如果你经常使用docker-compose
启动服务的话,可能会遇到下面的问题:服务 B 依赖服务 A,需要服务 A 先启动,再启动服务 B
举个例子,在部署 kafka 集群的时候,需要启动两个kafka,并使用zookeeper做注册中心,docker-compose.yaml 文件如下
version: '3'
services:
zookeeper:
image: wurstmeister/zookeeper
container_name: zookeeper
ports:
- "2181:2181"
networks:
- kafka_net
kafka1:
image: wurstmeister/kafka:2.11-0.11.0.3
container_name: kafka1
ports:
- "9092:9092"
environment:
KAFKA_BROKER_ID: 1
# 对应 server.properties 中 advertised.listeners 配置
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka1:9092
# 对应 server.properties 中 listeners 配置
KAFKA_LISTENERS: PLAINTEXT://0.0.0.0:9092
KAFKA_ADVERTISED_PORT: 9092
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
volumes:
- ./data/kafka1:/kafka
networks:
- kafka_net
kafka2:
image: wurstmeister/kafka:2.11-0.11.0.3
container_name: kafka2
ports:
- "9093:9092"
environment:
KAFKA_BROKER_ID: 2
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka2:9092
KAFKA_LISTENERS: PLAINTEXT://0.0.0.0:9092
KAFKA_ADVERTISED_PORT: 9092
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
volumes:
- ./data/kafka2:/kafka
networks:
- kafka_net
networks:
kafka_net:
driver: bridge
此时会同时启动 3 个容器,zookeeper、kafka1 和 kafka2
$ docker-compose up -d
[+] Running 3/3
⠿ Container kafka1 Started 11.6s
⠿ Container kafka2 Started 11.5s
⠿ Container zookeeper Started 11.5s
使用docker logs
查看kafka1
启动日志
$ docker logs kafka1
...
[2023-05-06 02:20:49,851] FATAL [Kafka Server 1], Fatal error during KafkaServer startup. Prepare to shutdown (kafka.server.KafkaServer)
java.lang.RuntimeException: A broker is already registered on the path /brokers/ids/1. This probably indicates that you either have configured a brokerid that is already in use, or else you have shutdown this broker and restarted it faster than the zookeeper timeout so it appears to be re-registering.
at kafka.utils.ZkUtils.registerBrokerInZk(ZkUtils.scala:417)
at kafka.utils.ZkUtils.registerBrokerInZk(ZkUtils.scala:403)
at kafka.server.KafkaHealthcheck.register(KafkaHealthcheck.scala:70)
at kafka.server.KafkaHealthcheck.startup(KafkaHealthcheck.scala:50)
at kafka.server.KafkaServer.startup(KafkaServer.scala:280)
at kafka.server.KafkaServerStartable.startup(KafkaServerStartable.scala:38)
at kafka.Kafka$.main(Kafka.scala:65)
at kafka.Kafka.main(Kafka.scala)
[2023-05-06 02:20:49,854] INFO [Kafka Server 1], shutting down (kafka.server.KafkaServer)
[2023-05-06 02:20:49,860] INFO [Socket Server on Broker 1], Shutting down (kafka.network.SocketServer)
[2023-05-06 02:20:49,874] INFO [Socket Server on Broker 1], Shutdown completed (kafka.network.SocketServer)
...
日志抛出了个timeout
异常,连接zookeeper
超时了,这是因为在启动kafka1
的时候,zookeeper
还没启动完成,kafka1
在连接 zookeeper
的时候,就会报连接超时
这时候我们可以用depends_on
来解决容器依赖问题,depends_on
表示在启动本容器前,确保depends_on
的容器先启动
加上depends_on
后的docker-compose.yaml
文件如下
version: '3'
services:
zookeeper:
image: wurstmeister/zookeeper
container_name: zookeeper
ports:
- "2181:2181"
networks:
- kafka_net
kafka1:
image: wurstmeister/kafka:2.11-0.11.0.3
container_name: kafka1
ports:
- "9092:9092"
environment:
KAFKA_BROKER_ID: 1
# 对应 server.properties 中 advertised.listeners 配置
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka1:9092
# 对应 server.properties 中 listeners 配置
KAFKA_LISTENERS: PLAINTEXT://0.0.0.0:9092
KAFKA_ADVERTISED_PORT: 9092
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
volumes:
- ./data/kafka1:/kafka
depends_on:
- zookeeper
networks:
- kafka_net
kafka2:
image: wurstmeister/kafka:2.11-0.11.0.3
container_name: kafka2
ports:
- "9093:9092"
environment:
KAFKA_BROKER_ID: 2
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka2:9092
KAFKA_LISTENERS: PLAINTEXT://0.0.0.0:9092
KAFKA_ADVERTISED_PORT: 9092
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
volumes:
- ./data/kafka2:/kafka
depends_on:
- zookeeper
networks:
- kafka_net
