Load Balancing Affinity for Webex Bots

A reverse proxy to enables LB affinity (application layer persistance) based on the actorId property of a JSON Webhook event (ie, the personId of the Webex user interacting with the bot).

The typical use case for this proxy is to scale stateful Webex bots (such as Botkit conversations), by ensuring the Webhook events are routed to the bot instance holding the in-memory state of conversations from a group of users interacting with the bot.

The proxy accepts different configuration modes:

Affinity cookie: a cookie is setup by the load balancer in a Webhook HTTP response. The proxy associates the 'actorId' of the Webhook event being processed with the cookie. Next time the same 'actorId' is received, the proxy injects the cookie before forwarding the request to the load balancer. The LB then routes the request to the right bot instance.
ActorId injection: the proxy looks for an 'actorId' property in the incoming Webhook event payload. If found, the proxy add a configurable 'Actorid' HTTP header. The proxy then forwards the HTTP request to a target URL (generally a cluster of Webex bots sitting behind a load balancer). Choose this mode if your LB can persist sessions and route traffic based on the ActorId.

How to use

The proxy forwards to the the Load Balancer specified via the TARGET_URL env variable.

Instructions on Mac/Linux

git clone https://github.com/ObjectIsAdvantag/webhook-affinity
cd webhook-affinity
npm install
DEBUG=injector TARGET_URL=https://your-bot-server node server.js

Instructions on Windows

git clone https://github.com/ObjectIsAdvantag/webhook-affinity
cd webhook-affinity
npm install
set TARGET_URL=https://your-bot-server
set DEBUG=injector
node server.js

Testing 'ActorId injection' from your local machine

Create a test endpoint to receive Webex webhook notifications
- Example: https://requestb.in/10zyvg01
Run the proxy on your local machine with Requestb.in as the destination endpoint.
- Make sure you specify 'https://requestb.in' and not the full path to your requestb.in endpoint, ie no suffix as show below:
```
cd webhook-affinity
TARGET_URL=https://requestb.in  node server.js
```
Expose your local proxy via ngrok. Your proxy is running on port 9090 by default, for which ngrok creates a temporary public endpoint thanks to the command below:
```
ngrok http 9090
```
Create a Webhook for (Messages/Created) events with name "Actorid Injection Test" from a Bot Account token and pointing to the ngrok URL, suffixed with your requestb.in identifier.
- Example: https://e7957132.ngrok.io/10zyvg01
Now interact with the bot in a Webex Messaging Space and check the enriched JSON payload at requestb.in's inspect URL.
- Example: https://requestb.in/10zyvg01?inspect

Architecture

Webex webhooks send notification events via POST requests, with the JSON payload documented here.

In order to enable LB affinity, a proxy is responsible for extracting the actorId of the incoming payload from the Webex cloud platform, and maintain sessions based on this actorId, or inject headers.

actorId is the personId of the user that caused the webhook to be sent. For example, on a messsage created webhook, the author of the message will be the actorId. On a membership deleted webhook, the actor is the person who removed a user from a room.

{
  "id":"Y2lzY29zcGFyazovL3VzL1dFQkhPT0svZjRlNjA1NjAtNjYwMi00ZmIwLWEyNWEtOTQ5ODgxNjA5NDk3",
  "name":"Guild Chat to http://requestb.in/1jw0w3x1",
  "resource":"messages",
  "event":"created",
  "filter":"roomId=Y2lzY29zcGFyazovL3VzL1JPT00vY2RlMWRkNDAtMmYwZC0xMWU1LWJhOWMtN2I2NTU2ZDIyMDdi",
  "orgId": "Y2lzY29zcGFyazovL3VzL09SR0FOSVpBVElPTi8xZWI2NWZkZi05NjQzLTQxN2YtOTk3NC1hZDcyY2FlMGUxMGY",
  "createdBy": "Y2lzY29zcGFyazovL3VzL1BFT1BMRS8xZjdkZTVjYi04NTYxLTQ2NzEtYmMwMy1iYzk3NDMxNDQ0MmQ",
  "appId": "Y2lzY29zcGFyazovL3VzL0FQUExJQ0FUSU9OL0MyNzljYjMwYzAyOTE4MGJiNGJkYWViYjA2MWI3OTY1Y2RhMzliNjAyOTdjODUwM2YyNjZhYmY2NmM5OTllYzFm",
  "ownedBy": "creator",
  "status": "active",
  "actorId": "Y2lzY29zcGFyazovL3VzL1BFT1BMRS8xZjdkZTVjYi04NTYxLTQ2NzEtYmMwMy1iYzk3NDMxNDQ0MmQ",
  "data":{
    "id":"Y2lzY29zcGFyazovL3VzL01FU1NBR0UvMzIzZWUyZjAtOWFhZC0xMWU1LTg1YmYtMWRhZjhkNDJlZjlj",
    "roomId":"Y2lzY29zcGFyazovL3VzL1JPT00vY2RlMWRkNDAtMmYwZC0xMWU1LWJhOWMtN2I2NTU2ZDIyMDdi",
    "personId":"Y2lzY29zcGFyazovL3VzL1BFT1BMRS9lM2EyNjA4OC1hNmRiLTQxZjgtOTliMC1hNTEyMzkyYzAwOTg",
    "personEmail":"person@example.com",
    "created":"2015-12-04T17:33:56.767Z"
  }
}