docker - 为什么这个docker-compose yml文件不执行该dockerfile中详细说明的命令？

Question

我有两个docker镜像:生产者和RabbitMQ队列。我的目标是让生产者(Python)将条目吐入队列。然后，我想调用docker-compose up并观看生产者将内容添加到队列中。

现在，我不是盒子里最亮的蜡笔，如果有人能为我指出为什么事情没有按我的预期去做，我将不胜感激。我的生产者是./producer目录中的两个简单文件。该目录的dockerfile如下所示:

FROM ubuntu:latest

ENV DEBIAN_FRONTEND=noninteractive

# Prepare to install 3.7 + GDAL libraries
RUN apt-get update --fix-missing
RUN apt-get install -y software-properties-common apt-utils
RUN add-apt-repository ppa:ubuntugis/ppa
RUN add-apt-repository ppa:deadsnakes/ppa
RUN apt-get update --fix-missing

# Install the packages for GDAL
RUN apt-get install libgdal-dev gdal-bin -y
# Install the packages for python
RUN apt-get install python3.7 python3-pip python3.7-dev -y

RUN python3.7 -m pip install pika

COPY ./example.py example.py

CMD [ "/bin/bash", "-c \"python3.7 example.py\"" ]

我一直在交换最后一行与 ENTRYPOINT， CMD，各个版本的 /bin/bash， python3， python3.7。运行 docker build -t blah && docker run --rm blah会产生我期望的行为(无法连接到队列，因为它没有运行异常)。

在保存 ./producer的目录中，我有一个 docker-compose.yml文件，如下所示:

version: "3.3"
services:

  # RabbitMQ that connects the backend to the frontend
  queue:
    image: rabbitmq:3-management
    expose:
      # The standard AMQP protocol port
      - 5672
    ports:
      # HTTP management UI
      - '15672:15672'
    environment:
      RABBITMQ_DEFAULT_USER: "guest"
      RABBITMQ_DEFAULT_PASS: "guest"
    networks:
      rakan:
        ipv4_address: 172.16.238.10
    deploy:
      replicas: 1
      update_config:
        parallelism: 1
        delay: 10s
      restart_policy:
        condition: on-failure
        delay: 10s
        max_attempts: 3
        window: 120s
    healthcheck:
      test: [ "CMD", "nc", "-z", "localhost", "5672" ]
      interval: 5s
      timeout: 15s
      retries: 1


  producer:
    depends_on: 
      - queue
    build: 
      context: ./producer
      dockerfile: dockerfile
    # entrypoint: "/bin/bash -c \"python example.py\""
    expose:
      - "5672"
    networks:
      rakan:
        ipv4_address: 172.16.238.11
    links:
      - "queue"
    networks:
      - rakan

networks:
  rakan:
    ipam:
      driver: default
      config:
        - subnet: "172.16.238.0/24"

令人沮丧的是， docker-compose up不再执行 ./producer/dockerfile中的命令。它将启动队列，但是它将选择忽略我想要的命令，说:

Attaching to toyexample_queue_1, toyexample_producer_1
toyexample_producer_1 exited with code 0
... All the logs of the RabbitMQ ...

为什么会这样呢？为什么执行docker run时，它的行为方式不一样？ 任何帮助将不胜感激。

我尝试过的事情:

将entrypoint添加到docker-compose.yml中，形式为python3.7 example.py，bin/bash python3.7 example.py，bash python example.py。所有命令都将以错误代码127终止，声称python或python3.7是无法识别的命令。

将cmd添加到docker-compose.yml中，其结果与最后一个项目符号点

完全相同

用CMD中的ENTRYPOINT替换./producer/dockerfile

尝试在python和python3.7中使用不同的docker-compose.yml和dockerfile变体。

我不知道的事情是相关的，但可能会有所帮助

我正在Windows 10(AMD Ryzen CPU)上运行docker v19.03.8

0个其他容器正在运行

docker-compose down，docker network/container/image prune是我在这段史诗般的旅程中尝试过的所有命令

example.py中的代码是这样的:

import pika

connection = pika.BlockingConnection(pika.ConnectionParameters('172.16.238.10'))
channel = connection.channel()

for i in range(100):
    # make a lot of noise
    channel.queue_declare(queue=f'hello_{i}')
    channel.basic_publish(exchange='',
                        routing_key='hello_{i}',
                        body='Hello World!')
    print(f" [x] Sent 'Hello World!' to {i}")

connection.close()

