Clustered NodeBB and plugin socket methods

razibal

I'm trying to debug an issue with maintaining sync for plugin settings between nodes of a NodeBB cluster running on 2 different machines. I've set isCluster on both instances, however the SocketPlugins method only triggers on one instance when the hook is fired from the client. Any suggestions on where to look would be much appreciated.

razibal

I've verified that both are using Redis for pubsub and the hook data is being received and emitted on both in src/database/redis/pubsub.js :

self.emit(msg.event, msg.data);

Instance 1

instance 1 mongo-object:cache:del [ 'settings:customMod' ]
instance 1 local:cache:del [ 'settings:customMod' ]
instance 1 action:settings.set.customMod{
  enableQuickReply: 'on',
  featuredTopic: '',
  shared: '88,89, 90, 91,105,',
  searchable: '88, 89, 90, 91,105,',
  articles: '1, 2, 102, 103, 104',
  hideSubCategories: 'off',
  hideCategoryLastPost: 'off'
}

Instance 2

instance 2 mongo-object:cache:del [ 'settings:customMod' ]
instance 2 local:cache:del [ 'settings:customMod' ]
instance 2 action:settings.set.customMod{
  enableQuickReply: 'on',
  featuredTopic: '',
  shared: '88,89, 90, 91,105,',
  searchable: '88, 89, 90, 91,105,',
  articles: '1, 2, 102, 103, 104',
  hideSubCategories: 'off',
  hideCategoryLastPost: 'off'
}

However, only one instance of the plugin triggers from the hook

<baris>

When you do a socket.emit('someplugin.method') it will only trigger the method in the instance that you are connected, this is intended. If you want to update a local settings object in your plugin you need to listen to action:settings.et.customMod and update you local object.

razibal

@baris That's exactly what I am doing
{ "hook": "action:settings.set.customMod", "method": "updateSettings" }
However, only one instance of the plugin gets triggered. I am trying to follow the event path to debug the issue but I'm not clear on the pubsub architecture. I can see that pubsub.js uses Redis via a channel named db:${nconf.get('redis:database')}:pubsub_channel, while the socket.io Redis adapter uses multiple channels prefixed with: db:${nconf.get('redis:database')}:adapter_key ? I can listen to the pubsub_channel and see all the traffic

redis db:11:pubsub_channel {"event":"analytics:publish","data":{"local":{"counters":{},"pageViews":0,"pageViewsRegistered":0,"pageViewsGuest":0,"pageViewsBot":0,"uniqueIPCount":0,"uniquevisitors":0}}}
redis db:11:pubsub_channel {"event":"analytics:publish","data":{"local":{"counters":{"pageviews:byCid:122":1},"pageViews":1,"pageViewsRegistered":0,"pageViewsGuest":0,"pageViewsBot":1,"uniqueIPCount":0,"uniquevisitors":0}}}

Where does pubsub.js fit into the overall architecture? and a followup question, is there a mechanism to trigger execution of a method in all instances of a plugin? Either directly from the client, or by propagating the triggered hook on the one instance that received the hook would work.

<baris>

{ "hook": "action:settings.set.customMod", "method": "updateSettings" }
This won't work since it is not a hook, plugin.json hooks object is used for listening to plugin hooks that are fired with plugins.hooks.fire.

In this case you want to listen for messages on pubsub so you need to use. pubsub.on('action:settings.set.customMod', handler); in your plugin.

NodeBB/src/meta/settings.js at master · NodeBB/NodeBB

Node.js based forum software built for the modern web - NodeBB/src/meta/settings.js at master · NodeBB/NodeBB

GitHub (github.com)

If you want to use a plugin hook it is called action:settings.set and that can be added to plugin.json

razibal

So, if I understood you correctly, in order to propagate local variables across instances, I should use pubsub after receiving a hook?

Following this suggestion, I set up the flow like below.

The plugin gets triggered by the ACP save and publishes a notification for the other instances:

socketAdmin.plugins.customMod.save = async function(socket, data) {                                                           
  await db.set('plugins.customMod.settings', JSON.stringify(data));   
   // perfom required lookups and transformations to data
   pubsub.publish('plugins.customMod:updated', updatedData);
 };

And then set up a listener for applying the changes to the local variables in all instances

pubsub.on(`plugins.customMod:updated`, (async (data) => {                                                                                                                                                                                          
    categoryArticles = data.categoryArticles                                                                                 
    articleCategories = data.articleCategories                                                                               
    shareCategories = data.shareCategories                                                                                   
    searchableCategories = data.searchableCategories                                                                         
));

I understand why socket.emit should only trigger on a single instance in most cases, but perhaps it would be useful to have a way to automatically trigger on all instances?

<baris>

Yeah your flow should work, we don't trigger it on all instances as that would cause issues if the function is doing db writes for example. You would have 2+ instances trying to create the same records etc.