• 使用StatefulSet部署有状态应用
    • 部署Zookeeper
    • 部署kafka
    • 参考

    使用StatefulSet部署有状态应用

    StatefulSet 这个对象是专门用来部署用状态应用的,可以为Pod提供稳定的身份标识,包括hostname、启动顺序、DNS名称等。

    下面以在kubernetes1.6版本中部署zookeeper和kafka为例讲解StatefulSet的使用,其中kafka依赖于zookeeper。

    Dockerfile和配置文件见 zookeeper 和 kafka。

    注:所有的镜像基于CentOS系统的JDK制作,为我的私人镜像,外部无法访问,yaml中没有配置持久化存储。

    部署Zookeeper

    Dockerfile中从远程获取zookeeper的安装文件,然后在定义了三个脚本:

    • zkGenConfig.sh:生成zookeeper配置文件
    • zkMetrics.sh:获取zookeeper的metrics
    • zkOk.sh:用来做ReadinessProb

    我们在来看下这三个脚本的执行结果:

    zkGenConfig.sh

    zkMetrics.sh脚本实际上执行的是下面的命令:

    1. $ echo mntr | nc localhost $ZK_CLIENT_PORT >& 1
    2. zk_version 3.4.6-1569965, built on 02/20/2014 09:09 GMT
    3. zk_avg_latency 0
    4. zk_max_latency 5
    5. zk_min_latency 0
    6. zk_packets_received 427879
    7. zk_packets_sent 427890
    8. zk_num_alive_connections 3
    9. zk_outstanding_requests 0
    10. zk_server_state leader
    11. zk_znode_count 18
    12. zk_watch_count 3
    13. zk_ephemerals_count 4
    14. zk_approximate_data_size 613
    15. zk_open_file_descriptor_count 29
    16. zk_max_file_descriptor_count 1048576
    17. zk_followers 1
    18. zk_synced_followers 1
    19. zk_pending_syncs 0

    zkOk.sh脚本实际上执行的是下面的命令:

    1. $ echo ruok | nc 127.0.0.1 $ZK_CLIENT_PORT
    2. imok

    zookeeper.yaml

    下面是启动三个zookeeper实例的yaml配置文件:

    1. ---
    2. apiVersion: v1
    3. kind: Service
    4. metadata:
    5. name: zk-svc
    6. labels:
    7. app: zk-svc
    8. spec:
    9. ports:
    10. - port: 2888
    11. name: server
    12. - port: 3888
    13. name: leader-election
    14. clusterIP: None
    15. selector:
    16. app: zk
    17. ---
    18. apiVersion: v1
    19. kind: ConfigMap
    20. metadata:
    21. name: zk-cm
    22. data:
    23. jvm.heap: "1G"
    24. tick: "2000"
    25. init: "10"
    26. sync: "5"
    27. client.cnxns: "60"
    28. snap.retain: "3"
    29. purge.interval: "0"
    30. ---
    31. apiVersion: policy/v1beta1
    32. kind: PodDisruptionBudget
    33. metadata:
    34. name: zk-pdb
    35. spec:
    36. selector:
    37. matchLabels:
    38. app: zk
    39. minAvailable: 2
    40. ---
    41. apiVersion: apps/v1beta1
    42. kind: StatefulSet
    43. metadata:
    44. name: zk
    45. spec:
    46. serviceName: zk-svc
    47. replicas: 3
    48. template:
    49. metadata:
    50. labels:
    51. app: zk
    52. spec:
    53. affinity:
    54. podAntiAffinity:
    55. requiredDuringSchedulingIgnoredDuringExecution:
    56. - labelSelector:
    57. matchExpressions:
    58. - key: "app"
    59. operator: In
    60. values:
    61. - zk
    62. topologyKey: "kubernetes.io/hostname"
    63. containers:
    64. - name: k8szk
    65. imagePullPolicy: Always
    66. image: sz-pg-oam-docker-hub-001.tendcloud.com/library/zookeeper:3.4.6
    67. resources:
    68. requests:
    69. memory: "2Gi"
    70. cpu: "500m"
    71. ports:
    72. - containerPort: 2181
    73. name: client
    74. - containerPort: 2888
    75. name: server
    76. - containerPort: 3888
    77. name: leader-election
    78. env:
    79. - name : ZK_REPLICAS
    80. value: "3"
    81. - name : ZK_HEAP_SIZE
    82. valueFrom:
    83. configMapKeyRef:
    84. name: zk-cm
    85. key: jvm.heap
    86. - name : ZK_TICK_TIME
    87. valueFrom:
    88. configMapKeyRef:
    89. name: zk-cm
    90. key: tick
    91. - name : ZK_INIT_LIMIT
    92. valueFrom:
    93. configMapKeyRef:
    94. name: zk-cm
    95. key: init
    96. - name : ZK_SYNC_LIMIT
    97. valueFrom:
    98. configMapKeyRef:
    99. name: zk-cm
    100. key: tick
    101. - name : ZK_MAX_CLIENT_CNXNS
    102. valueFrom:
    103. configMapKeyRef:
    104. name: zk-cm
    105. key: client.cnxns
    106. - name: ZK_SNAP_RETAIN_COUNT
    107. valueFrom:
    108. configMapKeyRef:
    109. name: zk-cm
    110. key: snap.retain
    111. - name: ZK_PURGE_INTERVAL
    112. valueFrom:
    113. configMapKeyRef:
    114. name: zk-cm
    115. key: purge.interval
    116. - name: ZK_CLIENT_PORT
    117. value: "2181"
    118. - name: ZK_SERVER_PORT
    119. value: "2888"
    120. - name: ZK_ELECTION_PORT
    121. value: "3888"
    122. command:
    123. - sh
    124. - -c
    125. - zkGenConfig.sh && zkServer.sh start-foreground
    126. readinessProbe:
    127. exec:
    128. command:
    129. - "zkOk.sh"
    130. initialDelaySeconds: 10
    131. timeoutSeconds: 5
    132. livenessProbe:
    133. exec:
    134. command:
    135. - "zkOk.sh"
    136. initialDelaySeconds: 10
    137. timeoutSeconds: 5
    138. securityContext:
    139. runAsUser: 1000
    140. fsGroup: 1000

