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Troubleshooting

You can view the migration Custom Resources (CRs) and download logs to troubleshoot a failed migration.

If the application was stopped during the failed migration, you must roll it back manually in order to prevent data corruption.

Manual rollback is not required if the application was not stopped during migration because the original application is still running on the source cluster.

Viewing migration Custom Resources

The Migration Toolkit for Containers (MTC) creates the following Custom Resources (CRs):

migration architecture diagram

20 MigCluster (configuration, MTC cluster): Cluster definition

20 MigStorage (configuration, MTC cluster): Storage definition

20 MigPlan (configuration, MTC cluster): Migration plan

The MigPlan CR describes the source and target clusters, replication repository, and namespaces being migrated. It is associated with 0, 1, or many MigMigration CRs.

Deleting a MigPlan CR deletes the associated MigMigration CRs.

20 BackupStorageLocation (configuration, MTC cluster): Location of Velero backup objects

20 VolumeSnapshotLocation (configuration, MTC cluster): Location of Velero volume snapshots

20 MigMigration (action, MTC cluster): Migration, created every time you stage or migrate data. Each MigMigration CR is associated with a MigPlan CR.

20 Backup (action, source cluster): When you run a migration plan, the MigMigration CR creates two Velero backup CRs on each source cluster:

  • Backup CR #1 for Kubernetes objects

  • Backup CR #2 for PV data

20 Restore (action, target cluster): When you run a migration plan, the MigMigration CR creates two Velero restore CRs on the target cluster:

  • Restore CR #1 (using Backup CR #2) for PV data

  • Restore CR #2 (using Backup CR #1) for Kubernetes objects

Procedure

  1. View the CR:

    $ oc get <cr> -n openshift-migration (1)
    1 Specify the migration CR, for example, migmigration.
    Example output
    NAME                                   AGE
88435fe0-c9f8-11e9-85e6-5d593ce65e10   6m42s

  2. Inspect the migmigration CR:

    $ oc describe <migmigration> <88435fe0-c9f8-11e9-85e6-5d593ce65e10> -n openshift-migration

    The output is similar to the following examples.

MigMigration example output
name:         88435fe0-c9f8-11e9-85e6-5d593ce65e10
namespace:    openshift-migration
labels:       <none>
annotations:  touch: 3b48b543-b53e-4e44-9d34-33563f0f8147
apiVersion:  migration.openshift.io/v1alpha1
kind:         MigMigration
metadata:
  creationTimestamp:  2019-08-29T01:01:29Z
  generation:          20
  resourceVersion:    88179
  selfLink:           /apis/migration.openshift.io/v1alpha1/namespaces/openshift-migration/migmigrations/88435fe0-c9f8-11e9-85e6-5d593ce65e10
  uid:                 8886de4c-c9f8-11e9-95ad-0205fe66cbb6
spec:
  migPlanRef:
    name:        socks-shop-mig-plan
    namespace:   openshift-migration
  quiescePods:  true
  stage:         false
status:
  conditions:
    category:              Advisory
    durable:               True
    lastTransitionTime:  2019-08-29T01:03:40Z
    message:               The migration has completed successfully.
    reason:                Completed
    status:                True
    type:                  Succeeded
  phase:                   Completed
  startTimestamp:         2019-08-29T01:01:29Z
events:                    <none>
Velero backup CR #2 example output that describes the PV data
apiVersion: velero.io/v1
kind: Backup
metadata:
  annotations:
    openshift.io/migrate-copy-phase: final
    openshift.io/migrate-quiesce-pods: "true"
    openshift.io/migration-registry: 172.30.105.179:5000
    openshift.io/migration-registry-dir: /socks-shop-mig-plan-registry-44dd3bd5-c9f8-11e9-95ad-0205fe66cbb6
  creationTimestamp: "2019-08-29T01:03:15Z"
  generateName: 88435fe0-c9f8-11e9-85e6-5d593ce65e10-
  generation: 1
  labels:
    app.kubernetes.io/part-of: migration
    migmigration: 8886de4c-c9f8-11e9-95ad-0205fe66cbb6
    migration-stage-backup: 8886de4c-c9f8-11e9-95ad-0205fe66cbb6
    velero.io/storage-location: myrepo-vpzq9
  name: 88435fe0-c9f8-11e9-85e6-5d593ce65e10-59gb7
  namespace: openshift-migration
  resourceVersion: "87313"
  selfLink: /apis/velero.io/v1/namespaces/openshift-migration/backups/88435fe0-c9f8-11e9-85e6-5d593ce65e10-59gb7
  uid: c80dbbc0-c9f8-11e9-95ad-0205fe66cbb6
spec:
  excludedNamespaces: []
  excludedResources: []
  hooks:
    resources: []
  includeClusterResources: null
  includedNamespaces:
  - sock-shop
  includedResources:
  - persistentvolumes
  - persistentvolumeclaims
  - namespaces
  - imagestreams
  - imagestreamtags
  - secrets
  - configmaps
  - pods
  labelSelector:
    matchLabels:
      migration-included-stage-backup: 8886de4c-c9f8-11e9-95ad-0205fe66cbb6
  storageLocation: myrepo-vpzq9
  ttl: 720h0m0s
  volumeSnapshotLocations:
  - myrepo-wv6fx
status:
  completionTimestamp: "2019-08-29T01:02:36Z"
  errors: 0
  expiration: "2019-09-28T01:02:35Z"
  phase: Completed
  startTimestamp: "2019-08-29T01:02:35Z"
  validationErrors: null
  version: 1
  volumeSnapshotsAttempted: 0
  volumeSnapshotsCompleted: 0
  warnings: 0
Velero restore CR #2 example output that describes the Kubernetes resources
apiVersion: velero.io/v1
kind: Restore
metadata:
  annotations:
    openshift.io/migrate-copy-phase: final
    openshift.io/migrate-quiesce-pods: "true"
    openshift.io/migration-registry: 172.30.90.187:5000
    openshift.io/migration-registry-dir: /socks-shop-mig-plan-registry-36f54ca7-c925-11e9-825a-06fa9fb68c88
  creationTimestamp: "2019-08-28T00:09:49Z"
  generateName: e13a1b60-c927-11e9-9555-d129df7f3b96-
  generation: 3
  labels:
    app.kubernetes.io/part-of: migration
    migmigration: e18252c9-c927-11e9-825a-06fa9fb68c88
    migration-final-restore: e18252c9-c927-11e9-825a-06fa9fb68c88
  name: e13a1b60-c927-11e9-9555-d129df7f3b96-gb8nx
  namespace: openshift-migration
  resourceVersion: "82329"
  selfLink: /apis/velero.io/v1/namespaces/openshift-migration/restores/e13a1b60-c927-11e9-9555-d129df7f3b96-gb8nx
  uid: 26983ec0-c928-11e9-825a-06fa9fb68c88
spec:
  backupName: e13a1b60-c927-11e9-9555-d129df7f3b96-sz24f
  excludedNamespaces: null
  excludedResources:
  - nodes
  - events
  - events.events.k8s.io
  - backups.velero.io
  - restores.velero.io
  - resticrepositories.velero.io
  includedNamespaces: null
  includedResources: null
  namespaceMapping: null
  restorePVs: true
status:
  errors: 0
  failureReason: ""
  phase: Completed
  validationErrors: null
  warnings: 15

