能否用Apache Camel搭建SFTP代理？实现带延迟的文件中转测试

Absolutely! You can absolutely build an Apache Camel-based SFTP proxy to inject delays during file transfers—without breaking any native SFTP behaviors your Java app relies on. Here's how to make it work:

Your Java app will send files to a Camel-hosted SFTP proxy instead of the actual target server. The proxy will:

1. Receive the file (just like a regular SFTP server)
2. Hold onto it for your configured delay period
3. Forward it to the real SFTP server
   All SFTP semantics (authentication, file operations, error handling) stay intact—your app won’t know it’s talking to a proxy.

We’ll use Camel’s SFTP component (which can act as both server and client) to build the proxy. Below is a Java DSL example (Spring Boot-friendly):

import org.apache.camel.builder.RouteBuilder;
import org.apache.camel.component.sftp.SftpComponent;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class SftpDelayProxyRoute extends RouteBuilder {

    // Proxy SFTP server config
    @Value("${proxy.sftp.port}")
    private int proxyPort;
    @Value("${proxy.sftp.username}")
    private String proxyUser;
    @Value("${proxy.sftp.password}")
    private String proxyPass;

    // Target SFTP server config
    @Value("${target.sftp.host}")
    private String targetHost;
    @Value("${target.sftp.port}")
    private int targetPort;
    @Value("${target.sftp.username}")
    private String targetUser;
    @Value("${target.sftp.password}")
    private String targetPass;

    // Delay in milliseconds
    @Value("${transfer.delay.ms:5000}")
    private long transferDelay;

    @Override
    public void configure() throws Exception {
        // 1. Configure proxy SFTP server component
        SftpComponent proxySftp = getContext().getComponent("proxy-sftp", SftpComponent.class);
        proxySftp.setHost("0.0.0.0"); // Listen on all interfaces
        proxySftp.setPort(proxyPort);
        proxySftp.setUsername(proxyUser);
        proxySftp.setPassword(proxyPass);
        // Use local temp storage to mimic SFTP server behavior
        proxySftp.setFileSystem("file://./proxy-temp-storage");

        // 2. Configure target SFTP client component
        SftpComponent targetSftp = getContext().getComponent("target-sftp", SftpComponent.class);
        targetSftp.setHost(targetHost);
        targetSftp.setPort(targetPort);
        targetSftp.setUsername(targetUser);
        targetSftp.setPassword(targetPass);

        // 3. Core proxy route: Receive → Delay → Forward
        from("proxy-sftp://./inbox?noop=true")
            .log("Received file ${file:name} from client; adding ${transferDelay}ms delay")
            .delay(transferDelay) // Inject the test delay here
            .log("Forwarding ${file:name} to target SFTP server")
            .to("target-sftp://./remote-inbox");
    }
}

To ensure your app interacts with the proxy exactly like a real SFTP server:

• Match Authentication Methods: If your target SFTP uses SSH keys instead of passwords, configure the proxy component with the same key pair. Camel supports both password and public key auth.
• Support Full SFTP Operations: The proxy can handle put, get, rm, and mkdir commands just like a regular server. For download scenarios, add a reverse route to pull files from the target server and serve them to your app:

  // Reverse route for file downloads: Client ← Proxy ← Target SFTP
  from("target-sftp://./remote-outbox?noop=true")
      .delay(transferDelay)
      .to("proxy-sftp://./outbox");
  

• Handle Errors Gracefully: Add exception handling to mirror native SFTP error behavior (e.g., retry on connection failures, return appropriate error codes):

  onException(Exception.class)
      .log("Failed to forward ${file:name}: ${exception.message}")
      .maximumRedeliveries(3)
      .redeliveryDelay(1000)
      .handled(true);
  

• Clean Up Temp Storage: Add a route to delete processed files from the proxy’s temp directory to avoid bloat:

  from("file://./proxy-temp-storage/inbox?delete=true&delay=10000")
      .log("Cleaning up processed file ${file:name}");
  

1. Update your Java app’s SFTP configuration to point to the proxy’s host/port instead of the target server.
2. Upload a file from your app—check Camel logs to confirm the delay is applied.
3. Verify the file appears in the target SFTP server’s directory after the delay.
4. Test edge cases: interrupted transfers, failed target server connections, and multiple concurrent file uploads to ensure behavior matches a real SFTP setup.

• Performance Considerations: If you’re testing high-throughput scenarios, adjust the delay and monitor Camel’s thread pool to avoid bottlenecks.
• Compatibility: Ensure Camel’s SFTP component version matches your target server’s SFTP protocol version (most modern servers support SFTPv3/v4, which Camel handles well).

内容的提问来源于stack exchange，提问作者Chinna