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Add troubleshooting of node maintenance mode
Signed-off-by: Jian Wang <jian.wang@suse.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,139 @@ | ||
| --- | ||
| sidebar_position: 6 | ||
| sidebar_label: Host | ||
| title: "Host" | ||
| --- | ||
|
|
||
| <head> | ||
| <link rel="canonical" href="https://docs.harvesterhci.io/v1.3/troubleshooting/host"/> | ||
| </head> | ||
|
|
||
| ## Node in Maintenance Mode Becomes Stuck in Cordoned State | ||
|
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| When you enable Maintenance Mode on a node using the Harvester UI, the node becomes stuck in the `Cordoned` state and the menu shows the **Enable Maintenance Mode** option instead of **Disable Maintenance Mode**. | ||
|
|
||
|  | ||
|
|
||
| The Harvester pod logs contain messages similar to the following: | ||
|
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||
| ``` | ||
| time="2024-08-05T19:03:02Z" level=info msg="evicting pod longhorn-system/instance-manager-68cd2514dd3f6d59b95cbd865d5b08f7" | ||
| time="2024-08-05T19:03:02Z" level=info msg="error when evicting pods/\"instance-manager-68cd2514dd3f6d59b95cbd865d5b08f7\" -n \"longhorn-system\" (will retry after 5s): Cannot evict pod as it would violate the pod's disruption budget." | ||
| time="2024-08-05T19:03:07Z" level=info msg="evicting pod longhorn-system/instance-manager-68cd2514dd3f6d59b95cbd865d5b08f7" | ||
| time="2024-08-05T19:03:07Z" level=info msg="error when evicting pods/\"instance-manager-68cd2514dd3f6d59b95cbd865d5b08f7\" -n \"longhorn-system\" (will retry after 5s): Cannot evict pod as it would violate the pod's disruption budget." | ||
| time="2024-08-05T19:03:12Z" level=info msg="evicting pod longhorn-system/instance-manager-68cd2514dd3f6d59b95cbd865d5b08f7" | ||
| time="2024-08-05T19:03:12Z" level=info msg="error when evicting pods/\"instance-manager-68cd2514dd3f6d59b95cbd865d5b08f7\" -n \"longhorn-system\" (will retry after 5s): Cannot evict pod as it would violate the pod's disruption budget." | ||
| ``` | ||
|
|
||
| The Longhorn Instance Manager uses a PodDisruptionBudget (PDB) to protect itself from accidental eviction, which results in loss of volume data. When the Maintenance Mode error occurs, it indicates that the `instance-manager` pod is still serving volumes or replicas. | ||
|
|
||
| The following sections describe the known causes and their corresponding workarounds. | ||
|
|
||
| ### Manually Attached Volumes | ||
|
|
||
| A volume that is attached to a node using the [embedded Longhorn UI](./harvester.md#access-embedded-rancher-and-longhorn-dashboards) can cause the error. This is because the object is attached to a node name instead of the pod name. | ||
|
|
||
| You can check it from the [Embedded Longhorn UI](./harvester.md#access-embedded-rancher-and-longhorn-dashboards). | ||
|
|
||
|  | ||
|
|
||
| The manually attached object is attached to a node name instead of the pod name. | ||
|
|
||
| You can also use the CLI to retrieve the details of the CRD object `VolumeAttachment`. | ||
|
|
||
| Example of a volume that was attached using the Longhorn UI: | ||
|
|
||
| ``` | ||
| - apiVersion: longhorn.io/v1beta2 | ||
| kind: VolumeAttachment | ||
| ... | ||
| spec: | ||
| attachmentTickets: | ||
| longhorn-ui: | ||
| id: longhorn-ui | ||
| nodeID: node-name | ||
| ... | ||
| volume: pvc-9b35136c-f59e-414b-aa55-b84b9b21ff89 | ||
| ``` | ||
|
|
