`RoundRobinLoadBalancer` will raise `ArrayIndexOutOfBoundsException` when position positive overflow

[jizhuozhi]

Describe the bug
RoundRobinLoadBalancer is using an AtomicInteger to represent current position, when positive overflow, we are just using Math.abs to fix it, it will raise ArrayIndexOutOfBoundsException.

Sample
It's to hard to reproduce this issue in production environment, so I using jshell to reproduce it.

jshell> import java.util.concurrent.atomic.AtomicInteger
jshell> var instances = Arrays.asList("1", "2", "3", "4", "5")
jshell> var position = new AtomicInteger(Integer.MAX_VALUE)
jshell> var pos = Math.abs(position.incrementAndGet())
pos ==> -2147483648
jshell> var instance = instances.get(pos % instances.size())
|  java.lang.ArrayIndexOutOfBoundsException：Index -3 out of bounds for length 5
|        at Arrays$ArrayList.get (Arrays.java:4165)
|        at do_it$Aux (#5:1)
|        at (#5:1)

It as same as the source code

[jizhuozhi]

@OlgaMaciaszek Hello?

[guerlab]

This problem is caused by the overflow of int type. The maximum value of int type is 2147483647 and the minimum value is - 2147483648, math abs(-2147483648) => -2147483648

[jizhuozhi]

This problem is caused by the overflow of int type. The maximum value of int type is 2147483647 and the minimum value is - 2147483648, math abs(-2147483648) => -2147483648

Absolutely right. In the doc of Math.abs we could see

Note that if the argument is equal to the value of Integer.MIN_VALUE, the most negative representable int value, the result is that same value, which is negative. In contrast, the absExact(int) method throws an ArithmeticException for this value.

[OlgaMaciaszek]

Hello @jizhuozhi, thanks for reporting the issue. Will take a look this week.

[jizhuozhi]

@OlgaMaciaszek Thank you for your reply, I opened a PR to fix her, can I take some of your time to review it?

[OlgaMaciaszek]

Yes, @jizhuozhi - thank. Will review it.