java - Akka + Camel + FTP2 + localWorkingDirectory 不能可靠地工作

Question

我在使用 Camel 的 FTP2 组件时遇到问题，消费者参与者生活在 Akka 系统中。

基本思想是监视文件的 FTP 目录，然后生成一个子 actor 来单独处理每个文件。 Akka 被用来管理并发性和可靠性。父消费者 actor 使用 noop=true 轮询目录，因此它什么都不做，然后子消费者 actor 应该下载文件，并使用“include”Camel 选项进行过滤。重要的是下载是并发的，并且文件没有加载到内存中(因此使用 localWorkDirectory)。

我写了一个简单的重现:

package camelrepro;

import java.io.InputStream;

import org.mockftpserver.core.command.Command;
import org.mockftpserver.core.command.ReplyCodes;
import org.mockftpserver.core.session.Session;
import org.mockftpserver.core.session.SessionKeys;
import org.mockftpserver.fake.FakeFtpServer;
import org.mockftpserver.fake.UserAccount;
import org.mockftpserver.fake.command.AbstractFakeCommandHandler;
import org.mockftpserver.fake.filesystem.FileEntry;
import org.mockftpserver.fake.filesystem.UnixFakeFileSystem;

import akka.actor.ActorSystem;
import akka.actor.Props;
import akka.camel.CamelMessage;
import akka.camel.javaapi.UntypedConsumerActor;
import akka.testkit.JavaTestKit;

public class Main {

    public static class ParentActor extends UntypedConsumerActor {

        public ParentActor() {
            System.out.println("Parent started");
        }
        @Override
        public String getEndpointUri() {
            return "ftp://anonymous@localhost:8021?password=password&readLock=changed&initialDelay=0&delay=200&noop=true";
        }

        @Override
        public void onReceive(Object msg) throws Exception {
            if (msg instanceof CamelMessage) {
                getContext().actorOf(new Props(ChildActor.class), "0");
            } else {
                unhandled(msg);
            }
        }
    }

    public static class ChildActor extends UntypedConsumerActor {

        public ChildActor() {
            System.out.println("Child started");
        }

        @Override
        public String getEndpointUri() {
            return "ftp://anonymous@localhost:8021?password=password&readLock=changed&initialDelay=0&delay=200&include=test.txt&localWorkDirectory=/tmp";
        }

        @Override
        public void onReceive(Object msg) throws Exception {
            if (msg instanceof CamelMessage) {
                System.out.println("Child got message");
                CamelMessage camelMsg = (CamelMessage) msg;

                InputStream source = camelMsg.getBodyAs(InputStream.class, getCamelContext());
                System.out.println(source.getClass().getName());
                System.exit(0);
            } else {
                unhandled(msg);
            }
        }
    }

    public static void main(String[] args) {

        ActorSystem system = ActorSystem.create("default");

        FakeFtpServer ftpServer = new FakeFtpServer();
        UnixFakeFileSystem ftpFileSystem = new UnixFakeFileSystem();
        ftpServer.setFileSystem(ftpFileSystem);
        ftpServer.addUserAccount(new UserAccount("anonymous", "password", "/"));
        ftpServer.setServerControlPort(8021);

        // fix bug in PWD handling (either Apache FTP client or mock server depending on opinion)
        ftpServer.setCommandHandler("PWD", new AbstractFakeCommandHandler() {
            @Override
            protected void handle(Command command, Session session) {
                String currentDirectory = (String) session.getAttribute(SessionKeys.CURRENT_DIRECTORY);
                this.replyCodeForFileSystemException = ReplyCodes.READ_FILE_ERROR;
                verifyFileSystemCondition(notNullOrEmpty(currentDirectory), currentDirectory, "filesystem.currentDirectoryNotSet");
                int replyCode = ReplyCodes.PWD_OK;
                String replyText = String.format("\"%s\" OK", currentDirectory.replaceAll("\"", "\"\""));
                session.sendReply(replyCode, replyText);
            }
        });
        ftpFileSystem.add(new FileEntry("/test.txt", "hello world"));
        ftpServer.start();

        new JavaTestKit(system) {{
            getSystem().actorOf(new Props(ParentActor.class));
        }};
    }
}

显示版本的 Maven 依赖项:

    <dependencies>
        <dependency>
            <groupId>com.typesafe.akka</groupId>
            <artifactId>akka-actor_2.10</artifactId>
            <version>2.1.0</version>
        </dependency>
        <dependency>
            <groupId>com.typesafe.akka</groupId>
            <artifactId>akka-remote_2.10</artifactId>
            <version>2.1.0</version>
        </dependency>
        <dependency>
            <groupId>com.typesafe.akka</groupId>
            <artifactId>akka-camel_2.10</artifactId>
            <version>2.1.0</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.typesafe.akka</groupId>
            <artifactId>akka-testkit_2.10</artifactId>
            <version>2.1.0</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.camel</groupId>
            <artifactId>camel-ftp</artifactId>
            <version>2.10.3</version>
        </dependency>
        <dependency>
            <groupId>org.mockftpserver</groupId>
            <artifactId>MockFtpServer</artifactId>
            <version>2.4</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-io</artifactId>
            <version>1.3.2</version>
        </dependency>
        <dependency>
            <groupId>commons-net</groupId>
            <artifactId>commons-net</artifactId>
            <version>3.2</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-simple</artifactId>
            <version>1.7.2</version>
        </dependency>
    </dependencies>

我希望看到 BufferedInputStream 写入标准输出 - 并检查 ByteArrayInputStream 是否不是。

但相反，我看到文件未找到异常:

[ERROR] [02/15/2013 10:53:32.951] [default-akka.actor.default-dispatcher-7] [akka://default/user/$a/0] Error during type conversion from type: org.apache.camel.component.file.remote.RemoteFile to the required type: java.io.InputStream with value GenericFile[test.txt] due java.io.FileNotFoundException: /tmp/test.txt (No such file or directory)
org.apache.camel.TypeConversionException: Error during type conversion from type: org.apache.camel.component.file.remote.RemoteFile to the required type: java.io.InputStream with value GenericFile[test.txt] due java.io.FileNotFoundException: /tmp/test.txt (No such file or directory)
    at org.apache.camel.impl.converter.BaseTypeConverterRegistry.mandatoryConvertTo(BaseTypeConverterRegistry.java:162)

有几次，它奏效了，让我怀疑它可能是某处的一场比赛。但它几乎总是失败。

有什么线索、想法、建议吗？

FWW:

uname -a: Linux 3.2.0-37-generic #58-Ubuntu SMP Thu Jan 24 15:28:10 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
java: 1.7.0_11-b21

Answer 1

我已经找到了上述问题的解决方案。

事实是 child 消费者autoAck()返回 true(默认情况下这样做)。在这种情况下，akka-camel 将发送 CamelMessage即发即弃，然后继续清理。与此同时， child Actor 实际上并没有打开 InputStream直到 getBodyAs() 调用的类型转换器之一打开它。因此，通过 getBodyAs() 打开文件的 child Actor 之间存在竞争。 ，并且 Camel 清理在异步发送消息后删除文件。

因此解决方法是覆盖 autoAck()返回 false，并发送 Ack.getInstance() (或 new Status.Failure(<cause>)，如果您愿意)在子消息处理程序的末尾。