RFR: 8353013: java.net.URI.create(String) may have low performance to scan the host/domain name from URI string when the hostname starts with number

[Johannes Graham]

On Fri, 28 Mar 2025 15:19:46 GMT, Rohitash <duke at openjdk.org> wrote:

> `scanByte` throws `NumberFormatException` for URIs that start with numbers, e.g., https://11111111.x.y/
> The current flow is `parseIPv4Address` → `scanIPv4Address` → `scanByte`. `parseIPv4Address` uses `NumberFormatException` for control flow, so it captures the exception, ignores it, and returns -1. This has been reported by AWS customer to cause low performance. Details: [JDK-8353013](https://bugs.openjdk.org/browse/JDK-8353013) & https://github.com/aws/aws-sdk-java-v2/issues/5933
> 
> This PR avoids NumberFormatException by skipping calls to `Integer.parseInt` if the number of digits in the octet is > 3.
> 
> I benchmarked on local machine for potential regressions.
> https://gist.github.com/rk-kmr/cb1a3d59225c17b180a29cc125ebf887
> 
> 
> Benchmark                                     Mode     Cnt        Score       Error   Units
> URIBenchMark.newImplWithNormalUrl            thrpt      10        0.004 ±     0.001  ops/ns
> URIBenchMark.newImplWithNumberlUrl           thrpt      10        0.004 ±     0.001  ops/ns
> URIBenchMark.oldImplWithNormalUrl            thrpt      10        0.004 ±     0.001  ops/ns
> URIBenchMark.oldImplWithNumUrl               thrpt      10        0.001 ±     0.001  ops/ns
> URIBenchMark.newImplWithNormalUrl             avgt      10      236.762 ±     8.700   ns/op
> URIBenchMark.newImplWithNumberlUrl            avgt      10      264.017 ±     7.274   ns/op
> URIBenchMark.oldImplWithNormalUrl             avgt      10      233.853 ±     6.539   ns/op
> URIBenchMark.oldImplWithNumUrl                avgt      10     1183.572 ±    29.242   ns/op
> 
> 
> I ran following tests.
> 
> make test-tier1
> make test-tier2
> make test TEST=jdk/java/net

src/java.base/share/classes/java/net/URI.java line 3438:

> 3436: 
> 3437:             // If no significant digits (all zeros), the value is 0
> 3438:             if (significantDigitsNum == 0)  return q;

Can avoid parseInt for short strings
Suggestion:

            if (significantDigitsNum < 3)  return q; // definitely < 255

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/24295#discussion_r2027378782