# Restart individual containers in Amazon ECS tasks with container restart policies
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You can enable a restart policy for each essential and non-essential container defined in your task definition, to overcome transient failures faster and maintain task availability. When you enable a restart policy for a container, Amazon ECS can restart the container if it exits, without needing to replace the task.

Restart policies are not enabled for containers by default. When you enable a restart policy for a container, you can specify exit codes that the container will not be restarted on. These can be exit codes that indicate success, like exit code `0`, that don't require a restart. You can also specify how long a container must run succesfully before a restart can be attempted. For more information about these parameters, see [Restart policy](task_definition_parameters.md#container_definition_restart_policy). For an example task definition that specifies these values, see [Specifying a container restart policy in an Amazon ECS task definition](container-restart-policy-example.md).

You can use the Amazon ECS task metadata endpoint or CloudWatch Container Insights to monitor the number of times a container has restarted. For more information about the task metadata endpoint, see [Amazon ECS task metadata endpoint version 4](task-metadata-endpoint-v4.md) and [Amazon ECS task metadata endpoint version 4 for tasks on Fargate](task-metadata-endpoint-v4-fargate.md). For more information about Container Insights metrics for Amazon ECS, see [Amazon ECS Container Insights metrics](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/Container-Insights-metrics-ECS.html) in the *Amazon CloudWatch User Guide*.

Container restart policies are supported by tasks hosted on Fargate, Amazon EC2 instances, and external instances using Amazon ECS Anywhere.

## Considerations
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Consider the following before enabling a restart policy for your container:
+ Restart policies aren't supported for Windows containers on Fargate.
+ For tasks hosted on Amazon EC2 instances, this feature requires version `1.86.0` or later of the container agent. However, we recommend using the latest container agent version. For information about how to check your agent version and update to the latest version, see [Updating the Amazon ECS container agent](ecs-agent-update.md).
+ If you're using EC2 with the `bridge` network mode, the `FLUENT_HOST` environment variable in your application container can become inaccurate after a restart of the FireLens log router container (the container with the `firelensConfiguration` object in its container definition). This is because `FLUENT_HOST` is a dynamic IP address and can change after a restart. Logging directly from the application container to the `FLUENT_HOST` IP address can start failing after the address changes. For more information about `FLUENT_HOST`, see [Configuring Amazon ECS logs for high throughput](firelens-docker-buffer-limit.md).
+ The Amazon ECS agent handles the container restart policies. If for some unexpected reason the Amazon ECS agent fails or is no longer running, the container won't be restarted.
+  The restart attempt period defined in your policy determines the period of time (in seconds) that the container must run for before Amazon ECS restarts a container.