Periodimail: send e-mails every two days if deretheni backups fail.

chileh-backups.nix

@@ -1,11 +1,16 @@
 { config, lib, pkgs, ... }:
 
+let two-days = 60 * 60 * 24 * 2 - 60; in
 {
   config = lib.mkIf config.host.chileh-backups.enable {
+    services.periodimail.intervals = [ two-days ];
     systemd.services.backup-deretheni = {
       description = "Backup deretheni";
       path = with pkgs; [ borgbackup bup rsync openssh ];
       wants = [ "network-online.target" ];
+      unitConfig = {
+        OnFailure = "periodimail-${builtins.toString two-days}@%n.service";
+      };
       serviceConfig = {
         User = "edanaher";
         Group = "users";

configuration.nix

@@ -16,6 +16,7 @@
       ./exim
       ./pulseaudio
       ./xserver.nix
+      ./scripts/periodimail.nix
     ];
 
   boot.kernelParams = lib.optional (config.host.class != "server")

scripts/periodimail.nix

@@ -0,0 +1,53 @@
+{ config, lib, pkgs, ... }:
+
+let periodimail = pkgs.writeScript "periodimail" ''
+  #!/bin/sh
+  unit=''${2//\//_}
+  mkdir -p /tmp/.periodimail
+  MARKFILE=/tmp/.periodimail/$unit
+  if [ -f $MARKFILE ]; then
+    echo File exists for $unit
+    if [[ $((`stat -c %Y $MARKFILE` + $1)) -lt `date +%s` ]]; then
+      echo Removing stale file $unit
+      rm $MARKFILE
+    fi
+  fi
+  if [ ! -f $MARKFILE ]; then
+    echo Mailing for $unit
+    touch $MARKFILE
+    exim [email protected] <<EOF
+  From: [email protected]
+  To: [email protected]
+  Subject: Chileh unit '$2' failed
+  
+  $(journalctl -u $2 -n 10)
+  EOF
+  fi
+  echo Finished $unit
+'';
+  serviceForInterval = interval: {
+    name = "periodimail-${builtins.toString interval}@";
+    value = {
+      description = "Send e-mail on unit failure, but only every ${builtins.toString interval} seconds";
+      path = with pkgs; [ systemd exim ];
+      wants = [ "network-online.target" ];
+      serviceConfig = {
+        ExecStart = "${periodimail} ${builtins.toString interval} %I";
+      };
+    };
+  };
+in
+{
+  options = {
+    services.periodimail.intervals =
+      lib.mkOption {
+        type = lib.types.listOf lib.types.int;
+        default = [];
+        description = "Intervals to run periodimail on (in seconds)";
+      };
+  };
+
+  config = {
+    systemd.services = lib.listToAttrs (map serviceForInterval config.services.periodimail.intervals);
+  };
+}