Twitch Hermes Endpoint

[mpforce1]

While investigating issue #634 I noticed that the Twitch web client had a 3rd WebSocket open while watching streams. I only remember it using 2 WS endpoints (IRC and PubSub). The Hermes endpoint is at wss://hermes.twitch.tv/v1?clientId=..... After some digging I could see that this API appears to implement some PubSub topics, e.g.:

Request:

{
    "type": "subscribe",
    "id": "...",
    "subscribe": {
        "id": "...",
        "type": "pubsub",
        "pubsub": {
            "topic": "raid.[channel id]"
        }
    },
    "timestamp": "..."
}

Response:

{
    "id": "...",
    "parentId": "...",
    "type": "subscribeResponse",
    "timestamp": "...",
    "subscribeResponse": {
        "result": "ok",
        "subscription": {
            "id": "..."
        },
        "telemetry": {
            "variations": [{
                    "cellHash": "...",
                    "subjectHash": "...",
                    "eventHash": "...",
                    "filterHash": "..."
                }
            ],
            "intervalSeconds": 60
        }
    }
}

Keepalive:

{
    "id": "",
    "type": "keepalive",
    "timestamp": "..."
}

The Request is one of the subscription messages sent by the client at startup, it appears to subscribe to the raid topic. In fact, all of the subscriptions I could see were "type": "pubsub". The Response appears to suggest that the subscription will update at 60 second intervals, I'm guessing that's what the Keepalive messages are for.

Looking through the source code I can see that this endpoint is only used if Twitch experiments enable it, so this must be a new experimental API that they're testing. In particular, my settings.[hash].js file contains entries for twilight_hermes_rollout_ variables that contain PubSub topic names, e.g.:

{
    ...
    twilight_hermes_rollout_device_blue: [
        "channel-bits-onetap-events",
        "channel-emote-updates",
        "shared-chat-channel-v1",
        ...
    ]
    ...
}

My suspicion is that Twitch may be planning to drop the PubSub endpoint and replace it with this Hermes endpoint, possibly as part of the deprecation of 3rd party PubSub. Does anyone have any more information about this?

[Veatra]

Not sure how reliant the miner is on PubSub currently, but yeah twitch will decommission that system down in 2 months in favor of EventSub