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Can I implemengt REST request/reply mechanism using Rest Delivery Points

Susi Dman
Susi Dman Member Posts: 10 ✭
edited January 2023 in General Discussions #1

Hi Team

I followed this tutorial and it seems it is possible to route a request to a REST backend via Solace

https://tutorials.solace.dev/rest-messaging/publish-subscribe/

Is there any way that the response from the backend REST service can be routed back to the API client who invokes the solace REST endpoint?

This blog discusses a similar system, but in this case, the backend is JMS listener.

https://solace.com/blog/pubsub-postman-restful-request-reply/


My requirement is to implement API proxy kind of solution where I can log all api requests/responses to a database using solace in between or any other means. I'm looking for a solution with minimal changes for the existing rest backends or introducing minimal services.

Thanks

Susi

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Answers

  • Aaron
    Aaron Member, Administrator, Moderator, Employee Posts: 644 admin
    #2

    Hi @Susi Dman ..! Yup, all you have to do is populate the Solace-Reply-To-Destination in your request message, and you should get the response routed back to the topic or queue that you specify.

    Format:

    Solace-Reply-To-Destination: /(QUEUE |TOPIC)/<destination_string>

    See this page for more info: https://docs.solace.com/API/RESTMessagingPrtl/Solace-REST-Message-Encoding.htm

    Alternatively, you could explore using the REST Gateway mode (instead of REST Messaging mode), where the broker acts completely as a proxy, and will accept a variety of REST verbs (GET, PATCH, DELETE, etc.) instead of just the POST of the REST Messaging API. See here for more: https://docs.solace.com/API/REST/REST-get-start.htm#When

    Hope that helps!

  • Susi Dman
    Susi Dman Member Posts: 10 ✭
    #3

    Hi Aaron

    Many thanks for pointing out the REST Gateway option. I was able to give a try with this blog post

    https://codelabs.solace.dev/codelabs/solace-event-enable-rest/#0

    I have a requirement that I want to proxy 2 backends with different context paths. Does something like URL-rewrite is possible with REST Gateway, if so where to configure it? For example, I want to achieve something like below

    https://<myconn>.messaging.solace.cloud:9443/hr/*  --> https://my.hr.backend/*

    https://<myconn>.messaging.solace.cloud:9443/payroll/*  --> https://my.payroll.com/<some>/<path>/*

    Thanks

    Susi

  • Aaron
    Aaron Member, Administrator, Moderator, Employee Posts: 644 admin
    edited January 2023 #4

    Ok... if you use the Gateway mode, the URL is passed through exactly as is... you can't rewrite it. That is only possible with REST Messaging mode. In Gateway, if you just want the URL to remain the same, then that's what it does... the broker acts as a proxy.

    So if you want to do some target rewriting, you'll want to use Messaging mode, have 2 RDPs, and then inside your two RDPs' queue bindings you can configure a custom target. Your first queue would be listening to hr/> and your second RDP queue would be listening to payrole/> . Then each inside the queue binding of each RDP you could specify your custom path for the downstream REST server.

    And remember that your REST publisher will need to insert that header that I was talking about: Solace-Reply-To-Destination in order for the backend response to get routed back to the publisher.

    Take a look at this video I made which shows some of what I'm talking about substitution expressions for the downstream target: https://youtu.be/INMrSL2fA3E?t=439 (don't worry that the video is for S3, doesn't really matter).

  • Susi Dman
    Susi Dman Member Posts: 10 ✭
    #5

    Hi Aaron

    Thanks for your response.

    For the time being, I managed to do it with Gateway. Followed a couple of your articles and videos, which are very informative.

    Thanks again

    Susi

  • Susi Dman
    Susi Dman Member Posts: 10 ✭
    #6

    Hi Aron

    I managed to get the reply back to the REST client using the 'Solace-Reply-Wait-Time-In-ms' header, but it isn't working 'Solace-Reply-To-Destination' header, I'm not sure what to use as the header value here, I tried with the same topic name (as published), and using the same queue name, but none of those worked.

    My setup is as follows, Postman --> (send to https://my-solace-host:9443/TOPIC/java ) --> JavaApp

    Where JavaApp is listening to a queue called 'q_java' and this has a TOPIC subscription to the topic 'java'

    Any advice on this is appreciated.

    Also If I want to replace the above JavaApp with Boomi (should I use Solace PubSub Partner connector or a Jms connector )? I tried using the Solace connector but could not get the reply back to Postman using 'Solace-Reply-Wait-Time-In-ms' header which works for Java.


    Thanks

    Susi

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