使用JAI从url提取图像时线程被阻塞

Question

I am running a service which starts multiple threads processing images using JAI. Each thread downloads the image from a url and then applies logic on this image. The threads are getting stuck (in waiting) while getting height of the PlanarImage. Any idea why is this happening and how I can avoid it? Also, the thread which had acquired the lock for the object (on which other threads are waiting) is stuck at socket read. Is there any socket read timeout while reading the images from url?

Code:

public static PlanarImage readImageFromUrl(String url) throws Exception
{
    String urlAddr = URLDecoder.decode(url, Constants.UTF8);
    URL urlS = new URL(urlAddr);

    String operationName = "url";

    ParameterBlockJAI pb = new ParameterBlockJAI(operationName);
    pb.setParameter("URL", urlS);
    pb.setParameter("param", null);

    PlanarImage image = null;
    try
    {
           /** Create a new tilecache object in RenderingHints**/
        image = JAI.create(operationName,pb, (RenderingHints)RenderingHintsFactory.createDefaultRenderingHintsInstance());


        int h = image.getHeight();
        int w = image.getWidth();
        logger.info("Image is "+h +"x"+w+" dim");
        return image;
    }
    catch(Exception e)
    {
        //Release tile cache memory in case of exception
        RenderingHintsFactory.releaseRenderingHints(image);
        throw e;
    }
}

Sample thead stuck at waiting:

"pool-2-thread-97" prio=10 tid=0x0000000050e0b000 nid=0x666d waiting for monitor entry [0x0000000048e74000]
java.lang.Thread.State: BLOCKED (on object monitor)
at com.sun.media.jai.codecimpl.JPEGImage.<init>(JPEGImageDecoder.java:105)
- **waiting to lock <0x00000007bca843b8> (a java.lang.Object)**
at com.sun.media.jai.codecimpl.JPEGImageDecoder.decodeAsRenderedImage(JPEGImageDecoder.java:46)
at com.sun.media.jai.opimage.CodecRIFUtil.create(CodecRIFUtil.java:88)
at com.sun.media.jai.opimage.JPEGRIF.create(JPEGRIF.java:43)
at sun.reflect.GeneratedMethodAccessor54.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at javax.media.jai.FactoryCache.invoke(FactoryCache.java:122)
at javax.media.jai.OperationRegistry.invokeFactory(OperationRegistry.java:1674)
at     javax.media.jai.ThreadSafeOperationRegistry.invokeFactory(ThreadSafeOperationRegistry.java:473)
at javax.media.jai.registry.RIFRegistry.create(RIFRegistry.java:332)
at com.sun.media.jai.opimage.StreamRIF.create(StreamRIF.java:102)
at sun.reflect.GeneratedMethodAccessor54.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at javax.media.jai.FactoryCache.invoke(FactoryCache.java:122)
at javax.media.jai.OperationRegistry.invokeFactory(OperationRegistry.java:1674)
at         javax.media.jai.ThreadSafeOperationRegistry.invokeFactory(ThreadSafeOperationRegistry.java:473)
at javax.media.jai.registry.RIFRegistry.create(RIFRegistry.java:332)
at com.sun.media.jai.opimage.URLRIF.create(URLRIF.java:74)
at sun.reflect.GeneratedMethodAccessor54.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at javax.media.jai.FactoryCache.invoke(FactoryCache.java:122)
at javax.media.jai.OperationRegistry.invokeFactory(OperationRegistry.java:1674)
at     javax.media.jai.ThreadSafeOperationRegistry.invokeFactory(ThreadSafeOperationRegistry.java:473)
at javax.media.jai.registry.RIFRegistry.create(RIFRegistry.java:332)
at javax.media.jai.RenderedOp.createInstance(RenderedOp.java:819)
- locked <0x00000007f6a5e3a0> (a javax.media.jai.RenderedOp)
at javax.media.jai.RenderedOp.createRendering(RenderedOp.java:867)
- locked <0x00000007f6a5e3a0> (a javax.media.jai.RenderedOp)
at javax.media.jai.RenderedOp.getHeight(RenderedOp.java:2188)
at com.amazon.lmclassifier.daemon.image.util.ImageUtils.readImageFromUrl(ImageUtils.java:66)

THREAD WHICH HAS LOCKED THE OBJECT:

