RFR: 8372526: Add support for ZLIB TLS Certificate Compression [v17]

[Xue-Lei Andrew Fan]

On Thu, 5 Feb 2026 02:13:38 GMT, Artur Barashev <abarashev at openjdk.org> wrote:

>> src/java.base/share/classes/sun/security/ssl/SSLContextImpl.java line 236:
>> 
>>> 234:         return compCertCache;
>>> 235:     }
>>> 236: 
>> 
>> Thank you for the update, @artur-oracle!   As sslContext instance are normally run in multiple threads context, could cache operation synchronization be a concern?
>
> I considered synchronization but I don't think it's really needed, the situation is the same as with cache being static actually:
> 
> - `SoftMemoryCache` being used is already synchronized internally for `get` and `put` operations.
> -  Race condition is possible in between `get` and `put` operations in `CompressedCertProducer`, but the worst that can happen is that we compress and insert the same certMsg into cache twice. Not something worth locking the whole cache while we compress IMO.
> - I chose `SoftMemoryCache` over `ConcurrentHashMap` because of LRU and soft reference mechanisms. Otherwise the former provides finer per-bucket synchronization and atomic `computeIfAbsent` call.

Make sense to me. Thank you @artur-oracle!

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PR Review Comment: https://git.openjdk.org/jdk/pull/28682#discussion_r2766962306