main/runit: Improve logic around shoelaces mappings

Containerfile

@@ -17,6 +17,8 @@ WORKDIR /
 COPY --from=build /netbox-dhcp-hosts /usr/local/bin/netbox-dhcp-hosts
 COPY runit/dnsmasq /etc/service/dnsmasq
 COPY runit/netbox-dnsmasq-dhcp /etc/service/netbox-dnsmasq-dhcp
+ENV DNSMASQ_HOSTSFILE=/run/dhcp-hosts.next
+ENV REFRESH_INTERVAL=600
 RUN apk update && \
     apk add tini runit dnsmasq && \
     rm -rf /var/cache/apk && \
@@ -33,7 +35,7 @@ RUN apk add git && \
 
 FROM base as shoelaces
 WORKDIR /
-ENV SHOELACES_MAPFILE=/var/lib/shoelaces/mappings.yaml
+ENV SHOELACES_MAPFILE=/var/lib/shoelaces/mappings.yaml.next
 COPY --from=shoelaces_build /shoelaces/shoelaces /usr/local/bin/shoelaces
 COPY --from=shoelaces_build /shoelaces/web /usr/share/shoelaces/web
 COPY runit/shoelaces /etc/service/shoelaces

README.md

@@ -19,6 +19,9 @@ in the environment:
   * `DNSMASQ_TEMPLATE` - A go template expression for the dhcp-hosts
     file.  Defaults to a suitable configuration for IPv4.  The default
     template is `{{JoinStrings .HWAddr ","}},{{.Addr}}`.
+  * `DNSMASQ_HOSTSFILE` - A file to write out the dhcp hosts
+    configuration to.  This must match wherever you configure your
+    dnsmasq config file to search for dhcp hosts.
   * `SHOELACES_MAPFILE` - A file to write out shoelaces mappings too.
     Must be named `mappings.yaml` and at the path expected by
     shoelaces.  Only relevant in images that contain shoelaces.

main.go

@@ -132,20 +132,31 @@ func main() {
 		}
 	}
 
-	for _, host := range hosts {
-		if err := hostTmpl.Execute(os.Stdout, host); err != nil {
-			log.Println("Error executing template", err)
+	if os.Getenv("DNSMASQ_HOSTSFILE") != "" {
+		f, err := os.Create(os.Getenv("DNSMASQ_HOSTSFILE"))
+		if err != nil {
+			log.Println("Error writing out hosts file", err)
+			os.Exit(1)
+		}
+		defer f.Close()
+
+		for _, host := range hosts {
+			if err := hostTmpl.Execute(f, host); err != nil {
+				log.Println("Error executing template", err)
+			}
 		}
 	}
 
 	if os.Getenv("SHOELACES_MAPFILE") != "" {
-		bytes, err := json.Marshal(ShoelacesNetworkMap{NetworkMaps: shoenets})
+		f, err := os.Create(os.Getenv("SHOELACES_MAPFILE"))
 		if err != nil {
-			log.Println("Error marshalling shoelaces mappings", err)
+			log.Println("Error opening shoelaces map file", err)
 			os.Exit(1)
 		}
+		defer f.Close()
 
-		if err := os.WriteFile(os.Getenv("SHOELACES_MAPFILE"), bytes, 0644); err != nil {
+		enc := json.NewEncoder(f)
+		if err := enc.Encode(ShoelacesNetworkMap{NetworkMaps: shoenets}); err != nil {
 			log.Println("Error writing shoelaces mappings", err)
 			os.Exit(1)
 		}

runit/netbox-dnsmasq-dhcp/run

@@ -1,17 +1,19 @@
 #!/bin/sh
 
 while true ; do
-    if /usr/local/bin/netbox-dhcp-hosts | sort > /run/dhcp-hosts.next ; then
+    if /usr/local/bin/netbox-dhcp-hosts ; then
         if ! diff /run/dhcp-hosts /run/dhcp-hosts.next ; then
             echo "Updated host mappings, reloading services"
             mv /run/dhcp-hosts.next /run/dhcp-hosts
-
             pkill -SIGHUP dnsmasq
+        fi
 
+        if ! diff /var/lib/shoelaces/mappings.yaml /var/lib/shoelaces/mappings.yaml.next ; then
             if [ -n "$SHOELACES_TAG_PREFIX" ] ; then
+                mv /var/lib/shoelaces/mappings.yaml.next /var/lib/shoelaces/mappings.yaml
                 sv restart shoelaces
             fi
         fi
     fi
-    sleep 600
+    sleep "$REFRESH_INTERVAL"
 done