413 lines
13 KiB
Markdown
413 lines
13 KiB
Markdown
# 使用Ceph做持久化存储创建MySQL集群
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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。
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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。
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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。
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## 使用 kubernetes 集群外部的 Ceph 存储
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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。
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```bash
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yum install -y ceph-common
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```
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还需要将 ceph 的配置文件 `ceph.conf` 放在所有节点的 `/etc/ceph` 目录下。
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Kubernetes 使用 ceph 存储需要用到如下配置：
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- Monitors: Ceph montors 列表
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- Path：作为挂载的根路径，默认是 /
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- User：RADOS用户名，默认是 admin
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- 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
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- secretRef：Ceph 认证 secret 的引用，如果配置了将会覆盖 secretFile。
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- readOnly：该文件系统是否只读。
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## Galera Cluster介绍
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Galera是一个MySQL(也支持MariaDB，Percona)的同步多主集群软件。
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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。
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## 详细步骤
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以下步骤包括创建 Ceph 的配置 和 MySQL 的配置两部分。
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### 配置 Ceph
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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。
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#### 1. 生成 Ceph secret
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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。
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```bash
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grep key /etc/ceph/ceph.client.admin.keyring |awk '{printf "%s", $NF}'|base64
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```
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将获得加密后的 key：`QVFDWDA2aFo5TG5TQnhBQVl1b0lUL2V3YlRSaEtwVEhPWkxvUlE9PQ==`，我们将在后面用到。
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#### 2. 创建租户namespace
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创建 `galera-namespace.yaml` 文件内容为：
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```yaml
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apiVersion: v1
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kind: Namespace
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metadata:
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name: galera
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```
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#### 3. 创建 Ceph secret
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创建 `ceph-secret.yaml` 文件内容为：
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```yaml
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apiVersion: v1
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kind: Secret
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metadata:
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name: ceph-secret
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namespace: galera
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type: "kubernetes.io/rbd"
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data:
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key: QVFDWDA2aFo5TG5TQnhBQVl1b0lUL2V3YlRSaEtwVEhPWkxvUlE9PQ==
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```
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#### 4. 创建 StorageClass
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创建 `ceph-class.yaml` 文件内容为：
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```yaml
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apiVersion: storage.k8s.io/v1
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kind: StorageClass
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metadata:
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name: ceph-web
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provisioner: kubernetes.io/rbd
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parameters:
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monitors: 172.28.7.98,172.28.7.99,172.28.7.100
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adminId: admin
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adminSecretName: ceph-secret
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adminSecretNamespace: galera
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pool: rbd #此处默认是rbd池，生产上建议自己创建存储池隔离
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userId: admin
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userSecretName: ceph-secret
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```
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此配置请参考 kubernetes 官方文档：https://kubernetes.io/docs/concepts/storage/persistent-volumes/#ceph-rbd
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### 配置 MySQL
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#### 1. 创建 MySQL 配置文件
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创建 `mysql-config.yaml` 文件内容为：
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```yaml
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apiVersion: v1
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kind: ConfigMap
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metadata:
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name: mysql-config-vol
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namespace: galera
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labels:
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app: mysql
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data:
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mariadb.cnf: |
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[client]
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default-character-set = utf8
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[mysqld]
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character-set-server = utf8
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collation-server = utf8_general_ci
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# InnoDB optimizations
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innodb_log_file_size = 64M
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galera.cnf: |
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[galera]
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user = mysql
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bind-address = 0.0.0.0
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# Optimizations
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innodb_flush_log_at_trx_commit = 0
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sync_binlog = 0
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expire_logs_days = 7
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# Required settings
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default_storage_engine = InnoDB
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binlog_format = ROW
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innodb_autoinc_lock_mode = 2
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query_cache_size = 0
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query_cache_type = 0
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# MariaDB Galera settings
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#wsrep_debug=ON
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wsrep_on=ON
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wsrep_provider=/usr/lib/galera/libgalera_smm.so
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wsrep_sst_method=rsync
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# Cluster settings (automatically updated)
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wsrep_cluster_address=gcomm://
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wsrep_cluster_name=galera
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wsrep_node_address=127.0.0.1
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```
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#### 2. 创建 MySQL root 用户和密码
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**创建加密密码**
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```bash
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$ echo -n jimmysong|base64
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amltbXlzb25n
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```
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注意：一定要用-n 去掉换行符，不然会报错。
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**创建 root 用户**
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```bash
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$ echo -n root |base64
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cm9vdA==
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```
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**创建 MySQL secret**
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创建 `mysql-secret.yaml` 文件内容为：
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```yaml
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apiVersion: v1
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kind: Secret
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metadata:
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name: mysql-secrets
