Apache Tomcat Development
Apache Portable Runtime (APR) based Native library for Tomcat
Tomcat can use the Apache Portable Runtime to
provide superior scalability, performance, and better integration with native server
technologies. The Apache Portable Runtime is a highly portable library that is at
the heart of Apache HTTP Server 2.x. APR has many uses, including access to advanced IO
functionality (such as sendfile, epoll and OpenSSL), OS level functionality (random number
generation, system status, etc), and native process handling (shared memory, NT
pipes and Unix sockets).
These features allows making Tomcat a general purpose webserver, will enable much better
integration with other native web technologies, and overall make Java much more viable as
a full fledged webserver platform rather than simply a backend focused technology.
APR support requires three main native components to be installed:
- APR library
- JNI wrappers for APR used by Tomcat (libtcnative)
- OpenSSL libraries
Windows binaries are provided for tcnative-1, which is a statically compiled .dll which includes
OpenSSL and APR. It can be downloaded from here
as 32bit or AMD x86-64 binaries.
In security conscious production environments, it is recommended to use separate shared dlls
for OpenSSL, APR, and libtcnative-1, and update them as needed according to security bulletins.
Windows OpenSSL binaries are linked from the Official OpenSSL
website (see related/binaries).
Once the libraries are properly installed and available to Java (if loading fails, the library path
will be displayed), the Tomcat connectors will automatically use APR. Configuration of the connectors
is similar to the regular connectors, but have a few extra attributes which are used to configure
APR components. Note that the defaults should be well tuned for most use cases, and additional
tweaking shouldn't be required.
When APR is enabled, the following features are also enabled in Tomcat:
- Secure session ID generation by default on all platforms (platforms other than Linux required
random number generation using a configured entropy)
- OS level statistics on memory usage and CPU usage by the Tomcat process are displayed by
the status servlet