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PASSEDcache / swap_thrashing
Varnish 7.5 Causing Swap Thrashing — System Unresponsive on Amazon Linux 2023
Varnish 7.5 is consuming excessive memory, pushing the system into heavy swap usage. All processes on the host are severely impacted.
Pattern
MEMORY_EXHAUSTION
Severity
CRITICAL
Confidence
72%
Remediation
Auto-Heal
Test Results
| Metric | Expected | Actual | Result |
|---|---|---|---|
| Pattern Recognition | MEMORY_EXHAUSTION | MEMORY_EXHAUSTION | |
| Severity Assessment | CRITICAL | CRITICAL | |
| Incident Correlation | N/A | None | |
| Cascade Escalation | N/A | No | |
| Remediation | — | Auto-Heal — Corax resolves autonomously |
Scenario Conditions
Amazon Linux 2023. Varnish 7.5 RSS at 3GB. Swap usage 100%. System load 10. IO wait 90%+. All services on host degraded.
Injected Error Messages (1)
Varnish 7.5 memory pressure critical on Amazon Linux 2023 — swap full, system unresponsive, varnishd consuming 3GB RAM, iowait 90%, all co-hosted services degraded, out of memory imminent
Neural Engine Root Cause Analysis
Memory exhaustion detected — the system has run out of available memory, triggering the OOM killer or forcing heavy swap usage. This causes severe performance degradation and can result in random process termination. Memory leaks in long-running applications are a common root cause, especially after deployments or configuration changes.
Remediation Plan
1. Check which process was OOM-killed using 'dmesg | grep -i oom' or journal logs.
2. Review memory usage by process with 'ps aux --sort=-%mem | head -20'.
3. Restart the affected service to reclaim leaked memory.
4. If a memory leak is suspected, enable heap profiling and analyze memory allocation patterns.
5. Consider increasing server memory or setting appropriate memory limits (cgroups/container limits).
Tested: 2026-04-02Monitors: 1 | Incidents: 1Test ID: cmnhnv70400dmlijgat6wsoe8