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namespace: galera
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labels:
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app: mysql
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data:
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# Root password: changeit run echo -n jimmysong|base64
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root-password: amltbXlzb25n
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# Root user: root
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root-user: cm9vdA==
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```
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#### 3. 创建 yaml 配置文件
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创建 MySQL 的 yaml 文件 `galera-mariadb.yaml` 内容为：
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```yaml
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apiVersion: v1
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kind: Service
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metadata:
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annotations:
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service.alpha.kubernetes.io/tolerate-unready-endpoints: "true"
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name: mysql
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namespace: galera
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labels:
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app: mysql
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tier: data
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spec:
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ports:
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- port: 3306
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name: mysql
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clusterIP: None
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selector:
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app: mysql
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---
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apiVersion: apps/v1beta1
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kind: StatefulSet
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metadata:
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name: mysql
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namespace: galera
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spec:
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serviceName: "mysql"
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replicas: 3
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template:
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metadata:
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labels:
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app: mysql
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tier: data
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annotations:
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pod.beta.kubernetes.io/init-containers: '[
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{
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"name": "galera-init",
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"image": "harbor-001.jimmysong.io/library/k8s-galera-init:latest",
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"args": ["-service=mysql"],
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"env": [
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{
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"name": "POD_NAMESPACE",
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"valueFrom": {
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"fieldRef": { "apiVersion": "v1", "fieldPath": "metadata.namespace" }
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}
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},
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{
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"name": "SAFE_TO_BOOTSTRAP",
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"value": "1"
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},
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{
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"name": "DEBUG",
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"value": "1"
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}
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],
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"volumeMounts": [
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{
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"name": "config",
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"mountPath": "/etc/mysql/conf.d"
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},
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{
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"name": "data",
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"mountPath": "/var/lib/mysql"
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}
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]
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}
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]'
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spec:
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terminationGracePeriodSeconds: 10
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containers:
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- name: mysql
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image: harbor-001.jimmysong.io/library/mariadb:10.1
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imagePullPolicy: IfNotPresent
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ports:
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- containerPort: 3306
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name: mysql
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- containerPort: 4444
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name: sst
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- containerPort: 4567
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name: replication
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- containerPort: 4568
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name: ist
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env:
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- name: MYSQL_ROOT_PASSWORD
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valueFrom:
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secretKeyRef:
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name: mysql-secrets
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key: root-password
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- name: MYSQL_ROOT_USER
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valueFrom:
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secretKeyRef:
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name: mysql-secrets
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key: root-user
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- name: MYSQL_INITDB_SKIP_TZINFO
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value: "yes"
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livenessProbe:
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exec:
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command: ["sh", "-c", "mysql -u\"${MYSQL_ROOT_USER:-root}\" -p\"${MYSQL_ROOT_PASSWORD}\" -e 'show databases;'"]
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initialDelaySeconds: 60
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timeoutSeconds: 5
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readinessProbe:
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exec:
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command: ["sh", "-c", "mysql -u\"${MYSQL_ROOT_USER:-root}\" -p\"${MYSQL_ROOT_PASSWORD}\" -e 'show databases;'"]
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initialDelaySeconds: 20
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timeoutSeconds: 5
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volumeMounts:
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- name: config
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mountPath: /etc/mysql/conf.d
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- name: data
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mountPath: /var/lib/mysql
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volumes:
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- name: config
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configMap:
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name: mysql-config-vol
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imagePullSecrets:
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- name: "registrykey"
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volumeClaimTemplates:
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- metadata:
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name: data
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annotations:
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volume.beta.kubernetes.io/storage-class: "ceph-web" #引用ceph class 的类
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spec:
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accessModes: [ "ReadWriteOnce" ]
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resources:
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requests:
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storage: 3Gi
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```
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## 部署 MySQL 集群
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在 `/etc/mariadb-cluster` 目录下执行：
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```bash
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kubectl create -f .
