From 1bee8e81f99a64ad21774d8bee9b8b1957b7e485 Mon Sep 17 00:00:00 2001
From: Joe Mou <dev@mou.fo>
Date: Tue, 11 Jun 2024 15:46:58 -0400
Subject: Fix dynamic DNS retries and e-mail alert throttling

---
 hostnix/elmo/dyndns.nix | 12 ++++++++----
 hostnix/elmo/system.nix |  5 +++++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/hostnix/elmo/dyndns.nix b/hostnix/elmo/dyndns.nix
index 5abe98c..33ce19d 100644
--- a/hostnix/elmo/dyndns.nix
+++ b/hostnix/elmo/dyndns.nix
@@ -27,15 +27,19 @@
     after = [ "network-online.target" ];
     unitConfig = {
       AssertPathExists = "/var/secrets/dyndns";
-      # Defer errors for ~45min, throttle e-mails to ~hourly.
-      StartLimitIntervalSec = "1hr";
-      StartLimitBurst = "45";
+      # Retry ~3min before giving up.
+      StartLimitIntervalSec = "5min";
+      StartLimitBurst = "7";
       OnFailure = "status-email@%n.service";
     };
     serviceConfig = {
       Type = "oneshot";
       Restart = "on-failure";
-      RestartSec = "1min";
+      # Restart must be faster than the regular timer interval to exceed the
+      # start limit when flapping.
+      RestartSec = "30";
+      # Defer OnFailure until after retries.
+      RestartMode = "direct";
     };
     path = [ pkgs.dnsutils pkgs.gawk pkgs.iproute2 ];
     scriptArgs = config.networking.fqdn;
diff --git a/hostnix/elmo/system.nix b/hostnix/elmo/system.nix
index 23a6aa6..d98d1ff 100644
--- a/hostnix/elmo/system.nix
+++ b/hostnix/elmo/system.nix
@@ -56,6 +56,11 @@
   # https://wiki.archlinux.org/index.php/Systemd/Timers#MAILTO
   systemd.services."status-email@" = {
     description = "Status email for %i";
+    unitConfig = {
+      # Throttle notifications to twice daily.
+      StartLimitIntervalSec = "12hr";
+      StartLimitBurst = "1";
+    };
     serviceConfig = {
       Type = "oneshot";
     };
-- 
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