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Deploy TiFlash in Kubernetes

This document describes how to deploy TiFlash in Kubernetes.

Prerequisites

Fresh TiFlash deployment

To deploy TiFlash when deploying the TiDB cluster, refer to Deploy TiDB on General Kubernetes.

Add TiFlash to an existing TiDB cluster

Edit the TidbCluster Custom Resource:

kubectl eidt tc ${cluster_name} -n ${namespace}

Add the TiFlash configuration as follows:

spec:
  tiflash:
    baseImage: pingcap/tiflash
    maxFailoverCount: 3
    replicas: 1
    storageClaims:
    - resources:
        requests:
          storage: 100Gi
      storageClassName: local-storage

To configure other parameters, refer to Configure a TiDB Cluster.

To deploy Enterprise Edition of TiFlash, edit the dm.yaml file above to set spec.tiflash.baseImage to the enterprise image (pingcap/tiflash-enterprise).

For example:

spec:
  tiflash:
    baseImage: pingcap/tiflash-enterprise

TiFlash supports mounting multiple Persistent Volumes (PVs). If you want to configure multiple PVs for TiFlash, configure multiple resources in tiflash.storageClaims, each resources with a separate storage request and storageClassName. For example:

  tiflash:
    baseImage: pingcap/tiflash
    maxFailoverCount: 3
    replicas: 1
    storageClaims:
    - resources:
        requests:
          storage: 100Gi
      storageClassName: local-storage
    - resources:
        requests:
          storage: 100Gi
      storageClassName: local-storage

Warning:

Since TiDB Operator will mount PVs automatically in the order of the items in the storageClaims list, if you need to add more disks to TiFlash, make sure to append the new item only to the end of the original items, and DO NOT modify the order of the original items.

TiDB Operator manages TiFlash by creating StatefulSet. Since StatefulSet does not support modifying volumeClaimTemplates after creation, updating storageClaims to add the disk cannot mount the additional PV to the Pod. There are two solutions:

  • When deploying the TiFlash cluster for the first time, determine how many PVs are required and configure storageClaims.
  • If you really want to add a PV, after configuring storageClaims, you need to manually delete the TiFlash StatefulSet (kubectl delete sts -n ${namespace} ${cluster_name}-tiflash) and wait for the TiDB Operator to recreate it.

To add TiFlash component to an existing TiDB cluster, you need to set replication.enable-placement-rules: true in PD. After you add the TiFlash configuration in TidbCluster by taking the above steps, TiDB Operator automatically configures replication.enable-placement-rules: true in PD.

If the server does not have an external network, refer to deploy the TiDB cluster to download the required Docker image on the machine with an external network and upload it to the server.

Remove TiFlash

  1. Adjust the number of replicas of the tables replicated to the TiFlash cluster.

    To completely remove TiFlash, you need to set the number of replicas of all tables replicated to the TiFlash to 0.

    1. To connect to the TiDB service, refer to the steps in Access the TiDB Cluster in Kubernetes.

    2. To adjust the number of replicas of the tables replicated to the TiFlash cluster, run the following command:

      alter table <db_name>.<table_name> set tiflash replica 0;
  2. Wait for the TiFlash replicas of the related tables to be deleted.

    Connect to the TiDB service and run the following command. If you can not find the replication information of the related tables, it means that the replicas are deleted:

    SELECT * FROM information_schema.tiflash_replica WHERE TABLE_SCHEMA = '<db_name>' and TABLE_NAME = '<table_name>';
  3. To remove TiFlash Pods, run the following command to modify spec.tiflash.replicas to 0:

    kubectl edit tidbcluster ${cluster_name} -n ${namespace}
  4. Check the state of TiFlash Pods and TiFlash stores.

    First, run the following command to check whether you delete the TiFlash Pod successfully:

    kubectl get pod -n ${namespace} -l app.kubernetes.io/component=tiflash,app.kubernetes.io/instance=${cluster_name}

    If the output is empty, it means that you delete the Pod of the TiFlash cluster successfully.

