What parts of the trigger are available for other input bindings?

[oadrian2]

I'm trying to figure out what values are populated for use in other kinds of binding. E.g., in SignalR, invocation arguments are available for binding, but I'm not seeing an equivalent here. triggerMetadata seems to be empty in the SWA-compatible WebPubSubContext version meaning we can't tie event-messages to other inputs and outputs (e.g., CosmosDB). And based on the lack of documentation of binding information, I imagine they're unavailable even in the WebPubSubTrigger version.

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Document Details

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• ID: 0c4c897d-50cd-34e9-c2e7-7ca235090b8c
• Version Independent ID: 65d9edff-959a-e5d7-1164-947261bb592a
• Content: Reference - Azure Web PubSub trigger and bindings for Azure Functions
• Content Source: articles/azure-web-pubsub/reference-functions-bindings.md
• Service: azure-web-pubsub
• GitHub Login: @JialinXin
• Microsoft Alias: jixin

[ManoharLakkoju-MSFT]

@oadrian2 Thanks for your feedback! We will investigate and update as appropriate.

[AjayKumar-MSFT]

Your feedback has been shared with the content owner for further review. Thanks again for the feedback!

[JialinXin]

@oadrian2 I'm not quite understand your question. SWA only support HttpTrigger, that's why Web PubSub has a WebPubSubContext to deserialize the Web PubSub service http request to Web PubSub protocol input object. What do you mean by tie event message to CosmosDB input? Why you need to make it a CosmosDB input when the request is actually from Web PubSub service?

[oadrian2]

I'm referring to cosmos DB inputs rather than triggers. Basically a way of a database query based on the event that was triggering of the web pub/sub similar to how you would with an HTTP request. With SignalR triggers, the parameters on the invocation can be mapped to cosmos DB bindings on the input which allows you to retrieve the data without having to actually invoke the client yourself.

[JialinXin]

Sorry I still couldn't get your idea. Would you share a sample code, maybe SignalR one that meet your ask?

[oadrian2]

This is the doing a pseudo-patch operation, which is invoked through a SignalR trigger. Non-relevant code has been omitted. Let me know if you want further clarification on anything. Thank you for taking the time.

const updateTokenInput = input.cosmosDB({
  databaseName: DATABASE_NAME,
  collectionName: TOKENS_CONTAINER,
  connectionStringSetting: 'CosmosDBConnection',
  id: '{token.id}', // using token triggerMetadata (see below)
  partitionKey: '{mapId.game}', // using mapId triggerMetadata (see below)
});

//
app.generic('updateToken', {
  trigger: trigger.generic({
    type: 'signalRTrigger',
    hubName: 'map',
    category: 'messages',
    event: 'updateToken',
    // parameter names here will bind the arguments of the invoke to trigger bindings usable by inputs/outputs
    parameterNames: ['mapId', 'token'], 
  }),
  extraInputs: [updateTokenInput],
  extraOutputs: [signalRMessagesOutput, tokenContainerOutput],
  handler: async (_request, context) => {
    const mapId = context.triggerMetadata!.mapId as { id: string; game: string }; // id coming from patch request
    const token = context.triggerMetadata!.token as Token`; // patch data

    const { id: map, game } = mapId;
    const documentIn = (context.extraInputs.get(updateTokenInput) || {}) as object;
    const documentOut = { ...documentIn, ...token };

    context.extraOutputs.set(tokenContainerOutput, documentOut);
    context.extraOutputs.set(signalRMessagesOutput, [
      {
        target: 'tokenUpdated', // event name
        arguments: [mapId, documentOut], // arguments to event
      },
    ]);
  },
});

[JialinXin]

When work with WebPubSubTrigger, triggerMetadata is all the metadata pre-bind with it, where you can refer to section https://learn.microsoft.com/en-us/azure/azure-web-pubsub/reference-functions-bindings?tabs=csharp#usages about available items under different requests.

Example:

I'm working on a chat sample under v4 model. And probably would help you easier get started.

[JialinXin]

You can refer to this chat sample: https://github.com/JialinXin/azure-webpubsub/tree/jixin/v4-js/samples/functions/js/simplechat_v4

[oadrian2]

When work with WebPubSubTrigger, triggerMetadata is all the metadata pre-bind with it, where you can refer to section https://learn.microsoft.com/en-us/azure/azure-web-pubsub/reference-functions-bindings?tabs=csharp#usages about available items under different requests.

Example:

I'm working on a chat sample under v4 model. And probably would help you easier get started.

What about in the SWA-style HTTP triggers?

[JialinXin]

Then you need to work with WebPubSubContext input binding and in the function, you can get the values by context.extraInputs.get('wpsContext'). And inner structure is described here: https://learn.microsoft.com/en-us/azure/azure-web-pubsub/reference-functions-bindings?tabs=csharp#webpubsubcontext-1

For example:

const wpsContext= input.generic({
    type: 'webPubSubContext',
    name: 'wpsContext',
    hub: 'sample_funcchatv4'
});

app.http('message', {
    methods: ['GET', 'POST'],
    authLevel: 'anonymous',
    extraInputs: [wpsContext],
    handler: async (request, context) => {
        let wpsRequest = context.extraInputs.get('wpsContext').request;
        let data = request.data;
        ....
    },
});

[oadrian2]

Then you need to work with WebPubSubContext input binding and in the function, you can get the values by context.extraInputs.get('wpsContext'). And inner structure is described here: https://learn.microsoft.com/en-us/azure/azure-web-pubsub/reference-functions-bindings?tabs=csharp#webpubsubcontext-1

For example:

const wpsContext= input.generic({
    type: 'webPubSubContext',
    name: 'wpsContext',
    hub: 'sample_funcchatv4'
});

app.http('message', {
    methods: ['GET', 'POST'],
    authLevel: 'anonymous',
    extraInputs: [wpsContext],
    handler: async (request, context) => {
        let wpsRequest = context.extraInputs.get('wpsContext').request;
        let data = request.data;
        ....
    },
});

Is it the case that since the WebPubSubContext is an input and not a trigger, the trigger metadata isn't present like they are with the WebPubSubTrigger? If they aren't there when using WebPubSubContext then you can't use those values to populate other Input bindings (e.g., CosmosDB or Storage) since there isn't any binding metadata. This does limit its usefulness.

[JialinXin]

It's correct that WebPubSubContext is an input binding instead of trigger binding, so triggerMetadata is not valid for building WebPubSub metadata here. I'm not sure that if it's possible to bind single request to multiple input bindings. When you work with WebPubSubContext, it means the request is a Web PubSub request, why would you treat it as a Cosmos DB document? Should it read the request and then convert to a Cosmos DB document in other way? Would you describe your scenario a little bit more?

[hhunter-ms]

It looks like this has been resolved. Closing! #please-close