APIM to send message to multiple backend

Question

APIM to send message to multiple backend

Yang Chow Mun 121

Hi all, I would like to set up something like this using APIM

A source is pushing message to apim.
APIM is sending the message to the corresponding subscribers.
I am expecting to have a few subscribers, is there a way to achieve this in apim?

Thanks!

MuthuKumaranMurugaachari-MSFT 22,431 Reputation points Moderator

2024-01-08T20:21:57.49+00:00

Yang Chow Mun Thanks for posting your question in Microsoft Q&A. From the description above, Pinaki Ghatak is right about using Service Bus for pub/sub pattern instead of APIM flow.

With further discussion happened below, I think term subscribers might be interpreted in a different way. If I understand correctly, a data source based on some events will call APIM and APIM in turns needs to call multiple APIs (or service endpoint) with the message payload.

In that scenario, you can configure a single primary backend API (Functions, Logic Apps, or Container Apps etc.) for sending a message from APIM and this can also be set dynamically using set-backend-service policy based on incoming requests. You can call other backend APIs via send-request or send-one-way-request policy in the request pipeline and process the responses accordingly.

I hope this helps and let us know if you have any questions.
MuthuKumaranMurugaachari-MSFT 22,431 Reputation points Moderator

2024-01-10T14:31:40.9966667+00:00

Yang Chow Mun Just a follow up to see if it helped or still have any questions.

Accepted answer

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Your answer

MuthuKumaranMurugaachari-MSFT 22,431 Reputation points Moderator

2024-01-08T20:21:57.49+00:00

Yang Chow Mun Thanks for posting your question in Microsoft Q&A. From the description above, Pinaki Ghatak is right about using Service Bus for pub/sub pattern instead of APIM flow.

With further discussion happened below, I think term subscribers might be interpreted in a different way. If I understand correctly, a data source based on some events will call APIM and APIM in turns needs to call multiple APIs (or service endpoint) with the message payload.

In that scenario, you can configure a single primary backend API (Functions, Logic Apps, or Container Apps etc.) for sending a message from APIM and this can also be set dynamically using set-backend-service policy based on incoming requests. You can call other backend APIs via send-request or send-one-way-request policy in the request pipeline and process the responses accordingly.

I hope this helps and let us know if you have any questions.
MuthuKumaranMurugaachari-MSFT 22,431 Reputation points Moderator

2024-01-10T14:31:40.9966667+00:00

Yang Chow Mun Just a follow up to see if it helped or still have any questions.

Answer 1

Pinaki Ghatak 5,600 Microsoft Employee Volunteer Moderator

Hello @Yang Chow Mun

Your question is a bit unclear. It seems you are trying to adopt a publish / subscribe pattern, and in this case there are many subscribers.

If this is the case, a Azure Service bus with topics will be the correct way to go. Please read more here.

https://learn.microsoft.com/en-us/azure/service-bus-messaging/service-bus-dotnet-how-to-use-topics-subscriptions?tabs=passwordless

Let us know, if this helps you to go further, and if so, please mark this answer as accepted to help further readers who are seeking similar questions.

Thank you

Yang Chow Mun 121 Reputation points

2024-01-07T06:13:10.1166667+00:00

@Pinaki Ghatak thanks for your reply.

I do notice that service bus could achieve this purpose. But I would like to utilize api for message exchange between data source. example, if I push a notification to apim, apim will route to different subscribers. So the communication between different data source is via apim instead of other azure services.
Pinaki Ghatak 5,600 Reputation points Microsoft Employee Volunteer Moderator

2024-01-07T12:06:44.5266667+00:00
Hello @Yang Chow Mun

Azure API Management is a forward proxy and management plane for governance of your API's. In this context, subscription means an RBAC and keys with which you can access the API's, and. is not meant for a Publish / subscribe pattern, since there is nothing in API Management that will do something by itself. API Management will delegate the task to the backend API's, who will do the work.

Also please know, that in a publish / subscribe system, JSON messages is not the only formats, as you. can use other formats too.

Here is a summary of the differences between Azure API Management and Azure Service Bus Topics in bullet points:

Azure API Management:

A turnkey solution for publishing APIs to external and internal customers.

Allows you to create consistent and modern API gateways for existing back-end services hosted anywhere.

Provides tools to analyze and optimize your APIs.

Azure Service Bus Topics:

A fully managed enterprise message broker with message queues and publish-subscribe topics.

Used to decouple applications and services from each other.

Provides benefits such as load-balancing work across competing workers, safely routing and transferring data and control across service and application boundaries, and coordinating transactional work that requires a high-degree of reliability.

In short, Azure API Management is used for managing APIs, while Azure Service Bus Topics is used for reliable cloud messaging between applications and services.
Yang Chow Mun 121 Reputation points

2024-01-08T00:50:07.61+00:00

hi @Pinaki Ghatak , thanks for your advice.

I have a data source which will push events as and when there is an update. Currently I have tried using apim to set the endpoint as azure function which is working fine. The flow will be like data source -> apim -> azure function

I would like to achieve something like this data source -> apim -> azure functions and other end points.

Are you able to share a general flow on how the above can be achieved via apim and other azure services.

Thanks!
Pinaki Ghatak 5,600 Reputation points Microsoft Employee Volunteer Moderator

2024-01-10T16:09:35.5233333+00:00
Hello @Yang Chow Mun

Yes, you can achieve this using Azure API Management (APIM) and Azure Event Grid. Here’s a general flow:

Data Source -> APIM: Your data source pushes events to APIM.

APIM -> Azure Functions/Other Endpoints: You can use APIM policies to route the incoming requests to different backend services based on certain conditions. For example, you can use the set-backend-service policy to change the backend service dynamically. Here’s a sample policy that routes to 2 different function apps based on a condition:

<policies> <inbound> <choose> <when condition="@(context.User.Groups.Select(g => g.Name).Contains(\"group1\"))"> <set-backend-service base-url="https://abc-apim.azure-api.net/app1" /> </when> <when condition="@(context.User.Groups.Select(g => g.Name).Contains(\"group2\"))"> <set-backend-service base-url="https://abc-apim.azure-api.net/app2" /> </when> </choose> </inbound> </policies>

In this example, the policy checks the group of the user and routes the request to a different backend service accordingly.

APIM -> Azure Event Grid: If you want to route events to multiple endpoints, Azure Event Grid can be a good choice. Event Grid allows you to route your messages to Azure services or webhooks for further processing. You can create an Event Grid topic where all messages will be routed. Once the messages are in the topic, you can configure an event subscription to consume the messages from the topic.

Remember, the exact implementation will depend on your specific requirements and the nature of your data source and endpoints. It’s always a good idea to refer to the official Azure documentation and resources for the most accurate and up-to-date information.

This should get you started.
Yang Chow Mun 121 Reputation points

2024-01-12T00:37:41.15+00:00

thanks for the advice.

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APIM to send message to multiple backend

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