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Image pull takes a long time to complete

This article discusses possible causes for an image pull taking long time to complete on Microsoft Azure Container Instances.

Prerequisites

Symptoms

  • Container groups are stuck in a Creating status for a significant amount of time.
  • The image size is large.

Cause

In Container Instances, images aren't cached forever. If the image isn't cached, the image is pulled from the registry. A registry pull can take a long time if the image is large. This is expected behavior for large, uncached images.

If you need faster pull times, you might want to check whether one of the listed cached images would work successfully for your use case.

Solution

To view the timeline of the container events, run the following az container show command:

az container show --resource-group <resource-group-name> --name <container-group-name>

The time span between the Pulling and Pulled events allows you to determine whether the image pull time is expected or abnormal. The following is a sample command output:

{
  "containers": [
    {
      "command": null,
      "environmentVariables": [],
      "image": "pbdockerregistry-on.azurecr.io/<image-name>:<tag>",
      "instanceView": {
        "currentState": {
          "detailStatus": "",
          "exitCode": null,
          "finishTime": null,
          "startTime": "2019-01-22T16:49:11+00:00",
          "state": "Running"
        },
        "events": [
          {
            "count": 1,
            "firstTimestamp": "2019-01-22T16:30:51+00:00",
            "lastTimestamp": "2019-01-22T16:30:51+00:00",
            "message": "pulling image \"pbdockerregistry-on.azurecr.io/<image-name>:<tag>\"",
            "name": "Pulling",
            "type": "Normal"
          },
          {
            "count": 1,
            "firstTimestamp": "2019-01-22T16:48:43+00:00",
            "lastTimestamp": "2019-01-22T16:48:43+00:00",
            "message": "Successfully pulled image \"pbdockerregistry-on.azurecr.io/<image-name>:<tag>\"",
            "name": "Pulled",
            "type": "Normal"
          },
          {
            "count": 1,
            "firstTimestamp": "2019-01-22T16:48:43+00:00",
            "lastTimestamp": "2019-01-22T16:48:43+00:00",
            "message": "Created container with docker id <id>",
            "name": "Created",
            "type": "Normal"
          },
          {
            "count": 1,
            "firstTimestamp": "2019-01-22T16:49:11+00:00",
            "lastTimestamp": "2019-01-22T16:49:11+00:00",
            "message": "Started container with docker id <id>",
            "name": "Started",
            "type": "Normal"
          }
        ],
        "previousState": null,
        "restartCount": 0
      },
      "livenessProbe": null,
      "name": "<container-name>",
      "ports": [
        {
          "port": 443,
          "protocol": "TCP"
        }
      ],
      "readinessProbe": null,
      "resources": {
        "limits": null,
        "requests": {
          "cpu": 4.0,
          "memoryInGb": 4.0
        }
      },
      "volumeMounts": null
    }
  ],
  "diagnostics": null,
  "id": "/subscriptions/<subscription-id>/resourceGroups/<resource-group-name>/providers/Microsoft.ContainerInstance/containerGroups/<container-name>",
  "identity": null,
  "imageRegistryCredentials": [
    {
      "password": null,
      "server": "<user-name>.azurecr.io",
      "username": "<user-name>"
    }
  ],
  "instanceView": {
    "events": [],
    "state": "Running"
  },
  "ipAddress": {
    "dnsNameLabel": "<container-name>",
    "fqdn": "<container-name>.<region>.azurecontainer.io",
    "ip": "<IP>",
    "ports": [
      {
        "port": 443,
        "protocol": "TCP"
      }
    ],
    "type": "Public"
  },
  "location": "<region>",
  "name": "<container-name>",
  "networkProfile": null,
  "osType": "Windows",
  "provisioningState": "Succeeded",
  "resourceGroup": "<resource-group-name>",
  "restartPolicy": "Always",
  "tags": {},
  "type": "Microsoft.ContainerInstance/containerGroups",
  "volumes": null
}

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