I was curious about this and did a quick search. It appears that this approach is generally considered an anti pattern [1].
Please do not take this as an authoritative opinion as that's my only source. I am simply trying to understand why such a large header is required and if the problem could be solved using the request body or any other way like a proxy. Jetty does have a rationale for these limits, as they are based on the HTTP specification. On that note, something you should consider is that If you have other systems in between your client and Kafka Connect (such as load balancers, and friends), you may face the same issue there as well In any case, if we decide to take the KIP approach to enable this, I assume we will need to provide a justification that goes beyond citing "business requirements" to explain the effort involved in building it and the overall benefits it'll bring to the framework Thanks! [1] https://github.com/jetty/jetty.project/issues/12071 From: Chris Egerton <[email protected]> To: "Users"<[email protected]> Date: Thu, 22 Jan 2026 21:49:25 -0500 Subject: Re: Increasing/Exposing requestHeaderSize for Kafka Connect REST API Ah, I see! Sorry about that, been a sec since I've gotten my hands dirty with the server logic for Connect. I can't think of any other workarounds, unfortunately. I'd be in favor of a small KIP to plug the gap though! On Thu, Jan 22, 2026, 15:19 Chitra Elangovan < mailto:[email protected] > wrote: > Hi Chris, > > We looked at the ConnectRestExtension.html > < > https://kafka.apache.org/39/javadoc/org/apache/kafka/connect/rest/ConnectRestExtension.html > > >, > but since the 8KB limit is enforced at the Jetty Server level, the > extension isn't invoked until after the 431 error is already triggered. Are > there any other workarounds that are currently available? > > Thanks, > Chitra Elangovan > > > On Wed, Jan 21, 2026 at 5:23 PM Chris Egerton < > mailto:[email protected] > > wrote: > > > Hi Chitra, > > > > Unsure about whether this will help with your specific requirements or > not > > but have you looked into the REST extension API? Linking to the 3.9.x > docs > > since that's the version you're running but AFAIK the feature hasn't > > changed much or even at all in a few years: > > > > > https://kafka.apache.org/39/javadoc/org/apache/kafka/connect/rest/ConnectRestExtension.html > > > > > If this doesn't help, I think a KIP could make sense. > > > > Cheers, > > > > Chris > > > > > > On Wed, Jan 21, 2026, 19:57 Chitra Elangovan < mailto:[email protected] > > wrote: > > > > > Hello Kafka Community, > > > > > > I am reaching out to discuss a limitation regarding the Kafka Connect > > REST > > > API's embedded Jetty server (we are using kafka 3.9.0 version). > > > > > > Currently, the default header size limit is 8KB. In our environment, we > > are > > > exceeding this limit due to our business needs. When this limit is > > > exceeded, Jetty returns a 431 Request Header Fields Too Large error. > > > > > > I've noted that while listeners and a few other properties are > > configurable > > > via the Worker properties, there doesn't seem to be a straightforward > way > > > to increase the requestHeaderSize for the internal HttpConfiguration. > > > > > > Questions for the group: > > > > > > - Is there an existing JVM system property or undocumented config that > > can > > > override this in the current version? > > > > > > - If not, would the community be open to a KIP (Kafka Improvement > > Proposal) > > > to expose this as a worker configuration (e.g., > > > rest.request.header.size.default)? > > > > > > - Are there any known workarounds for Kafka Connect distributed workers > > > without using an external reverse proxy to strip headers?Looking > forward > > to > > > your insights. > > > > > > Best regards, > > > Chitra Elangovan > > > > > >
