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

[Rohitash]

On Mon, 31 Mar 2025 12:40:27 GMT, Mikhail Yankelevich <myankelevich 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 3429:
> 
>> 3427:             int q = scan(p, n, L_DIGIT, H_DIGIT);
>> 3428:             if (q <= p) return q;
>> 3429: 
> 
> Nit: Copyright year

Updated.

> src/java.base/share/classes/java/net/URI.java line 3435:
> 
>> 3433: 
>> 3434:             // Calculate the number of significant digits (after leading zeros)
>> 3435:             int significantDigits = q - i;
> 
> Nit: Do you think it might be more clear if this is named something like `significantDigitsNum` or similar? No strong feelings, just confused me a little when I was reading this.

I can see it leading to confusion. I have changed it to `significantDigitsNum`

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PR Review Comment: https://git.openjdk.org/jdk/pull/24295#discussion_r2021131607
PR Review Comment: https://git.openjdk.org/jdk/pull/24295#discussion_r2021131283