Hiya Alvis I do quite a bit of daemon/service kina work in Linux/Lazarus so I'll try to help.
In this week I did a small prototype of an application that I'm doing for linux with Lazarus. It open socket for remote visual control, mysql connections, and other nice things.
This is a cool idea, but please keep the following in mind: When you create your project. You MUST choose "commandline application" - NOT graphical application, else your daemon will refuse to start (since gtk linked apps need to be stared INSIDE an active X-server, which is not existing in the init-phases of a Linux system).
So my questions are...: 1) Does the kill on a linux service launch some "onkill" functions, or that's a kill-without-doing-anithing-else ? I'm thinking about using a soft close through the tcp connection with a command in the init.d/my_service stop like that: telnect localhost myport /my_service_suicide Are'nt there any ways to put some code into a "onkill" event of a linux process?
This is not actually true :) The init scripts generally only make stop, start and restart available - but there are far more options in the Linux world. The kill command technically doesn't "end" a process, it sends it a signal which the process should respond to. Signal 15 is the one sent if none is specified and it means "soft-kill" - the application is TOLD to die, and left to do so by itself. Signal 9 is hard kill - which yanks the proggie right out of the system and kills it dead right away. This is typically used when a process crashed and it cannot do a proper soft-kill anymore. Other signals that a daemon should handle include signals for "reload all configs" etc. as well (many init scripts have a 'reload' option which triggers this, it is NOT meant to restart the daemon, but to force it to reread it's config files - for daemons supporting this, you can use it to load in updated config files without taking the service down first). The linux daemon demo shows how to handle all the important services.
2) How do I configure threads in linux? I mean... I'd like to change their name and aspect like other services do, and keep under control their behaviour (state, resume call times, speed, cpu usage, ecc).
Threads and daemons aren't directly related. You create a daemon by FORK'ing the application. See yet again the daemon example which shows how this works very well. I personally suggest ANY modern daemon should AFTER the fork have code to get it's NEW pid and save this to /var/run/daemonname.pid so that init scripts can CLEANLY stop or restart it - this is the only thing NOT in the demo though (catch it sorta requires that your daemon have root privs but they usually do anyway). Threads CAN be used with daemons, usually AFTER the fork to allow the daemon to handle multiple tasks at once (e.g. multiple simultaneous clients will usually require threading the app). The best advice I can give HERE is to have a look at the TThread tutorial in the wiki - I learned threading from there -this is entirely platform neutral.
3) Does killing the main_unit (father) kills the processes? I tryed an example in wich I launch 2 thread before the main closes with the .end and they seem to "survive", but having the father alive can be useful to control purposes...
Like I said above - use a fork to create the daemon, not a thread, you can thread INSIDE but do it carefully.
4) What does the fpfork command used in the "doing a service under linux" example on your wiki? I'm a bit confused about it's behaviour, cause doing an if block with (pid=0) on it makes the program do both the if and the else in the same time...
Nope it does not. :) A fork means the program creates a copy of itself into ram with all the same variable data etc. - but as a sepperate process. In the master, fpFork returns the pid of the fork, in the newly forked slave, it returns 0 - this means lets you know which process to end and which to keep running. Now you see why I say you thread AFTER forking ?
5) How can I access classes istances (or threads) created by their father from the different childs? I got a lot of recursive declaration errors trying to do that but I failed to access them with "self.father.class" like calls.
This one I don't know, sorry. Ciao A.J. -- A.J. Venter CEO - OutKast Solutions C.C. http://www.outkastsolutions.co.za Cell: +27 83 455 9978 Fax: +27 21 413 2800 Office: +27 21 591 6766 _________________________________________________________________ To unsubscribe: mail [EMAIL PROTECTED] with "unsubscribe" as the Subject archives at http://www.lazarus.freepascal.org/mailarchives
