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  1. Documentation / 
  2. Project User Guide / 
  3. Application Workloads / 
  4. Container Image Settings

Project User Guide

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    Container Image Settings

    When you create Deployments, StatefulSets or DaemonSets, you need to specify a container image. At the same time, KubeSphere provides users with various options to customize workload configurations, such as health check probes, environment variables and start commands. This page illustrates detailed explanations of different properties in Container Image.

    Tip

    You can enable Edit Mode in the top right corner to see corresponding values in the manifest file (YAML format) of properties on the dashboard.

    Container Image

    Pod Replicas

    Set the number of replicated Pods by clicking the plus or minus icon, indicated by the .spec.replicas field in the manifest file. This option is not available for DaemonSets.

    pod-replicas

    Add Container Image

    After you click Add Container Image, you will see an image as below.

    add-container-explan

    You can click the cube icon on the right to select an image from the list or input an image name to search it. KubeSphere provides Docker Hub images and your private image repository. If you want to use your private image repository, you need to create an Image Registry Secret first in Secrets under Configurations.

    Note

    Remember to press Enter on your keyboard after you input an image name in the search bar.

    Image Tag

    You can input a tag like imagename:tag. If you do not specify it, it will default to the latest version.

    Container Name

    The container name is automatically created by KubeSphere, which is indicated by .spec.containers.name.

    Container Type

    If you choose Init Container, it means the init container will be created for the workload. For more information about init containers, please visit Init Containers.

    Resource Request

    The resource quota reserved by the container includes both CPU and memory resources. It means the container monopolizes the resource, preventing other services or processes from competing for resources due to insufficient resources, causing the application to become unavailable.

    • The CPU request is indicated by .spec.containers[].resources.requests.cpu in the manifest file. The CPU request can be exceeded.
    • The memory request is indicated by .spec.containers[].resources.requests.memory in the manifest file. The memory request can be exceeded but the container may clear up when node memory is insufficient.

    resource-request-limit

    Resource Limit

    You can specify the upper limit of the resources that the application can use, including CPU and memory, to prevent excessive resources from being occupied.

    • The CPU limit is indicated by .spec.containers[].resources.limits.cpu in the manifest file. The CPU limit can be exceeded for a short time, and the container will not be stopped.
    • The memory limit is indicated by .spec.containers[].resources.limits.memory in the manifest file. The memory limit cannot be exceeded. If it exceeds, the container may be stopped or scheduled to another machine with sufficient resources.

    Note

    The CPU resource is measured in CPU units, or Core in KubeSphere. The memory resource is measured in bytes, or Mi in KubeSphere.

    Port/Service Settings

    You need to set the access protocol for the container as well as port information. To use the default setting, click Use Default Ports.

    Image Pull Policy

    This value is indicated by the imagePullPolicy field. On the dashboard, you can choose one of the following three options from the drop-down list.

    image-pull-policy

    • Use Local Image First (ifNotPresent): It means that the image is pulled only if it does not exist locally.

    • Redownload Image (Always): It means that the image is pulled whenever the pod starts.

    • Only Use Local Image (Never): It means that the image is not pulled no matter the image exists or not.

    Tip

    • The default value is IfNotPresent, but the value of images tagged with :latest is Always by default.
    • Docker will check it when pulling the image. If MD5 has not changed, it will not pull.
    • The :latest tag should be avoided as much as possible in the production environment, and the latest image can be automatically pulled by the :latest tag in the development environment.

    Health Checker

    Support Liveness, Readiness, and Startup.

    container-health-check

    • Container Liveness Check: Liveness probes are used to know whether a container is running, indicated by livenessProbe.

    • Container Readiness Check: Readiness probes are used to know whether a container is ready to serve requests, indicated by readinessProbe.

    • Container Startup Check: Startup probes are used to know whether a container application has started, indicated by startupProbe.

