Monitoring Stoplight with Vigilmon: API Documentation Uptime, Mock Server Health, Webhook Endpoints & SSL Alerts

Stoplight is the API design, documentation, and governance platform used by API-first organizations to design OpenAPI specifications, publish developer portals, enforce API style guides with Spectral, and run Prism mock servers for contract-based development. When the Stoplight-published API documentation portal goes down, external developers lose access to your API reference and integration guides. When your Prism mock server is unreachable, frontend developers lose the contract stub they depend on to build against your API before the real backend is finished. When a governance webhook stops receiving events, API style violations accumulate silently. Vigilmon gives you external visibility into the Stoplight-adjacent infrastructure your team depends on: documentation portal uptime, Prism mock server health, governance webhook endpoints, and SSL certificate validity.

What You'll Build

• An HTTP monitor on your Stoplight-published API documentation portal
• An HTTP monitor on your Prism mock server to catch contract stub failures
• A webhook endpoint monitor to verify your Spectral/governance notification receiver is reachable
• SSL certificate monitoring for your API documentation domain
• Alerting that distinguishes documentation outages from mock server failures

Prerequisites

• A Stoplight-published documentation portal (Stoplight Platform, Stoplight Studio, or self-hosted Elements)
• Stoplight Prism mock server running (self-hosted or in CI/CD)
• A governance webhook receiver for Spectral lint events (optional but common in enterprise setups)
• A free account at vigilmon.online

Step 1: Understand the Stoplight Ecosystem and Failure Points

Stoplight is a design-time and documentation platform with several independently hosted components:

Documentation Portals (Stoplight Platform / Elements): Published from OpenAPI or Stoplight flavor Markdown files. Hosted on your-org.stoplight.io (SaaS) or self-hosted with Stoplight Elements as a static site. If your docs portal goes down, external API consumers and internal developers lose access to endpoint references, request/response examples, and authentication guides.

Prism Mock Server: A lightweight HTTP server that reads your OpenAPI spec and serves realistic mock responses based on example fields. Teams run Prism during development to build against a stable contract before the real API is implemented. If Prism crashes or the port closes, developers calling http://localhost:4010 receive ECONNREFUSED and lose their development workflow.

Spectral Governance Webhooks: Enterprise and CI/CD setups send Spectral lint results (API style violations) to a webhook receiver for routing to Slack, Jira, or custom dashboards. If the webhook receiver goes down, governance events are silently dropped.

Self-hosted Stoplight Elements: Organizations embedding Elements as a static React/Vue app on their own CDN can experience outages independent of Stoplight SaaS uptime.

Step 2: Monitor the API Documentation Portal

Your Stoplight-published portal is the front door for API consumers. Monitor it continuously:

# Stoplight SaaS portal
curl -I https://your-org.stoplight.io/docs/your-api/

# Self-hosted Elements portal
curl -I https://developers.example.com/api-reference/

# Check that the OpenAPI spec file is reachable
curl -I https://developers.example.com/openapi.yaml

1. Log in to Vigilmon → Add Monitor → HTTP.
2. URL: https://your-org.stoplight.io/docs/your-api/ (your documentation portal URL).
3. Check interval: 5 minutes.
4. Response timeout: 15 seconds.
5. Expected status: 200.
6. Keyword: a stable string in your docs page (e.g., your API name from the OpenAPI info.title field).
7. Label: Stoplight API docs portal.
8. Click Save.

For self-hosted portals, also add a monitor for the raw OpenAPI spec file — if the spec cannot be fetched, Elements will render an empty page even though the HTML shell returns 200:

1. Add Monitor → HTTP.
2. URL: https://developers.example.com/openapi.yaml.
3. Expected status: 200.
4. Keyword: openapi: or info: (present in all valid OpenAPI YAML files).
5. Label: OpenAPI spec file.
6. Click Save.

Step 3: Monitor the Prism Mock Server

Prism mock servers run on port 4010 by default and expose the same paths as your OpenAPI spec:

# Start Prism (for reference — you would typically have this running already)
prism mock openapi.yaml --port 4010

# Test that Prism is serving mock responses
curl http://prism.example.com:4010/api/v1/users
# Returns: [{"id":"abc123","name":"Jane Doe"}] (from OpenAPI examples)

# Test a specific endpoint
curl -I http://prism.example.com:4010/health

For Prism servers accessible over the network (team dev environments, CI/CD containers):

1. Add Monitor → HTTP.
2. URL: http://prism.example.com:4010/ (replace with a real route from your API spec, not the root — Prism returns 404 on paths not in your spec).
3. Check interval: 2 minutes.
4. Response timeout: 10 seconds.
5. Expected status: 200 (or 404 if using root — pick a real spec path).
6. Label: Prism mock server.
7. Click Save.

