java synchronization javax.imageio

java - ImageIO está sincronizado



synchronization javax.imageio (2)

Tengo una aplicación web donde los usuarios cargan imágenes. Validamos los datos de imagen a través de ImageIO.read () y realizamos algunas transformaciones simples en la Imagen Buffered resultante antes de guardarla en el disco.

Al realizar pruebas de carga, nos dimos cuenta de que cuando muchas solicitudes entran al mismo tiempo, se bloquean en la llamada ImageIO.read (). Profundizando más, notamos que el JPEGImageReader está sincronizado y que solo se está creando una imagen Buffered a la vez.

¿Alguien más se ha encontrado con esto? He estado buscando en Google esto por unos días y no me he encontrado con otra persona que haya tenido este problema, así que tal vez estoy haciendo algo mal. No puedo pensar en ninguna razón lógica por la que esto sea. Parece que no se pueden crear lectores y escritores individuales por imagen para problemas de pérdida de memoria, pero esa explicación me parece bastante débil.

EDITAR: Aquí hay una herramienta de rendimiento que analiza lo que lleva tanto tiempo. Creo que esto se debe a todos los hilos esperando el bloqueo de sincronización, fuente JPEGImageReader .

EDITAR: las bibliotecas de JAI habrían funcionado, excepto que OpenJDK ha eliminado el soporte para partes críticas de él, explícitamente el códec JPEG.

SOLUCIÓN: dada la cantidad de tiempo que pasé tratando de encontrar una solución alternativa y no hacerlo, mi mejor solución fue procesar las imágenes de forma asíncrona, con respecto a las solicitudes. Entonces, cuando llega una solicitud, los datos de imagen en bruto se almacenan como una imagen supuestamente válida; luego, un proceso asincrónico fuera de los hilos de solicitud procesará cada imagen de a una por vez. Debido a la sincronicidad de la biblioteca de ImageIO, no hay ganancia al tratar de hacer múltiples a la vez. Las imágenes podrían procesarse en paralelo dado que la biblioteca no es síncrona, solo ineficaz.

Si bien el procesamiento de forma asíncrona agrega un nivel de complejidad, probablemente sea una buena idea con respecto a la modificación de la imagen. Lo que no funciona es que no podemos procesar la imagen original en cada solicitud, lo que significa que nuestro sistema debe suponer que cada imagen es válida. Cuando el procesador asíncrono se ocupa de procesar una imagen, pueden producirse incoherencias en el sistema si los datos son malos.

Al realizar pruebas de carga, nos dimos cuenta de que cuando muchas solicitudes entran al mismo tiempo, se bloquean en la llamada ImageIO.read (). Profundizando más, notamos que el JPEGImageReader está sincronizado y que solo se está creando una imagen Buffered a la vez.

¿Alguien más se ha encontrado con esto?

Como mencioné en la sección de comentarios: a partir del análisis de rendimiento, parece un problema de rendimiento en el sistema de gestión de color de OpenJDK (lcms), porque la conversión de color no debería llevar tanto tiempo. Supongo que, sin poder seguir depurando, es que este problema hace que la decodificación (aparezca) se sincronice, incluso si ImageIO es capaz de decodificar en paralelo.

Aquí hay un SSCCE que muestra ImageIO perfectamente capaz de decodificar múltiples imágenes a la vez.