    Liveness, Readiness and Startup Check have all included the configurations below:

    • HTTPGetAction (HTTP Request Check): Perform an HTTP Get request on the specified port and path on the IP address of the container. If the response status code is greater than or equal to 200 and less than 400, the diagnosis is considered successful. The supported parameters include:

      http-request-check

      • Scheme: HTTP or HTTPS, specified by scheme.
      • Path: The path to access the HTTP server, specified by path.
      • Port: The access port or port name is exposed by the container. The port number must be between 1 and 65535. The value is specified by port.
      • Initial Delays: The number of seconds after the container has started before liveness probes are initiated, specified by initialDelaySeconds. It defaults to 0.
      • Period Seconds: The probe frequency (in seconds), specified by periodSeconds. It defaults to 10. The minimum value is 1.
      • Timeouts: The number of seconds after which the probe times out, specified by timeoutSeconds. It defaults to 1. The minimum value is 1.
      • Success Threshold: The minimum consecutive successes for the probe to be considered successful after having failed, specified by successThreshold. It defaults to 1 and must be 1 for liveness and startup. The minimum value is 1.
      • Failure Threshold: The minimum consecutive failures for the probe to be considered failed after having succeeded, specified by failureThreshold. It defaults to 3. The minimum value is 1.

    • TCPSocketAction (TCP Port Check): Perform a TCP check on the specified port on the IP address of the container. If the port is open, the diagnosis is considered successful. The supported parameters include:

      tcp-port-check

      • Port: The access port or port name is exposed by the container. The port number must be between 1 and 65535. The value is specified by port.
      • Initial Delays: The number of seconds after the container has started before liveness probes are initiated, specified by initialDelaySeconds. It defaults to 0.
      • Period Seconds: The probe frequency (in seconds), specified by periodSeconds. It defaults to 10. The minimum value is 1.
      • Timeouts: The number of seconds after which the probe times out, specified by timeoutSeconds. It defaults to 1. The minimum value is 1.
      • Success Threshold: The minimum consecutive successes for the probe to be considered successful after having failed, specified by successThreshold. It defaults to 1 and must be 1 for liveness and startup. The minimum value is 1.
      • Failure Threshold: The minimum consecutive failures for the probe to be considered failed after having succeeded, specified by failureThreshold. It defaults to 3. The minimum value is 1.

    • ExecAction (Exec Command Check): Execute the specified command in the container. If the return code is 0 when the command exits, the diagnosis is considered successful. The supported parameters include:

      exec-command-check

      • Command: A detection command used to detect the health of the container, specified by exec.command.
      • Initial Delays: The number of seconds after the container has started before liveness probes are initiated, specified by initialDelaySeconds. It defaults to 0.
      • Period Seconds: The probe frequency (in seconds), specified by periodSeconds. It defaults to 10. The minimum value is 1.
      • Timeouts: The number of seconds after which the probe times out, specified by timeoutSeconds. It defaults to 1. The minimum value is 1.
      • Success Threshold: The minimum consecutive successes for the probe to be considered successful after having failed, specified by successThreshold. It defaults to 1 and must be 1 for liveness and startup. The minimum value is 1.
      • Failure Threshold: The minimum consecutive failures for the probe to be considered failed after having succeeded, specified by failureThreshold. It defaults to 3. The minimum value is 1.

    For more information about health checks, please visit Container Probes.

    Start Command

    By default, the container runs the default image command.

    start-command

    • Run Command refers to the command field of containers in the manifest file.
    • Parameters refers to the args field of containers in the manifest file.

    For more information about the command, please visit Define a Command and Arguments for a Container.

    Environment Variables

    Configure environment variables for Pods in the form of key-value pairs.

    envi-var

    • name: The name of the environment variable, specified by env.name.
    • value: The value of the variable reference, specified by env.value.
    • type: The type of environment variables. It supports customization, configuration items, keys, and variable/variable references.

    For more information about the command, please visit Pod variable.

    Container Security Context

    A security context defines privilege and access control settings for a Pod or Container. For more information about the security context, please visit Pod Security Policies.

    security-context

    Sync Host Timezone

    The time zone of the container will be consistent with that of the host after synchronization.

