fix: add maxSize and periodic eviction to TTLCache to prevent memory leak

[ionfwsrijan]

Bug: Unbounded TTLCache Causes Memory Leak in Long-Running Processes

Problem

The TTLCache class in lib/cache.ts stores entries in a plain Map with no maximum size limit and no proactive cleanup of expired entries. Expired entries are only removed on get() (lazy eviction). In long-running Node.js processes, expired entries accumulate indefinitely, causing unbounded memory growth and potential OOM crashes.

Changes

lib/cache.ts

• Added maxSize constructor parameter (default 500) to cap total entries per cache instance
• Added periodic evictExpired() sweep via setInterval with .unref() so it doesn't keep Node.js alive
• Added FIFO eviction on set() when cache is at capacity (after expired cleanup)
• Expired entries are now proactively reclaimed even for keys that are never accessed again

lib/github.ts

• Updated contributionsCache, profileCache, and reposCache instances to use maxSize=500

Behavior

• Each cache is now capped at 500 entries (configurable via constructor)
• Expired entries are swept every 60 seconds automatically
• When the cache is full and a new key is inserted, the oldest entry is evicted (FIFO)
• The cleanup timer uses .unref() so it doesn't prevent graceful process shutdown

Closes

#8269

[retenta-bot]

This PR addresses a critical issue with the TTLCache class by implementing memory management features such as a maximum size limit and periodic cleanup of expired entries. This aligns with previous decisions made to enhance memory management in the TTLCache, ensuring that we avoid unbounded memory growth in long-running processes. Thank you for your contribution!

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[ionfwsrijan]

@Aamod007 Please review this

[github-actions]

📦 Next.js Bundle Size Report (Gzipped Sizes)

✨ No significant bundle size changes detected.

📊 Summary of Totals

Category	PR Size	Base Size	Difference
Total JS	4052.50 KB	4052.50 KB	0 B
Total CSS	338.94 KB	338.94 KB	0 B

[Aamod007]

Adding periodic eviction and cleanup on clear() to TTLCache is the right fix for the memory leak. The private evictExpired method is clean and simple. CI is failing though — please investigate and push fixes.

Labels: level:beginner (1 file, targeted fix), quality:clean, type:bug, mentor:Aamod007

[ionfwsrijan]

@Aamod007 No CI check is failing wrong observation

[Aamod007]

Re-reviewing after noting the only CI failure is Vercel authorization (not code-related). All other checks (Format · Lint · Typecheck · Test, Production Build, CodeQL) pass. Approving — the Vercel deploy auth is a repo-level config issue, not a code problem.