Tomcat 9.0.16 Java 11 HTTP/2

Question

Is TLS still a prerequisite for using HTTP/2 on the latest Java and Tomcat? Can I add <UpgradeProtocol className="org.apache.coyote.http2.Http2Protocol"/> to HTTP port 8080 and expect HTTP/2 to work? How to actually test / see that HTTP/2 is actually being used instead of HTTP? Any command line / browswer tool? Thanks.

Answer 1

You can use curl -v --http2 localhost:8080 to check the actions after applying the UpgradeProtocol and restarting Tomcat server.

Answer 2

As the HTTP Connector howto states:

HTTP/2 is support is provided for TLS (h2), non-TLS via HTTP upgrade (h2c) and direct HTTP/2 (h2c) connections. To enable HTTP/2 support for an HTTP connector the following UpgradeProtocol element must be nested within the Connector with a className attribute of org.apache.coyote.http2.Http2Protocol.

This suggests TLS is not a requirement. Question still is if your browser supports h2c upgrade.

Using Firefox, press (F12) to open the developer tools, navigate to Networkanalysis. There you see a table showing several attributes per request. If not present, add the Protocol column which tells you whether HTTP/1, h2c or any other protocol is being used for each request. Chrome also provides protocol information in a similar way:

Simply rightclick a column in the developer tools Netowrk section and you get an overview of all available columns:

Another alternative to debug protocol used by clients is access logging. Simply create a context.xhtml within the default ROOT webapp in \apache-tomcat\webapps\ROOT\META-INF\ with this content:

<?xml version="1.0" encoding="UTF-8"?>
<Context>
  <Valve className="org.apache.catalina.valves.AccessLogValve"/>
</Context>

After restarting Tomcat and doing some requests you'll find a \apache-tomcat\logs\localhost_access_log.2019-03-12.txt which exactly states the protocol used for each request:

... - - [12/Mar/2019...] "GET / HTTP/1.1" 200 11488
... - - [12/Mar/2019...] "GET / HTTP/1.1" 200 11488
... - - [12/Mar/2019...] "GET / HTTP/2.0" 200 11468

In my case, both first requests where done using Chrome and Firefox, third request was done using the command curl -v --http2 localhost:8080 you wrote in your other answer.