import javax.imageio.ImageIO; import javax.imageio.ImageReader; import javax.imageio.event.IIOReadProgressListener; import javax.imageio.stream.ImageInputStream; import java.io.File; import java.util.Iterator; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.atomic.AtomicInteger; class MultipleJPEGDecoding { private static int threads = Runtime.getRuntime().availableProcessors(); private static ExecutorService executorService = Executors.newFixedThreadPool(threads * 4); public static void main(final String[] args) throws InterruptedException { for (int i = 0; i < 100; i++) { final int index = i; executorService.submit(new Runnable() { public void run() { try { ImageInputStream stream = ImageIO.createImageInputStream(new File(args[index % args.length])); try { Iterator<ImageReader> readers = ImageIO.getImageReaders(stream); if (!readers.hasNext()) { System.err.println("No reader!"); return; } ImageReader reader = readers.next(); reader.setInput(stream); reader.addIIOReadProgressListener(new ProgressListener(index)); try { reader.read(0); } finally { reader.dispose(); } } finally { stream.close(); } } catch (Exception e) { System.err.printf("Error reading %d/n", index); e.printStackTrace(); } } }); } executorService.shutdown(); } static class ProgressListener implements IIOReadProgressListener { final static AtomicInteger simultaneous = new AtomicInteger(0); final int index; int nextProgress = 25; public ProgressListener(int index) { this.index = index; } public void imageStarted(ImageReader source, int imageIndex) { int inProgress = simultaneous.incrementAndGet(); System.err.printf("Started reading image %d (now decoding %d images simultaneous).../n", index, inProgress); } public void imageComplete(ImageReader source) { int inProgress = simultaneous.decrementAndGet(); System.err.printf("Done reading image %d%s./n", index, inProgress > 0 ? String.format(" (still decoding %d other images)", inProgress) : ""); } public void imageProgress(ImageReader source, float percentageDone) { if (percentageDone > nextProgress) { int inProgress = simultaneous.get(); System.err.printf("Progress on image %d (now decoding %d images simultaneous).../n", index, inProgress); nextProgress += 25; } } public void sequenceStarted(ImageReader source, int minIndex) { } public void sequenceComplete(ImageReader source) { } public void thumbnailStarted(ImageReader source, int imageIndex, int thumbnailIndex) { } public void thumbnailProgress(ImageReader source, float percentageDone) { } public void thumbnailComplete(ImageReader source) { } public void readAborted(ImageReader source) { } } }

La salida se ve así:

Started reading image 5 (now decoding 2 images simultaneous)... Started reading image 0 (now decoding 16 images simultaneous)... Started reading image 14 (now decoding 15 images simultaneous)... Started reading image 4 (now decoding 14 images simultaneous)... Started reading image 13 (now decoding 1 images simultaneous)... Started reading image 11 (now decoding 13 images simultaneous)... Started reading image 2 (now decoding 12 images simultaneous)... Started reading image 15 (now decoding 4 images simultaneous)... Started reading image 8 (now decoding 11 images simultaneous)... Started reading image 7 (now decoding 10 images simultaneous)... Started reading image 9 (now decoding 9 images simultaneous)... Started reading image 6 (now decoding 8 images simultaneous)... Started reading image 10 (now decoding 7 images simultaneous)... Started reading image 1 (now decoding 6 images simultaneous)... Started reading image 3 (now decoding 5 images simultaneous)... Started reading image 12 (now decoding 3 images simultaneous)... Progress on image 11 (now decoding 16 images simultaneous)... Progress on image 15 (now decoding 16 images simultaneous)... Progress on image 13 (now decoding 16 images simultaneous)... Progress on image 13 (now decoding 16 images simultaneous)... Progress on image 9 (now decoding 16 images simultaneous)... Progress on image 9 (now decoding 16 images simultaneous)... Progress on image 1 (now decoding 16 images simultaneous)... Progress on image 3 (now decoding 16 images simultaneous)... Progress on image 1 (now decoding 16 images simultaneous)... Progress on image 3 (now decoding 16 images simultaneous)... Progress on image 1 (now decoding 16 images simultaneous)... Progress