Date: 05 May 2002 00:08:06 +0300 From: zoidberg <dr.zoidberg@telia.com> To: Helmut Hissen <helmut@zeebar.com> Cc: freebsd-java@FreeBSD.ORG Subject: Re: java program as service Message-ID: <1020546490.515.6.camel@BSD-buddha.my.router> In-Reply-To: <20020504122441.A1230@zeebar.com> References: <20020504122441.A1230@zeebar.com>
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On Sat, 2002-05-04 at 22:24, Helmut Hissen wrote:
>
> going from a run-once-inside-test-environment to persistent
> server brings up a number of issues, especially if you are
> beating up the JVM.
>
> I used to run Java chat servers with hunders/thousands of
> IRC and HTTP connections, and every single time we switched JVMs,
> some other totally bizarre and obscure thing happened, never right
> away tho, but only after running for 6 hours and only at 2am
> and especially on holidays :-).
>
> starting through rc.d is fine, but consider this...
>
>
> - get the user/group and file protections right, especially
> if you are planning to access or create files incl log files
> in various places, and think about how you are planning to
> clean them up
>
> - if you write your own service and its open to the world,
> make sure you dont open the flood gates to hackers. most
> existing network services out there have had the benefit
> of having been hacked-into and fixed a few times (and being
> hardened as a result).
>
> - get you path, and CLASSPATH right. you wont be able to
> rely on your .{c,ba}shrc you tested with, but its nice to
> make that stuff explicit anyways
>
> - you may discover that you forgot to close a file somewhere
> in the code and/or that you are hanging on to more objects
> than you realize. this is where good logging and debugging
> hooks comes in handy.
>
> - if you are keeping the Java process around, and you are
> giving it an ongoing good workout, you may join the league
> of people who get to deal with the ever-evolving JVM
> bug-du-jour.
>
> - depending on the OS and system kernel parameters, you may run
> into process limits (max # of open files)
>
> - the JVM may well die after a while, depending on which one
> and what you are doing to it. best to assume that will hapen
> and run your service from a non-Java wrapper script, (csh, sh,
> tclsh, perl) that goes something like this:
>
> set path/classpath
> set per-process limits
> while (true) {
> save previous logfile
> java ...... >& logfile
> if (being shutdown)
> exit
> email cause-of-death to cell phone / pager
> }
>
> - keep a backup copy of the JDK and OS so that if you need to
> reinstall you wont be hostage to JVM-bug-du-jour on the new
> JVM/OS combination
>
> - we used to run a watchdog thread whose only job was to wake up
> at a scheduled time. it would then look at the clock and if it
> woke up late, it would send out a warning. The freequency of
> these warnings turned out to be one of the best indicators for
> impending user-visible trouble.
>
> I alluded to "obscure problems" you are more likely to run into
> in a persistent server... here are two particular annoying examples
> of ther kind of things I have run into in the past:
>
> - JVM did not properly close sockets if the connection was
> terminated by certain errors (even though our application code
> released the associated objects), causing process to run out
> of file descriptors after a few days..
>
> - forking image utilities as subprocess from Java server
> (specifically, exit of the spawned process) caused a completely
> unrelated thread to wake up from a sleep, but only after a couple
> of hours of server uptime when things got really busy and during
> garbage collection.
>
> seems like every JVM we tried had some such quirk, no matter what
> color threads, and you would only run into this only on a fullmoon
> and you're about to go out to have dinner with someone special.
>
> sorry for ranting a bit ... I hope you wont run into anything
> particularly annoying. chances are you wont. may your special
> dinners be uninterrupted.
>
> cheers
>
> Helmut Hissen
> helmut@dialabc.com
>
>
> >hello!
> >
> >if i want to run a java program as a service, how is this done in the
> >best way? can i do as an ordinary service that i start through a script
> >in rc.d, or is there something special i have to think about?
> >
> >br
> >.z
>
thanks alot for your answer! most helpfull!!
br
.z
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