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Custom check - Get started

How to create a Custom Check?

Go to ITCare → Resources → URLs → Actions → Add Custom Check

Both Custom Check and External Custom Check share the same interface. For the complete field reference, see Custom Check - Features.

Real-world scenario: WordPress

WordPress is the most widely used open source CMS in the world. The following scenarios illustrate how to configure monitoring checks on a WordPress application.

Scenario 1 — Verify the homepage is available and displays the correct content

Context: your WordPress site is in production. You want to be alerted if the homepage stops responding, or if it responds but no longer displays the expected content (database disconnected, broken theme, etc.).

WordPress renders homepage content from the database. If the database goes down, WordPress may return HTTP 200 (page loaded) but display an error such as "Error establishing a database connection" instead of normal content. Checking the HTTP status code alone is not sufficient — you must also verify the content.

Custom Check configuration

Field
Value
Purpose

URL

https://mysite.example.com/

Page to monitor

Expected content

Welcome to my site

✅ If present → OK

Critical content

Error establishing a database connection

❌ If present → CRITICAL

Critical code

500:599

❌ Server error → CRITICAL

External Custom Check configuration

Field
Value
Purpose

URL

https://mysite.example.com/

Page to monitor

Detection method

Pass if

✅ If in range and content → OK

Status on content

Welcome to my site

Text to find in response body

Status on code

200:299

Acceptable HTTP status range

Results comparison

Situation
Custom Check
External Custom Check

Site OK, correct content

✅ OK

✅ OK from Marseille and Paris

Database down (HTTP 200 but wrong content)

❌ CRITICAL

❌ CRITICAL from Marseille and Paris

Server down (HTTP 500)

❌ CRITICAL

❌ CRITICAL from Marseille and Paris

Site OK internally but unreachable from Paris

✅ OK

❌ CRITICAL from Paris only → network issue


Scenario 2 — Verify that two-factor authentication (2FA) is working

Context: your WordPress uses a 2FA plugin (e.g. WP 2FA). Login is a two-step process: credentials → then OTP code. You want to verify that the authentication endpoint responds correctly and that the login flow is not broken.

Rather than testing with a real OTP code, the check verifies that the login page properly presents the 2FA challenge — confirming the mechanism is active and functional.

💡 This pattern — verifying that a security mechanism correctly presents its challenge — is a standard monitoring technique. The absence of the OTP form is the alert signal.

Custom Check configuration

Field
Value
Purpose

URL

https://mysite.example.com/wp-login.php

Auth endpoint to monitor

Expected content

Authenticator Code

✅ 2FA form is displayed → OK

Critical content

500:599

❌ Server error → CRITICAL

Critical code

200:200

⚠️ Unexpected HTTP 200 → 2FA might be bypassed

External Custom Check configuration

Field
Value
Purpose

URL

https://mysite.example.com/wp-login.php

Auth endpoint to monitor

Detection method

Pass if

✅ If in range and content → OK

Status on content

Authenticator Code

Expected text in response

Status on code

!= 5xx

Server success range

Results comparison

Situation
Custom Check
External Custom Check

Login OK, 2FA challenge displayed

✅ OK

✅ OK from Marseille and Paris

2FA plugin disabled (login without OTP)

⚠️ WARNING

❌ CRITICAL (pattern absent)

Auth server down (HTTP 500)

❌ CRITICAL

❌ CRITICAL from Marseille and Paris

Auth OK internally, unreachable externally

✅ OK

❌ CRITICAL → network exposure issue


Summary — When to use which?

Need
Custom Check
External Custom Check

Monitor that a page responds

Verify response content

Detect internal application failure

Simulate real user access from the internet

Detect network/CDN/DNS issues

Get per-location results

Included at no extra cost

✅ (with Load Balancer)

❌ Paid option

💡 Recommendation: use both. Custom Check monitors application health continuously at no extra cost. External Custom Check ensures your real users can actually reach your application from the internet.

To subscribe to External Custom Check, contact your SDM.

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