on image 13 (now decoding 16 images simultaneous)... Progress on image 5 (now decoding 16 images simultaneous)... Progress on image 9 (now decoding 16 images simultaneous)... Progress on image 3 (now decoding 16 images simultaneous)... Done reading image 3 (still decoding 15 other images). Started reading image 16 (now decoding 15 images simultaneous)... Progress on image 11 (now decoding 15 images simultaneous)... Done reading image 13 (still decoding 14 other images). Started reading image 17 (now decoding 15 images simultaneous)... Progress on image 5 (now decoding 15 images simultaneous)... Progress on image 4 (now decoding 15 images simultaneous)... Progress on image 11 (now decoding 15 images simultaneous)... Done reading image 9 (still decoding 14 other images). Progress on image 5 (now decoding 15 images simultaneous)... Progress on image 17 (now decoding 15 images simultaneous)... Done reading image 11 (still decoding 14 other images). Started reading image 19 (now decoding 15 images simultaneous)... Progress on image 17 (now decoding 15 images simultaneous)... Done reading image 5 (still decoding 14 other images). Started reading image 18 (now decoding 15 images simultaneous)... Progress on image 15 (now decoding 15 images simultaneous)... Done reading image 1 (still decoding 14 other images). Started reading image 21 (now decoding 15 images simultaneous)... Progress on image 15 (now decoding 15 images simultaneous)... Progress on image 21 (now decoding 15 images simultaneous)... Done reading image 15 (still decoding 14 other images). Progress on image 6 (now decoding 14 images simultaneous)... Progress on image 21 (now decoding 14 images simultaneous)... Progress on image 7 (now decoding 14 images simultaneous)... Progress on image 21 (now decoding 14 images simultaneous)... Progress on image 7 (now decoding 14 images simultaneous)... Progress on image 19 (now decoding 14 images simultaneous)... Progress on image 19 (now decoding 14 images simultaneous)... Progress on image 7 (now decoding 14 images simultaneous)... Progress on image 19 (now decoding 14 images simultaneous)... Done reading image 7 (still decoding 13 other images). Started reading image 23 (now decoding 14 images simultaneous)... Progress on image 10 (now decoding 14 images simultaneous)... Progress on image 23 (now decoding 14 images simultaneous)... Progress on image 14 (now decoding 14 images simultaneous)... Started reading image 22 (now decoding 15 images simultaneous)... Progress on image 0 (now decoding 15 images simultaneous)... Done reading image 21 (still decoding 14 other images). Started reading image 24 (now decoding 15 images simultaneous)... Started reading image 20 (now decoding 16 images simultaneous)... Progress on image 2 (now decoding 16 images simultaneous)... Progress on image 8 (now decoding 16 images simultaneous)... Progress on image 17 (now decoding 15 images simultaneous)... Done reading image 17 (still decoding 14 other images). Started reading image 25 (now decoding 15 images simultaneous)... Progress on image 23 (now decoding 15 images simultaneous)... Done reading image 19 (still decoding 15 other images). Started reading image 26 (now decoding 16 images simultaneous)... Progress on image 23 (now decoding 16 images simultaneous)... Done reading image 23 (still decoding 15 other images). Started reading image 27 (now decoding 16 images simultaneous)... Progress on image 4 (now decoding 16 images simultaneous)... Progress on image 27 (now decoding 16 images simultaneous)... Progress on image 27 (now decoding 16 images simultaneous)... Progress on image 6 (now decoding 16 images simultaneous)... Progress on image 12 (now decoding 16 images simultaneous)... Progress on image 20 (now decoding 16 images simultaneous)... Progress on image 0 (now decoding 16 images simultaneous)... Progress on image 25 (now decoding 16 images simultaneous)... Progress on image 25 (now decoding 16 images simultaneous)... Progress on image 25 (now decoding 16 images simultaneous)... Progress on image 14 (now decoding 16 images simultaneous)... Progress on image 10 (now decoding 16 images simultaneous)... Progress on image 8 (now decoding 16 images simultaneous)... Progress on image 18 (now decoding 16 images simultaneous)... Done reading image 25 (still decoding 15 other images).

