Google App Engine错误：获取既不是原始请求线程也不是ThreadManager

时间：2017-06-29 17:59:07

标签： java multithreading google-app-engine servlets

App Engine会出错：

com.google.apphosting.api.ApiProxy$CallNotFoundException: Can't make API call urlfetch.Fetch in a thread that is neither the original request thread nor a thread created by ThreadManager

当我在异步Servlet中调用Callable中的Google Vision API时。 如何使它工作？

的servlet：

public class OcrForTextServlet extends HttpServlet {
    @Override
    public void doPost(HttpServletRequest req, HttpServletResponse response) {
            byte[] file = extractFile(req);
            String[] languages = req.getParameterValues("language");
            ExecutorService executor = Executors.newFixedThreadPool(2);
            Future<String> result = executor.submit(new OcrCallableTask(file, languages));
            executor.shutdown();
            response.getWriter().write(result.get()); //ERROR HERE

完整堆栈跟踪：

[INFO] java.util.concurrent.ExecutionException: com.google.apphosting.api.ApiProxy$CallNotFoundException: Can't make API call urlfetch.Fetch in a thread that is neither the original request thread nor a thread created by ThreadManager
[INFO]  at java.util.concurrent.FutureTask.report(FutureTask.java:122)
[INFO]  at java.util.concurrent.FutureTask.get(FutureTask.java:192)
[INFO]  at ocrme_backend.servlets.ocr.OcrForTextServlet.doPost(OcrForTextServlet.java:49)
[INFO]  at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
[INFO]  at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
[INFO]  at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:848)
[INFO]  at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1772)
[INFO]  at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74)
[INFO]  at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1759)
[INFO]  at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:134)
[INFO]  at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1759)
[INFO]  at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
[INFO]  at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1759)
[INFO]  at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:63)
[INFO]  at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1759)
[INFO]  at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:48)
[INFO]  at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1759)
[INFO]  at com.google.appengine.tools.development.jetty9.StaticFileFilter.doFilter(StaticFileFilter.java:122)
[INFO]  at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1759)
[INFO]  at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectRequest(DevAppServerModulesFilter.java:366)
[INFO]  at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectModuleRequest(DevAppServerModulesFilter.java:349)
[INFO]  at com.google.appengine.tools.development.DevAppServerModulesFilter.doFilter(DevAppServerModulesFilter.java:116)
[INFO]  at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1751)
[INFO]  at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:582)
[INFO]  at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
[INFO]  at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:524)
[INFO]  at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:226)
[INFO]  at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1180)
[INFO]  at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:512)
[INFO]  at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
[INFO]  at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1112)
[INFO]  at com.google.appengine.tools.development.jetty9.DevAppEngineWebAppContext.doScope(DevAppEngineWebAppContext.java:112)
[INFO]  at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
[INFO]  at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:134)
[INFO]  at com.google.appengine.tools.development.jetty9.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:596)
[INFO]  at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:134)
[INFO]  at org.eclipse.jetty.server.Server.handle(Server.java:534)
[INFO]  at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:320)
[INFO]  at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:251)
[INFO]  at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:283)
[INFO]  at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:108)
[INFO]  at org.eclipse.jetty.io.SelectChannelEndPoint$2.run(SelectChannelEndPoint.java:93)
