java in /etc/init.d script (newbie sa question)

SuSE 8.2 Intel

One of our java developers wants to have his app (.jar) start up in a
/etc/init.d script for run levels 3 and 5 (/etc/init.d/rc{3,5}.d

He says the command-line invocation is

java -jar hisProg.jar

to run in the foreground, or (obviously)

java -jar hisProg.jar &

to run in the background.

I'm willing to experiment with this, but as it's a production app I'd
be a lot more comfortable if I was fully versed in what's involved in
getting this running as a daemon process.

Clues, URLs, or other references greatly appreciated.

On Wed, 28 Jan 2004 03:17:04 GMT, Richard wrote:
> SuSE 8.2 Intel
>
> One of our java developers wants to have his app (.jar) start up in a
> /etc/init.d script for run levels 3 and 5 (/etc/init.d/rc{3,5}.d

If loaded, you may want to read some of the files found here, try
locate /doc/initscripts
and cut/paste something like
/usr/share/doc/initscripts-7.06
into your browser.

You could build a script and use
service script_name start/stop/reset

Example:
http://groups.google.com/advanced_group_search
slrnblf7e0.4dt.BitTwister@wb.home in the message id box
*linux* in Newsgroup, U need 2 use *, pick English

man chkconfig

BitTwister@localhost.localdomain wrote...
> On Wed, 28 Jan 2004 03:17:04 GMT, Richard wrote:
> > SuSE 8.2 Intel
> >
> > One of our java developers wants to have his app (.jar) start up in a
> > /etc/init.d script for run levels 3 and 5 (/etc/init.d/rc{3,5}.d
>
> If loaded, you may want to read some of the files found here, try
> locate /doc/initscripts
> and cut/paste something like
> /usr/share/doc/initscripts-7.06
> into your browser.
>
> You could build a script and use
> service script_name start/stop/reset
>
> Example:
> http://groups.google.com/advanced_group_search
> slrnblf7e0.4dt.BitTwister@wb.home in the message id box
> *linux* in Newsgroup, U need 2 use *, pick English
>
> man chkconfig

Thanks, and I'll look into these. Maybe 'service' turns its
arguments into a daemon.

Just to be more specific, I'm familiar with init.d scripts. But if
java is invoked as I've described (java -jar hisprog.jar) in a
startup script, won't it exit after the shell interpreting the script
(the #! /bin/sh line) exits?

On Wed, 28 Jan 2004 15:02:27 GMT, Richard wrote:

> Thanks, and I'll look into these.

> Maybe 'service' turns its
> arguments into a daemon.

No it does not.

> Just to be more specific, I'm familiar with init.d scripts. But if
> java is invoked as I've described (java -jar hisprog.jar) in a
> startup script, won't it exit after the shell interpreting the script
> (the #! /bin/sh line) exits?

The script will exit when it completes all the
commands in the script.

You need a testbed, non production, to test in before going into
production.

Bit Twister wrote:
> On Wed, 28 Jan 2004 15:02:27 GMT, Richard wrote:
>
>
>>Thanks, and I'll look into these.
>
>
>>Maybe 'service' turns its
>>arguments into a daemon.
>
>
> No it does not.
>
>
>>Just to be more specific, I'm familiar with init.d scripts. But if
>>java is invoked as I've described (java -jar hisprog.jar) in a
>>startup script, won't it exit after the shell interpreting the script
>>(the #! /bin/sh line) exits?
>
>
> The script will exit when it completes all the
> commands in the script.
>
> You need a testbed, non production, to test in before going into
> production.

I take it you're talking about the startup script, not the java app. The
Java app will continue until it is finished.

Just thought it needed some clarification for the OP.

--
Ben M.

----------------
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To protect the small enterprise from bigger companies.

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In its current form, they protect only companies with
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a.) Patent everything no matter how general
b.) Sue everybody. Even if the patent can be argued
invalid, small companies can ill-afford the
typical $500k cost of a law-suit (not to mention
years of harassment).

Don't let them take away your right to program
whatever you like. Make a stand on Software Patents
before its too late.

Read about the ongoing battle at http://swpat.ffii.org/
----------------

saint_abroadremove@removehotmail.com wrote...
> Bit Twister wrote:
> > On Wed, 28 Jan 2004 15:02:27 GMT, Richard wrote:
> >
> >
> >>Thanks, and I'll look into these.
> >
> >
> >>Maybe 'service' turns its
> >>arguments into a daemon.
> >
> >
> > No it does not.
> >
> >
> >>Just to be more specific, I'm familiar with init.d scripts. But if
> >>java is invoked as I've described (java -jar hisprog.jar) in a
> >>startup script, won't it exit after the shell interpreting the script
> >>(the #! /bin/sh line) exits?
> >
> >
> > The script will exit when it completes all the
> > commands in the script.
> >
> > You need a testbed, non production, to test in before going into
> > production.

Of course. What I think I really need is clarity of the mechanisms
involved rather than saying "it seemed to work in testing" and then
taking it to production.

What happens to the running java invocation after the shell it's
running in exits? Does the init process get it?