Choosing the right Prism monitor path: Monitor a lightweight endpoint that exists in your OpenAPI spec and has an example response defined — for example, a GET /status or GET /version endpoint. Avoid paths that require request body validation unless you configure Vigilmon's request body option.

For Prism running in CI/CD: If Prism only runs during CI pipelines and not continuously, skip this step and instead monitor the CI artifact storage where your built OpenAPI spec is published (Step 4 covers webhooks for this pattern).

Step 4: Monitor Your Spectral Governance Webhook Receiver

If your organization uses Spectral for API style enforcement and routes lint events to a webhook receiver:

# Check that the governance webhook receiver is reachable
curl https://governance.example.com/api/spectral/events
# Returns: {"status":"listening","processedToday":47}

# Verify the receiver returns a valid response to a HEAD request
curl -I https://governance.example.com/api/spectral/events

1. Add Monitor → HTTP.
2. URL: https://governance.example.com/api/spectral/events.
3. Check interval: 5 minutes.
4. Expected status: 200.
5. Keyword: listening or status.
6. Label: Spectral governance webhook receiver.
7. Click Save.

If you use Stoplight's built-in governance notifications (routed to Slack via Stoplight Platform): you cannot directly monitor the delivery path, but you can monitor the Slack channel for expected notification frequency using a separate observability tool. For the Prism/Spectral self-hosted setup, the webhook receiver monitor above is the right approach.

Step 5: Monitor SSL Certificates

Your API documentation portal and any self-hosted Prism endpoints must maintain valid SSL certificates. An expired certificate causes browsers to block the docs page with a security warning — a critical failure for external API consumers:

# Check documentation portal certificate
openssl s_client -connect developers.example.com:443 2>/dev/null | openssl x509 -noout -dates

# Check governance webhook receiver certificate
openssl s_client -connect governance.example.com:443 2>/dev/null | openssl x509 -noout -dates

For the documentation portal:

1. Add Monitor → SSL Certificate.
2. Domain: developers.example.com.
3. Alert when expiry is within: 30 days.
4. Alert again: 14 days, 7 days, 3 days, 1 day.
5. Click Save.

Repeat for the governance webhook domain if it is separate.

Stoplight SaaS SSL: For portals hosted on your-org.stoplight.io, SSL is managed by Stoplight and you do not need to monitor it. Monitor only domains that your team controls the TLS certificate for.

Step 6: Configure Alerting for API Platform Scenarios

In Vigilmon under Settings → Notifications, configure your alert channels:

| Monitor | Trigger | Action | |---|---|---| | Docs portal | Non-200 or keyword missing | Check Stoplight Platform status; verify CDN deployment; check self-hosted Elements server | | OpenAPI spec file | Non-200 or keyword missing | Check spec file upload pipeline; verify storage bucket/CDN config; re-push spec from CLI | | Prism mock server | Non-200 or connection refused | Restart Prism process; check openapi.yaml for validation errors that prevent Prism from starting | | Spectral webhook | Non-200 or timeout | Webhook receiver is down; Spectral lint events are being dropped; governance reporting is broken | | SSL certificate | < 30 days to expiry | Renew certificate; check Certbot cron or ACM auto-renewal |

Developer impact escalation: An API docs outage impacts external consumers and partner integrations directly. Configure a Vigilmon alert channel that reaches your developer relations or API team immediately — not just on-call engineering — when the documentation portal goes down during business hours.

Common Stoplight Failure Modes and What Vigilmon Catches

| Scenario | Vigilmon monitor | |---|---| | Stoplight Platform SaaS outage | Docs portal monitor returns non-200 | | Self-hosted Elements CDN misconfiguration | Docs portal 404 or keyword missing | | OpenAPI spec file deleted from storage | Spec file monitor 404; docs portal renders empty | | Prism process OOM killed | Prism monitor connection refused | | Prism fails to start due to invalid OpenAPI spec | Prism monitor 500 or connection refused | | Spectral webhook receiver pod restarted | Webhook monitor 503 during restart window | | SSL certificate expired on docs domain | SSL monitor fires 30 days before; browser blocks docs | | CDN purge removes spec file | Spec file 404; docs portal loses API reference | | Prism mock returns wrong status code (spec mismatch) | Prism monitor catches unexpected status | | Self-hosted Elements build broken after upgrade | Docs portal keyword missing (UI blank) |

Stoplight makes API design and documentation a first-class engineering practice — but the portals, mock servers, and governance hooks that your teams depend on are infrastructure that can fail independently of Stoplight's SaaS platform. Vigilmon monitors the external availability of your documentation portals, Prism mock servers, and governance webhooks continuously, so your developers always know within 5 minutes when the API design platform they rely on has gone dark.

Start monitoring your Stoplight API platform in under 5 minutes — register free at vigilmon.online.