> For the complete documentation index, see [llms.txt](https://docs.openg2p.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openg2p.org/platform/platform-services/websub.md).

# WebSub

Shared WebSub hub used by OpenG2P products to register topics and deliver events to subscriber callbacks.

OpenG2P uses a [WebSub](https://www.w3.org/TR/websub/) hub as a shared delivery service. Publishers register a topic and post content to the hub. The hub verifies subscriber callbacks and delivers that content to them.

The hub is not part of the Registry application. Registry, and any other product that needs push delivery, calls the hub over HTTP. Commons Services deploys the MOSIP hub and consolidator.

## What the hub does

* Accepts topic registration from a publisher.
* Accepts subscriptions from callbacks and checks that the callback is controlled by the subscriber.
* Stores topic and subscriber changes as Kafka events.
* Delivers a publish to every verified subscriber of that topic.
* Signs each delivery with the subscriber's `hub.secret` when one was supplied.

The hub is stateless. The consolidator folds the Kafka events into the state that every hub instance reads. Both components are required.

## Who publishes

| Publisher            | What it sends                                             |
| -------------------- | --------------------------------------------------------- |
| Registry outgestion  | Approved register changes, after template transformation. |
| Registry Partner API | Asynchronous DCI `on-search` results for one partner.     |

Those products choose the topic name and the payload. Subscription, the callback challenge, and `X-Hub-Signature` are hub behaviour and are the same for every publisher.

## Pages

{% content-ref url="/pages/7dHQTqF3kS2l6VbCX2vK" %}
[Subscription and delivery](/platform/platform-services/websub/subscription.md)
{% endcontent-ref %}

{% content-ref url="/pages/GCDoHmcgYmkKIsrEyIFK" %}
[Deployment](/platform/platform-services/websub/deployment.md)
{% endcontent-ref %}

Registry uses of the hub:

{% content-ref url="/pages/SfsQOtHFbteKMi3f6DgY" %}
[Outgestion Pipeline](/products/registry/registry/design/outgestion-pipeline.md)
{% endcontent-ref %}

{% content-ref url="/pages/pHFvHyQhXwzc4g0bBuTs" %}
[DCI partner search](/products/registry/registry/design/partner-register-search/dci-search.md)
{% endcontent-ref %}


---

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