Checkly Constructs

checkly constructs

The Checkly constructs system provides type-safe abstractions for monitoring resources.

Core concepts

Construct hierarchy

Construct (base)
├── Check
│   ├── RuntimeCheck
│   │   ├── ApiCheck
│   │   ├── BrowserCheck
│   │   └── MultiStepCheck
│   └── PlaywrightCheck
├── Monitor
│   ├── HeartbeatMonitor
│   ├── TcpMonitor
│   ├── DnsMonitor
│   └── UrlMonitor
├── CheckGroup
└── AlertChannel

Logical IDs

Every construct needs a unique logical ID:

new ApiCheck('api-status-check', {  // <- logical ID
  name: 'API Status Check',  // <- display name
})

Rules:

• Must be unique within resource type
• Pattern: [A-Za-z0-9_-/#.]+
• Use descriptive IDs: 'homepage-check' not 'check-1'

Construct lifecycle

1. Construction: Instance created and registered
2. Validation: Configuration checked for errors
3. Bundling: Code and dependencies packaged
4. Synthesis: Converted to API payload
5. Deployment: Created/updated in Checkly

Session and Project

The Session singleton manages global state:

// Internal - you don't normally interact with this
Session.current().addConstruct(check)

The Project aggregates all constructs:

// Internal - happens automatically
project.addResource('check', check)

Configuration inheritance

// checkly.config.ts - global
checks: {
  frequency: 10,
  locations: ['us-east-1'],
}

// CheckGroup - group-level
const group = new CheckGroup('api', {
  frequency: 5,  // Overrides global
})

// Check - check-level
new ApiCheck('critical-api', {
  group: group,
  frequency: 1,  // Overrides group
})

Related Skills

• See checkly-checks for practical check creation
• See checkly-groups for organization