eureka-1134: fix for StringIndexOutOfBoundsException

[JosephWitthuhnTR]

It looks like a -1 was used when it should be comparing against 3. Based on line 353, beginIndex will always be larger than -1, but it will be 3 if there is no "ec2-" in the URL.

This is for issue #1134 which I reported earlier this morning.

[qiangdavidliu]

@jawitthuhn thanks for the PR, this does look like a bug. Given what the logic is trying express, it would make this code block much easier to read if we apply the below changes (and also add a test case):

for (String cname : ec2Urls) {
            int beginIndex = cname.indexOf("ec2-");
            if (-1 < beginIndex) {  // contains "ec2-"
                int endIndex = cname.indexOf(regionPhrase + ".compute");
                String eipStr = cname.substring(beginIndex + 4, endIndex);
                String eip = eipStr.replaceAll("\\-", ".");
                returnedUrls.add(eip);
            } else {  // do nothing
              // Handle case where there are no cnames containing "ec2-"
              // Reasons include:
              //  Systems without public addresses - purely attached to corp lan via AWS Direct Connect             
              //  Use of EC2 network adapters that are attached to an instance after startup
            }
}

Would you mind updating the PR? Thanks!

[JosephWitthuhnTR]

@qiangdavidliu - I believe I've made the requested changes. Could you check?