[...]

Progress on image 75 (now decoding 12 images simultaneous)... Started reading image 73 (now decoding 13 images simultaneous)... Progress on image 75 (now decoding 13 images simultaneous)... Progress on image 73 (now decoding 13 images simultaneous)... Progress on image 75 (now decoding 13 images simultaneous)... Started reading image 74 (now decoding 14 images simultaneous)... Progress on image 66 (now decoding 14 images simultaneous)... Progress on image 64 (now decoding 14 images simultaneous)... Progress on image 73 (now decoding 14 images simultaneous)... Progress on image 60 (now decoding 14 images simultaneous)... Progress on image 74 (now decoding 14 images simultaneous)... Progress on image 58 (now decoding 14 images simultaneous)... Done reading image 75 (still decoding 13 other images). Progress on image 73 (now decoding 13 images simultaneous)... Started reading image 77 (now decoding 14 images simultaneous)... Done reading image 73 (still decoding 13 other images). Progress on image 77 (now decoding 13 images simultaneous)... Started reading image 78 (now decoding 14 images simultaneous)... Progress on image 60 (now decoding 14 images simultaneous)... Done reading image 48 (still decoding 13 other images). Progress on image 77 (now decoding 13 images simultaneous)... Started reading image 79 (now decoding 14 images simultaneous)... Started reading image 70 (now decoding 15 images simultaneous)... Progress on image 52 (now decoding 15 images simultaneous)... Progress on image 71 (now decoding 15 images simultaneous)... Started reading image 72 (now decoding 16 images simultaneous)... Progress on image 71 (now decoding 16 images simultaneous)... Progress on image 54 (now decoding 16 images simultaneous)... Progress on image 68 (now decoding 16 images simultaneous)... Progress on image 64 (now decoding 16 images simultaneous)... Progress on image 66 (now decoding 16 images simultaneous)... Progress on image 62 (now decoding 16 images simultaneous)... Progress on image 79 (now decoding 16 images simultaneous)... Progress on image 79 (now decoding 16 images simultaneous)... Progress on image 79 (now decoding 16 images simultaneous)... Progress on image 77 (now decoding 16 images simultaneous)... Progress on image 68 (now decoding 16 images simultaneous)... Done reading image 79 (still decoding 15 other images). Done reading image 77 (still decoding 14 other images). Started reading image 81 (now decoding 15 images simultaneous)... Progress on image 74 (now decoding 15 images simultaneous)... Progress on image 81 (now decoding 15 images simultaneous)... Progress on image 81 (now decoding 15 images simultaneous)... Progress on image 78 (now decoding 15 images simultaneous)... Done reading image 60 (still decoding 14 other images). Started reading image 82 (now decoding 15 images simultaneous)... Started reading image 80 (now decoding 16 images simultaneous)... Progress on image 76 (now decoding 14 images simultaneous)... Progress on image 66 (now decoding 14 images simultaneous)... Progress on image 70 (now decoding 14 images simultaneous)... Done reading image 52 (still decoding 14 other images). Done reading image 71 (still decoding 15 other images). Progress on image 81 (now decoding 16 images simultaneous)... Started reading image 84 (now decoding 15 images simultaneous)... Started reading image 83 (now decoding 16 images simultaneous)... Progress on image 58 (now decoding 16 images simultaneous)... Progress on image 83 (now decoding 16 images simultaneous)... Progress on image 83 (now decoding 16 images simultaneous)... Progress on image 83 (now decoding 16 images simultaneous)... Done reading image 81 (still decoding 15 other images). Started reading image 85 (now decoding 16 images simultaneous)... Progress on image 85 (now decoding 16 images simultaneous)... Progress on image 74 (now decoding 16 images simultaneous)... Done reading image 66 (still decoding 15 other images). Started reading image 86 (now decoding 16 images simultaneous)... Progress on image 64 (now decoding 16 images simultaneous)... Progress on image 70 (now decoding 16 images simultaneous)... Progress on image 78 (now decoding 16 images simultaneous)... Progress on image 54 (now decoding 16 images simultaneous)... Done reading image 58 (still decoding 15 other images). Started reading image 87 (now decoding 16 images simultaneous)... Progress on image 87 (now decoding 16 images simultaneous)... Progress on image 84 (now decoding 16 images simultaneous)... Progress on image 87 (now decoding 16 images simultaneous)... Done reading image 64 (still decoding 15 other images). Started reading image 88 (now decoding 16 images simultaneous)... Progress on image 76 (now decoding 16 images simultaneous)... Done reading image 83 (still decoding 15 other images). Progress on image 62 (now decoding 15 images simultaneous)... Progress on image 70 (now decoding 16 images simultaneous)... Progress on image 85 (now decoding 16 images simultaneous)... Started reading image 89 (now decoding 16 images simultaneous)... Progress on image 72 (now decoding 16 images simultaneous)... Progress on image 85 (now decoding 16 images simultaneous)... Progress on image 89 (now decoding 16 images simultaneous)... Done reading image 85 (still decoding 15 other images). Progress on image 89 (now decoding 15 images simultaneous)... Progress on image 82 (now decoding 15 images simultaneous)... Progress on image 80 (now decoding 15 images simultaneous)... Done reading