"pool-2-thread-96" prio=10 tid=0x0000000050e08800 nid=0x666c runnable [0x0000000048d72000]
java.lang.Thread.State: RUNNABLE
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
at java.io.BufferedInputStream.read1(BufferedInputStream.java:258)
at java.io.BufferedInputStream.read(BufferedInputStream.java:317)
- locked <0x00000007f6af46f0> (a java.io.BufferedInputStream)
at sun.net.www.MeteredStream.read(MeteredStream.java:116)
- locked <0x00000007f6af4718> (a sun.net.www.http.KeepAliveStream)
at java.io.FilterInputStream.read(FilterInputStream.java:116)
at sun.net.www.protocol.http.HttpURLConnection$HttpInputStream.read(HttpURLConnection.java:2668)
at com.sun.media.jai.codec.FileCacheSeekableStream.readUntil(FileCacheSeekableStream.java:125)
at com.sun.media.jai.codec.FileCacheSeekableStream.read(FileCacheSeekableStream.java:258)
at com.sun.media.jai.codec.ForwardSeekableStream.read(ForwardSeekableStream.java:54)
at java.io.FilterInputStream.read(FilterInputStream.java:116)
at sun.awt.image.codec.JPEGImageDecoderImpl.readJPEGStream(Native Method)
- locked <0x00000007f6af47e8> (a sun.awt.image.codec.JPEGImageDecoderImpl)
at sun.awt.image.codec.JPEGImageDecoderImpl.decodeAsBufferedImage(JPEGImageDecoderImpl.java:210)
- locked <0x00000007f6af47e8> (a sun.awt.image.codec.JPEGImageDecoderImpl)
at com.sun.media.jai.codecimpl.JPEGImage.<init>(JPEGImageDecoder.java:110)
**- locked <0x00000007bca843b8> (a java.lang.Object)**
at com.sun.media.jai.codecimpl.JPEGImageDecoder.decodeAsRenderedImage(JPEGImageDecoder.java:46)
at com.sun.media.jai.opimage.CodecRIFUtil.create(CodecRIFUtil.java:88)
at com.sun.media.jai.opimage.JPEGRIF.create(JPEGRIF.java:43)
at sun.reflect.GeneratedMethodAccessor54.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at javax.media.jai.FactoryCache.invoke(FactoryCache.java:122)
at javax.media.jai.OperationRegistry.invokeFactory(OperationRegistry.java:1674)
at javax.media.jai.ThreadSafeOperationRegistry.invokeFactory(ThreadSafeOperationRegistry.java:473)
at javax.media.jai.registry.RIFRegistry.create(RIFRegistry.java:332)
at com.sun.media.jai.opimage.StreamRIF.create(StreamRIF.java:102)
at sun.reflect.GeneratedMethodAccessor54.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at javax.media.jai.FactoryCache.invoke(FactoryCache.java:122)
at javax.media.jai.OperationRegistry.invokeFactory(OperationRegistry.java:1674)
at javax.media.jai.ThreadSafeOperationRegistry.invokeFactory(ThreadSafeOperationRegistry.java:473)
at javax.media.jai.registry.RIFRegistry.create(RIFRegistry.java:332)
at com.sun.media.jai.opimage.URLRIF.create(URLRIF.java:74)
at sun.reflect.GeneratedMethodAccessor54.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at javax.media.jai.FactoryCache.invoke(FactoryCache.java:122)
at javax.media.jai.OperationRegistry.invokeFactory(OperationRegistry.java:1674)
at javax.media.jai.ThreadSafeOperationRegistry.invokeFactory(ThreadSafeOperationRegistry.java:473)
at javax.media.jai.registry.RIFRegistry.create(RIFRegistry.java:332)
at javax.media.jai.RenderedOp.createInstance(RenderedOp.java:819)
- locked <0x00000007f6af49e0> (a javax.media.jai.RenderedOp)
at javax.media.jai.RenderedOp.createRendering(RenderedOp.java:867)
- locked <0x00000007f6af49e0> (a javax.media.jai.RenderedOp)
at javax.media.jai.RenderedOp.getHeight(RenderedOp.java:2188)
at com.amazon.lmclassifier.daemon.image.util.ImageUtils.readImageFromUrl(ImageUtils.java:66)
‹ ImageReader thread safety Threads getting blocked while fetching image from url › 

I figured out from some other post that the JPEGImageDecoder.java uses a mutex object to syncronize image reads. And hence the threads are getting blocked. http://www.java.net/node/677181 Any idea on how can I resolve this?

Answer 1

In some cases for images loading occurs lazily in the background, until getHeight() or getWidth() is called, which then wait for the loading to be finished. One just has to postpone using the image to a point in the future.

To have less problems, you might first load the files from the net, and then load them as images from your local file system. This would allow indicating the progress too.