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Memory Leaks and OOM (Out of Memory) Errors

Problem Symptoms​

uyarı

Memory leaks and OOM errors usually manifest themselves with the following symptoms:

  • Pods continuously restarting
  • OutOfMemoryError log records
  • Slowly increasing memory usage
  • Decrease in system performance
  • Pods transitioning to OOMKilled state in Kubernetes

Problem Causes​

Memory leaks and OOM errors can usually be caused by the following factors:

  • Insufficient Heap Settings: JVM heap size may be insufficient
  • Memory Leaks: Unused objects not being cleaned by garbage collection
  • Large Data Processing: Processing large message bodies
  • Cache Sizes: Cache growing unlimited
  • Connection Pool Issues: Connections not being closed
  • Thread Pool Issues: Threads not being properly cleaned

Detection Methods​

1. Log Analysis​

Search for OOM errors in log files:

kubectl logs <pod-name> | grep -i "OutOfMemoryError"
kubectl logs <pod-name> | grep -i "java.lang.OutOfMemoryError"

2. Monitoring Memory Metrics​

Monitor memory usage with Prometheus metrics:

  • jvm_memory_used_bytes
  • jvm_memory_max_bytes
  • container_memory_usage_bytes

3. Heap Dump Analysis​

Take Heap Dump

Detect memory leaks by taking heap dump:

# Taking heap dump
kubectl exec <pod-name> -- jmap -dump:format=b,file=/tmp/heapdump.hprof <pid>

# Copying heap dump from pod
kubectl cp <namespace>/<pod-name>:/tmp/heapdump.hprof ./heapdump.hprof

Solution Recommendations​

1. Optimizing JVM Heap Settings​

bilgi

Set JVM parameters in Pod deployment:

env:
  - name: JAVA_OPTS
    value: "-Xms2g -Xmx4g -XX:+UseG1GC -XX:MaxGCPauseMillis=200"
not

Recommendations:

  • Apinizer's automatic memory profile selects the appropriate GC and heap percentage based on container memory (Serial GC at ≤768 MB, G1GC at 769-1536 MB, ZGC at >1536 MB)
  • For containers with more than 1536 MB, ZGC is auto-selected with 70% heap — providing sub-millisecond GC pauses
  • If you prefer manual configuration, use G1GC with MaxGCPauseMillis for predictable pause times
  • See JVM Garbage Collector Tuning for detailed GC configuration options

2. Increasing Memory Limits​

Increase memory limits in Kubernetes deployment:

resources:
  limits:
    memory: "4Gi"
  requests:
    memory: "2Gi"

3. Optimizing Cache Configuration​

Set cache TTL and size limits:

  • Optimize cache TTL values
  • Determine cache size limits
  • Clean unnecessary cache entries

4. Optimizing Connection Pool Settings​

Check connection pool settings:

  • Limit maximum connection count
  • Set connection timeout values
  • Regularly clean idle connections

5. Thread Pool Management​

Optimize thread pool settings:

  • Limit maximum thread count
  • Set thread timeout values
  • Ensure threads are properly cleaned

6. Optimizing Large Message Processing​

When processing large message bodies:

  • Use streaming
  • Determine message size limits
  • Avoid unnecessary data copying

Preventive Measures​

1. Regular Monitoring​

  • Regularly monitor memory usage
  • Get early warning by setting up alerts
  • Detect problems in advance by performing trend analysis

2. Load Testing​

  • Perform regular load tests
  • Detect memory leaks early
  • Perform capacity planning

3. Code Review​

  • Review code that may cause memory leaks
  • Check resource management
  • Follow best practices
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