add dig for on change checking rfc2136

README.md

@@ -75,6 +75,7 @@ docker run --name traefik-rfc2136-demo \
 | `LABELS_TIMEOUT` | how many seconds after an interval the keys should stay till they expire in seconds | 30 |
 | `LABELS_WEBHOOK` | URL to call on each event or poll for each container |  |
 | `LABELS_WEBHOOK_AUTH_BASIC` | Basic authentication to use in the form of "username:password" for the webhook |  |
+| `LABELS_RFC2136_ONLY_UPDATE_ON_CHANGE` | Only update DNS entries if they are new or changed (will use dig on each call!) | false |
 
 ## Parent image
 * [11notes/node:stable](https://hub.docker.com/r/11notes/node)

rootfs/labels/dig.js

@@ -0,0 +1,25 @@
+const { spawn } = require('node:child_process');
+
+exports.dig = async(resolver, type, record) => {
+  return(new Promise((resolve, reject) => {
+    const dig = spawn('/usr/bin/dig', ['+short', '+answer', type, record, `@${resolver}`]);
+    const io = {stdout:'', stderr:''};
+    dig.stderr.on('data', data => {io.stderr += data.toString()});
+    dig.stdout.on('data', data => {io.stdout += (data.toString()).replace(/[\r\n]*$/ig, '')});
+    dig.on('error', error => {reject(error)});
+    dig.on('close', code =>{
+      switch(true){
+        case /no servers could be reached/ig.test(io.stdout): io.stderr += io.stdout; break;
+      }
+      if(code === 0){
+        if(io.stderr.length > 0){
+          reject(io.stderr);
+        }else{
+          resolve(io.stdout);
+        }
+      }else{
+        reject(io.stderr);
+      }
+    });
+  }));
+}

rootfs/labels/main.js

@@ -4,12 +4,14 @@ process.once('SIGINT', () => process.exit(0));
 const Docker = require('dockerode');
 const redis = require('redis');
 const { nsupdate } = require('./nsupdate');
+const { dig } = require('./dig');
 const { elevenLogJSON } = require('/labels/lib/util.js');
 
 const ENV_REDIS_INTERVAL = parseInt(process.env?.LABELS_INTERVAL || 300);
 const ENV_REDIS_TIMEOUT = parseInt(process.env?.LABELS_TIMEOUT|| 30);
 const ENV_LABELS_WEBHOOK = process.env?.LABELS_WEBHOOK;
 const ENV_LABELS_WEBHOOK_AUTH_BASIC = process.env?.LABELS_WEBHOOK_AUTH_BASIC;
+const ENV_LABELS_RFC2136_ONLY_UPDATE_ON_CHANGE = process.env?.LABELS_RFC2136_ONLY_UPDATE_ON_CHANGE || false;
 
 elevenLogJSON('info', {config:{
   LABELS_INTERVAL :ENV_REDIS_INTERVAL,
@@ -100,6 +102,7 @@ class Labels{
         if(!error){
           const update = (/start|poll/i.test(status)) ? true : false;
           const container = {
+            name:(data?.Name || data?.id).replace(/^\//i, ''),
             event:status,
             labels:{
               traefik:[],
@@ -112,7 +115,7 @@ class Labels{
             LAN:{server:'', key:'', commands:[]},
           }
 
-          elevenLogJSON('info', `inspect container {${(data?.Name || data?.id).replace(/^\//i, '')}}${(
+          elevenLogJSON('info', `container {${container.name}}.inspect()${(
             (null === status) ? '' : ` event[${status}]`
           )}`);
       
@@ -143,7 +146,9 @@ class Labels{
                     if(!update){
                       data.Config.Labels[label] = data.Config.Labels[label].replace(/update add/i, 'update delete');
                     }
-                    rfc2136[type].commands.push(data.Config.Labels[label]);
+                    if((ENV_LABELS_RFC2136_ONLY_UPDATE_ON_CHANGE && !await this.rfc2136KnownRecord(rfc2136[type].server, data.Config.Labels[label])) || true){                      
+                      rfc2136[type].commands.push(data.Config.Labels[label]);
+                    }
                 }
               break;
             }
@@ -152,6 +157,7 @@ class Labels{
           for(const type in rfc2136){
             if(rfc2136[type].commands.length > 0 && rfc2136[type].server && rfc2136[type].key){
               try{
+                elevenLogJSON('info', `container {${container.name}}.rfc2136() update ${type} DNS entries`);
                 await nsupdate(rfc2136[type].server, rfc2136[type].key, rfc2136[type].commands);
               }catch(e){
                 elevenLogJSON('error', e);
@@ -174,6 +180,19 @@ class Labels{
       });
     }));
   }
+
+  async rfc2136KnownRecord(server, nsupdate){
+    const matches = nsupdate.match(/update add (\S+) \d+ (\S+) (\S+)/i);
+    if(matches && matches.length >= 4){
+      try{
+        const record = await dig(server, matches[2], matches[1]);
+        return(matches[1].match(new RegExp(record, 'ig')));
+      }catch(e){
+        elevenLogJSON('error', e);
+        return(false);
+      }
+    }    
+  }
 }
 
 new Labels().watch();

rootfs/labels/nsupdate.js

@@ -1,22 +1,26 @@
 const { spawn } = require('node:child_process');
 
 exports.nsupdate = async(server, key, commands) => {
+
   commands.unshift(`server ${server}`);
   commands.push('send');
+  commands.push('quit');
+
   return(new Promise((resolve, reject) => {
     const nsupdate = spawn('/usr/bin/nsupdate', ['-y', key]);
-    let errors = '';
-    nsupdate.stderr.on('data', data  =>{errors += data.toString()});
+    const io = {stdout:'', stderr:''};
+    nsupdate.stderr.on('data', data => {io.stderr += data.toString()});
+    nsupdate.stdout.on('data', data => {io.stdout += (data.toString()).replace(/[\r\n]*$/ig, '')});
     nsupdate.on('error', error => {reject(error)});
-    nsupdate.on('exit', code =>{
+    nsupdate.on('close', code =>{
       if(code === 0){
-        if(errors.length > 0){
-          reject(errors);
+        if(io.stderr.length > 0){
+          reject(io.stderr);
         }else{
-          resolve(true);
+          resolve(io.stdout);
         }
       }else{
-        reject(errors);
+        reject(io.stderr);
       }
     });
     for(const command of commands){