# 使用Ceph做持久化存储创建MySQL集群 本文中用到的 yaml 文件可以在 [../manifests/mariadb-cluster](https://github.com/rootsongjc/kubernetes-handbook/blob/master/manifests/mariadb-cluster) 目录下找到。 下面我们以部署一个高可用的 MySQL 集群为例,讲解如何使用 Ceph 做数据持久化,其中使用 StorageClass 动态创建 PV,Ceph 集群我们使用 kubernetes 集群外部的已有的集群,我们没有必要重新部署了。 在 1.4 以后,kubernetes 提供了一种更加方便的动态创建 PV 的方式;也就是说使用 StoragaClass 时无需预先创建固定大小的 PV,等待使用者创建 PVC 来使用;而是直接创建 PVC 即可分配使用。 ## 使用 kubernetes 集群外部的 Ceph 存储 在部署 kubernetes 之前我们就已经有了 Ceph 集群,因此我们可以直接拿来用。但是 kubernetes 的所有节点(尤其是 master 节点)上依然需要安装 ceph 客户端。 ```bash yum install -y ceph-common ``` 还需要将 ceph 的配置文件 `ceph.conf` 放在所有节点的 `/etc/ceph` 目录下。 Kubernetes 使用 ceph 存储需要用到如下配置: - Monitors: Ceph montors 列表 - Path:作为挂载的根路径,默认是 / - User:RADOS用户名,默认是 admin - secretFile:keyring 文件路径,默认是 /etc/ceph/user.secret,我们 Ceph 集群提供的文件是 `ceph.client.admin.keyring`,将在下面用到 - secretRef:Ceph 认证 secret 的引用,如果配置了将会覆盖 secretFile。 - readOnly:该文件系统是否只读。 ## Galera Cluster介绍 Galera是一个MySQL(也支持MariaDB,Percona)的同步多主集群软件。 从用户视角看,一组Galera集群可以看作一个具有多入口的MySQL库,用户可以同时从多个IP读写这个库。目前Galera已经得到广泛应用,例如Openstack中,在集群规模不大的情况下,稳定性已经得到了实践考验。真正的multi-master,即所有节点可以同时读写数据库。 ## 详细步骤 以下步骤包括创建 Ceph 的配置 和 MySQL 的配置两部分。 ### 配置 Ceph 关于 Ceph 的 yaml 文件可以在 [../manifest/mariadb-cluster](https://github.com/rootsongjc/kubernetes-handbook/tree/master/manifests/mariadb-cluster) 目录下找到。 #### 1. 生成 Ceph secret 使用 Ceph 管理员提供给你的 `ceph.client.admin.keyring` 文件,我们将它放在了 `/etc/ceph` 目录下,用来生成 secret。 ```bash grep key /etc/ceph/ceph.client.admin.keyring |awk '{printf "%s", $NF}'|base64 ``` 将获得加密后的 key:`QVFDWDA2aFo5TG5TQnhBQVl1b0lUL2V3YlRSaEtwVEhPWkxvUlE9PQ==`,我们将在后面用到。 #### 2. 创建租户namespace 创建 `galera-namespace.yaml` 文件内容为: ```yaml apiVersion: v1 kind: Namespace metadata: name: galera ``` #### 3. 创建 Ceph secret 创建 `ceph-secret.yaml` 文件内容为: ```yaml apiVersion: v1 kind: Secret metadata: name: ceph-secret namespace: galera type: "kubernetes.io/rbd" data: key: QVFDWDA2aFo5TG5TQnhBQVl1b0lUL2V3YlRSaEtwVEhPWkxvUlE9PQ== ``` #### 4. 创建 StorageClass 创建 `ceph-class.yaml` 文件内容为: ```yaml apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: name: ceph-web provisioner: kubernetes.io/rbd parameters: monitors: 172.28.7.98,172.28.7.99,172.28.7.100 adminId: admin adminSecretName: ceph-secret adminSecretNamespace: galera pool: rbd #此处默认是rbd池,生产上建议自己创建存储池隔离 userId: admin userSecretName: ceph-secret ``` 此配置请参考 kubernetes 官方文档:https://kubernetes.io/docs/concepts/storage/persistent-volumes/#ceph-rbd ### 配置 MySQL #### 1. 创建 MySQL 配置文件 创建 `mysql-config.yaml` 文件内容为: ```yaml apiVersion: v1 kind: ConfigMap metadata: name: mysql-config-vol namespace: galera labels: app: mysql data: mariadb.cnf: | [client] default-character-set = utf8 [mysqld] character-set-server = utf8 collation-server = utf8_general_ci # InnoDB optimizations innodb_log_file_size = 64M galera.cnf: | [galera] user = mysql bind-address = 0.0.0.0 # Optimizations innodb_flush_log_at_trx_commit = 0 sync_binlog = 0 expire_logs_days = 7 # Required settings default_storage_engine = InnoDB binlog_format = ROW innodb_autoinc_lock_mode = 2 query_cache_size = 0 query_cache_type = 0 # MariaDB Galera settings #wsrep_debug=ON wsrep_on=ON wsrep_provider=/usr/lib/galera/libgalera_smm.so wsrep_sst_method=rsync # Cluster settings (automatically updated) wsrep_cluster_address=gcomm:// wsrep_cluster_name=galera wsrep_node_address=127.0.0.1 ``` #### 2. 