Class HealthCheck

java.lang.Object
software.amazon.awssdk.services.ecs.model.HealthCheck
All Implemented Interfaces:
Serializable, SdkPojo, ToCopyableBuilder<HealthCheck.Builder,HealthCheck>
@Generated("software.amazon.awssdk:codegen") public final class HealthCheck extends Object implements SdkPojo, Serializable, ToCopyableBuilder<HealthCheck.Builder,HealthCheck>

An object representing a container health check. Health check parameters that are specified in a container definition override any Docker health checks that exist in the container image (such as those specified in a parent image or from the image's Dockerfile). This configuration maps to the HEALTHCHECK parameter of docker run.

The Amazon ECS container agent only monitors and reports on the health checks specified in the task definition. Amazon ECS does not monitor Docker health checks that are embedded in a container image and not specified in the container definition. Health check parameters that are specified in a container definition override any Docker health checks that exist in the container image.

You can view the health status of both individual containers and a task with the DescribeTasks API operation or when viewing the task details in the console.

The health check is designed to make sure that your containers survive agent restarts, upgrades, or temporary unavailability.

Amazon ECS performs health checks on containers with the default that launched the container instance or the task.

The following describes the possible healthStatus values for a container:

  • HEALTHY-The container health check has passed successfully.

  • UNHEALTHY-The container health check has failed.

  • UNKNOWN-The container health check is being evaluated, there's no container health check defined, or Amazon ECS doesn't have the health status of the container.

The following describes the possible healthStatus values based on the container health checker status of essential containers in the task with the following priority order (high to low):

  • UNHEALTHY-One or more essential containers have failed their health check.

  • UNKNOWN-Any essential container running within the task is in an UNKNOWN state and no other essential containers have an UNHEALTHY state.

  • HEALTHY-All essential containers within the task have passed their health checks.

Consider the following task health example with 2 containers.

  • If Container1 is UNHEALTHY and Container2 is UNKNOWN, the task health is UNHEALTHY.

  • If Container1 is UNHEALTHY and Container2 is HEALTHY, the task health is UNHEALTHY.

  • If Container1 is HEALTHY and Container2 is UNKNOWN, the task health is UNKNOWN .

  • If Container1 is HEALTHY and Container2 is HEALTHY, the task health is HEALTHY .

Consider the following task health example with 3 containers.

  • If Container1 is UNHEALTHY and Container2 is UNKNOWN, and Container3 is UNKNOWN, the task health is UNHEALTHY.

  • If Container1 is UNHEALTHY and Container2 is UNKNOWN, and Container3 is HEALTHY, the task health is UNHEALTHY.

  • If Container1 is UNHEALTHY and Container2 is HEALTHY, and Container3 is HEALTHY, the task health is UNHEALTHY.

  • If Container1 is HEALTHY and Container2 is UNKNOWN, and Container3 is HEALTHY, the task health is UNKNOWN.

  • If Container1 is HEALTHY and Container2 is UNKNOWN, and Container3 is UNKNOWN, the task health is UNKNOWN.

  • If Container1 is HEALTHY and Container2 is HEALTHY, and Container3 is HEALTHY, the task health is HEALTHY.

If a task is run manually, and not as part of a service, the task will continue its lifecycle regardless of its health status. For tasks that are part of a service, if the task reports as unhealthy then the task will be stopped and the service scheduler will replace it.

When a container health check fails for a task that is part of a service, the following process occurs:

  1. The task is marked as UNHEALTHY.

  2. The unhealthy task will be stopped, and during the stopping process, it will go through the following states:

    • DEACTIVATING - In this state, Amazon ECS performs additional steps before stopping the task. For example, for tasks that are part of services configured to use Elastic Load Balancing target groups, target groups will be deregistered in this state.

    • STOPPING - The task is in the process of being stopped.

    • DEPROVISIONING - Resources associated with the task are being cleaned up.

    • STOPPED - The task has been completely stopped.

  3. After the old task stops, a new task will be launched to ensure service operation, and the new task will go through the following lifecycle:

    • PROVISIONING - Resources required for the task are being provisioned.

    • PENDING - The task is waiting to be placed on a container instance.

    • ACTIVATING - In this state, Amazon ECS pulls container images, creates containers, configures task networking, registers load balancer target groups, and configures service discovery status.

    • RUNNING - The task is running and performing its work.

For more detailed information about task lifecycle states, see Task lifecycle in the Amazon Elastic Container Service Developer Guide.

The following are notes about container health check support:

  • If the Amazon ECS container agent becomes disconnected from the Amazon ECS service, this won't cause a container to transition to an UNHEALTHY status. This is by design, to ensure that containers remain running during agent restarts or temporary unavailability. The health check status is the "last heard from" response from the Amazon ECS agent, so if the container was considered HEALTHY prior to the disconnect, that status will remain until the agent reconnects and another health check occurs. There are no assumptions made about the status of the container health checks.

  • Container health checks require version 1.17.0 or greater of the Amazon ECS container agent. For more information, see Updating the Amazon ECS container agent.

  • Container health checks are supported for Fargate tasks if you're using platform version 1.1.0 or greater. For more information, see Fargate platform versions.

  • Container health checks aren't supported for tasks that are part of a service that's configured to use a Classic Load Balancer.

For an example of how to specify a task definition with multiple containers where container dependency is specified, see Container dependency in the Amazon Elastic Container Service Developer Guide.