    To check whether the stores of the TiFlash are in the Tombstone state, run the following command:

    kubectl get tidbcluster ${cluster_name} -n ${namespace} -o yaml

    The value of the status.tiflash field in the output result is similar to the example below.

    tiflash:
        ...
        tombstoneStores:
        "88":
            id: "88"
            ip: basic-tiflash-0.basic-tiflash-peer.default.svc
            lastHeartbeatTime: "2020-12-31T04:42:12Z"
            lastTransitionTime: null
            leaderCount: 0
            podName: basic-tiflash-0
            state: Tombstone
        "89":
            id: "89"
            ip: basic-tiflash-1.basic-tiflash-peer.default.svc
            lastHeartbeatTime: "2020-12-31T04:41:50Z"
            lastTransitionTime: null
            leaderCount: 0
            podName: basic-tiflash-1
            state: Tombstone

    Only after you delete all Pods of the TiFlash cluster successfully and all the TiFlash stores have changed to the Tombstone state, can you perform the next operation.

  5. Delete the TiFlash StatefulSet.

    To modify the TidbCluster CR and delete the spec.tiflash field, run the following command:

    kubectl edit tidbcluster ${cluster_name} -n ${namespace}

    To delete the TiFlash StatefulSet, run the following command:

    kubectl delete statefulsets -n ${namespace} -l app.kubernetes.io/component=tiflash,app.kubernetes.io/instance=${cluster_name}

    To check whether you delete the StatefulSet of the TiFlash cluster successfully, run the following command:

    kubectl get sts -n ${namespace} -l app.kubernetes.io/component=tiflash,app.kubernetes.io/instance=${cluster_name}

    If the output is empty, it means that you delete the StatefulSet of the TiFlash cluster successfully.

  6. (Optional) Delete PVC and PV.

    If you confirm that you do not use the data in TiFlash, and you want to delete the data, you need to strictly follow the steps below to delete the data in TiFlash:

    1. Delete the PVC object corresponding to the PV

      kubectl delete pvc -n ${namespace} -l app.kubernetes.io/component=tiflash,app.kubernetes.io/instance=${cluster_name}
    2. If the PV reclaim policy is Retain, the corresponding PV is still retained after you delete the PVC object. If you want to delete the PV, you can set the reclaim policy of the PV to Delete, and the PV can be deleted and recycled automatically.

      kubectl patch pv ${pv_name} -p '{"spec":{"persistentVolumeReclaimPolicy":"Delete"}}'

      In the above command, ${pv_name} represents the PV name of the TiFlash cluster. You can check the PV name by running the following command:

      kubectl get pv -l app.kubernetes.io/component=tiflash,app.kubernetes.io/instance=${cluster_name}

Configuration notes for different versions

Starting from TiDB Operator v1.1.5, the default configuration of spec.tiflash.config.config.flash.service_addr is changed from ${clusterName}-tiflash-POD_NUM.${clusterName}-tiflash-peer.${namespace}.svc:3930 to 0.0.0.0:3930, and TiFlash needs to configure spec.tiflash.config.config.flash.service_addr to 0.0.0.0:3930 since v4.0.5.

Therefore, for different TiFlash and TiDB Operator versions, you need to pay attention to the following configurations:

  • If the TiDB Operator version <= v1.1.4
    • If the TiFlash version <= v4.0.4, no need to manually configure spec.tiflash.config.config.flash.service_addr.
    • If the TiFlash version >= v4.0.5, you need to set spec.tiflash.config.config.flash.service_addr to 0.0.0.0:3930 in the TidbCluster CR.
  • If the TiDB Operator version >= v1.1.5
    • If the TiFlash version <= v4.0.4, you need to set spec.tiflash.config.config.flash.service_addr to ${clusterName}-tiflash-POD_NUM.${clusterName}-tiflash-peer.${namespace}.svc:3930 in the TidbCluster CR. ${clusterName} and ${namespace} need to be replaced according to the real case.
    • If the TiFlash version >= v4.0.5, no need to manually configure spec.tiflash.config.config.flash.service_addr.
    • If you upgrade from TiFlash v4.0.4 or lower versions to TiFlash v4.0.5 or higher versions, you need to delete the configuration of spec.tiflash.config.config.flash.service_addr in the TidbCluster CR.