Replace unbounded ConcurrentHashMap with bounded Caffeine cache in RateLimitingFilter#54
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…in RateLimitingFilter RateLimitingFilter stored per-client rate limit buckets in a ConcurrentHashMap that never evicted entries. Every unique client IP permanently allocated a Bucket object that was never removed, causing unbounded heap growth behind load balancers, CDNs, or under attack until OutOfMemoryError. Replace ConcurrentHashMap with a bounded Caffeine cache (default: 100,000 max entries, 5-minute expiry after last access). Caffeine is already a transitive dependency via Spring Boot; added as explicit dependency in runtime-starter pom.xml. Fixes: RateLimitingFilter unbounded memory leak
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Thanks for spotting this. A few minor comments. Can you also please add a test for bounded buckets and eviction?
| private final ConcurrentHashMap<String, Bucket> buckets = new ConcurrentHashMap<>(); | ||
| private static final long DEFAULT_MAX_BUCKETS = 100_000; | ||
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| private static final Duration DEFAULT_BUCKET_EXPIRY = Duration.ofMinutes(5); |
| private static final String UTF_8 = "UTF-8"; | ||
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| private final ConcurrentHashMap<String, Bucket> buckets = new ConcurrentHashMap<>(); | ||
| private static final long DEFAULT_MAX_BUCKETS = 100_000; |
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Should we have a lower default here? We assume to have buckets per Agentcore Runtime session.
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Summary
RateLimitingFilterstores per-client rate limit buckets in aConcurrentHashMapthat never evicts entries. Every unique client IP permanently allocates aBucketobject (~200-500 bytes) that is never removed. Behind a load balancer, CDN, or under attack, this causes unbounded heap growth untilOutOfMemoryError.Changes
spring-ai-agentcore-runtime-starter/pom.xml— Added explicitcaffeinedependency (already a transitive dependency via Spring Boot)RateLimitingFilter.java— ReplacedConcurrentHashMap<String, Bucket>with a boundedCaffeine Cache<String, Bucket>(default: 100,000 max entries, 5-minute expiry after last access)Before vs After
Backward Compatibility
ThrottleConfigurationor existing testsTesting
mvn test -pl spring-ai-agentcore-runtime-starter— 80 tests, 0 failuresmvn spring-javaformat:apply— cleanFixes #51