Add feature to publish mqttwarn status information

Author: amotl

CHANGES.rst

@@ -12,6 +12,7 @@ in progress
 - Allow parameters of the ``file`` service to be defined on a per-file basis.
   Thanks, @Gulaschcowboy!
 - Add software tests for ``file`` service.
+- Add feature to publish mqttwarn status information. Thanks, @psyciknz!
 
 
 2021-09-29 0.26.2

HANDBOOK.md

@@ -132,8 +132,9 @@ I've written an introductory post, explaining [what mqttwarn can be used for](ht
   ; name the service providers you will be using.
   launch   = file, log, osxnotify, mysql, smtp
 
-  ; Publish the current mqttwarn version to the topic (retained)
-  publishversion = mqttwarn/version
+  ; Publish mqttwarn status information (retained)
+  status_publish = True
+  ; status_topic = mqttwarn/$SYS
 
 
   ; optional: TLS parameters. (Don't forget to set the port number for
@@ -167,15 +168,21 @@ I've written an introductory post, explaining [what mqttwarn can be used for](ht
   
   You should launch every service you want to use from your topic/target definitions here.
   
-  ###### `publishversion`
+  ###### `status_publish`
 
-  A topic that, when it exists, mqttwarn will publish it's current version as a retained payload.
-  Useful for automated updates (docker watchtower and the like)
+  Like with Mosquitto's `$SYS` topic, `mqttwarn` can publish status information to the broker.
+  This is useful for automated updates (Docker Swarm, Watchtower, etc.).
+
+  To enable status information publishing, configure `status_publish = True`. The other option,
+  `status_topic`, defaults to `status_topic = mqttwarn/$SYS`.
+  The messages will be published with the `retained` flag.
 
   For example:
   ```
-  root@mymachine:~$  mosquitto_sub -v -t mqttwarn/version
-  mqttwarn/version 0.25.0
+  root@mymachine:~$ mosquitto_sub -t 'mqttwarn/$SYS/#' -v
+  mqttwarn/$SYS/version 0.26.2
+  mqttwarn/$SYS/platform darwin
+  mqttwarn/$SYS/python/version 3.9.7
   ```
 
 

mqttwarn/core.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # (c) 2014-2021 The mqttwarn developers
+import platform
 from builtins import object
 from past.builtins import cmp
 from builtins import chr
@@ -629,11 +630,8 @@ def connect():
     # Update our runtime context (used by functions etc) now we have a connected MQTT client
     context.invoker.srv.mqttc = mqttc
 
-    try:
-        if cf.publishversion:
-            mqttc.publish(cf.publishversion,__version__,retain=True)
-    except: 
-        pass
+    # Publish status information to `mqttwarn/$SYS` topic.
+    publish_status_information()
 
     # Launch worker threads to operate on queue
     start_workers()
@@ -654,6 +652,45 @@ def connect():
             time.sleep(reconnect_interval)
 
 
+def publish_status_information():
+    """
+    Implement `$SYS` topic, like Mosquitto's "Broker Status".
+    https://mosquitto.org/man/mosquitto-8.html#idm289
+
+    Idea from Mosquitto::
+
+      $ mosquitto_sub -t '$SYS/broker/version' -v
+      $SYS/broker/version mosquitto version 2.0.10
+
+    Synopsis::
+
+      $ mosquitto_sub -t 'mqttwarn/$SYS/#' -v
+
+      mqttwarn/$SYS/version 0.26.2
+      mqttwarn/$SYS/platform darwin
+      mqttwarn/$SYS/python/version 3.9.7
+
+    """
+    if cf.has_option("defaults", "status_publish") and cf.status_publish:
+
+        status_topic = cf.g("defaults", "status_topic", "mqttwarn/$SYS")
+        logger.info(f"Publishing status information to {status_topic}")
+
+        # Items are tuples of (subtopic, message)
+        publications = [
+            ("version", __version__),
+            ("platform", sys.platform),
+            ("python/version", platform.python_version()),
+        ]
+        try:
+            for publication in publications:
+                subtopic, message = publication
+                mqttc.publish(status_topic + "/" + subtopic, message, retain=True)
+
+        except:
+            logger.exception("Unable to publish status information")
+
+
 def start_workers():
 
     # Launch worker threads to operate on queue

mqttwarn/examples/basic/mqttwarn.ini

@@ -55,8 +55,9 @@ functions = 'samplefuncs.py'
 ; name the service providers you will be using.
 launch    = file, log
 
-; Publish the current mqttwarn version to the topic (retained)
-publishversion = mqttwarn/version
+; Publish mqttwarn status information (retained)
+status_publish = True
+; status_topic = mqttwarn/$SYS