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```
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## 验证
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存在 issue，参考 [Error creating rbd image: executable file not found in $PATH#38923](https://github.com/kubernetes/kubernetes/issues/38923)
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## 问题记录
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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：
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```bash
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Events:
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FirstSeen LastSeen Count From SubObjectPath Type Reason Message
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--------- -------- ----- ---- ------------- -------- ------ -------
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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:
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```
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检查 `kube-controller-manager` 的日志将看到如下错误信息：
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```bash
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journalctl -xe -u kube-controller-manager
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... rbd_util.go:364] failed to create rbd image, output
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... rbd.go:317] rbd: create volume failed, err: failed to create rbd image: executable file not found in $PATH, command output:
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```
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这是因为 `kube-controller-manager` 主机上没有安装 `ceph-common` 的缘故。
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但是安装了 `ceph-common` 之后依然有问题：
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```bash
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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
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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
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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
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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:
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```
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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)
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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）：
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```go
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func (util *RBDUtil) CreateImage(p *rbdVolumeProvisioner) (r *v1.RBDVolumeSource, size int, err error) {
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var output []byte
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capacity := p.options.PVC.Spec.Resources.Requests[v1.ResourceName(v1.ResourceStorage)]
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volSizeBytes := capacity.Value()
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// convert to MB that rbd defaults on
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sz := int(volume.RoundUpSize(volSizeBytes, 1024*1024))
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volSz := fmt.Sprintf("%d", sz)
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// rbd create
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l := len(p.rbdMounter.Mon)
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// pick a mon randomly
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start := rand.Int() % l
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// iterate all monitors until create succeeds.
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for i := start; i < start+l; i++ {
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mon := p.Mon[i%l]
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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)
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output, err = p.rbdMounter.plugin.execCommand("rbd",
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[]string{"create", p.rbdMounter.Image, "--size", volSz, "--pool", p.rbdMounter.Pool, "--id", p.rbdMounter.adminId, "-m", mon, "--key=" + p.rbdMounter.adminSecret, "--image-format", "1"})
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if err == nil {
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break
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} else {
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glog.Warningf("failed to create rbd image, output %v", string(output))
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}
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}
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if err != nil {
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return nil, 0, fmt.Errorf("failed to create rbd image: %v, command output: %s", err, string(output))
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}
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return &v1.RBDVolumeSource{
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CephMonitors: p.rbdMounter.Mon,
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RBDImage: p.rbdMounter.Image,
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RBDPool: p.rbdMounter.Pool,
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}, sz, nil
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}
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```
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该方法调用失败。
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## 参考
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https://github.com/kubernetes/examples/blob/master/staging/volumes/cephfs/README.md
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[k8s-ceph-statefulsets-storageclass-nfs 动态卷有状态应用实践](http://blog.csdn.net/idea77/article/details/72842723)
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[Kubernetes persistent storage with Ceph](https://crondev.com/kubernetes-persistent-storage-ceph/)
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https://kubernetes.io/docs/concepts/storage/persistent-volumes/#ceph-rbd
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[Error creating rbd image: executable file not found in $PATH#38923](https://github.com/kubernetes/kubernetes/issues/38923)
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