<s1>  <title>Resin HardCore<sup>tm</sup></title><summarylist/><note>Resin HardCore is experimental.</note><p>Resin HardCore is a Linux kernel module.  By pulling the webserverinto the kernel single-computer Resin servers and load-balancedservers can greatly improve their performance.  HardCorereplaces Apache as a web-server, grabbing HTTP requests and passing them tothe backend Resin JVMs.  Because HardCore operates entirely in the kernel,it has very low overhead.</p><s2 title="Basic Operation"><p>Resin HardCore works much like the Apache/mod_caucho combination.  When anew browser request appears on port 80, it accepts the request andparses the HTTP header.  It then selects a JVM and forwards the requestto the backend servlet runner.  When the servlet runner responds, HardCorewill send the response to the browser.</p><p>Unlike Apache/mod_caucho, HardCore passes every request to the servletrunner.  In essence, it's a kernel proxy.  Restricting HardCore to a proxytremendously simplifies the configuration and maintenance -- an importantconsideration when writing a kernel application.</p><p>Because HardCore is entirely in kernel space, it can quickly forwardthe requests without slow context switches or copying from user space.  Oncethe load-balancing is complete, an Linux box can serve as a low coststicky-session load balancer with much better performance than anApache load balancer.</p></s2><s2 title="Installation"><p>The Resin ./configure script will select the Linux sources.  Thestandard make; make install will put a <var/resin.o/> inresin-2.0.x/libexec.  <var/resin.o/> is the actual kernel module.</p><p>For standard configurations, ./configure will find the source, butyou can change it with configure arguments (or in the Makefile).</p><deftable><tr><td>--with-linux-src=/usr/src/linux<td>Selects the kernel source<tr><td>--enable-linux-smp<td>Compiles for an SMP system or not.</deftable><p>Once you've got a resin.o in libexec, you can install it as amodule.  The Linux command is <var/insmod/>.</p><p>HardCore can take an optional argument, <var/port/>, to select theserver port.  It defaults to the standard HTTP port 80.</p><example>unix> ./configure --with-linux-src=/usr/src/linux...unix> makeunix> make installunix> su rootunix# /sbin/insmod libexec/resin.o port=81...unix# /sbin/rmmod resin</example></s2><s2 title="Configuration in /proc/net/resin"><p>Once as a module, HardCore creates the <var//proc/net/resin/>directory for configuration. It currently contains three files:<var/server_port/> to configure the listening port, <var/srun-count/>to specify the number of load balancing servlet-runners, and<var/srun-n/> to configure each servlet runner.</p><deftable><tr><td>server_port<td>Configures the listening port, e.g. 80(currently read-only)<tr><td>srun-count<td>Configures how many servlet runners to use<tr><td>srun-0<td>The IP and port for the first servlet runner</deftable><p>You can look at those files to see their values:</p><example>unix# ls /proc/net/resinserver_port srun-0 srun-countunix# cat /proc/net/resin/server_port80unix# cat /proc/net/resin/srun-count1unix# cat /proc/net/resin/srun-0127.0.0.1 6802</example><p/>You can also configure <var/srun-0/> to change the servlet runner.<example>unix# echo "192.168.0.3 6810" > /proc/net/resin-srun-0</example></s2><s2 title="Caveats and Errata"><p>Any bugs in HardCore will likely crash or freeze your computer.  Intheory it could also do bad things to the filesystem, although thathasn't happened to us ... yet.  Working with kernel modules is notas safe as a C program and nowhere near as safe as running a Java program.</p><p>The 12/21 version handles basic GET requests.</p><p>The current errata:</p><ul><li>POST requests are not handled<li>Date routines have not yet been implemented<li>Load-balancing is not yet done<li>Failure to contact a srun results in a disconnect instead of anerror message.<li>/caucho-status isn't implemented yet.<li>Caching isn't implemented yet.<li>Logging isn't implemented yet.<li>HTTP/1.1 keepalive isn't implemented.</ul></s2></s1>