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# AWS::ServiceDiscovery::Service HealthCheckCustomConfig
<a name="aws-properties-servicediscovery-service-healthcheckcustomconfig"></a>

A complex type that contains information about an optional custom health check. A custom health check, which requires that you use a third-party health checker to evaluate the health of your resources, is useful in the following circumstances:
+ You can't use a health check that's defined by `HealthCheckConfig` because the resource isn't available over the internet. For example, you can use a custom health check when the instance is in an Amazon VPC. (To check the health of resources in a VPC, the health checker must also be in the VPC.)
+ You want to use a third-party health checker regardless of where your resources are located.

**Important**  
If you specify a health check configuration, you can specify either `HealthCheckCustomConfig` or `HealthCheckConfig` but not both.

To change the status of a custom health check, submit an `UpdateInstanceCustomHealthStatus` request. Amazon Cloud Map doesn't monitor the status of the resource, it just keeps a record of the status specified in the most recent `UpdateInstanceCustomHealthStatus` request.

Here's how custom health checks work:

1. You create a service.

1. You register an instance.

1. You configure a third-party health checker to monitor the resource that's associated with the new instance. 
**Note**  
Amazon Cloud Map doesn't check the health of the resource directly. 

1. The third-party health-checker determines that the resource is unhealthy and notifies your application.

1. Your application submits an `UpdateInstanceCustomHealthStatus` request.

1. Amazon Cloud Map waits for 30 seconds.

1. If another `UpdateInstanceCustomHealthStatus` request doesn't arrive during that time to change the status back to healthy, Amazon Cloud Map stops routing traffic to the resource.

## Syntax
<a name="aws-properties-servicediscovery-service-healthcheckcustomconfig-syntax"></a>

To declare this entity in your Amazon CloudFormation template, use the following syntax:

### JSON
<a name="aws-properties-servicediscovery-service-healthcheckcustomconfig-syntax.json"></a>

```
{
  "[FailureThreshold](#cfn-servicediscovery-service-healthcheckcustomconfig-failurethreshold)" : Number
}
```

### YAML
<a name="aws-properties-servicediscovery-service-healthcheckcustomconfig-syntax.yaml"></a>

```
  [FailureThreshold](#cfn-servicediscovery-service-healthcheckcustomconfig-failurethreshold): Number
```

## Properties
<a name="aws-properties-servicediscovery-service-healthcheckcustomconfig-properties"></a>

`FailureThreshold`  <a name="cfn-servicediscovery-service-healthcheckcustomconfig-failurethreshold"></a>
This parameter is no longer supported and is always set to 1. Amazon Cloud Map waits for approximately 30 seconds after receiving an `UpdateInstanceCustomHealthStatus` request before changing the status of the service instance.
The number of 30-second intervals that you want Amazon Cloud Map to wait after receiving an `UpdateInstanceCustomHealthStatus` request before it changes the health status of a service instance.  
Sending a second or subsequent `UpdateInstanceCustomHealthStatus` request with the same value before 30 seconds has passed doesn't accelerate the change. Amazon Cloud Map still waits `30` seconds after the first request to make the change.  
*Required*: No  
*Type*: Number  
*Minimum*: `1`  
*Maximum*: `10`  
*Update requires*: [Replacement](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-replacement)

## See also
<a name="aws-properties-servicediscovery-service-healthcheckcustomconfig--seealso"></a>
+ [Return values](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/aws-resource-servicediscovery-service.html#aws-resource-servicediscovery-service-return-values) in the topic [AWS::ServiceDiscovery::Service](https://docs.amazonaws.cn/AWSCloudFormation/latest/UserGuide/aws-resource-servicediscovery-service.html)
+ [HealthCheckCustomConfig](https://docs.amazonaws.cn/cloud-map/latest/api/API_HealthCheckCustomConfig.html) in the * Amazon Cloud Map API Reference *