Thanks, it seems like it must be one of Spring Boot's filters breaking
it. I should've tried without it first, mea culpa.
In a pure tomcat container it works as you described whereas with
Spring something inserts final 0 so the aborted connection looks like
a valid chunked response to clients.
I'll move my question to a more appropriate forum.
On Tue, 10 Aug 2021 at 02:45, Mark Thomas <ma...@apache.org> wrote:
>
> On 10/08/2021 02:25, Marcin Wisnicki wrote:
> > I have a servlet (it's really a SpringBoot controller but it shouldn't
> > matter?) in Tomcat 9.0.46 that streams responses of unknown size to
> > the browser.
> >
> > I've discovered that if the streaming process fails in the middle of
> > the write, the client will simply get an incomplete file and think it
> > was successful.
>
> Then you have a broken client.
>
> > Indeed there is no way to tell from the browser side there was an error.
>
> That statement is incorrect.
>
> > void doGet(HttpServletResponse resp) {
> > resp.setStatus(200);
> > resp.setHeader("Content-Disposition", "...");
> > resp.setContentType("application/octet-stream");
> > var out = resp.getOutputStream();
> > out.flush();
> > if (true) throw new RuntimeException("simulated error");
> > // status is already sent here, can't change it!
> > }
> >
> > As far as I can tell a web server should close connection with TCP RST
> > or write some garbage that's not a valid chunked response.
>
> You won't see a TCP RST. You will see invalid chunked encoding.
>
> > This is what some other servers do such as express.js.
> >
> > Unfortunately Tomcat does neither and also there seems to be no way to
> > trigger that using either Servlet or Tomcat api.
>
> Again, that statement is incorrect.
>
> > I've tested it by setting "Connection: close" then writing garbage and
> > it seems browser recognized download error.
> > But then I lose chunking in the output stream and can't actually write
> > a response.
> >
> > How do people solve it?
>
> Look at the following from a test using telnet to make a request to the
> sample servlet above:
>
> $ telnet localhost 8080
> Trying ::1...
> Connected to localhost.
> Escape character is '^]'.
> GET /tomcat-bugs/user004 HTTP/1.1
> Host: localhost
>
> HTTP/1.1 200
> Content-Type: text/plain
> Transfer-Encoding: chunked
> Date: Tue, 10 Aug 2021 06:38:06 GMT
>
> Connection closed by foreign host.
> $
>
> The headers are sent when the Servlet flushes the response. That is as
> required by the Servlet specification.
>
> What tells the client that the response is incomplete is that chunked
> encoding is being used but there is no final chunk.
>
> Mark
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