Downloading migration logs

You can download the Velero, Restic, and Migration controller logs in the MTC web console to troubleshoot a failed migration.

Procedure

  1. Log in to the MTC console.

  2. Click Plans to view the list of migration plans.

  3. Click the Options menu kebab of a specific migration plan and select Logs.

  4. Click Download Logs to download the logs of the Migration controller, Velero, and Restic for all clusters.

  5. To download a specific log:

    1. Specify the log options:

      • Cluster: Select the source, target, or MTC host cluster.

      • Log source: Select Velero, Restic, or Controller.

      • Pod source: Select the Pod name, for example, controller-manager-78c469849c-v6wcf

        The selected log is displayed.

        You can clear the log selection settings by changing your selection.

    2. Click Download Selected to download the selected log.

Optionally, you can access the logs by using the CLI, as in the following example:

$ oc logs <pod-name> -f -n openshift-migration (1)
1 Specify the Pod name.

Error messages and resolutions

This section describes common error messages and how to resolve their underlying causes.

Restic timeout error

If a migration fails because Restic times out, the following error is displayed in the Velero Pod log.

Example output
level=error msg="Error backing up item" backup=velero/monitoring error="timed out waiting for all PodVolumeBackups to complete" error.file="/go/src/github.com/heptio/velero/pkg/restic/backupper.go:165" error.function="github.com/heptio/velero/pkg/restic.(*backupper).BackupPodVolumes" group=v1

The default value of restic_timeout is one hour. You can increase this parameter for large migrations, keeping in mind that a higher value may delay the return of error messages.

Procedure

  1. In the OpenShift Container Platform web console, navigate to Operators → Installed Operators.

  2. Click MTC Operator.

  3. In the MigrationController tab, click migration-controller.

  4. In the YAML tab, update the following parameter value:

    spec:
  restic_timeout: 1h (1)
    1 Valid units are h (hours), m (minutes), and s (seconds), for example, 3h30m15s.

  5. Click Save.

ResticVerifyErrors in the MigMigration Custom Resource

If data verification fails when migrating a PV with the file system data copy method, the following error is displayed in the MigMigration Custom Resource (CR).

Example output
status:
  conditions:
  - category: Warn
    durable: true
    lastTransitionTime: 2020-04-16T20:35:16Z
    message: There were verify errors found in 1 Restic volume restores. See restore `<registry-example-migration-rvwcm>`
      for details (1)
    status: "True"
    type: ResticVerifyErrors (2)
1 The error message identifies the Restore CR name.
2 ResticErrors is a general error warning that includes verification errors.

A data verification error does not cause the migration process to fail.

