docs

API Reference

Top-Level Exports

• createHealthMonitor(targets, options)
• createHealthCheck(target)
• createHealthy(options)
• healthLogging(options)

Importing

Every function described above is a top-level export. You can import any of them like this:

import { createHealthMonitor } from '@meltwater/mlabs-health'

---

createHealthMonitor(targets, options)

Creates a new health monitor.

Arguments

1. targets (object): Health checks to use.
2. options (object):
   • delay (number): Milliseconds before health emits first event. Default: 0.
   • timeout (number): Milliseconds before health check times out with error. Default: 5000 (5 seconds).
   • ttl (number): Seconds to cache health check result. Default: 60 (1 minute).
   • cache (object|null): Default cache instance. Default: an in memory cache with the above ttl.
   • strategy: Health strategy for health. Default: the all-healthy strategy.
   • createHealthCheck: Function to wrap all targets with. Default: the createHealthCheck function provided in this module.

Returns

(object): The health monitor.

---

createHealthCheck(target)

Creates a health check for use by a health monitor.

1. target (any): Thing to convert to health check.
2. options (object):
   • timeout (number): Milliseconds before health check times out with error. Default: 60000 (1 minute).
   • ttl (number): Seconds to cache health check result. Default: 60 (1 minute).
   • cache (object|null): Default cache instance. Default: an in memory cache with the above ttl.

Returns

(function): An asynchronous health check function.

---

createHealthy(options)

Creates a function which maps health status objects to a boolean healthy status.

Arguments

1. options (object):
   • minAvailability (number): Minimum availability before unhealthy. Default: 0.9.
   • minReliability (number): Minimum reliability before unhealthy. Default: 0.9.
   • maxDowntime (number): Maximum downtime (in milliseconds) before unhealthy. Default: 5 minutes.

Returns

(function): Function that maps status to boolean.

---

healthLogging(options)

Logs all events in the status stream for all health checks in the health monitor.

Arguments

1. options (object):
   • healthMonitor (object): The health monitor to use.
   • log (object): A Bunyan compatible logger. Default: a new logger.

Returns

(undefined)