    Update Strategy

    Pod Update

    Update strategies are different for different workloads.

      The .spec.strategy field specifies the strategy used to replace old Pods with new ones. .spec.strategy.type can be Recreate or RollingUpdate. RollingUpdate is the default value.

      • RollingUpdate (Recommended)

        A rolling update means the instance of the old version will be gradually replaced with new ones. During the upgrade process, the traffic will be load balanced and distributed to the old and new instances simultaneously, so the service will not be interrupted.

      • Recreate

        All existing Pods will be killed before new ones are created. Please note that the service will be interrupted during the update process.

      For more information about update strategies, please visit Strategy in Deployments.

      The drop-down menu under Update Strategy is indicated by the .spec.updateStrategy field of a StatefulSet in the manifest file. It allows you to handle updates of Pod containers, tags, resource requests or limits, and annotations. There are two strategies:

      • RollingUpdate (Recommended)

        If .spec.template is updated, the Pods in the StatefulSet will be automatically deleted with new pods created as replacements. Pods are updated in reverse ordinal order, sequentially deleted and created. A new Pod update will not begin until the previous Pod becomes up and running after it is updated.

      • OnDelete

        If .spec.template is updated, the Pods in the StatefulSet will not be automatically updated. You need to manually delete old Pods so that the controller can create new Pods.

      For more information about update strategies, please visit StatefulSet Update Strategies.

      The drop-down menu under Update Strategy is indicated by the .spec.updateStrategy field of a DaemonSet in the manifest file. It allows you to handle updates of Pod containers, tags, resource requests or limits, and annotations. There are two strategies:

      • RollingUpdate (Recommended)

        If .spec.template is updated, old DaemonSet pods will be killed with new pods created automatically in a controlled fashion. At most one pod of the DaemonSet will be running on each node during the whole update process.

      • OnDelete

        If .spec.template is updated, new DaemonSet pods will only be created when you manually delete old DaemonSet pods. This is the same behavior of DaemonSets in Kubernetes version 1.5 or before.

      For more information about update strategies, please visit DaemonSet Update Strategy.

      The Number of Pods When Updated

        The number of Pods when updated in a Deployment is different from that of a StatefulSet.

        • The maximum unavailable number of Pods: The maximum number of Pods that can be unavailable during the update, specified by maxUnavailable. The default value is 25%.
        • The maximum surge number of Pods: The maximum number of Pods that can be scheduled above the desired number of Pods, specified by maxSurge. The default value is 25%.
        When you partition an update, all Pods with an ordinal greater than or equal to the value you set in Partition are updated when you update the StatefulSet’s Pod specification. This field is specified by .spec.updateStrategy.rollingUpdate.partition, whose default value is 0. For more information about partitions, please visit Partitions.

        The number of Pods when updated in a DaemonSet is different from that of a StatefulSet.

        • The maximum unavailable number of Pods: The maximum number of pods that can be unavailable during the update, specified by maxUnavailable. The default value is 20%.
        • MinReadySeconds: The minimum number of seconds before a newly created Pod of DaemonSet is treated as available, specified by minReadySeconds. The default value is 0.

        Pod Security Context

        A security context defines privilege and access control settings for a Pod or Container. For more information about Pod Security Policies, please visit Pod Security Policies.

        Deployment Mode

        You can select different deployment modes to switch between inter-pod affinity and inter-pod anti-affinity. In Kubernetes, inter-pod affinity is specified as field podAffinity of field affinity while inter-pod anti-affinity is specified as field podAntiAffinity of field affinity. In KubeSphere, both podAffinity and podAntiAffinity are set to preferredDuringSchedulingIgnoredDuringExecution. You can enable Edit Mode in the top right corner to see field details.

        • Pod Decentralized Deployment represents anti-affinity.
        • Pod Aggregation Deployment represents affinity.

        For more information about affinity and anti-affinity, please visit Pod affinity.

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