wait-for

Wait for another service to become available


Example usage · Submit a PR

./wait-for is a script designed to synchronize services like docker containers. It is sh and alpine compatible. It was inspired by vishnubob/wait-for-it, but the core has been rewritten at Eficode by dsuni and mrako.

The easiest way to get started using this tool is to include the wait-for file as part of your project. Then call this script as part of any automation script.

Usage

Locally

Download the wait-for file, either the latest from master or for a specific version check out the Releases-page.

With the file locally on your file system, you can directly invoke it.

./wait-for host:port|url [-t timeout] [-- command args]
  -q | --quiet                        Do not output any status messages
  -t TIMEOUT | --timeout=timeout      Timeout in seconds, zero for no timeout
                                      Defaults to 15 seconds
  -v | --version                      Show the version of this tool
  -- COMMAND ARGS                     Execute command with args after the test finishes

Alternatively, you could download the script and pipe it into sh:

$ wget -qO- https://raw.githubusercontent.com/eficode/wait-for/v2.2.3/wait-for | sh -s -- google.com:80 -- echo success

Note: When using the latter option, make sure to pin the version by commit hash. Future releases could introduce non-backwards compatible changes and leaves you vulnerable to malicious users modifying this script in the future (as has e.g. happened with Codecov).

GitHub Actions

Similarly to how we piped the script into our shell covered in local usage, we can also use this in GitHub Actions, like so:

      - name: Wait for the database to start
        run: wget -qO- https://raw.githubusercontent.com/eficode/wait-for/$WAIT_FOR_VERSION/wait-for | sh -s -- localhost:5132 -- echo "Database is up"
        env:
          WAIT_FOR_VERSION: 4df3f9262d84cab0039c07bf861045fbb3c20ab7 # v2.2.3

Docker

We also publish a container to Docker Hub at eficode/wait-for, where we publish under the tag latest what's in master and tags for each release. (Only tags newer van v2.2.3 are available.) You can use the container like this:

$ docker run --rm eficode/wait-for google.com:80 -- echo success
success

Note: We will refrain from changes in the container we are publishing from triggering releases, as our primary distributable remains the script itself. One exception might be urgent security fixes.

Examples

To check if www.eficode.com is available:

$ ./wait-for www.eficode.com:80 -- echo "Eficode site is up"
Eficode site is up

To wait for database container to become available:

version: "3"

services:
  db:
    image: postgres:9.4

  backend:
    build: backend
    command: sh -c './wait-for db:5432 -- npm start'
    depends_on:
      - db

To check if https://www.eficode.com is available over HTTPS:

$ ./wait-for https://www.eficode.com -- echo "Eficode is accessible over HTTPS"
Eficode is accessible over HTTPS

To wait for your API service to become available:

version: "3"

services:
  api:
    image: nginx

  tests:
    build: .
    command: sh -c './wait-for http://api -- echo "The api is up! Let's use it"'
    depends_on:
      - api

Testing

Testing is done using bats, which we install using npm.

For reproducibility, we run our tests inside Docker, such that we have control over the version of bash we're testing against.

docker build --target test-env --tag wait-for .
docker run --rm -t wait-for

Contributing

When creating PRs, please style your commit messages according to conventional commit, you can use a tool like commitizen to guide you. We will automatically infer the changelog from your commits. Alternatively, we can squash all commits when merging and update the commit message.

This project strongly prefers maintaining backwards compatibility, therefore some obvious "fixes" might not be accepted.

Also, please include or update the test cases whenever possible by extending wait-for.bats.

Note

Make sure netcat is installed in your Dockerfile before running the command if you test over plain TCP.

RUN apt-get -q update && apt-get -qy install netcat

https://stackoverflow.com/questions/44663180/docker-why-does-wait-for-always-time-out

If you are connecting over HTTP, then you will need to have wget available.