Add a healthcheck

Dockerfile

@@ -3,7 +3,10 @@ COPY requirements.txt /tmp
 RUN pip3 install --no-cache-dir -r /tmp/requirements.txt
 
 COPY exporter.py /usr/local/bin/homematic_exporter
+COPY healthcheck.sh /usr/local/bin/healthcheck.sh
 
 ENTRYPOINT [ "/usr/local/bin/homematic_exporter" ]
 
 EXPOSE 8010
+HEALTHCHECK --interval=20s --timeout=3s \
+    CMD bash /usr/local/bin/healthcheck.sh

healthcheck.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+# First argument is the maximum age in seconds (default: 60)
+maxage=${1:-60}
+
+# Get the age of the last successful metrics refresh in seconds
+age=$(curl -s http://localhost:9040/metrics | grep 'homematic_refresh_age{' | cut -d ' ' -f2 | cut -d '.' -f1)
+
+if [[ $age -lt $maxage ]]; then
+    exit 0
+else
+    # Maximum age exceeded → unhealthy
+    exit 1
+fi