Detect Garbage Collection Storms Before 14-Second Pauses Cause Timeout Cascades
Healthcare SaaS company scenario: HL7 FHIR API gateway (Spring Boot) processes 120K API requests/day from 200 hospital integrations (patient data queries, appointment scheduling, lab results). API SLA: 95th percentile response time <500ms. Spring Boot microservice configured with 8 GB heap (-Xmx8g), G1 garbage collector. Normal GC behavior: Young Gen collections every 5 seconds (20-40ms pause), Old Gen Full GC every 48 hours (200-400ms pause).
Before Nodinite: No GC monitoring (Spring Boot Actuator metrics tracked response times, not GC internals). Tuesday 2 PM: API response times degrade suddenly (P95: 500ms → 8,500ms). Hospital integrations start timing out (5-second timeouts), retry storm overwhelms API (120K requests/day → 340K requests/day with retries). Cascade failure: 12 downstream microservices unable to reach API gateway, patient appointment scheduling fails, lab result queries return errors. Outage duration: 22 minutes until dev team rolls back recent deployment (suspected cause).
Root cause investigation (post-mortem): Heap dump analysis reveals memory leak in patient cache logic (caching 500K patient records, no eviction policy, consuming 7.2 GB). Full GC triggered every 90 seconds (attempting to free space, unable to due to retained references), Full GC pause time: 14 seconds (entire JVM paused, no request processing). First Full GC at 2:00 PM → API unresponsive 14 seconds → upstream timeouts → retry storm → second Full GC 90 seconds later → 14-second pause again → cascade failure. Impact: 22-minute outage, 1,247 failed patient appointments, 340 lab result queries failed, $250K estimated revenue loss + patient care disruption.
With Nodinite JMX Monitoring: Configure GC monitoring for all Spring Boot microservices:
- Young Gen GC monitoring: Warning >100 collections/minute (abnormal frequency), Warning >100ms average pause time
- Old Gen Full GC monitoring: Error >5 Full GC events/hour (indicates heap exhaustion), Error >2000ms Full GC pause time
- GC Time monitoring: Warning >10% GC time per minute (JVM spending too much time collecting garbage, not processing requests)
- Heap trend correlation: Alert if Old Gen usage >90% AND Full GC frequency increasing (classic heap exhaustion pattern)
Tuesday 1:47 PM scenario with Nodinite: Patient cache memory leak present (deployment Monday 5 PM). Tuesday 1:47 PM: Nodinite Warning alert fires "FHIR API Gateway: Old Gen heap usage 92% (7.36 GB of 8 GB), Full GC frequency 3 events/hour (unusual, baseline 1 event/48 hours)". Operations team investigates, reviews heap trend chart (steady Old Gen climb from 45% Monday 5 PM → 92% Tuesday 1:47 PM, projecting heap exhaustion within 30 minutes). Team rolls back deployment 1:52 PM (5-minute investigation, 3-minute rollback). Full GC never triggered, zero API timeouts, zero patient appointment failures.
Additional value: Heap trend analysis identified memory leak pattern before critical threshold. Operations team generated heap dump during Warning state (92% heap, not crashed), sent to dev team for offline analysis. Dev team identified patient cache issue, implemented cache eviction policy (LRU eviction, max 100K patient records), redeployed Wednesday 10 AM with fix. Heap stabilized at 55% (4.4 GB of 8 GB), no memory leak, no further incidents.
Business value:
- $250K revenue loss prevented (avoided 22-minute outage, 1,247 patient appointments processed successfully)
- Patient care continuity maintained (zero lab result query failures, zero appointment scheduling disruptions)
- 14-second Full GC pauses prevented (proactive detection before heap exhaustion triggered Full GC)
- Root cause identified proactively (heap dump captured during Warning state, not crash post-mortem, faster remediation)