Tomcat 8.5.29 HTTP/2 is not supporting GZIP compression

Question

I am using Tomcat 8.5.29 and using the respective configuration,I have enabled the HTTP2 support for the site. Below is the configuration in server.xml file.

<Connector port="443" protocol="org.apache.coyote.http11.Http11AprProtocol"
           maxThreads="150" SSLEnabled="true" compressableMimeType="text/html,text/xml,text/plain,text/css,text/javascript,application/javascript,application/json" compression="on" compressionMinSize="1024"
           >
    <UpgradeProtocol className="org.apache.coyote.http2.Http2Protocol" />
    <SSLHostConfig>
        <Certificate certificateKeyFile="conf/localhost-key.pem"
                     certificateFile="conf/localhost-cert.pem"
                     certificateChainFile="conf/cacert.pem"
                     type="RSA" />
    </SSLHostConfig>
</Connector>

When i tried to compare the page load time for the site which is supporting HTTPS 1.1 and HTTP2, it is not consistent. Sometime it is taking more time to load and sometime it is taking less time to load compare to HTTPS 1.1.

To measure the page load time i am using Developer tools from Chrome Browser.

Later, I have found that Load time for HTTP/2 is higher because "content-encoding" in response is not gzip. Using HTTP/1.1, a script file size is 4 MB ( gzip) where as with HTTP/2, same file is of 8 MB ( no content-encoding). Compression is not happening. We have also tried with useSendfile and compression as "force" but it did not work.

We have also tried with Tomcat version 8.5.31 but no luck !! Facing same issue.

We have used Tomcat version 9 and using following configuration, got content in gzip (compressed). Now file size got reduced by 2 MB with a quick page load.

<Connector port="443" protocol="org.apache.coyote.http11.Http11AprProtocol"
           maxThreads="150" SSLEnabled="true" 
           >
    <UpgradeProtocol className="org.apache.coyote.http2.Http2Protocol" compressableMimeType="text/html,text/xml,text/plain,text/css,text/javascript,application/javascript,application/json" compression="on" compressionMinSize="1024" />
    <SSLHostConfig>
        <Certificate certificateKeyFile="conf/localhost-key.pem"
                     certificateFile="conf/localhost-cert.pem"
                     certificateChainFile="conf/cacert.pem"
                     type="RSA" />
    </SSLHostConfig>
</Connector>

It looks like Tomcat version 8.5 is not supporting gzip with HTTP2. Any idea on this?

Answer 1

According to the Tomcat documentation:

Note: There is a tradeoff between using compression (saving your bandwidth) and using the sendfile feature (saving your CPU cycles). If the connector supports the sendfile feature, e.g. the NIO2 connector, using sendfile will take precedence over compression. The symptoms will be that static files greater that 48 Kb will be sent uncompressed. You can turn off sendfile by setting useSendfile attribute of the protocol, as documented below, or change the sendfile usage threshold in the configuration of the DefaultServlet in the default conf/web.xml or in the web.xml of your web application.

So try adding useSendfile="false" to your UpgradeProtocol setting

<UpgradeProtocol className="org.apache.coyote.http2.Http2Protocol" compressableMimeType="text/html,text/xml,text/plain,text/css,text/javascript,application/javascript,application/json" compression="on" compressionMinSize="1024" useSendfile="false" />

Note this option does not appear in the 8.5 documentation so not sure if it exists for that (there is a reference to it "You can turn off sendfile by setting useSendfile attribute of the protocol, as documented below" but then nothing below), though you can also turn off at a server level.

Weirdly I wouldn't have expected this to work in Tomcat 9 either without turning off this option, but you say it does? Are you sure you have not turned this off? Or are you testing with a smaller than 48KB file on that?

Answer 2

Tomcat 8.5.33 fixes this issue; compression works with http/2 then.