创建 MySQL root 用户和密码 **创建加密密码** ```bash $ echo -n jimmysong|base64 amltbXlzb25n ``` 注意:一定要用-n 去掉换行符,不然会报错。 **创建 root 用户** ```bash $ echo -n root |base64 cm9vdA== ``` **创建 MySQL secret** 创建 `mysql-secret.yaml` 文件内容为: ```yaml apiVersion: v1 kind: Secret metadata: name: mysql-secrets namespace: galera labels: app: mysql data: # Root password: changeit run echo -n jimmysong|base64 root-password: amltbXlzb25n # Root user: root root-user: cm9vdA== ``` #### 3. 创建 yaml 配置文件 创建 MySQL 的 yaml 文件 `galera-mariadb.yaml` 内容为: ```yaml apiVersion: v1 kind: Service metadata: annotations: service.alpha.kubernetes.io/tolerate-unready-endpoints: "true" name: mysql namespace: galera labels: app: mysql tier: data spec: ports: - port: 3306 name: mysql clusterIP: None selector: app: mysql --- apiVersion: apps/v1beta1 kind: StatefulSet metadata: name: mysql namespace: galera spec: serviceName: "mysql" replicas: 3 template: metadata: labels: app: mysql tier: data annotations: pod.beta.kubernetes.io/init-containers: '[ { "name": "galera-init", "image": "harbor-001.jimmysong.io/library/k8s-galera-init:latest", "args": ["-service=mysql"], "env": [ { "name": "POD_NAMESPACE", "valueFrom": { "fieldRef": { "apiVersion": "v1", "fieldPath": "metadata.namespace" } } }, { "name": "SAFE_TO_BOOTSTRAP", "value": "1" }, { "name": "DEBUG", "value": "1" } ], "volumeMounts": [ { "name": "config", "mountPath": "/etc/mysql/conf.d" }, { "name": "data", "mountPath": "/var/lib/mysql" } ] } ]' spec: terminationGracePeriodSeconds: 10 containers: - name: mysql image: harbor-001.jimmysong.io/library/mariadb:10.1 imagePullPolicy: IfNotPresent ports: - containerPort: 3306 name: mysql - containerPort: 4444 name: sst - containerPort: 4567 name: replication - containerPort: 4568 name: ist env: - name: MYSQL_ROOT_PASSWORD valueFrom: secretKeyRef: name: mysql-secrets key: root-password - name: MYSQL_ROOT_USER valueFrom: secretKeyRef: name: mysql-secrets key: root-user - name: MYSQL_INITDB_SKIP_TZINFO value: "yes" livenessProbe: exec: command: ["sh", "-c", "mysql -u\"${MYSQL_ROOT_USER:-root}\" -p\"${MYSQL_ROOT_PASSWORD}\" -e 'show databases;'"] initialDelaySeconds: 60 timeoutSeconds: 5 readinessProbe: exec: command: ["sh", "-c", "mysql -u\"${MYSQL_ROOT_USER:-root}\" -p\"${MYSQL_ROOT_PASSWORD}\" -e 'show databases;'"] initialDelaySeconds: 20 timeoutSeconds: 5 volumeMounts: - name: config mountPath: /etc/mysql/conf.d - name: data mountPath: /var/lib/mysql volumes: - name: config configMap: name: mysql-config-vol imagePullSecrets: - name: "registrykey" volumeClaimTemplates: - metadata: name: data annotations: volume.beta.kubernetes.io/storage-class: "ceph-web" #引用ceph class 的类 spec: accessModes: [ "ReadWriteOnce" ] resources: requests: storage: 3Gi ``` ## 部署 MySQL 集群 在 `/etc/mariadb-cluster` 目录下执行: ```bash kubectl create -f . ``` ## 验证 存在 issue,参考 [Error creating rbd image: executable file not found in $PATH#38923](https://github.com/kubernetes/kubernetes/issues/38923) ## 问题记录 如果没有安装 `ceph-common` 的话,kubernetes 在创建 PVC 的时候会有如下报错信息: ```bash Events: FirstSeen LastSeen Count From SubObjectPath Type Reason Message --------- -------- ----- ---- ------------- -------- ------ ------- 1h 12s 441 {persistentvolume-controller } Warning ProvisioningFailed Failed to provision volume with StorageClass "ceph-web": failed to create rbd image: executable file not found in $PATH, command output: ``` 检查 `kube-controller-manager` 的日志将看到如下错误信息: ```bash journalctl -xe -u kube-controller-manager ... rbd_util.go:364] failed to create rbd image, output ... rbd.go:317] rbd: create volume failed, err: failed to create rbd image: executable file not found in $PATH, command output: ``` 这是因为 `kube-controller-manager` 主机上没有安装 `ceph-common` 的缘故。 