    我们再主要下上面那三个脚本的用途。

    部署kafka

    Kafka的docker镜像制作跟zookeeper类似,都是从远程下载安装包后,解压安装。

    与zookeeper不同的是,只要一个脚本,但是又依赖于我们上一步安装的zookeeper,kafkaGenConfig.sh用来生成kafka的配置文件。

    我们来看下这个脚本。

    1. #!/bin/bash
    2. HOST=`hostname -s`
    3. if [[ $HOST =~ (.*)-([0-9]+)$ ]]; then
    4. NAME=${BASH_REMATCH[1]}
    5. ORD=${BASH_REMATCH[2]}
    6. else
    7. echo "Failed to extract ordinal from hostname $HOST"
    8. exit 1
    9. fi
    10. MY_ID=$((ORD+1))
    11. sed -i s"/broker.id=0/broker.id=$MY_ID/g" /opt/kafka/config/server.properties
    12. sed -i s'/zookeeper.connect=localhost:2181/zookeeper.connect=zk-0.zk-svc.brand.svc:2181,zk-1.zk-svc.brand.svc:2181,zk-2.zk-svc.brand.svc:2181/g' /opt/kafka/config/server.properties

    该脚本根据statefulset生成的pod的hostname的后半截数字部分作为broker ID,同时再替换zookeeper的地址。

    Kafka.yaml

    下面是创建3个kafka实例的yaml配置。

    1. ---
    2. apiVersion: v1
    3. kind: Service
    4. metadata:
    5. name: kafka-svc
    6. labels:
    7. app: kafka
    8. spec:
    9. ports:
    10. - port: 9093
    11. name: server
    12. clusterIP: None
    13. selector:
    14. app: kafka
    15. ---
    16. apiVersion: policy/v1beta1
    17. kind: PodDisruptionBudget
    18. metadata:
    19. name: kafka-pdb
    20. spec:
    21. selector:
    22. matchLabels:
    23. app: kafka
    24. minAvailable: 2
    25. ---
    26. apiVersion: apps/v1beta1
    27. kind: StatefulSet
    28. metadata:
    29. name: kafka
    30. spec:
    31. serviceName: kafka-svc
    32. replicas: 3
    33. template:
    34. metadata:
    35. labels:
    36. app: kafka
    37. spec:
    38. affinity:
    39. podAntiAffinity:
    40. requiredDuringSchedulingIgnoredDuringExecution:
    41. - labelSelector:
    42. matchExpressions:
    43. - key: "app"
    44. operator: In
    45. values:
    46. - kafka
    47. topologyKey: "kubernetes.io/hostname"
    48. podAffinity:
    49. preferredDuringSchedulingIgnoredDuringExecution:
    50. - weight: 1
    51. podAffinityTerm:
    52. labelSelector:
    53. matchExpressions:
    54. - key: "app"
    55. operator: In
    56. values:
    57. - zk
    58. topologyKey: "kubernetes.io/hostname"
    59. terminationGracePeriodSeconds: 300
    60. containers:
    61. - name: k8skafka
    62. imagePullPolicy: Always
    63. image: sz-pg-oam-docker-hub-001.tendcloud.com/library/kafka:2.10-0.8.2.1
    64. resources:
    65. requests:
    66. memory: "1Gi"
    67. cpu: 500m
    68. env:
    69. - name: KF_REPLICAS
    70. value: "3"
    71. ports:
    72. - containerPort: 9093
    73. name: server
    74. command:
    75. - /bin/bash
    76. - -c
    77. - "/opt/kafka/bin/kafkaGenConfig.sh && /opt/kafka/bin/kafka-server-start.sh /opt/kafka/config/server.properties"
    78. env:
    79. - name: KAFKA_HEAP_OPTS
    80. value : "-Xmx512M -Xms512M"
    81. - name: KAFKA_OPTS
    82. value: "-Dlogging.level=DEBUG"
    83. readinessProbe:
    84. tcpSocket:
    85. port: 9092
    86. initialDelaySeconds: 15
    87. timeoutSeconds: 1

    参考

    https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/

    kubernetes contrib - statefulsets

    http://blog.kubernetes.io/2017/01/running-mongodb-on-kubernetes-with-statefulsets.html