Question

I use play to develop my project and embedded netty3 as my application server
Please check the following test code:

package controllers;  
import java.io.File;  
import java.io.IOException;  
import java.util.HashMap;  
import java.util.Map;  
import java.util.concurrent.atomic.AtomicInteger;  

import org.apache.commons.io.FileUtils;  

import play.Logger;  
import play.Play;  
import play.mvc.Controller;  
import play.mvc.results.RenderText;  

public class Upload extends Controller {  

    private static Integer counter = 0;  
    private static final Integer MAX = 1;  

    public static void index() {  
        render("/upload.html");  
    }  

    public static void upload(File file) {  
        System.out.println("start " + Thread.currentThread());  
        synchronized (counter) {  
            System.out.println("middle " + Thread.currentThread());  
            if (counter > MAX) {  
                renderText("Sorry, the max upload thread is " + MAX);  
            } else {  
                counter++;  
                uploadFile(file);  
                counter--;  
                renderText("Upload success");  
            }  
        }  
        System.out.println("end " + Thread.currentThread());  
    }  

    static void uploadFile(File imgFile) {  
        File file = Play.getFile("/uploads");  
        try {  
            FileUtils.copyFileToDirectory(imgFile, file);  
        } catch (IOException e) {  
            Logger.error("upload file error", e);  
        }  
    }  

}  

When I opened two browsers(Firefox and Chrome) to upload the files at the same time, I debugged breakpoint in the ‘ upload(File file)’ method. But I found only 1 thread was processing.
After that, then the second request came.

The output is :

start Thread[play-thread-1,5,main]
middle Thread[play-thread-1,5,main]
start Thread[play-thread-1,5,main]
middle Thread[play-thread-1,5,main]

But in Tomcat/Jetty, there were two threads output in the console.

Did any body meet the same problem before ?

Answer 1

I assume that you are running in Dev mode?

The play document says that to make debugging easier, by default Play runs in a single thread model in Dev mode, and in production mode it runs as numbers_of_cores + 1.

You can override this in the application.conf.

# example of using a thread pool of 3
play.pool=3