[INFO]  at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.executeProduceConsume(ExecuteProduceConsume.java:303)
[INFO]  at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.produceConsume(ExecuteProduceConsume.java:148)
[INFO]  at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.run(ExecuteProduceConsume.java:136)
[INFO]  at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:671)
[INFO]  at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:589)
[INFO]  at java.lang.Thread.run(Thread.java:745)
[INFO] Caused by: com.google.apphosting.api.ApiProxy$CallNotFoundException: Can't make API call urlfetch.Fetch in a thread that is neither the original request thread nor a thread created by ThreadManager
[INFO]  at com.google.apphosting.api.ApiProxy$CallNotFoundException.foreignThread(ApiProxy.java:844)
[INFO]  at com.google.apphosting.api.ApiProxy.makeSyncCall(ApiProxy.java:116)
[INFO]  at com.google.appengine.api.urlfetch.URLFetchServiceImpl.fetch(URLFetchServiceImpl.java:40)
[INFO]  at com.google.apphosting.utils.security.urlfetch.URLFetchServiceStreamHandler$Connection.fetchResponse(URLFetchServiceStreamHandler.java:543)
[INFO]  at com.google.apphosting.utils.security.urlfetch.URLFetchServiceStreamHandler$Connection.getInputStream(URLFetchServiceStreamHandler.java:422)
[INFO]  at com.google.apphosting.utils.security.urlfetch.URLFetchServiceStreamHandler$Connection.getResponseCode(URLFetchServiceStreamHandler.java:275)
[INFO]  at com.google.api.client.http.javanet.NetHttpResponse.<init>(NetHttpResponse.java:37)
[INFO]  at com.google.api.client.http.javanet.NetHttpRequest.execute(NetHttpRequest.java:94)
[INFO]  at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:972)
[INFO]  at com.google.api.client.auth.oauth2.TokenRequest.executeUnparsed(TokenRequest.java:283)
[INFO]  at com.google.api.client.auth.oauth2.TokenRequest.execute(TokenRequest.java:307)
[INFO]  at com.google.api.client.auth.oauth2.Credential.executeRefreshToken(Credential.java:570)
[INFO]  at com.google.api.client.googleapis.auth.oauth2.GoogleCredential.executeRefreshToken(GoogleCredential.java:362)
[INFO]  at com.google.api.client.auth.oauth2.Credential.refreshToken(Credential.java:489)
[INFO]  at com.google.api.client.googleapis.auth.oauth2.GoogleCredential.fromStreamUser(GoogleCredential.java:772)
[INFO]  at com.google.api.client.googleapis.auth.oauth2.GoogleCredential.fromStream(GoogleCredential.java:257)
[INFO]  at com.google.api.client.googleapis.auth.oauth2.DefaultCredentialProvider.getCredentialUsingWellKnownFile(DefaultCredentialProvider.java:249)
[INFO]  at com.google.api.client.googleapis.auth.oauth2.DefaultCredentialProvider.getDefaultCredentialUnsynchronized(DefaultCredentialProvider.java:117)
[INFO]  at com.google.api.client.googleapis.auth.oauth2.DefaultCredentialProvider.getDefaultCredential(DefaultCredentialProvider.java:91)
[INFO]  at com.google.api.client.googleapis.auth.oauth2.GoogleCredential.getApplicationDefault(GoogleCredential.java:213)
[INFO]  at com.google.api.client.googleapis.auth.oauth2.GoogleCredential.getApplicationDefault(GoogleCredential.java:191)
[INFO]  at ocrme_backend.ocr.OCRProcessorImpl.getVisionService(OCRProcessorImpl.java:40)
[INFO]  at ocrme_backend.ocr.OCRProcessorImpl.<init>(OCRProcessorImpl.java:32)
[INFO]  at ocrme_backend.servlets.ocr.OcrCallableTask.doStaff(OcrCallableTask.java:27)
[INFO]  at ocrme_backend.servlets.ocr.OcrCallableTask.call(OcrCallableTask.java:39)
[INFO]  at ocrme_backend.servlets.ocr.OcrCallableTask.call(OcrCallableTask.java:14)
[INFO]  at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[INFO]  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
[INFO]  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
[INFO]  ... 1 more

API调用产生错误：

/**
 * Connects to the Vision API using Application Default Credentials.
 */
public static Vision getVisionService() throws IOException, GeneralSecurityException {
    GoogleCredential credential =
            GoogleCredential.getApplicationDefault().createScoped(VisionScopes.all());
    com.google.api.client.json.JsonFactory jsonFactory = JacksonFactory.getDefaultInstance();
    return new Vision.Builder(GoogleNetHttpTransport.newTrustedTransport(), jsonFactory, credential)
            .setApplicationName(APPLICATION_NAME)
            .build();
}

我使用的是javax.servlet-api（3.1.0），GAE（1.9.52）和Java 8的最新版本。我需要从异步部分获取结果。 我怎样才能做到这一点？ 谢谢你的帮助。

