Update Dockerfile to report container health in docker ps

This commit adds a HEALTHCHECK instruction in Dockerfile.
The HEALTHCHECK instruction calls /docker/fetchstatus.sh
which in turn makes a HTTP request to
http://localhost:8000/api/v3/status/
This endpoint makes a test database query and returns non-200
response if the query fails. So, in short, if the Healthchecks
container for any reason is unable to query database, `docker ps`
will now show the container as "unhealthy".

cc: #1045

CHANGELOG.md

@@ -11,6 +11,7 @@ All notable changes to this project will be documented in this file.
 - Update the "Set Password" page to reject very weak passwords
 - Implement search by slug in the checks list (#1048)
 - Add support for $SLUG placeholder in webhook payloads (#1049)
+- Update Dockerfile to use HEALTHCHECK instruction and report container health (#1045)
 
 ### Bug Fixes
 - Fix Check.ping() to lock the check before updating (#1023)

docker/Dockerfile

@@ -43,4 +43,5 @@ RUN mkdir /data && chown hc /data
 USER hc
 
 ENV USE_GZIP_MIDDLEWARE=True
+HEALTHCHECK --interval=10s --start-period=10s --retries=1 CMD /opt/healthchecks/docker/fetchstatus.sh
 CMD [ "uwsgi", "/opt/healthchecks/docker/uwsgi.ini"]

docker/fetchstatus.sh

@@ -0,0 +1 @@
+python -c "from urllib.request import urlopen; urlopen('http://localhost:8000/api/v3/status/')"