> I take it you're talking about the startup script, not the java app. The
> Java app will continue until it is finished.

So, in /etc/init.d/myjar (ln'ed to, say, /etc/init.d/rc3.d/S50myjar)
with these lines, given correct values for ${JAVA} and {$JARPATH}...

#! /bin/bash
# the usual /etc/init.d start/stop/etc. script stuff, skipped ....

start)
echo "Starting myjar..."
${JAVA} -jar ${JARPATH}/myjar.jar &

# more of the usual /etc/init.d script stuff, skipped ....
# end of script

....myjar.jar will continue executing after the script terminates?

Again, I'm just trying to be clear on the mechanism involved rather
than just use it without understanding why it works.

> Just thought it needed some clarification for the OP.

Thank you.

On Wed, 28 Jan 2004 18:28:05 GMT, Richard wrote:
>
> Of course. What I think I really need is clarity of the mechanisms
> involved rather than saying "it seemed to work in testing" and then
> taking it to production.

The suggestion was so you could see what will happen not just checking
your installation/backout procedure.

> What happens to the running java invocation after the shell it's
> running in exits? Does the init process get it?

We cannot see what happens because you did not supply the java code.

> Again, I'm just trying to be clear on the mechanism involved rather
> than just use it without understanding why it works.

Tell you what, create a script "ping_loop" on a test bed, example

while [ 0 -eq 0 ] ; do
sleep 10
ping -c 1 localhost >> /tmp/ping.log
done

chmod +x ping_loop

then see what happens (ie ps aux | grep myjar)


with your myjar init script using
start)
echo "Starting myjar..."
/some/where/ping_loop
and
/some/where/ping_loop &

On Wed, 28 Jan 2004 21:40:24 GMT, Bit Twister wrote:
> On Wed, 28 Jan 2004 18:28:05 GMT, Richard wrote:
>>
>> Of course. What I think I really need is clarity of the mechanisms
>> involved rather than saying "it seemed to work in testing" and then
>> taking it to production.
>
> The suggestion was so you could see what will happen not just checking
> your installation/backout procedure.
>
>> What happens to the running java invocation after the shell it's
>> running in exits? Does the init process get it?
>
> We cannot see what happens because you did not supply the java code.
>
>> Again, I'm just trying to be clear on the mechanism involved rather
>> than just use it without understanding why it works.
>
> Tell you what, create a script "ping_loop" on a test bed, example
>
> while [ 0 -eq 0 ] ; do
> sleep 10
> ping -c 1 localhost >> /tmp/ping.log
> done
>
> chmod +x ping_loop
>
> then see what happens (ie ps aux | grep myjar)
>
>
> with your myjar init script using
> start)
> echo "Starting myjar..."
> /some/where/ping_loop
> and
> /some/where/ping_loop &
>

PS: forgot to add, I assume the testbed has no other users when you
test your myjar with a shutdown -r now

BitTwister@localhost.localdomain wrote...
> On Wed, 28 Jan 2004 18:28:05 GMT, Richard wrote:
> >
> > Of course. What I think I really need is clarity of the mechanisms
> > involved rather than saying "it seemed to work in testing" and then
> > taking it to production.
>
> The suggestion was so you could see what will happen not just checking
> your installation/backout procedure.

Eh? Installation and install backout is a completely different issue
than controlling an (obviously already-installed) process via an
/etc/init.d script.

My question really boils down to this:

By design of the boot process, and the way init is designed to
process /etc/init.d scripts, can a process that is not a daemon be
started and continue to run after the script that invokes it
terminates--AND (here's the important part) IF SO, WHY?

I'm getting the sense that the answer is: "I'm not really sure how
init is supposed to work in the case you've suggested, but here are
some ways that you can at least see what the behavior is."

That's a good answer, as far as it goes, and I thank you for it.

> > What happens to the running java invocation after the shell it's
> > running in exits? Does the init process get it?
>
> We cannot see what happens because you did not supply the java code.

I'm not sure it takes much imagination to figure, from my questions,
that it's an application whose intended lifetime is at least longer
than the /etc/init.d script that invokes it.

So, in a practical sense, it doesn't matter what the java code does.

> > Again, I'm just trying to be clear on the mechanism involved rather
> > than just use it without understanding why it works.
>
> Tell you what, create a script "ping_loop" on a test bed, example
>
> while [ 0 -eq 0 ] ; do
> sleep 10
> ping -c 1 localhost >> /tmp/ping.log
> done
>
> chmod +x ping_loop
>
> then see what happens (ie ps aux | grep myjar)
>
>
> with your myjar init script using
> start)
> echo "Starting myjar..."
> /some/where/ping_loop
> and
> /some/where/ping_loop &

I guess the "understand why it works" part got lost in translation.

Well, again, that's OK. Thanks very much for your help.

On Thu, 29 Jan 2004 05:45:22 GMT, Richard wrote:
>
> I'm not sure it takes much imagination to figure, from my questions,
> that it's an application whose intended lifetime is at least longer
> than the /etc/init.d script that invokes it.
> So, in a practical sense, it doesn't matter what the java code does.

Yeah, right.
You run the ping_loop as suggested and see what happens.