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Control upgrade failure behavior

  • Artikkeli

Overview

This guide describes the Azure Operator Service Manager (AOSM) upgrade failure behavior features for container network functions (CNFs). These features, as part of the AOSM safe upgrade practices initiative, offer a choice between faster retries, with pause on failure, versus return to starting point, with rollback on failure.

Pause on failure

Any upgrade using AOSM starts with a site network service (SNS) reput opreation. The reput operation processes the network function applications (NfApps) found in the network function design version (NFDV). The reput operation implements the following default logic:

  • NfApps are processed following either updateDependsOn ordering, or in the sequential order they appear.
  • NfApps with parameter "applicationEnabled" set to disable are skipped.
  • NFApps present, but not referenced by the new NFDV are deleted.
  • The execution sequence is paused if any of the NfApp upgrades fail and a rollback is considered.
  • The failure leaves the NF resource in a failed state.

With pause on failure, AOSM rolls back only the failed NfApp, via the testOptions, installOptions, or upgradeOptions parameters. No action is taken on any NfApps which proceed the failed NfApp. This method allows the end user to troubleshoot the failed NfApp and then restart the upgrade from that point forward. As the default behavior, this method is the most efficient method, but may cause network function (NF) inconsistencies while in a mixed version state.

Rollback on failure

To address risk of mismatched NfApp versions, AOSM now supports NF level rollback on failure. With this option enabled, if an NfApp operation fails, both the failed NfApp, and all prior completed NfApps, can be rolled back to initial version state. This method minimizes, or eliminates, the amount of time the NF is exposed to NfApp version mismatches. The optional rollback on failure feature works as follows:

  • A user initiates an sSNS reput operation and enables rollback on failure.
  • A snapshot of the current NfApp versions is captured and stored.
  • The snapshot is used to determine the individual NfApp actions taken to reverse actions that completed successfully.
    • "helm install" action on deleted components,
    • "helm rollback" action on upgraded components,
    • "helm delete" action on newly installed components
  • NfApp failure occurs, AOSM restores the NfApps to the snapshot version state before the upgrade, with most recent actions reverted first.

Note

  • AOSM doesn't create a snapshot if a user doesn't enable rollback on failure.
  • A rollback on failure only applies to the successfully completed NFApps.
    • Use the testOptions, installOptions, or upgradeOptions parameters to control rollback of the failed NfApp.

AOSM returns the following operational status and messages, given the respective results:

  - Upgrade Succeeded
    - Provisioning State: Succeeded
    - Message: <empty>

  - Upgrade Failed, Rollback Succeeded
    - Provisioning State: Failed
    - Message: Application(<ComponentName>) : <Failure Reason>; Rollback succeeded

  - Upgrade Failed, Rollback Failed
    - Provisioning State: Failed
    - Message: Application(<ComponentName>) : <Failure reason>; Rollback Failed (<RollbackComponentName>) : <Rollback Failure reason>

How to configure rollback on failure

The most flexible method to control failure behavior is to extend a new configuration group schema (CGS) parameter, rollbackEnabled, to allow for configuration group value (CGV) control via roleOverrideValues in the NF payload. First, define the CGS parameter:

{
  "description": "NF configuration",
  "type": "object",
  "properties": {
    "nfConfiguration": {
      "type": "object",
      "properties": {
        "rollbackEnabled": {
          "type": "boolean"
        }
      },
      "required": [
        "rollbackEnabled"
      ]
    }
  }
}

Note

  • If the nfConfiguration isn't provided through the roleOverrideValues parameter, by default the rollback is disabled.

With the new rollbackEnable parameter defined, the Operator can now provide a run time value, under roleOverrideValues, as part of NF reput payload.

example:
{
  "location": "eastus",
  "properties": {
    // ...
    "roleOverrideValues": [
          "{\"nfConfiguration\":{\"rollbackEnabled\":true}}",
            "{\"name\":\"nfApp1\",\"deployParametersMappingRuleProfile\":{\"applicationEnablement\" : \"Disabled\"}}",
            "{\"name\":\"nfApp2\",\"deployParametersMappingRuleProfile\":{\"applicationEnablement\" : \"Disabled\"}}",
          //... other nfapps overrides
       ]
  }
}

Note

  • Each roleOverrideValues entry overrides the default behavior of the NfAapps.
  • If multiple entries of nfConfiguration are found in the roleOverrideValues, then the NF reput is returned as a bad request.

How to troubleshoot rollback on failure

Understand pod states

Understanding the different pod states is crucial for effective troubleshooting. The following are the most common pod states:

  • Pending: Pod scheduling is in progress by Kubernetes.
  • Running: All containers in the pod are running and healthy.
  • Failed: One or more containers in the pod are terminated with a nonzero exit code.
  • CrashLoopBackOff: A container within the pod is repeatedly crashing and Kubernetes is unable to restart it.
  • ContainerCreating: Container creation is in progress by the container runtime.

Check pod status and logs

First start by checking pod status and logs using a kubectl command:

$ kubectl get pods
$ kubectl logs <pod-name>

The get pods command lists all the pods in the current namespace, along with their current status. The logs command retrieves the logs for a specific pod, allowing you to inspect any errors or exceptions. To troubleshoot networking problems, use the following commands:

$ kubectl get services
$ kubectl describe service <service-name>

The get services command displays all the services in the current namespace. The command provides details about a specific service, including the associated endpoints, and any relevant error messages. If you're encountering issues with PVCs, you can use the following commands to debug them:

$ kubectl get persistentvolumeclaims
$ kubectl describe persistentvolumeclaims <pvc-name>

The "get persistentvolumeclaims" command lists all the PVCs in the current namespace. The describe command provides detailed information about a specific PVC, including the status, associated storage class, and any relevant events or errors.