Fix/empty hostname cluster slots

[NeoPhi]

Summary

AWS ElastiCache (plaintext, cluster mode, Redis 7.2.4) returns hostname: "" (empty string) in the CLUSTER SLOTS metadata for every node. The parser was wrapping this in Some(""), which caused unwrap_or_else at line 252 to use the empty string instead of falling back to the IP address from the primary identifier.

This resulted in connection addresses like :6379 (no host), which fail immediately. Because refresh_slots_inner() silently drops connection errors, createClient resolves successfully but the client has zero usable connections. Every subsequent command fails with AllConnectionsUnavailable.

Issue link

This Pull Request is linked to issue (URL): #5367

Features / Behaviour Changes

The fix filters out empty hostname strings at parse time, so they are treated the same as absent hostnames, and the IP from the primary identifier is used instead.

Implementation

Checks for a non-empty hostname.

Limitations

Testing

Unit test added.

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one issue.
• Commit message has a detailed description of what changed and why.
• Tests are added or updated.
• CHANGELOG.md and documentation files are updated.
• Linters have been run (make *-lint targets) and Prettier has been run (make prettier-fix).
• Destination branch is correct - main or release
• Create merge commit if merging release branch into main, squash otherwise.

[avifenesh]

@NeoPhi please sign off on the commit to make DCO happy.

[Copilot]

Pull request overview

Fixes a cluster-topology parsing edge case in the shared Rust core (glide-core) where AWS ElastiCache returns hostname: "" in CLUSTER SLOTS metadata, which previously produced invalid connection addresses (e.g., :6379) and could lead to AllConnectionsUnavailable.

Changes:

• Treat empty-string hostname values in CLUSTER SLOTS metadata as absent during parsing (so IP-based fallback works).
• Add a unit test covering the empty-hostname metadata case (for both metadata formats).
• Document the fix in CHANGELOG.md.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
glide-core/redis-rs/redis/src/cluster_topology.rs	Filters out empty hostname metadata and adds a unit test to ensure fallback to IP-based addresses.
CHANGELOG.md	Adds a CORE “Fixes” entry describing the ElastiCache empty-hostname issue and resolution.

[Copilot]

String::from_utf8_lossy(value_bytes).into_owned() allocates even when the hostname is empty. You can avoid the allocation by keeping the Cow<str> and only calling into_owned() after the non-empty check (e.g., check is_empty() on the Cow first).

Suggested change

	let h = String::from_utf8_lossy(value_bytes).into_owned();
	if !h.is_empty() {
	metadata_hostname = Some(h);
	let h_cow = String::from_utf8_lossy(value_bytes);
	if !h_cow.is_empty() {
	metadata_hostname = Some(h_cow.into_owned());

[avifenesh]

Fair comment

[avifenesh]

@NeoPhi Other than the DCO and copilot small efficiency comment, LGTM.
Please update and ill merge.
Thanks!

[avifenesh]

@NeoPhi DCO still failing

[NeoPhi]

Sorry about that. Think I got it this time.

[avifenesh]

@NeoPhi merged, thanks!