[jira] [Work started] (CAMEL-23072) camel-as2 - Receiving messages: AS2 server endpoint does not support Expect: 100-continue — causes 3-second delay on every inbound message

["Guillaume Nodet (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CAMEL-23072?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Work on CAMEL-23072 started by Guillaume Nodet.
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> camel-as2 - Receiving messages: AS2 server endpoint does not support Expect: 100-continue — causes 3-second delay on every inbound message
> ------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: CAMEL-23072
>                 URL: https://issues.apache.org/jira/browse/CAMEL-23072
>             Project: Camel
>          Issue Type: Bug
>          Components: camel-as2
>    Affects Versions: 4.18.0
>            Reporter: Reto Peter
>            Assignee: Guillaume Nodet
>            Priority: Minor
>
> h3. Summary
>   The Camel AS2 server endpoint does not handle the HTTP \{{Expect: 100-continue}} protocol. When an AS2 client sends a request with the \{{Expect: 100-continue}} header (e.g., Mendelson AS2), the server never responds with \{{100 Continue}}. The client waits for
>   its timeout (typically 3 seconds) before sending the message body anyway, adding a 3-second delay to every inbound AS2 message.
>   This affects ALL Camel versions — the \{{BasicHttpServerExpectationDecorator}} has never been used in \{{AS2ServerConnection}}.
>   h3. Root Cause
>   In \{{AS2ServerConnection.RequestListenerService}}, the \{{HttpService}} is created using the 2-arg constructor without wrapping the request handler with \{{BasicHttpServerExpectationDecorator}}:
>   \{code:java|title=AS2ServerConnection.java (line ~388-391)}
>   registry = new RequestHandlerRegistry<>();
>   HttpServerRequestHandler handler = new BasicHttpServerRequestHandler(registry);
>   // Set up the HTTP service
>   httpService = new HttpService(inhttpproc, handler);
>   \{code}
>   HttpCore5's \{{HttpService.handleRequest()}} only sends a \{{100 Continue}} response if the request handler is wrapped with \{{BasicHttpServerExpectationDecorator}}. Without it, the server reads the request headers, sees \{{Expect: 100-continue}}, but never
>   acknowledges it. The client-side \{{HttpRequestExecutor}} waits for \{{DEFAULT_WAIT_FOR_CONTINUE}} (3 seconds) before giving up and sending the body.
>   h3. Proposed Fix
>   Wrap the handler with \{{BasicHttpServerExpectationDecorator}}:
>   \{code:java|title=AS2ServerConnection.java (proposed fix)}
>   registry = new RequestHandlerRegistry<>();
>   HttpServerRequestHandler handler = new BasicHttpServerRequestHandler(registry);
>   // Set up the HTTP service — wrap handler to support Expect: 100-continue
>   httpService = new HttpService(inhttpproc, new BasicHttpServerExpectationDecorator(handler));
>   \{code}
>   This is a one-line change. \{{BasicHttpServerExpectationDecorator}} is part of HttpCore5 (\{{org.apache.hc.core5.http.io.support.BasicHttpServerExpectationDecorator}}) and is already on the classpath.
>   When a client sends \{{Expect: 100-continue}}, the decorator automatically responds with \{{100 Continue}} before delegating to the actual handler, allowing the client to immediately send the body without waiting.
>   The same fix should also be applied to \{{AS2AsyncMDNServerConnection}} if it has the same pattern.
>   h3. How to Reproduce
>   # Set up a Camel AS2 server endpoint
>   # Send an AS2 message from a client that sends \{{Expect: 100-continue}} (e.g., Mendelson AS2 — enabled by default)
>   # Observe that the message takes ~3-4 seconds to arrive instead of <1 second
>   # With a network capture (Wireshark), you can see: client sends headers → 3-second gap → client sends body (no \{{100 Continue}} from server in between)
>   h3. Impact
>   Every inbound AS2 message from clients that use \{{Expect: 100-continue}} (which is common — Mendelson, many enterprise AS2 systems) is delayed by 3 seconds. For high-volume systems processing hundreds of messages per day, this adds significant cumulative
>   latency.
>   h3. Additional Notes
>   The same \{{AS2ServerConnection}} class also has a \{{RequestAcceptorThread}} that passes the \{{httpService}} directly to each \{{RequestHandlerThread}}:
>   \{code:java}
>   final Thread t = new RequestHandlerThread(this.service.httpService, inSocket);
>   \{code}
>   The fix at construction time (wrapping the handler before \{{HttpService}} is created) ensures all threads see the correct behavior without any threading concerns.
>   Ideally, this could also be made configurable via an endpoint parameter (e.g., \{{supportExpectContinue=true/false}}) for cases where the server explicitly does not want to send \{{100 Continue}}.



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