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From Christopher Schultz <>
Subject Re: Http 2 support in Tomcat
Date Fri, 15 May 2015 18:23:59 GMT
Hash: SHA256


On 5/15/15 12:59 PM, Mark Thomas wrote:
> On 15/05/2015 17:49, Christopher Schultz wrote:
>> Tony,
>> On 5/15/15 12:06 PM, PerfGuru wrote:
>>> Good news thanks for the update. It may be some time before
>>> servlet 4 support is released but good to know Tomcat will be
>>> ready then. But does APR support http/2? I know other web
>>> servers now do.
>> Mark's initial work on the HTTP/2 connector has been using APR.
>> Note that APR doesn't handle the HTTP protocol, it just helps
>> manage sockets, pools, etc. The protocol needs to be built on top
>> of those building blocks. Please see the dev list (archives) for
>> details. Just search for "HTTP/2" subjects.
> Correct. This is primarily because ALPN support is not there in
> JSSE yet and wont be until Java 9. That said, one of the reasons
> for the huge amount of connector refactoring that I did before
> starting on HTTP/2 was so that the connector implementation
> specific code was kept to a minimum (so far just ALPN). HTTP/2 will
> work just fine with NIO and NIO2 just as soon as JSSE support ALPN
> and we plumb it in.

Is this something that's workable with the current pre-release builds
of Java 9? Presumably, Servlet 4 will require Java 8. Does that mean
that HTTP/2 with the NIO connectors will only be available with a
higher JRE version?

> h2c support (HTTP/2 over a cleartext channel via HTTP upgrade
> rather than TLS) is also on the TODO list. It shouldn't be much
> work to add (less than a day) and it wil be available for all
> connectors.
>>> Also, I think Tomcat supports websockets which has the
>>> important capabilities that http/2 has and has been available
>>> longer.
>> Tomcat supports Websocket since Tomcat 7, as long as you are
>> running on Java 7 or higher.
>>> Depending upon your strategy you might want to go with that or
>>> wait a couple of years for http/2. Remember the firewalls,
>>> proxies and other network systems have to support http/2 before
>>> it can reach Tomcat. So it may be by the time http/3 is
>>> approved.
> Tomcat has no choice (application developers do). Servlet 4.0 will 
> require HTTP/2 so Tomcat has to support it.
>> Correct. Using Websocket through certain proxies (e.g. httpd) is
>> even still sometimes tricky.
> Yeah. We should touch base with jimjag and discuss this. I think
> the httpd thinking around WebSockets and the Java world thinking
> about WebSockets aren't quite lined up.


Perhaps there isn't much use for Websockets in the Perl or PHP world,
where a lot of httpd installations are being used.

Jim Riggs's (reprise, I believe) presentation at ApacheCon about how
"mod_php needs to die" (paraphrasing) advocates more extensive use of
mod_proxy_* to physically separate the web tier from the application
tier, in a way that more closely resembles how Java webapps are
deployed. Perhaps if the world starts listening to the Jim Riggses of
the world, the shortcomings of mod_proxy_websocket and friends will
become more apparent.

- -chris
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