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Message Dispatcher

Pattern	Message dispatcher coordinates message processing among multiple performers.
How Ballerina helps	Ballerina programs can maintain the state internally using variables and perform logic based on the state.

Message DispatcherCompeting ConsumersTransactional Client

import ballerina/http;

final http:Client ocrClient = check new ("http://api.ocr.com.balmock.io");

type OcrResponse record {|
    string[] lines;
    int noOfLines;
    string pdfUrl;
|};

final readonly & string[] ocrProcessors = ["processor1", "processor2", "processor3"];

⋯


service / on new http:Listener(8080) {
    int processorNo = 0;

    isolated resource function get ocr(string url) returns OcrResponse|error {
        int currentProcessor;
        lock {
            currentProcessor = self.processorNo;
            self.processorNo = currentProcessor == 2 ? 0 : currentProcessor + 1;
        }
        string processorId = ocrProcessors[currentProcessor];
        return check ocrClient->/[processorId]/parse/imageurl(url = url);
    }
}