Trigger notification after Computer Vision OCR extraction is complete

Question

I am exploring Microsoft Computer Vision's Read API (asyncBatchAnalyze) for extracting text from images. I found some sample code on Microsoft site to extract text from images asynchronously.It works in following way:

1) Submit image to asyncBatchAnalyze API. 2) This API accepts the request and returns a URI. 3) We need to poll this URI to get the extracted data.

Is there any way in which we can trigger some notification (like publishing an notification in AWS SQS or similar service) when asyncBatchAnalyze is done with image analysis?

public class MicrosoftOCRAsyncReadText {

    private static final String SUBSCRIPTION_KEY = “key”;
    private static final String ENDPOINT = "https://computervision.cognitiveservices.azure.com";
    private static final String URI_BASE = ENDPOINT + "/vision/v2.1/read/core/asyncBatchAnalyze";


    public static void main(String[] args) {

    CloseableHttpClient httpTextClient = HttpClientBuilder.create().build();
        CloseableHttpClient httpResultClient = HttpClientBuilder.create().build();;

        try {
            URIBuilder builder = new URIBuilder(URI_BASE);

            URI uri = builder.build();
            HttpPost request = new HttpPost(uri);

            request.setHeader("Content-Type", "application/octet-stream");
            request.setHeader("Ocp-Apim-Subscription-Key", SUBSCRIPTION_KEY);


            String image = "/Users/xxxxx/Documents/img1.jpg";
            File file = new File(image);       
            FileEntity reqEntity = new FileEntity(file);
            request.setEntity(reqEntity);

            HttpResponse response = httpTextClient.execute(request);

            if (response.getStatusLine().getStatusCode() != 202) {
                HttpEntity entity = response.getEntity();
                String jsonString = EntityUtils.toString(entity);
                JSONObject json = new JSONObject(jsonString);
                System.out.println("Error:\n");
                System.out.println(json.toString(2));
                return;
            }

            String operationLocation = null;

            Header[] responseHeaders = response.getAllHeaders();
            for (Header header : responseHeaders) {
                if (header.getName().equals("Operation-Location")) {
                    operationLocation = header.getValue();
                    break;
                }
            }

            if (operationLocation == null) {
                System.out.println("\nError retrieving Operation-Location.\nExiting.");
                System.exit(1);
            }

            /* Wait for asyncBatchAnalyze to complete. In place of this wait, can we trigger any notification from Computer Vision when the extract text operation is complete?
*/
            Thread.sleep(5000);

            // Call the second REST API method and get the response.
            HttpGet resultRequest = new HttpGet(operationLocation);
            resultRequest.setHeader("Ocp-Apim-Subscription-Key", SUBSCRIPTION_KEY);

            HttpResponse resultResponse = httpResultClient.execute(resultRequest);
            HttpEntity responseEntity = resultResponse.getEntity();

            if (responseEntity != null) {
                String jsonString = EntityUtils.toString(responseEntity);
                JSONObject json = new JSONObject(jsonString);
                System.out.println(json.toString(2));
            }
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }
}

Answer 1

There is no notification / webhook mechanism on those asynchronous operations.

The only thing that I can see right know is to change the implementation you mentioned by using a while condition which is checking regularly if the result is there or not (and a mechanism to cancel waiting - based on maximum waiting time or number of retries).

See sample in Microsoft docs here, especially this part:

// If the first REST API method completes successfully, the second 
// REST API method retrieves the text written in the image.
//
// Note: The response may not be immediately available. Text
// recognition is an asynchronous operation that can take a variable
// amount of time depending on the length of the text.
// You may need to wait or retry this operation.
//
// This example checks once per second for ten seconds.
string contentString;
int i = 0;
do
{
    System.Threading.Thread.Sleep(1000);
    response = await client.GetAsync(operationLocation);
    contentString = await response.Content.ReadAsStringAsync();
    ++i;
}
while (i < 10 && contentString.IndexOf("\"status\":\"Succeeded\"") == -1);

if (i == 10 && contentString.IndexOf("\"status\":\"Succeeded\"") == -1)
{
    Console.WriteLine("\nTimeout error.\n");
    return;
}

// Display the JSON response.
Console.WriteLine("\nResponse:\n\n{0}\n",
    JToken.Parse(contentString).ToString());