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Problem Symptoms

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

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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

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Detection Methods

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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"

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2. Monitoring Memory Metrics

Monitor memory usage with Prometheus metrics:
  • jvm_memory_used_bytes
  • jvm_memory_max_bytes
  • container_memory_usage_bytes

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3. Heap Dump Analysis

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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

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Solution Recommendations

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1. Optimizing JVM Heap Settings

Set JVM parameters in Pod deployment:
env:
  - name: JAVA_OPTS
    value: "-Xms2g -Xmx4g -XX:+UseG1GC -XX:MaxGCPauseMillis=200"
Recommendations:
  • Set heap size to about 75% of pod memory limit
  • Provide better memory management by using G1GC
  • Control GC pauses with MaxGCPauseMillis

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2. Increasing Memory Limits

Increase memory limits in Kubernetes deployment: 
resources:
  limits:
    memory: "4Gi"
  requests:
    memory: "2Gi"

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3. Optimizing Cache Configuration

Set cache TTL and size limits:
  • Optimize cache TTL values
  • Determine cache size limits
  • Clean unnecessary cache entries

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4. Optimizing Connection Pool Settings

Check connection pool settings:
  • Limit maximum connection count
  • Set connection timeout values
  • Regularly clean idle connections

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5. Thread Pool Management

Optimize thread pool settings:
  • Limit maximum thread count
  • Set thread timeout values
  • Ensure threads are properly cleaned

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6. Optimizing Large Message Processing

When processing large message bodies:
  • Use streaming
  • Determine message size limits
  • Avoid unnecessary data copying

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Preventive Measures

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1. Regular Monitoring

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

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2. Load Testing

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

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3. Code Review

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