networks:
kafka_net:
driver: bridge
再次启动服务
$ docker-compose up -d
[+] Running 3/3
⠿ Container zookeeper Started 0.5s
⠿ Container kafka2 Started 0.9s
⠿ Container kafka1 Started 1.0s
用docker logs
查看kafka
启动日志,发现容器正常启动
到这里我们已经解决了容器的启动顺序问题,但是多启动几次会发现,kafka
连接zookeeper
超时的问题还是会发生,而且是偶发性的,这是为什么呢?查阅资料发现,**depends_on**
只是解决容器启动顺序的问题,但是无法保证容器启动完成,或者说并不会等待**zookeeper**
就绪就直接启动**kafka**
了,这时候如果zookeeper
还在启动中,kafka
就发起连接请求,此时请求就会超时
解决方案是在depends_on
中加入condition
属性,conditon
能使用下面三种状态
-
serveice_started
: 容器启动完成 -
service_healthy
:容器处于healthy
状态,healthy
状态的检查依赖healthcheck
-
service_completed_successfully
:在启动依赖服务之前,需要确保依赖服务已经成功完成运行
这里我们使用service_healthy
,当zookeeper
处于healthy
状态的时候,再启动kafka
version: '3'
services:
zookeeper:
image: wurstmeister/zookeeper
container_name: zookeeper
ports:
- "2181:2181"
networks:
- kafka_net
kafka1:
image: wurstmeister/kafka:2.11-0.11.0.3
container_name: kafka1
ports:
- "9092:9092"
environment:
KAFKA_BROKER_ID: 1
# 对应 server.properties 中 advertised.listeners 配置
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka1:9092
# 对应 server.properties 中 listeners 配置
KAFKA_LISTENERS: PLAINTEXT://0.0.0.0:9092
KAFKA_ADVERTISED_PORT: 9092
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
volumes:
- ./data/kafka1:/kafka
depends_on:
zookeeper:
condition: service_healthy
networks:
- kafka_net
kafka2:
image: wurstmeister/kafka:2.11-0.11.0.3
container_name: kafka2
ports:
- "9093:9092"
environment:
KAFKA_BROKER_ID: 2
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka2:9092
KAFKA_LISTENERS: PLAINTEXT://0.0.0.0:9092
KAFKA_ADVERTISED_PORT: 9092
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
volumes:
- ./data/kafka2:/kafka
depends_on:
zookeeper:
condition: service_healthy
networks:
- kafka_net
networks:
kafka_net:
driver: bridge
启动服务试一下
$ docker-compose up -d
[+] Running 3/4
⠿ Network kafka_kafka_net Created 0.0s
⠿ Container zookeeper Waiting 1.0s
⠿ Container kafka1 Created 0.1s
⠿ Container kafka2 Created 0.1s
container for service "zookeeper" has no healthcheck configured
这里提示zookeeper
服务没有配置healthcheck
,这是因为,docker 只能启动服务,并不知道容器内的进程什么时候处于healthy
状态,所以需要我们自己配置健康检查,不同的进程有不同的健康检查方法,检查zookeeper
是否正常启动完成,可以执行echo 'stat' | nc localhost 2181 || exit 1
命令,命令返回 0 表示容器healthy
,返回 1 表示unhealthy
,healthy
还能配置其他参数,如时间间隔、超时等,完整的配置如下
version: '3'
services:
zookeeper:
image: wurstmeister/zookeeper
container_name: zookeeper
ports:
- "2181:2181"
networks:
- kafka_net
healthcheck:
test: echo 'stat' | nc localhost 2181 || exit 1
interval: 5s
timeout: 5s
retries: 6
kafka1:
image: wurstmeister/kafka:2.11-0.11.0.3
container_name: kafka1
ports:
- "9092:9092"
environment:
KAFKA_BROKER_ID: 1
# 对应 server.properties 中 advertised.listeners 配置
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka1:9092
# 对应 server.properties 中 listeners 配置
KAFKA_LISTENERS: PLAINTEXT://0.0.0.0:9092
KAFKA_ADVERTISED_PORT: 9092
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
volumes:
- ./data/kafka1:/kafka
depends_on:
zookeeper:
condition: service_healthy
networks:
- kafka_net
kafka2:
image: wurstmeister/kafka:2.11-0.11.0.3
container_name: kafka2
ports:
- "9093:9092"
environment:
KAFKA_BROKER_ID: 2
KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka2:9092
KAFKA_LISTENERS: PLAINTEXT://0.0.0.0:9092
KAFKA_ADVERTISED_PORT: 9092
KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
volumes:
- ./data/kafka2:/kafka
depends_on:
zookeeper:
condition: service_healthy
networks:
- kafka_net
networks:
kafka_net:
driver: bridge
$ docker-compose up -d
[+] Running 4/4
⠿ Network kafka_kafka_net Created 0.0s
⠿ Container zookeeper Healthy 6.0s
⠿ Container kafka1 Started 6.5s
⠿ Container kafka2 Started 6.4s
可以看到,kafka
会等待zookeeper
启动,并处于healthy
状态,再启动文章来源:https://www.toymoban.com/news/detail-719061.html
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