更新
我尝试use com.google.appengine.api.ThreadManager，如错误消息中所述，但它给出了相同的错误。这是我更新的servlet：

@Override
public void doPost(HttpServletRequest req, HttpServletResponse response) {

    try {
        byte[] file = extractFile(req);
        String[] languages = req.getParameterValues("language");

        ThreadFactory factory = ThreadManager.currentRequestThreadFactory();
        ExecutorService service = Executors.newCachedThreadPool(factory);
        Future<String> result =
                service.submit(new OcrCallableTask(file, languages));
        response.getWriter().write(result.get()); //ERROR HERE

接下来的测试通过OK：

public class OcrCallableTaskTest {
    @Test
    public void testCall() throws Exception {
        ExecutorService service = Executors.newFixedThreadPool(2);
        Future<String> result = service.submit(new OcrCallableTask(FileProvider.getFile(), null));
        Assert.assertTrue(result.get() != null);
        Assert.assertTrue(result.get().length() > 0);
    }
}

更新2：
（在请求的主题中回复提议的工作人员。）
真的，我的servlet不需要额外的线程。只是尝试修复错误。 如果我在我的应用程序中不使用多线程，我会遇到同样的错误：

[INFO] com.google.api.gax.grpc.ApiException: io.grpc.StatusRuntimeException: UNAUTHENTICATED
[INFO]  at com.google.api.gax.grpc.ExceptionTransformingCallable$ExceptionTransformingFuture.onFailure(ExceptionTransformingCallable.java:108)
[INFO]  at com.google.api.core.ApiFutures$1.onFailure(ApiFutures.java:52)
[INFO]  at com.google.common.util.concurrent.Futures$6.run(Futures.java:1310)
[INFO]  at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:457)
[INFO]  at com.google.common.util.concurrent.ExecutionList.executeListener(ExecutionList.java:156)
[INFO]  at com.google.common.util.concurrent.ExecutionList.execute(ExecutionList.java:145)
[INFO]  at com.google.common.util.concurrent.AbstractFuture.setException(AbstractFuture.java:202)
[INFO]  at io.grpc.stub.ClientCalls$GrpcFuture.setException(ClientCalls.java:463)
[INFO]  at io.grpc.stub.ClientCalls$UnaryStreamToFuture.onClose(ClientCalls.java:439)
[INFO]  at io.grpc.internal.ClientCallImpl.closeObserver(ClientCallImpl.java:428)
[INFO]  at io.grpc.internal.ClientCallImpl.access$100(ClientCallImpl.java:76)
[INFO]  at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl.close(ClientCallImpl.java:514)
[INFO]  at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl.access$700(ClientCallImpl.java:431)
[INFO]  at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl$1StreamClosed.runInContext(ClientCallImpl.java:546)
[INFO]  at io.grpc.internal.ContextRunnable.run(ContextRunnable.java:52)
[INFO]  at io.grpc.internal.SerializingExecutor$TaskRunner.run(SerializingExecutor.java:152)
[INFO]  at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
[INFO]  at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[INFO]  at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
[INFO]  at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
[INFO]  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
[INFO]  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
[INFO]  at java.lang.Thread.run(Thread.java:745)
[INFO] Caused by: io.grpc.StatusRuntimeException: UNAUTHENTICATED
[INFO]  at io.grpc.Status.asRuntimeException(Status.java:540)
[INFO]  ... 15 more
[INFO] Caused by: com.google.apphosting.api.ApiProxy$CallNotFoundException: Can't make API call urlfetch.Fetch in a thread that is neither the original request thread nor a thread created by ThreadManager
[INFO]  at com.google.apphosting.api.ApiProxy$CallNotFoundException.foreignThread(ApiProxy.java:844)
[INFO]  at com.google.apphosting.api.ApiProxy.makeSyncCall(ApiProxy.java:116)
[INFO]  at com.google.appengine.api.urlfetch.URLFetchServiceImpl.fetch(URLFetchServiceImpl.java:40)
[INFO]  at com.google.apphosting.utils.security.urlfetch.URLFetchServiceStreamHandler$Connection.fetchResponse(URLFetchServiceStreamHandler.java:543)
[INFO]  at com.google.apphosting.utils.security.urlfetch.URLFetchServiceStreamHandler$Connection.getInputStream(URLFetchServiceStreamHandler.java:422)
[INFO]  at com.google.apphosting.utils.security.urlfetch.URLFetchServiceStreamHandler$Connection.getResponseCode(URLFetchServiceStreamHandler.java:275)
[INFO]  at com.google.api.client.http.javanet.NetHttpResponse.<init>(NetHttpResponse.java:37)
[INFO]  at com.google.api.client.http.javanet.NetHttpRequest.execute(NetHttpRequest.java:94)
[INFO]  at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:972)
[INFO]  at com.google.auth.oauth2.UserCredentials.refreshAccessToken(UserCredentials.java:207)
[INFO]  at com.google.auth.oauth2.OAuth2Credentials.refresh(OAuth2Credentials.java:149)
[INFO]  at com.google.auth.oauth2.OAuth2Credentials.getRequestMetadata(OAuth2Credentials.java:135)
[INFO]  at io.grpc.auth.GoogleAuthLibraryCallCredentials$1.run(GoogleAuthLibraryCallCredentials.java:110)
[INFO]  ... 7 more

