Jenkins High Availability Solution¶

Due to the architecture design of Jenkins itself, it does not natively support a multi-node setup, making horizontal scaling for high availability unfeasible. However, leveraging Kubernetes' fault tolerance mechanism, when a Jenkins Pod fails, Kubernetes can schedule the Pod onto another node, thus achieving high availability.

Thus, the primary focus for Jenkins high availability is on ensuring high availability at the data storage layer.

In DCE 5.0, Jenkins high availability is achieved by utilizing the storage layer of HwameiStor. HwameiStor supports the use of DRBD (Distributed Replicated Block Device) to mount duplicate data copies simultaneously on multiple nodes. When the node hosting Jenkins goes down, Kubernetes can schedule the Pod onto another node seamlessly, allowing continued access to the previous data and thereby achieving high availability.

The following section will explain how to achieve Jenkins high availability based on HwameiStor.

Prerequisites¶

• To install HwameiStor, refer to https://hwameistor.io/cn/docs/intro. At least two nodes are required for high availability.
• Ensure that the system has available and clean disks (disks with no existing data or partition information), as HwameiStor cannot utilize disks that are already in use. You can use the kubectl get ld command to view disk information in the system.

Installation Steps¶

1. Confirm the availability of disks

   kubectl get ld
   

   The output should resemble:

   localdisk-f24ee676b24652341ed5d61560b7bb16   controller-node-1   /dev/sdb     Available   Active   51m
   

   New disks will have the status "Available" and can be detected after they are added.

2. Confirm disk type

   kubectl get ld localdisk-f24ee676b24652341ed5d61560b7bb16 -o yaml | grep type
   

   The output should resemble:

   type: HDD
   

   Pay attention to distinguish between HDD and SSD types.

3. Create a LocalDiskClaim to add the disk to HwameiStor's management.

   > kubectl apply -f - <<EOF
   apiVersion: hwameistor.io/v1alpha1
   kind: LocalDiskClaim
   metadata:
     name: controller-node-1      # Change to the current node's name
   spec:
     nodeName: controller-node-1  # Change to the current node's name (kubectl get node)
     owner: local-storage         # "owner" and "disk" types are different; only LVM types support HA (high availability) and scaling. Differentiate between LVM and disk types.
     description:
       diskType: HDD              # Change to the current node's disk type
   EOF
   

4. Verify successful inclusion.

   kubectl get localstoragenode $nodeName -o yaml
   

   The output should resemble:

   apiVersion: hwameistor.io/v1alpha1
   kind: LocalStorageNode
   metadata:
     name: controller-node-1
   spec:
     hostname: controller-node-1
     storageIP: 172.30.47.32
     topogoly:
       region: default
       zone: default
   status:
     conditions:
     - lastTransitionTime: "2023-09-11T06:33:57Z"
       lastUpdateTime: "2023-09-11T06:33:57Z"
       message: Successfully to expand storage capacity
       reason: StorageExpandSuccess
       status: "True"
       type: ExpandSuccess
     poolExtendRecords:
       LocalStorage_PoolHDD:
       - description:
           diskType: HDD
         diskRefs:
         - apiVersion: hwameistor.io/v1alpha1
           kind: LocalDisk
           name: localdisk-6285c10750cc3495c59e4cadf275621b
           resourceVersion: "24961890"
           uid: 3406c479-f4d9-4a94-8d84-69dd6f10f8d3
         nodeName: controller-node-1
         owner: local-storage
     pools: # (1)
       LocalStorage_PoolHDD:
         class: HDD
         disks:
         - capacityBytes: 42945478656
           devPath: /dev/sdc
           state: InUse
           type: HDD
         freeCapacityBytes: 38650511360
         freeVolumeCount: 999
         name: LocalStorage_PoolHDD
         totalCapacityBytes: 42945478656
         totalVolumeCount: 1000
         type: REGULAR
         usedCapacityBytes: 4294967296
         usedVolumeCount: 1
         volumeCapacityBytesLimit: 42945478656
         volumes:
         - pvc-26a63717-8b53-4c37-ad99-6d4394288192
     state: Ready
   

   1. If the above content is displayed, it signifies successful inclusion.

5. Modify Jenkins' storageClass

   • For Jenkins installed through the UI, you can set the storageClass (storage class hwameistor-storage-lvm-hdd-ha ) during installation.
   • For Jenkins installed using Helm, you can set the storageClassName in the Helm value.yaml file to hwameistor-storage-lvm-hdd-ha .

   Note

   • Before installation, ensure that the storageClass exists by running kubectl get sc .
   • Generally, after installing HwameiStor, the hwameistor-storage-lvm-hdd-ha storageClass is automatically created. If it does not exist, please contact the administrator.
   • Depending on the added disk type, it could also be hwameistor-storage-lvm-ssd-ha . Just specify a high availability (ha) type storageClass.

Once Jenkins is deployed, Jenkins' high availability functionality will be enabled.

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