel >= traceLevel) {
                traceNode.add(new TraceNode(message, timestamp(traceLevel, forceTimestamps)));
            }
        }
Adds a trace message to this trace, if this trace has at most the given trace level
container-core/src/main/java/com/yahoo/processing/execution/Execution.java