我如何使我的Docker组成“等待它”脚本调用原始容器ENTRYPOINT或CMD？ [英] How can I make my Docker compose "wait-for-it" script invoke the original container ENTRYPOINT or CMD?

问题描述

根据控制撰写中的启动顺序，可以控制 Docker Compose 通过使用等待它脚本。脚本 wait-for-it.sh 需要一个 host：port 参数以及脚本在端口可用时执行的命令。该文档建议Docker Compose使用 entrypoint：选项来调用此脚本。但是，如果使用此选项，容器将不再运行其默认的 ENTRYPOINT 或 CMD ，因为 entrypoint：覆盖默认值。

如何将这个默认命令提供给等待它。 sh ，以便脚本可以调用默认的 ENTRYPOINT 或 CMD 它等待满足？

在我的情况下，我已经实现了一个脚本 wait-for-file.sh 等待文件存在的投票：

 ＃！/ bin / bash 
 
 set -e 
 
 waitFile =$ 1
 shift 
 cmd =$ @
 
直到test -e $ waitFile 
 do 
>& 2 echo等待文件[$ waitFile]。 
 sleep 1 
 done 
 
>& 2 echo找到的文件[$ waitFile]。 
 exec $ cmd 
  

Docker Compose调用等待文件.sh 作为从 tomcat：8-jre8 ：

  oms：
 image：opes / platinum-oms 
 ports：
  - 8080：8080
 volumes_from：
  -  liquibase 
 links：
  -  postgres：postgres 
  -  activemq：activemq 
 depends_on：
  -  liquibase 
  -  activemq 
 entrypoint：/wait-for-file.sh / var / run /在其成功退出之前，另一个自定义容器 liquibase  
 $ b $ p 
 $ b 
 c $ c>创建 / var / run / liquibase / done ，因此 platinum-oms 有效地等待容器 liquibase 完成。
 
 
 
一旦容器 liquibase  c reates file  / var / run / liquibase / done ， wait-for-file.sh 打印找到文件[/ var / run / liquibase / done]。，但无法调用默认命令catalina.sh运行 在基础容器中 tomcat：8-jre8 。为什么？
 
 
 
测试场景
 
 
 
我创建了一个简化的测试场景  docker-compose-wait-for-file  来演示我的问题。容器 ubuntu-wait-for-file 等待容器 ubuntu-create-file 创建文件 / wait / done 然后我希望容器 ubuntu-wait-for-file 调用默认的 ubuntu 容器命令 / bin / bash ，而是退出。为什么不按照我的期望工作？
解决方案
 
 
 
但是，如果使用此选项，容器将不再运行其默认的 ENTRYPOINT 或 CMD 命令，因为 entrypoint：覆盖默认值。
 
 
这是预期的，这就是为什么  wait-for-it  被显示为包装器脚本。
 
它允许执行子命令：
 等待.sh host：port [-s] [-t timeout] [ -  command args] 
 ^^^^^^^^^^^ 
  
 
 
 
 
 
子命令将被执行，无论服务是否启动。
 
如果要执行子命令只要服务已经启动，请添加  -  strict 参数。
 
 
这意味着您的图像的 CMD 部分可以用于您的实际容器命令，因为其参数将通过参数传递到 ENTRYPOINT 命令：
  entrypoint：wait-for-it.sh host：port  -  
 cmd：mycmd myargs 
  
这应该工作...除了  docker-compose  issue 3140 （由OP Derek Mahar 在评论）
 
 
在 docker-compose.yml中定义的entrypoint 擦除在Dockerfile 
中定义的 CMD  
 
 
According to Controlling startup order in Compose, one can control the order in which Docker Compose starts containers by using a "wait-for-it" script.  Script wait-for-it.sh expects both a host:port argument as well as the command that the script should execute when the port is available.  The documentation recommends that Docker Compose invoke this script using the entrypoint: option. However, if one uses this option, the container will no longer run its default ENTRYPOINT or CMD because entrypoint: overrides the default.

How might one provide this default command to wait-for-it.sh so that the script can invoke the default ENTRYPOINT or CMD when the condition for which it waits is satisfied?

In my case, I've implemented a script wait-for-file.sh that polls waiting for a file to exist:
#!/bin/bash

set -e

waitFile="$1"
shift
cmd="$@"

until test -e $waitFile
do
  >&2 echo "Waiting for file [$waitFile]."
  sleep 1
done

>&2 echo "Found file [$waitFile]."
exec $cmd
Docker Compose invokes wait-for-file.sh as the entry-point to a slightly custom container derived from tomcat:8-jre8:
  platinum-oms:
    image: opes/platinum-oms
    ports:
      - "8080:8080"
    volumes_from:
      - liquibase
    links:
      - postgres:postgres
      - activemq:activemq
    depends_on:
      - liquibase
      - activemq
    entrypoint: /wait-for-file.sh /var/run/liquibase/done
Before it exits successfully, another custom container liquibase creates /var/run/liquibase/done and so platinum-oms effectively waits for container liquibase to complete.

Once container liquibase creates file /var/run/liquibase/done, wait-for-file.sh prints Found file [/var/run/liquibase/done]., but fails to invoke default command catalina.sh run in base container tomcat:8-jre8.  Why?

Test Scenario

I created a simplified test scenario docker-compose-wait-for-file to demonstrate my problem.  Container ubuntu-wait-for-file waits for container ubuntu-create-file to create file /wait/done and then I expect container ubuntu-wait-for-file to invoke the default ubuntu container command /bin/bash, but instead, it exits.  Why doesn't it work as I expect?
解决方案

  
However, if one uses this option, the container will no longer run its default ENTRYPOINT or CMD command because entrypoint: overrides the default.
That is expected, which is why the wait-for-it is presented as a wrapper script.

It does allow to execute a "subcommand" though:
wait-for-it.sh host:port [-s] [-t timeout] [-- command args]
                                               ^^^^^^^^^^^^



  
The subcommand will be executed regardless if the service is up or not.

  If you wish to execute the subcommand only if the service is up, add the --strict argument.
That means the CMD part of your image can be used for your actual container command, as its parameters will passed in parameters to the ENTRYPOINT command:
entrypoint: wait-for-it.sh host:port --
cmd: mycmd myargs
This should work... except for docker-compose issue 3140 (mentioned by the OP Derek Mahar in the comments)

  
entrypoint defined in docker-compose.yml wipes out CMD defined in Dockerfile


                        
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