[Memory] Unbounded static database cache in FoundationDB

[s2x]

Context / Problem

FoundationDB keeps a static cache of Database objects that is never evicted except by an explicit close():

src/FoundationDB.php:16-17 — private static array $databases = [];
src/FoundationDB.php:98-115 — openWithConnectionString() caches by 'conn:' . $connectionString

An application that opens many distinct cluster files or connection strings (multi-tenant, dynamic connection strings) holds a growing number of native FDBDatabase handles for the entire process lifetime.

Affected files / locations

• src/FoundationDB.php:16-17,59-116

Proposed approach

Document that cached databases live for the process lifetime and require close(), and bound the growth: either do not cache the connection-string variant, or apply a small bounded cache with explicit eviction. Ensure evicted databases are properly destroyed.

Acceptance Criteria

• Documentation updated/added (cache lifetime and ownership)
• Unit test(s) added covering cache insertion/eviction/close removal
• Functional test(s) added: opening many distinct connection strings does not retain unbounded handles
• Changelog entry added
• Post-implementation comment posted on this issue describing what was changed

Severity

Medium