Async (Metrics Health Checks 4.1.16 API)

```
@Retention(RUNTIME)
@Target(TYPE)
public @interface Async
```
An annotation for marking asynchronous health check execution.

Required Element Summary

Required Elements
Modifier and Type Required Element Description

long period
Period between executions.

Optional Element Summary

Optional Elements
Modifier and Type	Optional Element	Description
`long`	`healthyTtl`	How long a healthy result is considered valid before being ignored.
`long`	`initialDelay`	Initial delay of first execution.
`Async.InitialState`	`initialState`	Initial health state until first asynchronous execution completes.
`Async.ScheduleType`	`scheduleType`	Scheduling type of asynchronous executions.
`TimeUnit`	`unit`	Time unit of initial delay, period and healthyTtl.

- Element Detail
  - period
```
long period
```
    Period between executions.
    
    Returns:
    
    period
- - scheduleType
```
Async.ScheduleType scheduleType
```
    Scheduling type of asynchronous executions.
    
    Returns:
    
    schedule type
    
    Default:
    
    com.codahale.metrics.health.annotation.Async.ScheduleType.FIXED_RATE
- - initialDelay
```
long initialDelay
```
    Initial delay of first execution.
    
    Returns:
    
    initial delay
    
    Default:
    
    0L
- - unit
```
TimeUnit unit
```
    Time unit of initial delay, period and healthyTtl.
    
    Returns:
    
    time unit
    
    Default:
    
    java.util.concurrent.TimeUnit.SECONDS
- - initialState
```
Async.InitialState initialState
```
    Initial health state until first asynchronous execution completes.
    
    Returns:
    
    initial health state
    
    Default:
    
    com.codahale.metrics.health.annotation.Async.InitialState.HEALTHY
- - healthyTtl
```
long healthyTtl
```
    How long a healthy result is considered valid before being ignored. Handles cases where the asynchronous healthcheck did not run (for example thread starvation). Defaults to 2 * period
    
    Returns:
    
    healthy result time to live
    
    Default:
    
    -1L