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sdavids-docker-healthcheck-rust-https

Table of Contents

A Rust-based Docker health check for an HTTP(S) URL passed in via ENV.

ℹ️

The health check URL has to return HTTP 200.

The response body is not evaluated.
ℹ️

HTTP, HTTP with HTTPS redirect, and HTTPS URLs are supported.
💡

This health check uses the HTTP(S) URL passed in via the following ENV variable:

HEALTHCHECK_URL

the HTTP(S) URL to be used for the health check

If HEALTHCHECK_URL is not set https://localhost:3000/-/health/liveness will be used.

❗

The health check calls the URL from within the container therefore localhost is the running Docker image and not the localhost of the Docker host.
❗

There is no check whether the given HEALTHCHECK_URL is a syntactically correct HTTP(S) URL.

1. Development

1.1. Build

$ scripts/build.sh

⇒ target/debug/healthcheck

1.2. Test

$ scripts/test.sh

1.3. Run

$ target/debug/healthcheck
$ echo $?
0

$ HEALTHCHECK_URL=http://captive.apple.com target/debug/healthcheck
$ echo $?
0

$ HEALTHCHECK_URL=https://captive.apple.com target/debug/healthcheck
$ echo $?
0
0

the health check URL returned HTTP 200

69

the health check URL was unreachable

78

the runtime does not support HTTPS

100

the health check URL did not return HTTP 200

1.4. Format Source Code

$ scripts/format.sh

1.5. Lint Source Code

$ scripts/lint.sh

1.6. Release Build

$ scripts/build_release.sh

⇒ target/release/healthcheck

2. Usage

  1. Copy the health check into your container:

    Dockerfile
    COPY --from=healthcheck \
  /tmp/target/release/healthcheck \
  /usr/local/bin/healthcheck

  2. Configure the health check:

    Dockerfile
    HEALTHCHECK --interval=5s --timeout=5s --start-period=5s \
    CMD healthcheck || exit 1

    More information:

  3. (Optional) Pass the HEALTHCHECK_URL to the docker container run invocation:

    scripts/docker_start.sh
    docker container run \
...
  --env HEALTHCHECK_URL='https://localhost:3000/-/health/liveness' \
...

    Alternatively, add the HEALTHCHECK_URL to the Dockerfile:

    Dockerfile
    ENV HEALTHCHECK_URL="https://localhost:3000/-/health/liveness"

  4. (Optional) If you have an https healthcheck URL with a custom certificate authority you need to add the certificate authorities root certificate to your image; for example for Alpine-based images:

    COPY ca.crt /usr/local/share/ca-certificates/

# hadolint ignore=DL3018
RUN apk add --no-cache ca-certificates && \
    update-ca-certificates

3. Example

Dockerfile: a simple HTTPS server

  1. CA root certificate

    1. Create a new certificate authority and copy its root certificate:

      $ scripts/create_ca.sh
$ scripts/copy_ca_root_cert.sh

    2. Copy the existing certificate authorities root certificate:

      $ scripts/copy_ca_root_cert.sh

  2. localhost certificate

    1. Create a new localhost certificate:

      $ scripts/create_ca_based_cert.sh

    2. Copy the existing localhost certificate:

      $ scripts/copy_ca_based_cert.sh

  3. Build the image:

    $ scripts/docker_build.sh

  4. Start a container:

    $ scripts/docker_start.sh

Listen local: https://localhost:3000

The URL has been copied to the clipboard.

  5. Examine the two endpoints:

    $ curl -s -o /dev/null -w "%{http_code}" https://localhost:3000
200
$ curl -s -o /dev/null -w "%{http_code}" https://localhost:3000/-/health/liveness
200

  6. Get the health status:

    $ scripts/docker_health.sh
healthy 0

  7. Stop the container:

    $ scripts/docker_stop.sh

  8. Remove all Docker artifacts related to this project:

    $ scripts/docker_cleanup.sh

  9. (Optional) Delete the certificate authority.

    💡

    You usually want to keep the certificate authority so you can use for other projects.

    		 
    $ scripts/delete_ca.sh