||
| Example of a volume that was attached using the Longhorn CSI driver: | ||
|
|
||
| ``` | ||
| - apiVersion: longhorn.io/v1beta2 | ||
| kind: VolumeAttachment | ||
| spec: | ||
| attachmentTickets: | ||
| csi-b5097155cddde50b4683b0e659923e379cbfc3873b5b2ee776deb3874102e9bf: | ||
| id: csi-b5097155cddde50b4683b0e659923e379cbfc3873b5b2ee776deb3874102e9bf | ||
| nodeID: node-name | ||
| ... | ||
| volume: pvc-3c6403cd-f1cd-4b84-9b46-162f746b9667 | ||
| ``` | ||
|
|
||
| :::note | ||
|
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||
| Manually attaching a volume to the node is not recommended. | ||
|
|
||
| ::: | ||
|
|
||
| #### Workaround 1: Set `Detach Manually Attached Volumes When Cordoned` to `True` | ||
|
|
||
| The Longhorn setting [Detach Manually Attached Volumes When Cordoned](https://longhorn.io/docs/1.6.0/references/settings/#detach-manually-attached-volumes-when-cordoned) blocks node draining when there are volumes manually attached to the node. | ||
|
|
||
| The default value of this setting depends on the embedded Longhorn version: | ||
|
|
||
| | Harvester version | Embedded Longhorn version | Default value | | ||
| | --- | --- | --- | | ||
| | v1.3.1 | v1.6.0 | `true` | | ||
| | v1.4.0 | v1.7.0 | `false` | | ||
|
|
||
| Set this option to `true` from the [embedded Longhorn UI](./harvester.md#access-embedded-rancher-and-longhorn-dashboards). | ||
|
|
||
| #### Workaround 2: Manually Detach the Volume | ||
|
|
||
| Detach the volume using the [embedded Longhorn UI](./harvester.md#access-embedded-rancher-and-longhorn-dashboards). | ||
|
|
||
|  | ||
|
|
||
| Once the volume is detached, you can successfully enable Maintenance Mode on the node. | ||
|
|
||
|  | ||
|
|
||
| ### Single-Replica Volumes | ||
|
|
||
| Harvester allows you to create custom StorageClasses that describe how Longhorn must provision volumes. If necessary, you can create a StorageClass with the [Number of Replicas](../advanced/storageclass.md#number-of-replicas) parameter set to `1`. | ||
|
|
||
| When a volume is created using such a StorageClass and is attached to a node using the CSI driver or other methods, the lone replica stays on that node even after the volume is detached. | ||
|
|
||
| You can check this using the CRD object `Volume`. | ||
|
|
||
| ``` | ||
| - apiVersion: longhorn.io/v1beta2 | ||
| kind: Volume | ||
| ... | ||
| spec: | ||
| ... | ||
| numberOfReplicas: 1 // the replica number | ||
| ... | ||
| status: | ||
| ... | ||
| ownerID: nodeName | ||
| ... | ||
| state: attached | ||
| ``` | ||
|
|
||
| #### Workaround: Set `Node Drain Policy` | ||
|
|
||
| The Longhorn [Node Drain Policy](https://longhorn.io/docs/1.6.0/references/settings/#node-drain-policy) is set to `block-if-contains-last-replica` by default. This option forces Longhorn to block node draining when the node contains the last healthy replica of a volume. | ||
|
|
||
| To address the issue, change the value to `allow-if-replica-is-stopped` using the [embedded Longhorn UI](./harvester.md#access-embedded-rancher-and-longhorn-dashboards). | ||
|
|
||
| :::info important | ||
|
|
||
| If you plan to remove the node after Maintenance Mode is enabled, back up single-replica volumes or redeploy the related workloads to other nodes in advance so that the volumes are scheduled to other nodes. | ||
|
|
||
| ::: | ||
|
|
||
| Starting with Harvester v1.4.0, the `Node Drain Policy` is set to `allow-if-replica-is-stopped` by default. |
