Path parameters in Web PubSub Service

Martin Body 20

Hello,

I am trying to setup event handlers in Azure PubSub which reads and forwards path parameters, but I didn't find a way how to do it. Does it support such a scenario?

pubsub wss:

wss://mysite.webpubsub.azure.com/client/hubs/hubname/{pathParam}

event handler:

https://event-handler.net/api/connect/{pathParam}

Thank you.

Pinaki Ghatak 5,310 Reputation points Microsoft Employee

2024-12-09T09:57:25.8933333+00:00

Hello @Martin Body

Web PubSub Service supports path parameters. You can define path parameters in the URL template of the event handler. For example, if you want to forward the path parameter from the client URL to the event handler URL, you can define the URL template of the event handler as follows:

[https://event-handler.net/api/connect/{pathParam}]()

When a client connects to the Web PubSub Service with the following URL: wss://mysite.webpubsub.azure.com/client/hubs/hubname/{pathParam}

The {pathParam} will be replaced with the actual value of the path parameter.

Then, the Web PubSub Service will send a POST request to the event handler URL with the path parameter included in the URL.

I hope this helps
Martin Body 20 Reputation points

2024-12-10T10:30:59.88+00:00

I tried it, but it seems that it is working only for default parameters - "hub" and "event". See screenshot below.

I am not able to use my own parameters.
Martin Body 20 Reputation points

2024-12-13T11:11:12.63+00:00

Can I use my own parameters in Web PubSub in URL? Does anybody have experience with it? I tried it, but it seems that it is working only for default parameters - "hub" and "event". See screenshot below in my previous comment.
Laxman Reddy Revuri 1,130 Reputation points Microsoft Vendor

2024-12-16T16:04:35.5266667+00:00

Hi @Martin Body
Thanks for the question and using MS Q&A platform.
Yes, you can include your own parameters in the Azure Web PubSub Service URL, but there are a few limitations. The service allows certain predefined parameters, like {event} in the URL template for event handlers. This parameter is specifically used to route events to the right handlers based on the type of event being processed.

Default Parameters: As mentioned earlier the Azure Web PubSub Service has some default parameters, the most notable ones are “hub” and “event”. This implies that if you create a URL which has such parameters then clustering them on the same axis becomes a restriction.

Event Handler Configuration: While creating your event handler, one can include a URL which caters for the {event} parameter. An example is provided below

This service URL will include actual identifiers in the placement of the parameters{ (text, hub) (text, event)}, when the user connects to the hub and starts an event.

Limitations on Custom Parameters: If you are considering switching to using a URL template that requires you to use complete custom parameters (e.g., {pathParam}) then it may not be suited to this model. This is because the service was designed for recognizability through handles and hence is limited to the usage of such parameters only.
I hope this information is helpful.
Laxman Reddy Revuri 1,130 Reputation points Microsoft Vendor

2024-12-18T04:00:14.8266667+00:00

Hi @Martin Body
Following up to see if you have chance to check my previous response and help us with requested information to check and assist you further on this.
Martin Body 20 Reputation points

2024-12-18T08:24:25.1533333+00:00

Hi @Laxman Reddy Revuri

One more practical question:

We have Charging station SIMULATOR which is connecting to our PubSub with the following link:

wss://charing.pubsub.webpubsub.azure.com/client/hubs/hub_public_chargers?stationId=Station01&password=Start.123

This way we can forward stationId with queries.

Physical Charging station is using PATH parameters for stationId with the following link:

wss://charing.pubsub.webpubsub.azure.com/client/hubs/hub_public_chargers/Station01

Is there any way to forward the dynamic stationId with Handlers from PATH parameters through PubSub? Or is there some better (serverless) solution for our scenario?

Thank you.
Laxman Reddy Revuri 1,130 Reputation points Microsoft Vendor

2024-12-20T03:59:17.0633333+00:00

Hi @Martin Body
Following up to see if you have chance to check my previous response and help us with requested information to check and assist you further on this.
Martin Body 20 Reputation points

2024-12-20T08:08:31.3566667+00:00

Hi @Laxman Reddy Revuri

Your solution proposal looks good. We will test it.

Thank you.

Accepted answer

Laxman Reddy Revuri 1,130 Reputation points Microsoft Vendor

2024-12-19T01:00:07.24+00:00

Hi @Martin Body
The current approach with query parameters (?stationId=Station01) works but requires reconnecting if the stationId changes. It's simple but limited in flexibility. Web PubSub does not natively support extracting stationId from path parameters (/Station01).

When utilizing path parameters, one must have an additional layer such as Azure Functions or Azure API Management to:

Extract the stationId from the URL path.

Pass it on as a query parameter or metadata to Web PubSub.

Azure Functions:

A physical charging station connects to the Azure Function Websocket endpoint against the format, for instance, wss://.azurewebsites.net/Station01.

The Azure Function removes Station01 from the path and sends this connection to Web Pub Sub composed of the stationId in the query string or the metadata.

If you want a serverless, easy-to-maintain approach, Azure API Management is likely the best choice since it requires minimal logic changes and no custom gateway code. If you need more control or advanced logic, go with Azure Functions.

I hope this information is helpful.
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Laxman Reddy Revuri 1,130 Reputation points Microsoft Vendor

2024-12-23T00:42:17.8366667+00:00

Hi @Martin Body
Following up to see if you have chance to check my previous response and help us with requested information to check and assist you further on this.
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