Add HEALTHCHECK to domserver Docker container

When running the Docker container for domserver, it is possible that one
of nginx or php-fpm crashes/stops working. When this happens from
outside the container the effects can be quite mysterious. Adding an
health check allows the user to diagnose more quickly what happened.

Running `docker ps`, in the column `STATUS` it is shown: `Up X minutes
(healthy)` or `Up X minutes (unhealthy)` depending on the exit code of
the health check script. To further diagnose the problem one can run
`docker inspect domserver` (optionally piped to `jq '.[0].State.Health'`)
and this will report diagnostic information like:

```json
{
  "Status": "healthy",
  "FailingStreak": 0,
  "Log": [
    {
      "Start": "2021-12-19T19:22:53.555071655+01:00",
      "End": "2021-12-19T19:22:54.012109556+01:00",
      "ExitCode": 0,
      "Output": "nginx ok | php ok | http ok"
    },
    ...
  ]
}
```

This health check probes supervisord for the status of the two services
(nginx and php-fpm), as well as tries to reach the API with an HTTP
request.

This commit also fixes the deprecated `MAINTAINER` labels in the various
Dockerfiles.

Author: edomora97

docker/domserver/Dockerfile

@@ -1,5 +1,5 @@
 FROM debian:stable-slim AS domserver-build
-MAINTAINER DOMjudge team <[email protected]>
+LABEL org.opencontainers.image.authors="DOMjudge team <[email protected]>"
 
 ENV DEBIAN_FRONTEND=noninteractive
 
@@ -39,7 +39,7 @@ RUN /domjudge-src/build.sh
 
 # Now create an image with the actual build in it
 FROM debian:stable-slim
-MAINTAINER DOMjudge team <[email protected]>
+LABEL org.opencontainers.image.authors="DOMjudge team <[email protected]>"
 
 ENV DEBIAN_FRONTEND=noninteractive \
 	CONTAINER_TIMEZONE=Europe/Amsterdam \
@@ -85,4 +85,7 @@ RUN chmod 700 /configure.sh && /configure.sh && rm -f /configure.sh
 # Expose HTTP port
 EXPOSE 80
 
+# Healthchecking script
+HEALTHCHECK --interval=10s --timeout=10s --start-period=30s --retries=3 CMD [ "/scripts/bin/healthcheck" ]
+
 CMD ["/scripts/start.sh"]

docker/domserver/scripts/bin/healthcheck

@@ -0,0 +1,23 @@
+#!/bin/bash
+
+SERVICES=(nginx php)
+
+ret=0
+for service in "${SERVICES[@]}"; do
+    status=$(supervisorctl status "$service" | awk '{print $2}')
+    if [ "$status" = "RUNNING" ]; then
+        printf "%s ok | " "$service"
+    else
+        printf "%s %s | " "$service" "$status"
+        ret=1
+    fi
+done
+
+if php -r 'exit(@file_get_contents("http://localhost/api/") === false ? 1 : 0);'; then
+    printf "http ok"
+else
+    printf "http error"
+    ret=1
+fi
+
+exit $ret

docker/judgehost/Dockerfile

@@ -1,5 +1,5 @@
 FROM debian:stable
-MAINTAINER DOMjudge team <[email protected]>
+LABEL org.opencontainers.image.authors="DOMjudge team <[email protected]>"
 
 ENV DEBIAN_FRONTEND=noninteractive \
 	CONTAINER_TIMEZONE=Europe/Amsterdam \

docker/judgehost/Dockerfile.build

@@ -1,5 +1,5 @@
 FROM debian:stable-slim
-MAINTAINER DOMjudge team <[email protected]>
+LABEL org.opencontainers.image.authors="DOMjudge team <[email protected]>"
 
 ENV DEBIAN_FRONTEND=noninteractive