Reto Peter created CAMEL-23071:
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Summary: AS2 client should provide endpoint parameter to
optionally enable Expect: 100-continue
Key: CAMEL-23071
URL: https://issues.apache.org/jira/browse/CAMEL-23071
Project: Camel
Issue Type: Improvement
Components: camel-as2
Affects Versions: 4.18.0
Reporter: Reto Peter
h3. Summary
The Camel AS2 client component has no endpoint parameter to control the
\{{Expect: 100-continue}} HTTP header behavior. In Camel versions 4.10–4.17,
\{{RequestExpectContinue}} was hardcoded in the \{{HttpProcessor}} chain with
no way to disable it, causing a
3-second delay per message when the remote server didn't support
100-continue. In Camel 4.18.0, the interceptor was silently removed — now there
is no way to *enable* it either.
The \{{Expect: 100-continue}} protocol is useful in certain scenarios (large
payloads, servers that may reject based on headers alone), so this should be a
configurable option rather than hardcoded on or off.
h3. History
|| Camel Version || Behavior ||
| 4.10.x – 4.17.x | \{{RequestExpectContinue}} hardcoded in
\{{AS2ClientConnection}} HttpProcessor chain — always ON, no option to disable |
| 4.18.0 | \{{RequestExpectContinue}} removed from chain — always OFF, no
option to enable |
h3. Problem (Camel 4.10–4.17)
\{{AS2ClientConnection}} builds its \{{HttpProcessor}} with a hardcoded
\{{RequestExpectContinue}} interceptor:
\{code:java|title=AS2ClientConnection.java (Camel 4.17.0)}
httpProcessor = HttpProcessorBuilder.create()
.add(new RequestAS2(as2Version, clientFqdn))
.add(new RequestMDN())
.add(new RequestTargetHost())
.add(new RequestUserAgent(this.userAgent))
.add(new RequestDate())
.add(new RequestContent(true))
.add(new RequestExpectContinue()) // <-- hardcoded, no option to
disable
.add(new RequestConnControl()).build();
\{code}
This causes every outbound AS2 message to include the \{{Expect:
100-continue}} header. When the remote AS2 server (e.g., OpenAS2) does not
implement the 100-continue protocol, HttpCore5's \{{HttpRequestExecutor}} waits
for a \{{100 Continue}} response that never
comes, timing out after *3 seconds* (\{{DEFAULT_WAIT_FOR_CONTINUE}}) before
sending the message body.
For high-volume AS2 systems this adds significant latency — e.g., sending 100
messages per day wastes 5 minutes just on expect-continue timeouts.
h3. Current State (Camel 4.18.0)
\{{RequestExpectContinue}} was removed from the chain entirely:
\{code:java|title=AS2ClientConnection.java (Camel 4.18.0)}
httpProcessor = HttpProcessorBuilder.create()
.add(new RequestAS2(as2Version, clientFqdn))
.add(new RequestMDN())
.add(new RequestTargetHost())
.add(new RequestUserAgent(this.userAgent))
.add(new RequestDate())
.add(new RequestContent(true))
.add(new RequestConnControl()).build();
// RequestExpectContinue removed — no option to enable
\{code}
This fixes the 3-second delay problem but removes the ability to use
100-continue for partners that do support it.
h3. Proposed Fix
Add a new AS2 endpoint parameter \{{expectContinue}} (default: \{{false}} to
maintain 4.18.0 behavior):
\{code:java|title=AS2ClientConnection.java (proposed)}
HttpProcessorBuilder builder = HttpProcessorBuilder.create()
.add(new RequestAS2(as2Version, clientFqdn))
.add(new RequestMDN())
.add(new RequestTargetHost())
.add(new RequestUserAgent(this.userAgent))
.add(new RequestDate())
.add(new RequestContent(true))
.add(new RequestConnControl());
if (expectContinue) {
builder.add(new RequestExpectContinue());
}
httpProcessor = builder.build();
\{code}
The parameter should be exposed on the AS2 endpoint configuration so users
can set it per route:
\{code}
as2://client/send?...&expectContinue=true
\{code}
h3. Impact
- *No breaking change* — default \{{false}} preserves current 4.18.0 behavior
- Partners that support 100-continue can benefit from it (early rejection,
bandwidth savings on large payloads)
- Partners that don't support it (OpenAS2 and others) continue to work
without the 3-second delay
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