Add health check email notifications

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "reminder-rs"
-version = "1.6.17-1"
+version = "1.6.18"
 authors = ["Jude Southworth <judesouthworth@pm.me>"]
 edition = "2021"
 license = "AGPL-3.0 only"
@@ -44,6 +44,8 @@ assets = [
     ["conf/Rocket.toml", "etc/reminder-rs/Rocket.toml", "600"],
     ["web/static/**/*", "lib/reminder-rs/static", "644"],
     ["web/templates/**/*", "lib/reminder-rs/templates", "644"],
+    ["healthcheck", "lib/reminder-rs/healthcheck", "755"],
+    ["cron.d/reminder_health", "etc/cron.d", "644"],
 #    ["nginx/reminder-rs", "etc/nginx/sites-available/reminder-rs", "755"]
 ]
 conf-files = [

conf/default.env

@@ -14,3 +14,5 @@ REMIND_INTERVAL=
 OAUTH2_DISCORD_CALLBACK=
 OAUTH2_CLIENT_ID=
 OAUTH2_CLIENT_SECRET=
+
+REPORT_EMAIL=

cron.d/reminder_health

@@ -0,0 +1 @@
+*/10 * * * * reminders /lib/reminder-rs/healthcheck

healthcheck

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+export $(grep -v '^#' /etc/reminder-rs/config.env | xargs -d '\n')
+
+VAR=$(mysql -N -D reminders -e "SELECT COUNT(1) FROM reminders WHERE utc_time < NOW() - INTERVAL 10 MINUTE AND enabled = 1")
+
+if [ "$VAR" -gt 0 ]
+then
+  echo "This is to inform that there is a reminder backlog which must be resolved." | mail -s "Backlog: $VAR" "$REPORT_EMAIL"
+fi