External service health checks

Introduction

As of 10.10.0, Preside comes with an external service healthchecking system that allows your code to:

• Periodically check the up status of external services (e.g. every 30 seconds)
• Call isUp( "myservice" ) or isDown( "myservice" ) to check the result of the last status check, without calling the external service directly

Registering a healthcheck

In Config.cfc

First, you must register your healthcheck in your application or extension's Config.cfc$configure() method. The settings.healthcheckServices struct is used to configure healtcheck services. The struct keys indicate the service ID, e.g. for an "ElasticSearch" healthcheck:

settings.healthcheckServices.ElasticSearch = {
	interval = CreateTimeSpan( 0, 0, 0, 10 ) // default is 30 seconds
};

Possible settings for your healthcheck services are:

• interval: must be a timespan default is CreateTimeSpan( 0, 0, 0, 30 )

Create corresponding handler

For each configured service, there must be a corresponding handler with a check() method at: /handlers/healtchcheck/serviceid.cfc. For example, to create an ElasticSearch healthcheck, we'd create /handlers/healthcheck/ElasticSearch.cfc:

component {
	property name="elasticSearchService" inject="elasticSearchService";

	private boolean function check() {
		return elasticSearchService.ping();
	}
}

If the check action returns true the service is deemed to be up. Any other return value, or error thrown, will lead to the system marking the service as being down.

Checking service health in your code

Handlers and views

In your handlers and views, you can use the isUp( serviceId ) and isDown( serviceId ) helpers:

if ( isUp( "elasticsearch" ) ) {
	var results = elasticSearchService.search( ... );
} else {
	var results = searchFallBackService.search( ... );
}

Services

Services can use the $isUp( serviceId ) and $isDown( serviceId ) methods from the Preside Super Class. See Using the super class.

if ( $isDown( "elasticsearch" ) ) {
	var results = searchFallBackService.search( ... );
} else {
	var results = elasticSearchService.search( ... );
}