强制性:“这不是家庭作业，我不是在试图作弊，等等。”

Answer 1

首先，请注意以下几点:

Dockerfile中的

EXPOSE和expose中的docker-compose.yml在大多数情况下都是不必要的，除了作为一种文档形式。

只需将您的Dockerfile命名为“Dockerfile”，而不是覆盖docker-compose.yml中的名称即可。减少无关的配置数量使事情更容易阅读(对于其他人和您以后的人)。

不要将IP地址硬编码到您的代码中。请改用容器名称。

同样，请勿在撰写文件中使用links关键字。 docker提供的DNS更加灵活。

depends_on几乎完全没有用。它对应用程序一无所知，因此尽管它将确保一个容器在另一个容器之后启动，但它不知道您所依赖的服务是否实际上已启动并正在运行。在大多数情况下，您希望摆脱depends_on并仅在应用程序中实现重新连接逻辑。

最后一个项目符号实际上可能是问题的根源:至少在我的测试中，RabbitMQ开始接受请求所花的时间比 producer容器开始所花的时间长得多。

考虑到所有这些，我将您的 docker-compose.yml重写为如下所示:

version: "3.3"

services:

  # RabbitMQ that connects the backend to the frontend
  queue:
    image: rabbitmq:3-management
    environment:
      RABBITMQ_DEFAULT_USER: "guest"
      RABBITMQ_DEFAULT_PASS: "guest"

  producer:
    build: 
      context: ./producer

您的 example.py看起来像这样:

import pika
import time

while True:
    try:
        connection = pika.BlockingConnection(pika.ConnectionParameters('queue'))
    except pika.exceptions.AMQPConnectionError as err:
        print('rabbitmq connection failed; retrying in 1 second...')
        time.sleep(1)
    else:
        break

channel = connection.channel()

for i in range(100):
    # make a lot of noise
    channel.queue_declare(queue=f'hello_{i}')
    channel.basic_publish(exchange='',
                        routing_key='hello_{i}',
                        body='Hello World!')
    print(f" [x] Sent 'Hello World!' to {i}")

connection.close()

运行上述配置会(每次)生成:

[lars@madhatter npengra317] (master *)$ docker-compose up
Starting npengra317_queue_1    ... done
Starting npengra317_producer_1 ... done
Attaching to npengra317_queue_1, npengra317_producer_1
queue_1     | 2020-05-09 03:38:25.676 [info] <0.9.0> Feature flags: list of feature flags found:
.
.
.
queue_1     | 2020-05-09 03:38:26.599 [info] <0.9.0> Server startup complete; 3 plugins started.
queue_1     |  * rabbitmq_management
queue_1     |  * rabbitmq_web_dispatch
queue_1     |  * rabbitmq_management_agent
queue_1     |  completed with 3 plugins.
queue_1     | 2020-05-09 03:38:26.868 [info] <0.653.0> accepting AMQP connection <0.653.0> (172.25.0.3:34874 -> 172.25.0.2:5672)
producer_1  | rabbitmq connection failed; retrying in 1 second...
producer_1  | rabbitmq connection failed; retrying in 1 second...
producer_1  | rabbitmq connection failed; retrying in 1 second...
producer_1  | rabbitmq connection failed; retrying in 1 second...
producer_1  | rabbitmq connection failed; retrying in 1 second...
producer_1  | rabbitmq connection failed; retrying in 1 second...
producer_1  | rabbitmq connection failed; retrying in 1 second...
producer_1  | rabbitmq connection failed; retrying in 1 second...
producer_1  |  [x] Sent 'Hello World!' to 0
producer_1  |  [x] Sent 'Hello World!' to 1
.
.
.
producer_1  |  [x] Sent 'Hello World!' to 97
producer_1  |  [x] Sent 'Hello World!' to 98
producer_1  |  [x] Sent 'Hello World!' to 99
npengra317_producer_1 exited with code 0