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Learn more about bidirectional Unicode characters
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Learn more about bidirectional Unicode characters
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,139 @@ | ||
| --- | ||
| sidebar_position: 6 | ||
| sidebar_label: Host | ||
| title: "Host" | ||
| --- | ||
|
|
||
| <head> | ||
| <link rel="canonical" href="https://docs.harvesterhci.io/v1.3/troubleshooting/host"/> | ||
| </head> | ||
|
|
||
| ## Node in Maintenance Mode Becomes Stuck in Cordoned State | ||
|
|
||
| When you enable Maintenance Mode on a node using the Harvester UI, the node becomes stuck in the `Cordoned` state and the menu shows the **Enable Maintenance Mode** option instead of **Disable Maintenance Mode**. | ||
|
|
||
|  | ||
|
|
||
| The Harvester pod logs contain messages similar to the following: | ||
|
|
||
| ``` | ||
| time="2024-08-05T19:03:02Z" level=info msg="evicting pod longhorn-system/instance-manager-68cd2514dd3f6d59b95cbd865d5b08f7" | ||
| time="2024-08-05T19:03:02Z" level=info msg="error when evicting pods/\"instance-manager-68cd2514dd3f6d59b95cbd865d5b08f7\" -n \"longhorn-system\" (will retry after 5s): Cannot evict pod as it would violate the pod's disruption budget." | ||
| time="2024-08-05T19:03:07Z" level=info msg="evicting pod longhorn-system/instance-manager-68cd2514dd3f6d59b95cbd865d5b08f7" | ||
| time="2024-08-05T19:03:07Z" level=info msg="error when evicting pods/\"instance-manager-68cd2514dd3f6d59b95cbd865d5b08f7\" -n \"longhorn-system\" (will retry after 5s): Cannot evict pod as it would violate the pod's disruption budget." | ||
| time="2024-08-05T19:03:12Z" level=info msg="evicting pod longhorn-system/instance-manager-68cd2514dd3f6d59b95cbd865d5b08f7" | ||
| time="2024-08-05T19:03:12Z" level=info msg="error when evicting pods/\"instance-manager-68cd2514dd3f6d59b95cbd865d5b08f7\" -n \"longhorn-system\" (will retry after 5s): Cannot evict pod as it would violate the pod's disruption budget." | ||
| ``` | ||
|
|
||
| The Longhorn Instance Manager uses a PodDisruptionBudget (PDB) to protect itself from accidental eviction, which results in loss of volume data. When the Maintenance Mode error occurs, it indicates that the `instance-manager` pod is still serving volumes or replicas. | ||
|
|
||
| The following sections describe the known causes and their corresponding workarounds. | ||
|
|
||
| ### Manually Attached Volumes | ||
|
|
||
| A volume that is attached to a node using the [embedded Longhorn UI](./harvester.md#access-embedded-rancher-and-longhorn-dashboards) can cause the error. This is because the object is attached to a node name instead of the pod name. | ||
|
|
||
| You can check it from the [Embedded Longhorn UI](./harvester.md#access-embedded-rancher-and-longhorn-dashboards). | ||
|
|
||
|  | ||
|
|
||
| The manually attached object is attached to a node name instead of the pod name. | ||
|
|
||
| You can also use the CLI to retrieve the details of the CRD object `VolumeAttachment`. | ||
|
|
||
| Example of a volume that was attached using the Longhorn UI: | ||
|
|
||
| ``` | ||
| - apiVersion: longhorn.io/v1beta2 | ||
| kind: VolumeAttachment | ||
| ... | ||
| spec: | ||
| attachmentTickets: | ||
| longhorn-ui: | ||
| id: longhorn-ui | ||
| nodeID: node-name | ||
| ... | ||
| volume: pvc-9b35136c-f59e-414b-aa55-b84b9b21ff89 | ||
| ``` | ||
|
|
||