See Also:

  • Method Details

    • hasCommand

      public final boolean hasCommand()
      For responses, this returns true if the service returned a value for the Command property. This DOES NOT check that the value is non-empty (for which, you should check the isEmpty() method on the property). This is useful because the SDK will never return a null collection or map, but you may need to differentiate between the service returning nothing (or null) and the service returning an empty collection or map. For requests, this returns true if a value for the property was specified in the request builder, and false if a value was not specified.

    • command

      public final List<String> command()

      A string array representing the command that the container runs to determine if it is healthy. The string array must start with CMD to run the command arguments directly, or CMD-SHELL to run the command with the container's default shell.

      When you use the Amazon Web Services Management Console JSON panel, the Command Line Interface, or the APIs, enclose the list of commands in double quotes and brackets.

      [ "CMD-SHELL", "curl -f http://localhost/ || exit 1" ]

      You don't include the double quotes and brackets when you use the Amazon Web Services Management Console.

      CMD-SHELL, curl -f http://localhost/ || exit 1

      An exit code of 0 indicates success, and non-zero exit code indicates failure. For more information, see HealthCheck in the docker container create command.

      Attempts to modify the collection returned by this method will result in an UnsupportedOperationException.

      This method will never return null. If you would like to know whether the service returned this field (so that you can differentiate between null and empty), you can use the hasCommand() method.

      Returns:
      A string array representing the command that the container runs to determine if it is healthy. The string array must start with CMD to run the command arguments directly, or CMD-SHELL to run the command with the container's default shell.

      When you use the Amazon Web Services Management Console JSON panel, the Command Line Interface, or the APIs, enclose the list of commands in double quotes and brackets.

      [ "CMD-SHELL", "curl -f http://localhost/ || exit 1" ]

      You don't include the double quotes and brackets when you use the Amazon Web Services Management Console.

      CMD-SHELL, curl -f http://localhost/ || exit 1

      An exit code of 0 indicates success, and non-zero exit code indicates failure. For more information, see HealthCheck in the docker container create command.

    • interval

      public final Integer interval()

      The time period in seconds between each health check execution. You may specify between 5 and 300 seconds. The default value is 30 seconds. This value applies only when you specify a command.

      Returns:
      The time period in seconds between each health check execution. You may specify between 5 and 300 seconds. The default value is 30 seconds. This value applies only when you specify a command .

    • timeout

      public final Integer timeout()

      The time period in seconds to wait for a health check to succeed before it is considered a failure. You may specify between 2 and 60 seconds. The default value is 5. This value applies only when you specify a command.

      Returns:
      The time period in seconds to wait for a health check to succeed before it is considered a failure. You may specify between 2 and 60 seconds. The default value is 5. This value applies only when you specify a command.

    • retries

      public final Integer retries()

      The number of times to retry a failed health check before the container is considered unhealthy. You may specify between 1 and 10 retries. The default value is 3. This value applies only when you specify a command .

      Returns:
      The number of times to retry a failed health check before the container is considered unhealthy. You may specify between 1 and 10 retries. The default value is 3. This value applies only when you specify a command.

    • startPeriod

      public final Integer startPeriod()

      The optional grace period to provide containers time to bootstrap before failed health checks count towards the maximum number of retries. You can specify between 0 and 300 seconds. By default, the startPeriod is off. This value applies only when you specify a command.

      If a health check succeeds within the startPeriod, then the container is considered healthy and any subsequent failures count toward the maximum number of retries.

      Returns:
      The optional grace period to provide containers time to bootstrap before failed health checks count towards the maximum number of retries. You can specify between 0 and 300 seconds. By default, the startPeriod is off. This value applies only when you specify a command.

      If a health check succeeds within the startPeriod, then the container is considered healthy and any subsequent failures count toward the maximum number of retries.

    • toBuilder

      public HealthCheck.Builder toBuilder()
      Description copied from interface: ToCopyableBuilder
      Take this object and create a builder that contains all of the current property values of this object.
      Specified by:
      toBuilder in interface ToCopyableBuilder<HealthCheck.Builder,HealthCheck>
      Returns:
      a builder for type T

    • builder

      public static HealthCheck.Builder builder()

    • serializableBuilderClass

      public static Class<? extends HealthCheck.Builder> serializableBuilderClass()

    • hashCode

      public final int hashCode()
      Overrides:
      hashCode in class Object

    • equals

      public final boolean equals(Object obj)
      Overrides:
      equals in class Object

    • equalsBySdkFields

      public final boolean equalsBySdkFields(Object obj)
      Description copied from interface: SdkPojo
      Indicates whether some other object is "equal to" this one by SDK fields. An SDK field is a modeled, non-inherited field in an SdkPojo class, and is generated based on a service model.

      If an SdkPojo class does not have any inherited fields, equalsBySdkFields and equals are essentially the same.

      Specified by:
      equalsBySdkFields in interface SdkPojo
      Parameters:
      obj - the object to be compared with
      Returns:
      true if the other object equals to this object by sdk fields, false otherwise.

    • toString

      public final String toString()
      Returns a string representation of this object. This is useful for testing and debugging. Sensitive data will be redacted from this string using a placeholder value.
      Overrides:
      toString in class Object

    • getValueForField

      public final <T> Optional<T> getValueForField(String fieldName, Class<T> clazz)

    • sdkFields

      public final List<SdkField<?>> sdkFields()
      Specified by:
      sdkFields in interface SdkPojo
      Returns:
      List of SdkField in this POJO. May be empty list but should never be null.

    • sdkFieldNameToField

      public final Map<String,SdkField<?>> sdkFieldNameToField()
      Specified by:
      sdkFieldNameToField in interface SdkPojo
      Returns:
      The mapping between the field name and its corresponding field.