但是安装了 `ceph-common` 之后依然有问题: ```bash Sep 4 15:25:36 bj-xg-oam-kubernetes-001 kube-controller-manager: W0904 15:25:36.032128 13211 rbd_util.go:364] failed to create rbd image, output Sep 4 15:25:36 bj-xg-oam-kubernetes-001 kube-controller-manager: W0904 15:25:36.032201 13211 rbd_util.go:364] failed to create rbd image, output Sep 4 15:25:36 bj-xg-oam-kubernetes-001 kube-controller-manager: W0904 15:25:36.032252 13211 rbd_util.go:364] failed to create rbd image, output Sep 4 15:25:36 bj-xg-oam-kubernetes-001 kube-controller-manager: E0904 15:25:36.032276 13211 rbd.go:317] rbd: create volume failed, err: failed to create rbd image: fork/exec /usr/bin/rbd: invalid argument, command output: ``` 该问题尚未解决,参考 [Error creating rbd image: executable file not found in $PATH#38923](https://github.com/kubernetes/kubernetes/issues/38923) 从日志记录来看追查到 `pkg/volume/rbd/rbd.go` 的 `func (r *rbdVolumeProvisioner) Provision() (*v1.PersistentVolume, error) {` 方法对 `ceph-class.yaml` 中的参数进行了验证和处理后调用了 `pkg/volume/rbd/rdb_utils.go` 文件第 344 行 `CreateImage` 方法(kubernetes v1.6.1版本): ```go func (util *RBDUtil) CreateImage(p *rbdVolumeProvisioner) (r *v1.RBDVolumeSource, size int, err error) { var output []byte capacity := p.options.PVC.Spec.Resources.Requests[v1.ResourceName(v1.ResourceStorage)] volSizeBytes := capacity.Value() // convert to MB that rbd defaults on sz := int(volume.RoundUpSize(volSizeBytes, 1024*1024)) volSz := fmt.Sprintf("%d", sz) // rbd create l := len(p.rbdMounter.Mon) // pick a mon randomly start := rand.Int() % l // iterate all monitors until create succeeds. for i := start; i < start+l; i++ { mon := p.Mon[i%l] glog.V(4).Infof("rbd: create %s size %s using mon %s, pool %s id %s key %s", p.rbdMounter.Image, volSz, mon, p.rbdMounter.Pool, p.rbdMounter.adminId, p.rbdMounter.adminSecret) output, err = p.rbdMounter.plugin.execCommand("rbd", []string{"create", p.rbdMounter.Image, "--size", volSz, "--pool", p.rbdMounter.Pool, "--id", p.rbdMounter.adminId, "-m", mon, "--key=" + p.rbdMounter.adminSecret, "--image-format", "1"}) if err == nil { break } else { glog.Warningf("failed to create rbd image, output %v", string(output)) } } if err != nil { return nil, 0, fmt.Errorf("failed to create rbd image: %v, command output: %s", err, string(output)) } return &v1.RBDVolumeSource{ CephMonitors: p.rbdMounter.Mon, RBDImage: p.rbdMounter.Image, RBDPool: p.rbdMounter.Pool, }, sz, nil } ``` 该方法调用失败。 ## 参考 https://github.com/kubernetes/examples/blob/master/staging/volumes/cephfs/README.md [k8s-ceph-statefulsets-storageclass-nfs 动态卷有状态应用实践](http://blog.csdn.net/idea77/article/details/72842723) [Kubernetes persistent storage with Ceph](https://crondev.com/kubernetes-persistent-storage-ceph/) https://kubernetes.io/docs/concepts/storage/persistent-volumes/#ceph-rbd [Error creating rbd image: executable file not found in $PATH#38923](https://github.com/kubernetes/kubernetes/issues/38923)