Container Image Management

The activation path during Service Fabric containers deployment, handles the downloading of the container images to the VM on which the containers are running. Once the containers are removed from the cluster and their application types are unregistered, there's a cleanup cycle that deletes the container images. This container image cleanup works only if the container image was hard coded in the service manifest. For existing Service Fabric runtime versions, the configurations supporting the cleanup of the container images are as follows -

Settings

"fabricSettings": [
               {
                   "name": "Hosting",
                   "parameters": [
                      {
                           "name": "PruneContainerImages", 
                           "value": "true"
                      },
                      {
                           "name": "CacheCleanupScanInterval",
                           "value": "3600"
                      }
                   ]
               }
           ]

Setting	Description
PruneContainerImage	Setting to enable or disable pruning of container images when application type is unregistered.
CacheCleanupScanInterval	Setting in seconds determining how often the cleanup cycle runs.

Container Image Management v2

Starting Service Fabric version 10.0 there's a newer version of the container image deletion flow. This flow cleans up container images irrespective of how the container images were defined - either hard coded or parameterized during application deployment. PruneContainerImages and ContainerImageDeletionEnabled configuration are mutually exclusive and cluster upgrade validation exists to ensure one or the other is switched on but not both. The configuration supporting this feature are as follows -

Settings

 "fabricSettings": [
                {
                    "name": "Hosting",
                    "parameters": [
                       {
                            "name": "ContainerImageDeletionEnabled", 
                            "value": "true"
                       },
                       {
                            "name": "ContainerImageCleanupInterval",
                            "value": "3600"
                       },
                       {
                            "name": "ContainerImageTTL",
                            "value": "3600"
                       },
                       {
                            "name": "ContainerImageDeletionOnAppInstanceDeletionEnabled",
                            "value": "true"
                       },
                       {
                            "name": "ContainerImagesToSkip",
                            "value": "microsoft/windowsservercore|microsoft/nanoserver"
                       }
                    ]
                }
            ]

Setting	Description
ContainerImageDeletionEnabled	Setting to enable or disable deletion of container images.
ContainerImageCleanupInterval	Time interval for cleaning up unused container images.
ContainerImageTTL	Time to live for container images once they're eligible for removal (not referenced by containers on the VM and the application is deleted(if ContainerImageDeletionOnAppInstanceDeletionEnabled is enabled)).
ContainerImageDeletionOnAppInstanceDeletionEnabled	Setting to enable or disable deletion of expired ttl container images only after application was deleted as well.
ContainerImagesToSkip	When set enables the container runtime to skip deleting images that match any of the set of regular expressions. The | character separates each expression. Example: "mcr.microsoft.com/.+|docker.io/library/alpine:latest" - this example matches everything prefixed with "mcr.microsoft.com/" and matches exactly "docker.io/library/alpine:latest". By default we don't delete the known Windows base images microsoft/windowsservercore or microsoft/nanoserver.

Next steps

See the following article for related information:

• [Service Fabric and containers][containers-introduction-link]