doubt about default value of avgUsedTokens

[mjaow]

Issue Description

the default traffic limiter has code

    private int avgUsedTokens(Node node) {
        if (node == null) {
            return -1;
        }
        return grade == RuleConstant.FLOW_GRADE_THREAD ? node.curThreadNum() : (int)node.passQps();
    }

I'm not sure why return -1 as default value.Seems Zero is more meaningful

Type: bug report or feature request

bug report

Describe what happened (or what feature you want)

it return -1 as default value

Describe what you expected to happen

expected return 0 as default value

How to reproduce it (as minimally and precisely as possible)

Tell us your environment

Anything else we need to know?