Implement dry-run

README.md

@@ -0,0 +1,79 @@
+# Mythic Beasts DNS manager
+
+A simple management agent for controlling your DNS entries on the Mythic Beasts platform using a (version-controllable) YAML file.
+
+This client uses the DNSv2 API (https://www.mythic-beasts.com/support/api/dnsv2) for which you'll need to create a key (https://www.mythic-beasts.com/customer/api-users).
+
+## Configuration
+
+1. Create an API key via https://www.mythic-beasts.com/customer/api-users
+2. Create a YAML file
+
+```yaml
+defaults:
+  ttl:
+    example.com: 3600
+  api: https://api.mythic-beasts.com/dns/v2/zones
+  api_host: api.mythic-beasts.com:443
+  realm: Mythic Beasts DNS API
+
+auth:
+  key: mykey
+  secret: mysecret
+
+zones:
+  example.com:
+```
+
+3. Under `zones -> example.com`, prepare your DNS entries using the schema:
+
+```yaml
+zones:
+  example.com:
+    name1:
+      TYPE: value
+    name2:
+      TYPE:
+        - value1
+        - value2
+    name3.subdomain:
+      TYPE: value
+```
+
+Currently only a single zone is supported.
+
+## Supported types
+
+The client currently supports all of the Record Types implemented by the Mythic Beasts API except `SSHFP` and `TLSA`.
+
+## Value syntax
+
+The value for simple record types is the plain value as expected (eg. `A: 10.54.22.9` or `AAAA: 2a01:332::2`).
+
+The value for complex types, such as `MX` is as per the standard zone file (eg. `MX: 10 mta.example.com`) At some point this will become parametrised.
+
+## The Root object (`@`)
+To refer to the base/root domain, use the `"@"` key:
+```yaml
+zones:
+  example.com:
+    "@":
+      A: 10.54.22.9
+      AAAA: 2a01:332::2
+      MX:
+        - 10 mta1.example.com
+        - 10 mta2.example.com
+```
+
+# Running
+Invoke the docker container with the input yaml file:
+```bash
+docker run --rm -ti -v "${PWD}:/a" -w /a fooflington/mythic-beasts-dns mafoo.org.uk.yml
+```
+
+## Dry run
+Pass the environment variable `DRY_RUN` to prevent any changes:
+
+```bash
+docker run --rm -ti -v "${PWD}:/a" -w /a -e DRY_RUN=1 fooflington/mythic-beasts-dns mafoo.org.uk.yml
+```

manage-dns.pl

@@ -13,6 +13,7 @@ use WWW::Form::UrlEncoded::PP qw/build_urlencoded/;
 my $in = YAML::Tiny->read(shift);
 my $ua = LWP::UserAgent->new;
 my %seen;
+my $DRY_RUN = $ENV{DRY_RUN};
 
 sub _debug {
     print STDERR ("=== DEBUG ===\n", Dumper(@_), "=== END ===\n") if $ENV{DEBUG} or $in->[0]->{debug};
@@ -51,6 +52,8 @@ sub is_unsupported($) {
     return $supported_types{$type};
 }
 
+_notice("Dry run - no changes will be applied") if ${DRY_RUN};
+
 if($ENV{DEBUG} or $in->[0]->{debug}) {
     use LWP::Debug qw(+);
     $ua->add_handler(
@@ -178,31 +181,36 @@ sub check_and_update_record($$$$$) {
             # Update the record
             $record->{ttl} = $in->[0]->{defaults}->{ttl}->{$zone};
             _debug("Update ", $url, $record, to_json($record));
-            my $res = $ua->put(
+            unless ($DRY_RUN) {
-                $url,
+                my $res = $ua->put(
-                "Content-Type" => "application/json",
+                    $url,
-                "Content" => to_json({ records => [ $record ] }),
+                    "Content-Type" => "application/json",
-            );
+                    "Content" => to_json({ records => [ $record ] }),
-            warn "Failed to update $url: " . $res->status_line unless $res->is_success;
+                );
+                warn "Failed to update $url: " . $res->status_line unless $res->is_success;
+            }
         }
     } else {
         # Create new record
         my $new = format_record($zone, $type, $host, $value);
         _notice("Created new record: %s %s %s", $host, $type, $value);
         _debug($new);
-        my $res = $ua->post(
+        unless ($DRY_RUN) {
-            $url,
+            my $res = $ua->post(
-            "Content-Type" => "application/json",
+                $url,
-            Content => to_json({
+                "Content-Type" => "application/json",
-                records => [ $new ]
+                Content => to_json({
-            })
+                    records => [ $new ]
-        );
+                })
-        warn "Failed to create $url: " . $res->status_line . "\n" . $res->content unless $res->is_success;
+            );
+            warn "Failed to create $url: " . $res->status_line . "\n" . $res->content unless $res->is_success;
+        }
     }
 }
 
 sub delete_record($$) {
     my ($zone, $record) = @_;
+    return if $DRY_RUN;
 
     my $url = $in->[0]->{defaults}->{api} . "/$zone/records/$record->{host}/$record->{type}?host=$record->{host}&data=$record->{data}";
     my $res = $ua->delete($url);