You can check the Restore CR to identify the source of the data verification error.

Procedure

  1. Log in to the target cluster.

  2. View the Restore CR:

    $ oc describe <registry-example-migration-rvwcm> -n openshift-migration

    The output identifies the PV with PodVolumeRestore errors.

    Example output
    status:
  phase: Completed
  podVolumeRestoreErrors:
  - kind: PodVolumeRestore
    name: <registry-example-migration-rvwcm-98t49>
    namespace: openshift-migration
  podVolumeRestoreResticErrors:
  - kind: PodVolumeRestore
    name: <registry-example-migration-rvwcm-98t49>
    namespace: openshift-migration

  3. View the PodVolumeRestore CR:

    $ oc describe <migration-example-rvwcm-98t49>

    The output identifies the Restic Pod that logged the errors.

    Example output
      completionTimestamp: 2020-05-01T20:49:12Z
  errors: 1
  resticErrors: 1
  ...
  resticPod: <restic-nr2v5>

  4. View the Restic Pod log to locate the errors:

    $ oc logs -f <restic-nr2v5>

Manually rolling back a migration

If your application was stopped during a failed migration, you must roll it back manually in order to prevent data corruption in the PV.

This procedure is not required if the application was not stopped during migration, because the original application is still running on the source cluster.

Procedure

  1. On the target cluster, switch to the migrated project:

    $ oc project <project>

  2. Get the deployed resources:

    $ oc get all

  3. Delete the deployed resources to ensure that the application is not running on the target cluster and accessing data on the PVC:

    $ oc delete <resource_type>

  4. To stop a DaemonSet without deleting it, update the nodeSelector in the YAML file:

    apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: hello-daemonset
spec:
  selector:
      matchLabels:
        name: hello-daemonset
  template:
    metadata:
      labels:
        name: hello-daemonset
    spec:
      nodeSelector:
        role: worker (1)
    1 Specify a nodeSelector value that does not exist on any node.

  5. Update each PV’s reclaim policy so that unnecessary data is removed. During migration, the reclaim policy for bound PVs is Retain, to ensure that data is not lost when an application is removed from the source cluster. You can remove these PVs during rollback.

    apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv0001
spec:
  capacity:
    storage: 5Gi
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain (1)
  ...
status:
  ...
    1 Specify Recycle or Delete.

  6. On the source cluster, switch to your migrated project:

    $ oc project <project_name>

  7. Obtain the project’s deployed resources:

    $ oc get all

  8. Start one or more replicas of each deployed resource:

    $ oc scale --replicas=1 <resource_type>/<resource_name>

  9. Update the nodeSelector of a DaemonSet to its original value, if you changed it during the procedure.

Using must-gather to collect data

You must run the must-gather tool if you open a customer support case on the Red Hat Customer Portal.

The openshift-migration-must-gather-rhel8 image collects migration-specific logs and data that are not collected by the default must-gather image.

Procedure

  1. Navigate to the directory where you want to store the must-gather data.

  2. Run the must-gather command:

    $ oc adm must-gather --image=openshift-migration-must-gather-rhel8:v1.3.0

  3. Remove authentication keys and other sensitive information.

  4. Create an archive file containing the contents of the must-gather data directory:

    $ tar cvaf must-gather.tar.gz must-gather.local.<uid>/

  5. Upload the compressed file as an attachment to your customer support case.

Known issues

This release has the following known issues:

  • During migration, the Migration Toolkit for Containers (MTC) preserves the following namespace annotations:

    • openshift.io/sa.scc.mcs

    • openshift.io/sa.scc.supplemental-groups

    • openshift.io/sa.scc.uid-range

      These annotations preserve the UID range, ensuring that the containers retain their file system permissions on the target cluster. There is a risk that the migrated UIDs could duplicate UIDs within an existing or future namespace on the target cluster. (BZ#1748440)

  • If an AWS bucket is added to the MTC web console and then deleted, its status remains True because the MigStorage CR is not updated. (BZ#1738564)

  • Most cluster-scoped resources are not yet handled by MTC. If your applications require cluster-scoped resources, you may have to create them manually on the target cluster.

  • If a migration fails, the migration plan does not retain custom PV settings for quiesced pods. You must manually roll back the migration, delete the migration plan, and create a new migration plan with your PV settings. (BZ#1784899)

  • If a large migration fails because Restic times out, you can increase the restic_timeout parameter value (default: 1h) in the Migration Controller CR.

  • If you select the data verification option for PVs that are migrated with the file system copy method, performance is significantly slower.

  • If you are migrating data from NFS storage and root_squash is enabled, Restic maps to nfsnobody. The migration fails and a permission error is displayed in the Restic Pod log. You can resolve this issue by creating a supplemental group for Restic. (BZ#1873641)

  • If Velero has an invalid BackupStorageLocation during start-up, it will crash-loop until the invalid BackupStorageLocation is removed. This scenario is triggered by incorrect credentials, a non-existent S3 bucket, and other configuration errors. (BZ#1881707)