Reliability in Azure Container Instances

Raksts
10/14/2024

This article describes reliability support in Azure Container Instances (ACI) and covers both intra-regional resiliency with availability zones and information on Disaster Recovery. For a more detailed overview of reliability in Azure, see Azure reliability.

Availability zone support

Azure availability zones are at least three physically separate groups of datacenters within each Azure region. Datacenters within each zone are equipped with independent power, cooling, and networking infrastructure. In the case of a local zone failure, availability zones are designed so that if the one zone is affected, regional services, capacity, and high availability are supported by the remaining two zones.

Failures can range from software and hardware failures to events such as earthquakes, floods, and fires. Tolerance to failures is achieved with redundancy and logical isolation of Azure services. For more detailed information on availability zones in Azure, see Regions and availability zones.

Azure availability zones-enabled services are designed to provide the right level of reliability and flexibility. They can be configured in two ways. They can be either zone redundant, with automatic replication across zones, or zonal, with instances pinned to a specific zone. You can also combine these approaches. For more information on zonal vs. zone-redundant architecture, see Recommendations for using availability zones and regions.

Azure Container Instances supports zonal container group deployments, meaning the instance is pinned to a specific, self-selected availability zone. The availability zone is specified at the container group level. Containers within a container group can't have unique availability zones. To change your container group's availability zone, you must delete the container group and create another container group with the new availability zone.

Prerequisites

Zonal container group deployments are supported in most regions where ACI is available for Linux and Windows Server 2019 container groups. For details, see Regions and resource availability.

If using Azure CLI, ensure version 2.30.0 or later is installed.
If using PowerShell, ensure version 2.1.1-preview or later is installed.
If using the Java SDK, ensure version 2.9.0 or later is installed.
Availability zone support is only available on ACI API version 09-01-2021 or later.

Important

Container groups with GPU resources don't support availability zones at this time.

Availability zone redeployment and migration

To change your container group's availability zone, you must delete the container group and create another container group with the new availability zone.

Create a resource with availability zone enabled

To create a Container Instance resource with availability zone enabled, you'll need to deploy a container group using an Azure Resource Manager (ARM) template.

Note

Examples in this article are formatted for the Bash shell. If you prefer another shell, adjust the line continuation characters accordingly.

To deploy a container with ARM:

Copy-paste the following JSON into a new file named azuredeploy.json. This example template deploys a container group with a single container into availability zone 1 in East US.

{
    "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
    "contentVersion": "1.0.0.0",
    "metadata": {
        "_generator": {
            "name": "bicep",
            "version": "0.4.1.14562",
            "templateHash": "12367894147709986470"
        }
    },
    "parameters": {
        "name": {
            "type": "string",
            "defaultValue": "acilinuxpublicipcontainergroup",
            "metadata": {
                "description": "Name for the container group"
            }
        },
        "image": {
            "type": "string",
            "defaultValue": "mcr.microsoft.com/azuredocs/aci-helloworld",
            "metadata": {
                "description": "Container image to deploy. Should be of the form repoName/imagename:tag for images stored in public Docker Hub, or a fully qualified URI for other registries. Images from private registries require additional registry credentials."
            }
        },
        "port": {
            "type": "int",
            "defaultValue": 80,
            "metadata": {
                "description": "Port to open on the container and the public IP address."
            }
        },
        "cpuCores": {
            "type": "int",
            "defaultValue": 1,
            "metadata": {
                "description": "The number of CPU cores to allocate to the container."
            }
        },
        "memoryInGb": {
            "type": "int",
            "defaultValue": 2,
            "metadata": {
                "description": "The amount of memory to allocate to the container in gigabytes."
            }
        },
        "restartPolicy": {
            "type": "string",
            "defaultValue": "Always",
            "allowedValues": [
                "Always",
                "Never",
                "OnFailure"
            ],
            "metadata": {
                "description": "The behavior of Azure runtime if container has stopped."
            }
        },
        "location": {
            "type": "string",
            "defaultValue": "eastus",
            "metadata": {
                "description": "Location for all resources."
            }
        }
    },
    "functions": [],
    "resources": [
        {
            "type": "Microsoft.ContainerInstance/containerGroups",
            "apiVersion": "2021-09-01",
            "zones": [
                "1"
            ],
            "name": "[parameters('name')]",
            "location": "[parameters('location')]",
            "properties": {
                "containers": [
                    {
                        "name": "[parameters('name')]",
                        "properties": {
                            "image": "[parameters('image')]",
                            "ports": [
                                {
                                    "port": "[parameters('port')]",
                                    "protocol": "TCP"
                                }
                            ],
                            "resources": {
                                "requests": {
                                    "cpu": "[parameters('cpuCores')]",
                                    "memoryInGB": "[parameters('memoryInGb')]"
                                }
                            }
                        }
                    }
                ],
                "osType": "Linux",
                "restartPolicy": "[parameters('restartPolicy')]",
                "ipAddress": {
                    "type": "Public",
                    "ports": [
                        {
                            "port": "[parameters('port')]",
                            "protocol": "TCP"
                        }
                    ]
                }
            }
        }
    ],
    "outputs": {
        "containerIPv4Address": {
            "type": "string",
            "value": "[reference(resourceId('Microsoft.ContainerInstance/containerGroups', parameters('name'))).ipAddress.ip]"
        }
    }
}

Create a resource group with the az group create command:

az group create --name myResourceGroup --location eastus

Deploy the template with the az deployment group create command:

az deployment group create \
  --resource-group myResourceGroup \
  --template-file azuredeploy.json

To verify the container group deployed successfully into an availability zone, view the container group details with the az container show command:
```
az container show --name acilinuxpublicipcontainergroup --resource-group myResourceGroup
```

Zonal failover support

A container group of container instances is assigned to a single availability zone. As a result, that group of container instances won't be impacted by an outage that occurs in any other availability zone of the same region

If, however, an outage occurs in the availability zone of the container group, you can expect downtime for all the container instances within that group.

To avoid container instance downtime, we recommend that you create a minimum of two container groups across two different availability zones in a given region. This ensures that your container instance resources are up and running whenever any single zone in that region experiences outage.

Disaster recovery

When an entire Azure region or datacenter experiences downtime, your mission-critical code needs to continue processing in a different region. Azure Container Instances deployed with zonal configuration run in a specific zone within a specific region. There's no built-in redundancy available. To avoid loss of execution during region wide outages, you can redundantly deploy the container instances in other regions.

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