tutorial

Monitoring Wasmer WebAssembly Runtime with Vigilmon: Health Checks, API Endpoints, Registry & SSL Certificate Alerts

How to monitor Wasmer WebAssembly runtime infrastructure with Vigilmon — health endpoint checks, Wasmer Registry availability, TCP port monitoring, and SSL certificate alerts.

How to Monitor Wasmer WebAssembly Runtime Infrastructure with Vigilmon

Wasmer is the leading WebAssembly runtime for running Wasm modules server-side, on the edge, and embedded in applications — supporting multiple Wasm standards (WASIX, WASI, Emscripten) with a universal package registry and language-native bindings for Python, Go, Ruby, Java, and more. Production Wasmer deployments serve serverless Wasm functions, package registry traffic, and embedded runtime APIs handling critical application workloads.

But Wasmer's built-in process health and runtime introspection only reports what the server process sees internally. External monitoring with Vigilmon tells you what your clients, package consumers, and downstream applications actually experience — which often diverges precisely when it matters most.

Why Wasmer needs external monitoring

Wasmer exposes health and API endpoints, but internal checks miss the failure modes that affect real users:

  • Wasm module JIT compilation OOM — large Wasm modules exhaust compilation memory; the runtime process is alive but module load requests silently fail
  • Registry API returns 200 but wrong package version — a bad cache layer serves stale package manifests while the health endpoint stays green
  • TLS certificate expires on the runtime API endpoint — Wasm clients using HTTPS fail immediately while internal process checks pass
  • Sandboxed execution thread pool is exhausted — new Wasm invocations queue indefinitely; health checks pass because the HTTP layer is still responding
  • Package registry S3 backend becomes unreachable — module download requests fail while the registry API frontend continues accepting requests
  • Network namespace misconfiguration in Docker — the Wasmer process binds correctly but is unreachable from outside the container

External monitoring from a neutral vantage point catches what internal health endpoints miss.

What you'll need

  • A running Wasmer server instance (self-hosted registry, edge runtime, or API server)
  • HTTP endpoint accessible from outside the server
  • A free Vigilmon account (sign up takes 30 seconds)

Step 1: Understand Wasmer's HTTP endpoints

Wasmer's server mode and self-hosted registry expose HTTP endpoints you can monitor externally. For a self-hosted Wasmer registry:

# Health check — is the registry API responding?
curl -s -o /dev/null -w "%{http_code}" https://registry.yourdomain.com/health

# Registry GraphQL API
curl -s -o /dev/null -w "%{http_code}" https://registry.yourdomain.com/graphql

# Package listing (verifies package storage backend connectivity)
curl -s https://registry.yourdomain.com/api/v1/packages | head -c 100

For Wasmer's edge runtime serving Wasm modules:

# Runtime liveness — is the edge runtime accepting requests?
curl -s -o /dev/null -w "%{http_code}" https://runtime.yourdomain.com/health

# Module invocation test
curl -s -X POST https://runtime.yourdomain.com/run \
  -H "Content-Type: application/json" \
  -d '{"module": "your-namespace/your-module@1.0.0", "input": {}}'

Starting a self-hosted Wasmer registry with Docker

docker run -d \
  --name wasmer-registry \
  -p 8080:8080 \
  -p 8443:8443 \
  -e DATABASE_URL=postgresql://user:pass@db:5432/wasmer \
  -e S3_BUCKET=wasmer-packages \
  -e S3_REGION=us-east-1 \
  wasmerio/wasmer-registry:latest

Step 2: Create an HTTP monitor in Vigilmon

Log in to Vigilmon and create your primary monitor:

  1. Click Monitors → New Monitor
  2. Set the Type to HTTP
  3. Enter your endpoint: https://registry.yourdomain.com/health
  4. Set Check interval to 1 minute
  5. Set Expected status to 200
  6. Set Alert after to 1 failure — package registry outages immediately block Wasm deployments
  7. Click Save

Vigilmon begins checking from multiple geographic regions every minute.

What this monitor catches

| Failure | Vigilmon response | |---------|-----------------| | Registry process crashed | Connection refused → alert | | Database backend unavailable | HTTP 500 or 503 → alert | | S3 storage backend unreachable | HTTP 500 → alert | | Reverse proxy misconfigured | HTTP 502/504 → alert | | Out-of-memory crash | Connection refused → alert | | DNS resolution failed | DNS error → alert | | TLS certificate expired | SSL error → alert |

Step 3: Monitor the GraphQL API endpoint

Wasmer's registry API is GraphQL-based. Monitor that the API layer is actually responding to queries, not just that the process is alive:

  1. Click Monitors → New Monitor
  2. Set the Type to HTTP
  3. Enter: https://registry.yourdomain.com/graphql
  4. Set Method to POST
  5. Set Request body: 
    {"query": "{ __typename }"}
  6. Set Expected status: 200
  7. Set Keyword to find: __typename
  8. Set Check interval: 2 minutes
  9. Click Save

This verifies that the GraphQL layer is processing queries, not just accepting TCP connections.

Step 4: Add a TCP monitor for the runtime port

If you're running Wasmer's edge runtime or a custom API server, add a TCP port monitor:

  1. Click Monitors → New Monitor
  2. Set the Type to TCP
  3. Enter: registry.yourdomain.com:8080
  4. Set Check interval: 1 minute
  5. Click Save

This detects port binding failures independently of the HTTP layer — useful for distinguishing "HTTP handler crashed" from "process not listening at all."

