troubleshoot-apache-httpd

Troubleshoot Apache HTTPD

When to use this skill

• Worker exhaustion: All workers stuck (in W, R, D, or K states). New connections queue then drop. The most common "server down" symptom.
• Memory exhaustion: MaxRequestWorkers × per-child RSS > available RAM. System swaps, latency spikes, OOM kills cascade.
• Listen queue overflow: Workers occupied, backlog fills, SYN packets get RST. Server appears "up" (port open) but unreachable.
• Slow backend cascade: Proxied requests hold workers waiting for slow/dead backends. Workers fill up from the backend side, not from traffic overload.
• Log disk full / pipe stall: Workers finish requests but block in Logging state. Server appears alive but serves nothing.
• Graceful restart pile-up: Old-generation children linger during slow request completion. Multiple overlapping restarts multiply memory consumption.
• Any time the user reports a Apache HTTPD service behaving outside its expected envelope (elevated errors, latency, saturation, resource exhaustion, or unexpected restarts).
• An on-call engineer is paging on a Netdata alert tied to a Apache HTTPD instance and wants a structured triage path.

Key facts

• This skill wraps the Netdata operator playbook for Apache HTTPD. It does not replace the playbook; it routes a coding agent through MCP queries against the same signals the playbook relies on.
• Apache HTTPD is a process-based (or hybrid process+thread) HTTP server whose behavior is fundamentally shaped by its Multi-Processing Module (MPM). The MPM determines how incoming connections map to execution units. Knowing which MPM is active is the single most important prerequisite for interpreting any signal.
• The playbook decomposes Apache HTTPD health into 9 signal domains: Availability, Throughput, Latency, Errors, Saturation, Resource Utilization. Each domain maps to one rule file in this skill.
• Dominant failure archetypes the playbook calls out: Worker exhaustion; Memory exhaustion; Listen queue overflow; Slow backend cascade; Log disk full / pipe stall.
• Netdata observes the signals listed in the rule files via its native collectors, plus any OpenTelemetry-shipped metrics that your Apache HTTPD instrumentation adds. Both paths end at the same MCP query surface.
• Netdata's apache collector emits 20 context(s) under apache.*. The rule files enumerate which contexts surface which domain; the Verification section below names the load-bearing ones explicitly.