servlet代码 - 没有多线程：

 @Override
    public void doPost(HttpServletRequest req, HttpServletResponse response) {
        try {
            byte[] file = extractFile(req);
            String[] languages = req.getParameterValues("language");

            OCRProcessor processor = new OCRProcessorImpl();
            String jsonResult;

            if (languages == null || languages.length <= 0) { 
                jsonResult = processor.ocrForText(file);

接下来的测试通过了确认：

@Test
public void doOCR() throws Exception {
    byte[] file = FileProvider.getImageFile().getFile();
    String result = ocrProcessor.ocrForText(file);
    assertNotNull(result);
    assertTrue(result.length() > 0);
}

它接缝（GAE + API调用）与Servlet架构不兼容。谢谢你的任何建议。

1 个答案:

答案 0 :(得分：2)

异步？

也许我误解了你，但你的servlet似乎并不是异步的：

    Future<String> result =
            service.submit(new OcrCallableTask(file, languages));
    response.getWriter().write(result.get()); //ERROR HERE

你的servlet线程将阻塞，直到这个url fetch完成，因为Future#get()将等到任务完成。

并且，正如您的堆栈跟踪所示，ApiProxy也调用了snyc方法：

at com.google.apphosting.api.ApiProxy.makeSyncCall(ApiProxy.java:116)

建议

Google App Engine似乎仍然not open sourced，所以我可以给出一些可能的指示：

  • 从ApiProxy的文档中，此类可能使用某些变量（如ThreadLocal）来存储数据，因此使用Executors创建新线程可能会混淆App Engine;

      

    它还为每个线程存储一个Environment，其中包含有关请求的其他用户可见信息

  • 在你的情况下，我没有看到使用多线程的必要性，你可能想尝试使用请求线程获取信息;

  • 如果你确实需要异步调用，你可能需要使用后台线程，然后在通话结束时通知用户;

更多

我尝试运行您的示例，但您的Vision类无法编译。所以我写了另一个例子，here，运行正常。

以下是从sdk反编译的异常发生的源代码：

    ApiProxy.Environment threadLocalEnvironment = (ApiProxy.Environment)environmentThreadLocal.get();
    if(threadLocalEnvironment != null) {
        return threadLocalEnvironment;
    } else {
        ApiProxy.EnvironmentFactory envFactory = getEnvironmentFactory();
        if(envFactory != null) {
            ApiProxy.Environment environment = envFactory.newEnvironment();
            environmentThreadLocal.set(environment);
            return environment;
        } else {
            return null;
        }
    }

在你的情况下，因为它无法获得环境工厂，然后它无法获得环境，这导致你的例外。

当谈到为什么它缺乏环境工厂时，我猜你做错了配置（你是否用GAE的服务器进行了战争？如果你在本地进行测试，这是必要的。）

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