API Gateway Websocket Integration with Rest Endpoint

Question

I have been trying to convert our REST APIs running on EC2 instance to websocket APIs, by redericting  we wanted to send event data in format of 
{ 
    body : {
       ...
    } , 
    query : {
      ....
    } , 
    headers : {
        .....
    }, 
    path : {
        ....
    } 
}, in the http integration request for the websocket API  we want to dynamically set the body, query, headers and path params of the integration request, based on these event inputs. What would be the integration template for one of the parameter

SeanSi · Answer

To set the integration request parameters dynamically based on event data in an Amazon API Gateway WebSocket API, you can use the Velocity Template Language (VTL) in the integration request mapping template.

Here is an example integration request mapping template that sets the body, query, headers, and path parameters of the integration request based on the event data:

#set($inputRoot = $input.path('$'))
{
  "body" : "$inputRoot.body",
  "query" : {
    #foreach($param in $inputRoot.query.keySet())
      "$param" : "$inputRoot.query.get($param)"
    #if( $foreach.hasNext ),#end
    #end
  },
  "headers" : {
    #foreach($param in $inputRoot.headers.keySet())
      "$param" : "$inputRoot.headers.get($param)"
    #if( $foreach.hasNext ),#end
    #end
  },
  "path" : {
    #foreach($param in $inputRoot.path.keySet())
      "$param" : "$inputRoot.path.get($param)"
    #if( $foreach.hasNext ),#end
    #end
  }
}

This template first sets the $inputRoot variable to the root of the input event data. It then sets the body, query, headers, and path parameters of the integration request to the corresponding values in the event data.

You can then use this integration request mapping template in the integration request of your WebSocket API to dynamically set the integration request parameters based on the event data.

betterpanel · Answer

Hi I am looking to do exactly the same thing - take a WebSocket request and transform it so that I can set the method, path, body, query and headers in the integration request before it gets send to the HTTP endpoint. The only thing I noticed by using a similar template to the one in the accepted answer is that the entire transformation gets placed into the HTTP request body. How do I set/modify the HTTP request path, headers and query without having to invoke a Lambda to do all the heavy lifting - negating the real benefit of the HTTP integration from WS -> HTTP if all that can be modified by a straight passthrough is the request body?

Anyone got this to work?

API Gateway Websocket Integration with Rest Endpoint

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