Fix hot file replication by handling null criteria in PSU match

[greenc-FNAL]

Fixed hot file replication by correctly handling null protocol and network criteria in PoolSelectionUnitV2.match. Introduced cached wildcard units to satisfy link constraints for unspecified dimensions. Added regression test.

---

PR created automatically by Jules for task 5324923451457271853 started by @greenc-FNAL

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.

[Copilot]

Pull request overview

This PR addresses a regression in hot file replication by updating PoolSelectionUnitV2.match to treat null protocol and network criteria as wildcards, so links with protocol/net requirements can still be matched. It also adds a regression test to verify READ matching succeeds when both protocol and net are unspecified.

Changes:

• Add cached “wildcard” protocol/net units when match criteria are null, allowing link constraints to be satisfied for unspecified dimensions.
• Invalidate the wildcard caches on PSU write-lock acquisition (setup changes).
• Add a regression test covering READ matching with null protocol and net.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
modules/dcache/src/main/java/diskCacheV111/poolManager/PoolSelectionUnitV2.java	Adds wildcard unit logic and cached wildcard fields to allow null protocol/net to match link constraints.
modules/dcache/src/test/java/diskCacheV111/poolManager/PoolSelectionUnitV2Test.java	Adds regression coverage for READ matching with null protocol and net criteria.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Same thread-safety concern as with _wildcardProtocolUnit: _wildcardNetUnit is initialized and assigned while holding the read-lock, which allows concurrent writers. Consider switching to a volatile field with CAS-style initialization (or performing initialization under the write-lock) to avoid races and ensure safe publication.

Suggested change

	Unit wildcard = _wildcardNetUnit;
	if (wildcard == null) {
	wildcard = wildcardUnit(NET);
	_wildcardNetUnit = wildcard;
	}
	Unit wildcard = wildcardUnit(NET);

[Copilot]

With this change, match now supports netUnitName == null / protocolUnitName == null by adding wildcard units. If _cachingEnabeled is ever true, the earlier cache-key generation path still attempts to derive netUnitGroup via _netHandler.match(netUnitName) and assumes a non-null result; for null net (or missing default net units) that can throw before cacheKey is assigned. Please adjust the caching logic to handle null/unspecified net+protocol explicitly (use stable placeholders and avoid dereferencing a null net match) so enabling caching does not reintroduce failures for the new null-criteria behavior.

[Copilot]

_wildcardProtocolUnit is lazily initialized and written while the read-lock is held. Because multiple threads can hold the read-lock concurrently, this introduces unsynchronized writes to shared state and can lead to redundant initialization and unclear memory-visibility guarantees. Consider making the field volatile and using a compare-and-set style initialization (or initializing under the write-lock) to keep the cache thread-safe and avoid writes under the read path.

Suggested change

	Unit wildcard = _wildcardProtocolUnit;
	if (wildcard == null) {
	wildcard = wildcardUnit(PROTOCOL);
	_wildcardProtocolUnit = wildcard;
	}
	Unit wildcard = wildcardUnit(PROTOCOL);