Re: [jetty-users] Building response for request that is sleeping

[Olivier Lamy <olamy@xxxxxxxxxxx>]

Hi 

You should have a look at AsyncMiddleManServlet. It's in jetty-proxy module.

On Thu, Jul 8, 2021 at 2:45 PM Aniruddha Tekade via jetty-users <jetty-users@xxxxxxxxxxx> wrote:

Hi All,

I am trying to build a response for a request that is saved in hashmap. But I am not sure how can I solve this problem - should I use async mechanism or multithreading and how? 

• Request A is sent to a doGET() method to be served but doGET makes some changes and makes another request B to the outside server. 
• I save the request with its UUID request ID into a hashmap 
• The outside server sends 200 OK back for new request B. 
• The outside server then makes a POST request which has data to be sent back to request A.

But I am super confused about how can I send this data with a response back to request A as a response? 

Can I use some kind of asynchronous mechanism or multithreading use? But I am super struggling with this? Even simplifying this approach would be great. But I must send the data received in the POST request back to request A. Please advise on how to progress on this.

My handler class code is as follows - 

    Map<String, HttpServletRequest> requestLookup = new HashMap<>();
    public void handle(String target, Request jettyReq, HttpServletRequest request, HttpServletResponse response) {
        // Redirect API control based on HTTP method type
        if (request.getMethod().equals(constGetRequest)) {
            getObject(jettyReq, request, response);
        }
        if (request.getMethod().equals(constPostRequest)) {
            writeGetObjectResponse(jettyReq, request, response);
        }
        jettyReq.setHandled(true);
    }

    public void doGET(Request jettyReq, HttpServletRequest request, HttpServletResponse response) {
        requestLookup.put(xRequestId, request);

        String requestURI = request.getRequestURI();
        String[] strs = requestURI.split("/");
        for (String str : strs) {
            System.out.println("item:" + str);
        }
        String object_key;
        String bucket_name;
        String lambdaFunc;
        if (strs.length <= 2) {
            try {
                throw new Exception("Can not get bucket and object key info");
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        bucket_name = strs[1];
        System.out.println("Handler -- bucketName received = " + bucket_name);

        // Redis class contains the mapping of bucket_name and function name to be executed in the Python server
        lambdaFunc = redis.getFuncFromRedis(bucket_name); // example function - "".upper()

        object_key = requestURI.substring(requestURI.indexOf(bucket_name) + bucket_name.length() + 1);
        System.out.println("objectKey = " + object_key);
        S3ObjectReader getObject = new S3ObjectReader(); 
        response.setContentType("text/html;charset=utf-8");
        response.setStatus(HttpServletResponse.SC_OK);

        List<String> result = getObject.printOriginalObjectContent(bucket_name,object_key);
        System.out.println("Print original object content:");
        for (String s : result) {
            System.out.println(s);
        }
        System.out.println("Print transformed object content:");
        LambdaFunctionConnector connectLambdaFunc = new LambdaFunctionConnector();

        connectLambdaFunc.sendRequest(lambdaFunc,result);
    }

    public void  doPOST(Request jettyReq, HttpServletRequest req, HttpServletResponse res) {
        // retrieve request from the lookup table
       String requestID = request.getHeader("X-Request-ID");
       HttpServletRequest originalRequest = requestLookup.get(requestID);
    }

- aniruddha

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--

Olivier