Usage with Docker about wait-for-it HOT 16 OPEN

Thanks @agustisanchez - I like it. Depending on your setup, you might also copy wait-for-it.sh in as a mounted volume, such as this:

version: '3'

services:
  hello-world:
    image: ubuntu
    volumes:
      - ./wait-for-it.sh:/usr/local/bin/wait-for-it.sh
    command:
      - wait-for-it.sh
      - github.com:80
      - --
      - echo
      - "hello world"

from wait-for-it.

Multistage builds can be leveraged to install wait-for-it with apt-get:

FROM debian:buster-slim as wait-for-it
RUN apt-get update && apt-get install -y "wait-for-it"

FROM debian:buster-slim
COPY --from=wait-for-it /usr/bin/wait-for-it /usr/bin/wait-for-it

If there was an official docker image for wait-for-it (i.e. wait-for-it/wait-for-it) we could potentially do:

FROM debian:buster-slim
COPY --from=wait-for-it/wait-for-it /usr/bin/wait-for-it /usr/bin/wait-for-it

from wait-for-it.

Can you tell me what my Entrypoint is?
Given are the following snippets.

#Dockerfile

FROM java:8
VOLUME /tmp
EXPOSE 8080
COPY wait-for-mysql.sh /wait-for-mysql.sh
RUN chmod +x /wait-for-mysql.sh
ADD target/App.jar App.jar.
ENTRYPOINT ["java","-jar","App.jar"]

Im not shure with my ENTRYPOINT. I do the follwoing.
#docker-compose.yml

...
  mysql-docker-container:
  ..
  .
  my-service:
    build:
      context: "."
      container_name: my_container
      command: ["./wait-for-mysql.sh", "mysql-docker-container:3306", "--", "java", "App.jar"]
....

Is the Entrypoint correct?

from wait-for-it.

For a dependency that you don't need to build (i.e. also create Dockerfile and specify context), you can make it work with the volumes config only:

1. chmod 755 wait-for-it.sh

# docker-compose.yml
…
volumes:
  - "./wait-for-it.sh:/wait-for-it.sh:ro"
…

Good to know:

• Bind mounts keep the host's permissions[source], so step 1) is obligatory.
• The read-only (ro) segment is optional.

from wait-for-it.

wait-for-it.sh is not trapping SIGTERM so, to be able to gracefully stop a service that is stuck waiting, the stop signal needs to be overridden in docker-compose.yml:

version: '3'

services:
  wait-for-app:
    image: ubuntu
    volumes:
      - ./wait-for-it.sh:/usr/local/bin/wait-for-it.sh
    command: wait-for-it.sh app:8080 -- echo ok
    stop_signal: SIGINT

from wait-for-it.

https://docs.docker.com/compose/compose-file/#command
https://docs.docker.com/compose/compose-file/#entrypoint
there is some difference between command and entrypoint.
personally I prefer to use entrypoint config and don't use command.

from wait-for-it.

I want to share my case. I investigated.

I using openjdk:8-jdk-alpine image docker.
My environment:

• OS: window 10 Pro
• Docker engine: 19.03.2

My Dockerfile

FROM openjdk:8-jdk-alpine

RUN apk add --no-cache bash

COPY ./wait-for-it.sh /wait-for-it.sh

RUN chmod +x wait-for-it.sh

RUN ls -la

and used it in docker-compose.yml file
command: bash ./wait-for-it.sh my-service:8080 --strict -- java -jar app.jar
But it was failed!!! @@

This issue is EOL(end of line). My wait_for_it.sh file has CRLF (windows). I changed it into LF (for Unix and MacOs). It worked!

from wait-for-it.

Depending on the base image used there will be no netcat available in the container. The description pure bash conflicts in this case with the fact that netcat is no shell builtin. No offense intended.

Cheers

from wait-for-it.

I think that your command should look like this:
command: ["./wait-for-mysql.sh", "mysql-docker-container:3306", "--", "sh", "-c", "java", "App.jar"]

from wait-for-it.

to find out what is default entrypoint - do next steps:

1. comment entrypoint config line in docker-compose.yml
2. start service (docker-compose up -d)
3. inspect service (docker inspect my_container) and find info about entrypoint. also it's possible to view entrypoint via docker ps, but string is truncated.
4. modify your entrypoint: "wait-for-it mysql-docker-container:3306 -- default-entrypoint", replace "default-entrypoint" to your actual command

from wait-for-it.

In order to use it with Docker and docker-compose,
place it alongside Dockerfile, build it into the image with exec permissions and reference it in docker-compose.yml.

- Dockerfile
- wait-for-it.sh

#Dockerfile
...
COPY wait-for-it.sh /wait-for-it.sh
RUN chmod +x /wait-for-it.sh
...

#docker-compose.yml
...
  my-service:
    build:
      context: "."
      container_name: my_container
      command: ["/wait-for-it.sh", "mysql:3306", "--", [entrypoint function]]
...

@agustisanchez what is the "entrypoint function" in docker-compose.yml

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@agustisanchez if i want to run a java project, what is the "entrypoint function"

from wait-for-it.

@douglas-gibbons Is it possible to use it with google distroless java images?

from wait-for-it.

I want to share my case. I investigated.

I using openjdk:8-jdk-alpine image docker.
My environment:

• OS: window 10 Pro
• Docker engine: 19.03.2

My Dockerfile

FROM openjdk:8-jdk-alpine

RUN apk add --no-cache bash

COPY ./wait-for-it.sh /wait-for-it.sh

RUN chmod +x wait-for-it.sh

RUN ls -la

and used it in docker-compose.yml file
command: bash ./wait-for-it.sh my-service:8080 --strict -- java -jar app.jar
But it was failed!!! @@

This issue is EOL(end of line). My wait_for_it.sh file has CRLF (windows). I changed it into LF (for Unix and MacOs). It worked!

Thanks, this really helped, I had spent hours figuring out why it's not working for me despite putting all the commands correctly. Changing from CRLF to LF worked like a charm.

from wait-for-it.

is there a way to retain the CMD in the Dockerfile so other users can easily opt-out of using docker-compose?

from wait-for-it.

I struggled with this problem for a long time and finally come up with a solution with reference from above. In case someone would come here for solutions, here is my working codes.

In your Dockerfile, you would add this for the wait-for-it.sh. The $APP_HOME is an ENV variable that you might define after FROM command for your specific project.

COPY wait-for-it.sh $APP_HOME/app

WORKDIR $APP_HOME/app

RUN chmod +x wait-for-it.sh

ENTRYPOINT ["/bin/bash", "-c"]

In your docker-compose.yml, you might add the following:

app:
  restart: on-failure
  command: ["./wait-for-it.sh db:3306 --strict --timeout=300 -- alembic upgrade head && python main.py"]

Note all the rest configurations were not mentioned here, but they could be found from other references as above.

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