Enabling HTTP/2 Support

The HttpService implementation comes with support for HTTP/2 protocol. To enable it for Bosch IoT Gateway Software the requirements for running HTTP/2 are:

• JDK 8 or greater
• ALPN (Application Layer Protocol Negotiation) support

ALPN Providers

There are three available providers for ALPN support:

• For JDK 8 or later, a provider based on the Conscrypt security provider
  • Works with JDK 8 or later and provides improved performance
  • Binds to the OpenSSL native library shipped by Conscrypt and is therefore only available on the platforms supported by Conscrypt
  • Does not support ARM CPU architectures
• For JDK 9 or later, a provider based on the ALPN APIs present in the JDK
  • Works with JDK 9 or later, pure Java implementation
  • Lower performance than Conscrypt
• For JDK 8 only, a provider based on modified OpenJDK classes
  • Only works with JDK 8, pure Java implementation
  • Requires ALPN boot artifact version that matches the version of the JRE

Bosch IoT Gateway Software comes with startup options for all these three providers:

• To use Conscrypt ALPN provider start the gateway with http2-conscrypt parameter:

  server http2-conscrypt

• To use JDK 9 ALPN provider start the gateway with http2-jdk9 parameter:

  server http2-jdk9

• To use JDK 8 ALPN provider:
  • on JVMs supporting Java Instrumentation (compact3+), it is sufficient to start the gateway with http2-jdk8 parameter:

  server http2-jdk8

  The http2-jdk8 startup script uses Jetty ALPN Agent, which automatically selects the appropriate alpn-boot.jar based on the JVM version.

  • on JVMs that do no support Java Instrumentation:
    • First find the correct ALPN boot artifact version that matches the version of your JRE and download it from the Maven Repository.
    • Then, set the ALPN_BOOT environment variable to point to the downloaded alpn-boot.jar and start the server with http2-jdk8 parameter.

  On Java 1.8.0u252 and above no alpn-boot JAR is required and the ALPN_BOOT environment variable should be set to the special value "none".

  – On Windows:

  set ALPN_BOOT=..\..\..\lib\alpn-boot.jar

  server.bat http2-jdk8

  – On Linux:

  export ALPN_BOOT=../../../lib/alpn-boot.jar

  ./server.sh http2-jdk8

You can also edit http2-jdk8.bat/http2-jdk8.sh in bin/vms/jdk directory and set the ALPN_BOOT environment variable there.

Enabling HTTP/2 Protocol

After the gateway is started with ALPN support, HTTP/2 can be enabled by setting http2Enabled property to true in HttpService configuration – factory configuration with PID mbs.http.config.

To be able to use HTTP/2 protocol with browsers, HTTPS should also be configured – all major browsers support HTTP/2 only over secure connections. However browser support for Websockets over HTTP/2 is currently limited. As of 02/2020 only Firefox is known to support it.

For mote details refer to Migrating from Bosch HttpService implementation and the Setup Guide.