Add watchdog

watchdog.sh

+#!/bin/bash
+
+TRAEFIK=https://traefik.fachschaft.cl.uni-heidelberg.de
+BASE_DIR=$(dirname $(realpath $0))
+LAST_KNOWN_DOWNTIME_FILE="${BASE_DIR}/last_known_downtime"
+LAST_KNOWN_RESTART_FILE="${BASE_DIR}/last_known_restart"
+
+# Return 0 (i.e. true) if the file $1 exists and was modified no more than $2 seconds ago.
+# Return 1 (i.e. false) otherwise
+younger_than () {
+    if [[ ! -f ${1} ]]
+    then
+        return 1
+    else
+        FILE_CHANGE=$(date -r ${1} +%s)
+        NOW=$(date +%s)
+        DIFFERENCE=$((${NOW}-${FILE_CHANGE}))
+
+        if [[ ${DIFFERENCE} -le ${2} ]]
+        then
+            return 0
+        else
+            return 1
+        fi
+    fi
+}
+
+# Return 0 (i.e. true) if Traefik is currently down.
+# Return 1 (i.e. false) if it is currently reachable.
+currently_down () {
+    curl ${TRAEFIK} > /dev/null 2> /dev/null
+
+    if [[ $? -eq 7 ]]
+    then
+        return 0
+    else
+        return 1
+    fi
+}
+
+# Return 0 (i.e. true) if Traefik was recently down, i.e. if the last
+# modified timestamp of ${LAST_KNOWN_DOWNTIME_FILE} is not too far in the past.
+# Return 1 (i.e. false) if it was not recently down.
+recently_down () {
+    # If the last known downtime was before no more than 600 seconds
+    # (i.e. 10 minutes), we consider Traefik to have recently been down.
+    return $(younger_than ${LAST_KNOWN_DOWNTIME_FILE} 600)
+}
+
+restart () {
+    touch ${LAST_KNOWN_RESTART_FILE}
+    "${BASE_DIR}/restart.sh"
+}
+
+recently_restarted() {
+    # If the last known restart was before no more than 36000 seconds
+    # (i.e. 10 hours), we consider Traefik to have recently been restarted.
+    return $(younger_than ${LAST_KNOWN_RESTART_FILE} 36000)
+}
+
+if currently_down
+then
+    if recently_down
+    then
+        if recently_restarted
+        then
+            exit 0
+        else
+            echo "${TRAEFIK} was unreachable in this and the previous check and hasn't been automatically restarted in a while."
+            echo "Restarting..."
+            restart
+        fi
+    else
+        echo "${TRAEFIK} was unreachable, but reachable in the previous check."
+        echo "Noting this down for the future..."
+        touch ${LAST_KNOWN_DOWNTIME_FILE}
+    fi
+fi