Customizable error page buffer size

[dkaukov]

Ability to increase buffer size past 8k in the custom ErrorHandler

[joakime]

The HttpConfiguration is how you control the output buffer size.

What is the use case for this?

[dkaukov]

True, but

    bufferSize = Math.min(8192, bufferSize); // TODO ?

limiting it to the 8k. We need a way to increase the limit.

[joakime]

limiting it to the 8k. We need a way to increase the limit.

I understand that you want to increase the buffer size limit, but why?
What's the use case for a larger buffer size? (I ask, as there's probably several different ways to accomplish your use case without increasing this specific buffer size)

[dkaukov]

Hi, In the

@Override
protected void writeErrorHtml(Request request, Writer writer, Charset charset, int code, String message, Throwable cause, boolean showStacks) throws IOException {
  ....
}

we are generating custom error page using Writer. Something like:

  themeLeafTemplate.execute(writer, errorInfo);

If error page is bigger than buffer size it is just trimmed.

[joakime]

Need to dig into why we are doing this via a static sized buffer.

I would like to see if this need can be accomplished via a Writer created with the Content.Sink features instead. (will try this in a different branch soon)

[dkaukov]

Hi @joakime , maybe we can merge this one in a meantime?

[gregw]

Need to dig into why we are doing this via a static sized buffer.

I believe the reasoning is that we don't want to get into complex responses when generating error pages, as if we are in an error state, we want simplicity.... otherwise we can get errors within errors within errors.....

I'll review this PR for merging now...

[gregw]

This is OK.... but I think I'd prefer a simple setBufferSize method, with a -1 meaning that a heuristic will be used (e.g. min(8K, httpConfig.bufferSize)). Default value will be -1 and public int getBufferSize() would return -1 (or the set value). Then have a protect int computeBufferSize(Request request) that would check for -1 and do the min(8k, config.bufferSize) thang.

[gregw]

Let's remove the TODO from the code

[gregw]

We need a bit of javadoc to say that this is getting the buffer size for the entire error response (any larger responses will be truncated). Then say that default implementation imposes an 8K limit on the standard buffer size, but that implementations may override the method to provide some other size.

[gregw]

This is OK.... but I think I'd prefer a simple setBufferSize method, with a -1 meaning that a heuristic will be used (e.g. min(8K, httpConfig.bufferSize)). Default value will be -1 and public int getBufferSize() would return -1 (or the set value). Then have a protect int computeBufferSize(Request request) that would check for -1 and do the min(8k, config.bufferSize) thang.

Note the reason I prefer a setter, is that it can be used from XML.

[dkaukov]

@gregw Could you please take a look now.

[gregw]

This looks good to me!

[gregw]

Hmmm why are these fields not private? Not a problem for this PR, but strange....

[gregw]

CI failure is a flake. rerunning