| Example of a volume that was attached using the Longhorn CSI driver: | ||
|
|
||
| ``` | ||
| - apiVersion: longhorn.io/v1beta2 | ||
| kind: VolumeAttachment | ||
| spec: | ||
| attachmentTickets: | ||
| csi-b5097155cddde50b4683b0e659923e379cbfc3873b5b2ee776deb3874102e9bf: | ||
| id: csi-b5097155cddde50b4683b0e659923e379cbfc3873b5b2ee776deb3874102e9bf | ||
| nodeID: node-name | ||
| ... | ||
| volume: pvc-3c6403cd-f1cd-4b84-9b46-162f746b9667 | ||
| ``` | ||
|
|
||
| :::note | ||
|
|
||
| Manually attaching a volume to the node is not recommended. | ||
|
|
||
| ::: | ||
|
|
||
| #### Workaround 1: Set `Detach Manually Attached Volumes When Cordoned` to `True` | ||
|
|
||
| The Longhorn setting [Detach Manually Attached Volumes When Cordoned](https://longhorn.io/docs/1.6.0/references/settings/#detach-manually-attached-volumes-when-cordoned) blocks node draining when there are volumes manually attached to the node. | ||
|
|
||
| The default value of this setting depends on the embedded Longhorn version: | ||
|
|
||
| | Harvester version | Embedded Longhorn version | Default value | | ||
| | --- | --- | --- | | ||
| | v1.3.1 | v1.6.0 | `true` | | ||
| | v1.4.0 | v1.7.0 | `false` | | ||
|
|
||
| Set this option to `true` from the [embedded Longhorn UI](./harvester.md#access-embedded-rancher-and-longhorn-dashboards). | ||
|
|
||
| #### Workaround 2: Manually Detach the Volume | ||
|
|
||
| Detach the volume using the [embedded Longhorn UI](./harvester.md#access-embedded-rancher-and-longhorn-dashboards). | ||
|
|
||
|  | ||
|
|
||
| Once the volume is detached, you can successfully enable Maintenance Mode on the node. | ||
|
|
||
|  | ||
|
|
||
| ### Single-Replica Volumes | ||
|
|
||
| Harvester allows you to create custom StorageClasses that describe how Longhorn must provision volumes. If necessary, you can create a StorageClass with the [Number of Replicas](../advanced/storageclass.md#number-of-replicas) parameter set to `1`. | ||
|
|
||
| When a volume is created using such a StorageClass and is attached to a node using the CSI driver or other methods, the lone replica stays on that node even after the volume is detached. | ||
|
|
||
| You can check this using the CRD object `Volume`. | ||
|
|
||
| ``` | ||
| - apiVersion: longhorn.io/v1beta2 | ||
| kind: Volume | ||
| ... | ||
| spec: | ||
| ... | ||
| numberOfReplicas: 1 // the replica number | ||
| ... | ||
| status: | ||
| ... | ||
| ownerID: nodeName | ||
| ... | ||
| state: attached | ||
| ``` | ||
|
|
||
| #### Workaround: Set `Node Drain Policy` | ||
|
|
||
| The Longhorn [Node Drain Policy](https://longhorn.io/docs/1.6.0/references/settings/#node-drain-policy) is set to `block-if-contains-last-replica` by default. This option forces Longhorn to block node draining when the node contains the last healthy replica of a volume. | ||
|
|
||
| To address the issue, change the value to `allow-if-replica-is-stopped` using the [embedded Longhorn UI](./harvester.md#access-embedded-rancher-and-longhorn-dashboards). | ||
|
|
||
| :::info important | ||
|
|
||
| If you plan to remove the node after Maintenance Mode is enabled, back up single-replica volumes or redeploy the related workloads to other nodes in advance so that the volumes are scheduled to other nodes. | ||
|
|
||
| ::: | ||
|
|
||
| Starting with Harvester v1.4.0, the `Node Drain Policy` is set to `allow-if-replica-is-stopped` by default. |
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