HttpServer performance issue / improvement

[Jaikiran Pai]

Recently on AIX the same change was needed to address the test time outs 
in the 
test/jdk/com/sun/net/httpserver/simpleserver/StressDirListings.java test 
- https://github.com/openjdk/jdk/pull/17363

-Jaikiran

On 08/04/24 1:50 pm, Daniel Jeliński wrote:
> Hi Robert,
> If you are on Linux, see test/jdk/java/net/vthread/HttpALot.java. That
> test was recently modified to add -Dsun.net.httpserver.nodelay=true
> [1], because it took forever to complete on LInux machines. On other
> OSes the problem is not visible in existing tests.
> Cheers,
> Daniel
>
> [1] https://github.com/openjdk/jdk/pull/10504
>
> sob., 6 kwi 2024 o 00:37 robert engels <rengels at ix.netcom.com> napisał(a):
>> Hi Daniel,
>>
>> I think I have a solution that would work. I will try to get a PR together. Do you know if there is an existing test case the demonstrates the issue? - if not, I will start with that.
>>
>> Robert
>>
>> On Apr 4, 2024, at 9:44 AM, Daniel Jeliński <djelinski1 at gmail.com> wrote:
>>
>> Hi Robert,
>> Thanks for bringing this up! We are aware of the issue, it's tracked under https://bugs.openjdk.org/browse/JDK-6968351.
>>
>> If you have an idea for a proper fix that doesn't add too much complexity, please open a PR, and we'll be happy to help.
>> Cheers,
>> Daniel
>>
>> czw., 4 kwi 2024, 14:55 użytkownik Robert Engels <rengels at ix.netcom.com> napisał:
>>> 
>>> When doing some testing on github.com/robaho/httpserver - which is a fork of the jdk http server, I discovered a significant performance issue.
>>>
>>> When an http connection is in ‘keep-alive’ - the default for http 1.1 - the headers are “flushed” here https://github.com/openjdk/jdk21/blob/890adb6410dab4606a4f26a942aed02fb2f55387/src/jdk.httpserver/share/classes/sun/net/httpserver/ExchangeImpl.java#L281
>>>
>>> This means that after the handler runs and it sends data - e.g. /hello sends “hello” on the connection, the connection will stall due to the Nagel algorithm - usually incurring a 50 ms delay. The stall occurs since the client will not see the expected data until after the delay, so it is unable to send the next (when reusing the same connection/HttpClient).
>>>
>>> You can set the TCP_NODELAY on the server to work-around this, but a better solution would be to override the flush() on the BufferedOutputStream to not flush() the underlying connection - i.e. only write the buffered bytes, or rework it a bit to only flush when there is no content to send.
>>>