I'm trying to get a Java8 app migrated to one of the modern Java runtimes and having the worst kind of problem imaginable.

After several hours running in the new runtime, my application starts behaving extremely erratically. I've tried the Java17 and Java21 runtimes, which behave slightly different but still eventually fail all requests.

With the Java17 runtime, I start seeing this:

Request failed: Unexpected Error: org.eclipse.jetty.http.HttpException$RuntimeException: 500: Response body is too large: 335544292061>33554432

With the Java21 runtime, I got some sort of 413 error and saw a lot of this in the logs (verbatum):

we actually read too much content in coreSizeLimitHandler for request size limit

Unfortunately, there's nothing else useful in the logs. I'm using the cloud logging logback adapter and I've correlated the logs, but the logs don't show any actual errors. I see 500 responses in the request log, but with normal (316 bytes) response size and normal application logging output, as if my code is returning success (316 bytes!).

Is this a problem in the runtime? That number in the error message is over 300 GB, which makes no sense to me.

Unfortunately, this only seems to happen under production load - the sandbox deployment of my app doesn't show the same behavior. And it only happens after several hours. I am totally at a loss as to how to go about debugging this, especially without further abusing my poor users :-(