Author: jfclere
Date: Thu Dec 8 02:21:06 2005
New Revision: 355064
URL: http://svn.apache.org/viewcvs?rev=355064&view=rev
Log:
Add a section "How jsvc works".
Modified:
jakarta/commons/proper/daemon/trunk/xdocs/jsvc.xml
Modified: jakarta/commons/proper/daemon/trunk/xdocs/jsvc.xml
URL:
http://svn.apache.org/viewcvs/jakarta/commons/proper/daemon/trunk/xdocs/jsvc.xml?rev=355064&r1=355063&r2=355064&view=diff
==============================================================================
--- jakarta/commons/proper/daemon/trunk/xdocs/jsvc.xml (original)
+++ jakarta/commons/proper/daemon/trunk/xdocs/jsvc.xml Thu Dec 8 02:21:06 2005
@@ -159,7 +159,7 @@
<p>
You have to write a Class (MyClass) that implements the following methods:
<ul>
- <li>void init(String[] arguments): Here open the configuration files, create
the trace file, create
+ <li>void load(String[] arguments): Here open the configuration files, create
the trace file, create
the ServerSockets, the Threads</li>
<li>void start(): Start the Thread, accept incomming connections</li>
<li>void stop(): Inform the Thread to live the run(), close the
ServerSockets</li>
@@ -168,6 +168,73 @@
Store it in a jarfile and use as above:
<source>
./jsvc -cp commons-daemon.jar:my.jar MyClass
+</source>
+</p>
+</subsection>
+</section>
+<section name="How jsvc works">
+<p>
+Jsvc uses 3 processes: a launcher process, a controller process and a
controlled process.
+The controlled process is also the main java thread, if the JVM crashes
+the controller will restart it in the next minute.
+Jsvc is a daemon process so it should be started as root and the -user
parameter
+allows to downgrade to an unprivilegded user.
+When -wait parameter is used, the launcher process waits until the controller
says
+"I am ready", otherwise it returns after creating the controller process.
+</p>
+
+<subsection name="Forks in jakarta-daemon">
+<p>
+Launcher process:
+<source>
+main()
+{
+ fork()
+ parent: wait_child(), wait until JAVA service started when the child says "I
am ready".
+ child: controller process.
+}
+</source>
+
+Controller process:
+<source>
+ while (fork()) {
+ parent: wait_for_child.
+ if exited and restart needed continue
+ else exit.
+ child: exit(child()). controlled process.
+ }
+</source>
+
+Controlled process:
+<source>
+In child(): controlled process.
+ init_JVM().
+ load_service().
+ start_service().
+ say "I am ready"
+ wait for signal or pool for stop
+ stop_service().
+ destroy_service().
+ destroy_JVM().
+ exit (with different codes so that parent knows if it has to restart us).
+</source>
+Note: The controller process uses signals to stop the controlled process.
+</p>
+</subsection>
+
+<subsection name="Downgrading user">
+<p>
+On linux setuid()/setgid() + capabilities are used on other unix
setgid/initgroups are used.
+
+we have something like:
+<source>
+/* as root */
+init_JVM().
+load_service. /* java_load() calls the load method */
+downgrade user (set_caps() or set_user_group())
+/* as the user $USER (from -user $USER parameter) */
+umask()
+start_service. /* java_start() calls the start method */
</source>
</p>
</subsection>
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