image 74 (still decoding 14 other images). Started reading image 91 (now decoding 15 images simultaneous)... Started reading image 90 (now decoding 16 images simultaneous)... Done reading image 62 (still decoding 15 other images). Progress on image 87 (now decoding 15 images simultaneous)... Progress on image 68 (now decoding 15 images simultaneous)... Done reading image 87 (still decoding 14 other images). Progress on image 91 (now decoding 14 images simultaneous)... Started reading image 93 (now decoding 15 images simultaneous)... Progress on image 93 (now decoding 15 images simultaneous)... Progress on image 91 (now decoding 15 images simultaneous)... Progress on image 91 (now decoding 15 images simultaneous)... Progress on image 80 (now decoding 15 images simultaneous)... Started reading image 92 (now decoding 16 images simultaneous)... Done reading image 91 (still decoding 15 other images). Started reading image 94 (now decoding 16 images simultaneous)... Progress on image 93 (now decoding 16 images simultaneous)... Progress on image 72 (now decoding 16 images simultaneous)... Progress on image 93 (now decoding 16 images simultaneous)... Done reading image 93 (still decoding 15 other images). Started reading image 95 (now decoding 16 images simultaneous)... Progress on image 95 (now decoding 16 images simultaneous)... Progress on image 95 (now decoding 16 images simultaneous)... Progress on image 76 (now decoding 16 images simultaneous)... Progress on image 95 (now decoding 16 images simultaneous)... Progress on image 72 (now decoding 16 images simultaneous)... Done reading image 95 (still decoding 15 other images). Started reading image 96 (now decoding 16 images simultaneous)... Progress on image 94 (now decoding 16 images simultaneous)... Progress on image 89 (now decoding 15 images simultaneous)... Done reading image 89 (still decoding 14 other images). Done reading image 54 (still decoding 15 other images). Started reading image 97 (now decoding 14 images simultaneous)... Started reading image 98 (now decoding 15 images simultaneous)... Done reading image 70 (still decoding 13 other images). Started reading image 99 (now decoding 16 images simultaneous)... Progress on image 82 (now decoding 16 images simultaneous)... Progress on image 99 (now decoding 16 images simultaneous)... Progress on image 99 (now decoding 16 images simultaneous)... Progress on image 97 (now decoding 16 images simultaneous)... Progress on image 97 (now decoding 16 images simultaneous)... Progress on image 97 (now decoding 16 images simultaneous)... Done reading image 68 (still decoding 15 other images). Done reading image 97 (still decoding 14 other images). Progress on image 78 (now decoding 14 images simultaneous)... Progress on image 99 (now decoding 14 images simultaneous)... Done reading image 99 (still decoding 13 other images). Progress on image 86 (now decoding 13 images simultaneous)... Done reading image 72 (still decoding 12 other images). Progress on image 82 (now decoding 12 images simultaneous)... Progress on image 98 (now decoding 12 images simultaneous)... Progress on image 84 (now decoding 12 images simultaneous)... Progress on image 90 (now decoding 12 images simultaneous)... Done reading image 76 (still decoding 11 other images). Progress on image 92 (now decoding 11 images simultaneous)... Progress on image 80 (now decoding 11 images simultaneous)... Progress on image 94 (now decoding 11 images simultaneous)... Progress on image 88 (now decoding 11 images simultaneous)... Progress on image 84 (now decoding 11 images simultaneous)... Progress on image 90 (now decoding 11 images simultaneous)... Progress on image 92 (now decoding 11 images simultaneous)... Progress on image 86 (now decoding 11 images simultaneous)... Progress on image 94 (now decoding 10 images simultaneous)... Done reading image 84 (still decoding 9 other images). Progress on image 92 (now decoding 9 images simultaneous)... Done reading image 78 (still decoding 10 other images). Progress on image 88 (now decoding 9 images simultaneous)... Progress on image 90 (now decoding 9 images simultaneous)... Done reading image 80 (still decoding 8 other images). Done reading image 82 (still decoding 7 other images). Progress on image 86 (now decoding 7 images simultaneous)... Progress on image 96 (now decoding 7 images simultaneous)... Progress on image 88 (now decoding 7 images simultaneous)... Done reading image 90 (still decoding 6 other images). Done reading image 92 (still decoding 5 other images). Progress on image 98 (now decoding 5 images simultaneous)... Done reading image 94 (still decoding 4 other images). Done reading image 86 (still decoding 3 other images). Progress on image 96 (now decoding 3 images simultaneous)... Done reading image 88 (still decoding 2 other images). Progress on image 98 (now decoding 2 images simultaneous)... Progress on image 96 (now decoding 2 images simultaneous)... Done reading image 98 (still decoding 1 other images). Done reading image 96.

EDITAR: En primer lugar, la respuesta de HaraldK es correcta y mi respuesta original fue incorrecta. No se puede eliminar, sin embargo, solo editado el OP debería reasignar el tic.

El mecanismo ThreadLock está ahí para detener el acceso de los subprocesos a diferentes lectores, no para evitar que los subprocesos accedan a sus propios lectores de forma independiente y simultánea con otros subprocesos.

Por lo tanto, JPEGImageReader de ImageIO debería funcionar bien de forma asíncrona.