Step 5: Monitor package download availability

The most critical user-facing function of a Wasmer registry is package downloads. Test it directly:

  1. Click Monitors → New Monitor
  2. Set the Type to HTTP
  3. Enter: https://registry.yourdomain.com/api/v1/packages
  4. Set Expected status: 200
  5. Set Check interval: 5 minutes
  6. Click Save

Alternatively, test a specific package manifest URL:

# Replace with a stable test package in your registry
curl -s "https://registry.yourdomain.com/api/v1/packages/namespace/package-name"

Monitor this URL to verify end-to-end package resolution works — HTTP 200 on /health doesn't prove storage backend connectivity.

Step 6: Configure alert channels

Navigate to Alerts → New Alert Channel:

Slack integration:

# In Slack, create an incoming webhook for #platform or #wasm-runtime-alerts
# In Vigilmon, paste the webhook URL under Alerts → Slack

PagerDuty / Opsgenie: Use Vigilmon's generic webhook output:

POST https://events.pagerduty.com/v2/enqueue
{
  "routing_key": "YOUR_INTEGRATION_KEY",
  "event_action": "trigger",
  "payload": {
    "summary": "Wasmer Registry is DOWN",
    "severity": "critical",
    "source": "vigilmon"
  }
}

Email: Configure alerts to your platform engineering on-call rotation.

Example Vigilmon webhook payload:

{
  "monitor_name": "Wasmer Registry /health",
  "status": "down",
  "url": "https://registry.yourdomain.com/health",
  "started_at": "2026-03-10T14:52:00Z",
  "duration_seconds": 120
}

Step 7: Correlate Vigilmon alerts with Wasmer diagnostics

When an alert fires, run this triage sequence:

# 1. Is the Wasmer registry process running?
docker ps | grep wasmer-registry
# or for systemd:
systemctl status wasmer-registry

# 2. Check application logs for errors
docker logs wasmer-registry --tail 100 | grep -E "ERROR|FAIL|panic|exception" -i

# 3. Test the health endpoint directly (bypass proxy)
curl -v http://localhost:8080/health

# 4. Verify database connectivity
docker exec wasmer-registry wasmer-registry db-check

# 5. Check S3 / package storage backend
curl -s https://s3.amazonaws.com/your-wasmer-bucket/ | head -c 200

# 6. Test GraphQL directly
curl -s -X POST http://localhost:8080/graphql \
  -H "Content-Type: application/json" \
  -d '{"query": "{ __typename }"}' | python3 -m json.tool

Triage decision tree:

  • Process not running → check host OOM (dmesg | grep killed), restart registry, investigate memory usage
  • Process running, /health returns 200, GraphQL returns 500 → database or storage backend issue; check database logs
  • Both return 200 from localhost, but Vigilmon shows down → reverse proxy or network path issue; check nginx/Traefik logs
  • Package downloads 404 but health is green → S3 credentials expired or storage bucket misconfigured

Step 8: Docker Compose deployment monitoring

A typical self-hosted Wasmer registry deployment:

version: "3.8"

services:
  wasmer-registry:
    image: wasmerio/wasmer-registry:latest
    restart: unless-stopped
    ports:
      - "8080:8080"
    environment:
      DATABASE_URL: postgresql://wasmer:secret@postgres:5432/wasmer
      S3_BUCKET: wasmer-packages
      S3_ENDPOINT: https://s3.amazonaws.com
      S3_ACCESS_KEY_ID: ${AWS_ACCESS_KEY_ID}
      S3_SECRET_ACCESS_KEY: ${AWS_SECRET_ACCESS_KEY}
      JWT_SECRET: ${JWT_SECRET}
    depends_on:
      - postgres
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:8080/health"]
      interval: 30s
      timeout: 10s
      retries: 3

  postgres:
    image: postgres:16-alpine
    restart: unless-stopped
    environment:
      POSTGRES_DB: wasmer
      POSTGRES_USER: wasmer
      POSTGRES_PASSWORD: secret
    volumes:
      - postgres-data:/var/lib/postgresql/data

volumes:
  postgres-data:

Monitor https://registry.yourdomain.com/health in Vigilmon — Docker's internal healthcheck tells you what the container scheduler sees, Vigilmon tells you what your users see.

Step 9: Create a status page for your Wasm platform

  1. Go to Status Pages → New Status Page
  2. Name it: "Wasmer Package Registry"
  3. Add your monitors grouped by component:
    • Registry API: health check, GraphQL endpoint
    • Package Downloads: package listing API, specific package manifests
    • Runtime: edge runtime health (if applicable)
  4. Publish and share with:
    • Development teams using your private registry
    • CI/CD pipelines that pull Wasm packages
    • Teams tracking package registry SLAs

Putting it all together

| Monitor | Type | What it catches | |---------|------|----------------| | https://registry.yourdomain.com/health | HTTP | Registry API availability, process crashes | | https://registry.yourdomain.com/graphql | HTTP keyword | GraphQL layer and database connectivity | | registry.yourdomain.com:8080 | TCP | Port-level availability, process binding | | https://registry.yourdomain.com/api/v1/packages | HTTP | Package storage backend connectivity |

What's next

  • Prometheus metrics — expose custom metrics from your Wasmer registry and scrape with Prometheus; use Vigilmon for external availability signal that internal metrics can't provide
  • SSL certificate monitoring — Vigilmon tracks TLS cert expiry for your registry endpoints automatically
  • Heartbeat monitors — use Vigilmon heartbeats to monitor CI/CD pipelines that build and publish Wasm packages on a schedule

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