| === sadmac_ is now known as sadmac | ||
| MarcWeber | Does it make sense to you introducing init --expected-pid=2 ? Why? I'm trying to run nixos on a vserver. I can't replace the default init so I have to run upstart using PID 2. Of course I can patch those two lines. But maybe other people do have this problem as well ? | 20:59 |
|---|---|---|
| Keybuk | Upstart depends on being pid 1 | 20:59 |
| Keybuk | and it expects the special behaviour afforded that process by the kernel | 20:59 |
| MarcWeber | That's bad news. the vserver even starts without /sbin/init.. So I can't change that so I can't use upstart without heavy patching? | 21:00 |
| MarcWeber | Keybuk: can you estimate the amount of work required to make this possible? I mean a PID 2 should be able to run jobs as well. (Maybe its killed by PID3 .. I think I must live with that..) | 21:02 |
| MarcWeber | Maybe the solution is to try yet another hosting provider.. | 21:03 |
| Keybuk | pid 2 would not have daemon process children reparented to it | 21:03 |
| Keybuk | which has always been a specific goal of upstart's to support | 21:03 |
| MarcWeber | Hmm I think I have to dive into some documentation first to understand that. | 21:04 |
| Keybuk | why can you not replace the existing pid #1 ? | 21:05 |
| MarcWeber | Cause I don't have control over pid #1. All it seems I can do is providing runlevel code. And thats pid > 1. But can send another ticket to clarify that.. | 21:06 |
| Keybuk | why don't you have control over it? | 21:06 |
| MarcWeber | because cat /proc/1/exe results in permission denied. I don't where the file is. It's a virtual server. | 21:07 |
| MarcWeber | Or do you have any idea how to find the location other then find . -name "init" (which showed only /sbin/init which isn't executed at all) | 21:08 |
| MarcWeber | If a process starts another doesn't the kernel setup a parent -> child relation automatically? | 21:09 |
| Keybuk | surely you have control over the distribution you installed? | 21:09 |
| MarcWeber | Keybuk All files but /dev/* I can't mknod | 21:10 |
| MarcWeber | I can start a repair system. This way I can access /vserver containing all files. | 21:10 |
| Keybuk | you're a nixos developer? | 21:10 |
| MarcWeber | When do you call somone a developer? I've been a contributor for over a year now. I haven't written much of the core C(++) code though. | 21:11 |
| MarcWeber | And we already talked about a similar problem a year ago. That time I tried setting up upstart-0.5. I had to patch it cause the other hosting used a kernel not providing a feature.. | 21:12 |
| Keybuk | are you attempting to replace sysvinit in nixos with Upstart? | 21:12 |
| MarcWeber | nixos has been using upstart-0.3 for years | 21:13 |
| Keybuk | and when installed into a vserver, its pid isn't 1? | 21:13 |
| MarcWeber | Eelco (core developper) told me he wants to start an upstart-0.5.1 branch now | 21:13 |
| MarcWeber | I don't know how to tell the vserver to run upstart at all :-( | 21:13 |
| Keybuk | :-/ | 21:14 |
| * Keybuk has heard of problems with vserver before | 21:14 | |
| Keybuk | I've had arguments with vserver upstream in fact | 21:14 |
| Keybuk | over things like vserver failing to provide init with the special signal handling it expects | 21:14 |
| Keybuk | which suggests that you can run upstart as init/pid #1 in a vserver | 21:14 |
| MarcWeber | Keybuk: Can you tell me briefly why I want this reparenting or can you give me some keywords so that I can google it up? | 21:15 |
| Keybuk | MarcWeber: supervision of daemon processes | 21:15 |
| MarcWeber | The first hosting provider lets me use /sbin/init. The trouble is that I can't use recent coreutils. That means that all software packages hashes would change. This means I can neither use nor provide binary packages.. So I know that some vservers can use #1. | 21:17 |
| MarcWeber | Reparenting = if a daemon dies its subprocesses are reparented to be direct childs of init so that init (upstart) can kill them ? | 21:25 |
| Keybuk | exactly | 21:36 |
| Keybuk | and more to the point | 21:36 |
| Keybuk | so init (upstart) is notified when they die | 21:36 |
| MarcWeber | So that it can restart the process. looking out wether a pid 10 still exists won't work cause the kernel might have given pid 10 to another process ? | 21:37 |
| Keybuk | no, more than that | 21:38 |
| Keybuk | upstart will never know that pid 10 has exited | 21:38 |
| MarcWeber | It could try to find pid 10 10 times a sec.. | 21:38 |
| sadmac2 | eew. | 21:38 |
| MarcWeber | But that's no option. | 21:38 |
| MarcWeber | So I'll look for yet another hosting service.. | 21:39 |
| sadmac2 | Keybuk: I have a good chunk of a replace-nih-config-with-bison patch. Its pretty ratty but worth a guided tour. How long will you be around today? | 21:41 |
| Keybuk | today is not a good day | 21:42 |
| sadmac2 | rgr | 21:43 |
| MarcWeber | What's wrong with waitpid to get notified when a child terminates? | 21:50 |
| sadmac2 | MarcWeber: only tells you /your/ children. we need to know about the /daemon/'s children. grandkids | 21:51 |
| MarcWeber | Ok. Then I was right. | 21:52 |
| Keybuk | sadmac2: ok, let's look at your patch ;) | 21:57 |
| sadmac2 | Keybuk: err... its kind of at home and in pieces. I was hoping to do it in about an hour :) | 21:58 |
| Keybuk | can I tell you my mad idea first? | 21:58 |
| sadmac2 | ghead | 21:58 |
| sadmac2 | Keybuk: still here? | 22:07 |
| Keybuk | yup | 22:09 |
| Keybuk | so you know how "initctl start" and "initctl stop" are just commands that muck around with the job state directly | 22:09 |
| Keybuk | what if they weren't? | 22:09 |
| Keybuk | by that I mean | 22:09 |
| Keybuk | if I do "stop somejob", the job stops | 22:09 |
| Keybuk | and if I reboot | 22:09 |
| Keybuk | the job is still stopped | 22:09 |
| Keybuk | and if I do "start someotherjob" to make a new copy | 22:09 |
| Keybuk | when I reboot, that is started again | 22:09 |
| sadmac2 | Keybuk: how do you handle single user mode? | 22:11 |
| Keybuk | no plans there | 22:11 |
| sadmac2 | I think you might be having those "neat when everything's running normally" type ideas. Hard to bootstrap, hard to deal with in an inconsistent state. | 22:12 |
| sadmac2 | Keybuk: actually, it could work. | 22:27 |
| sadmac2 | Keybuk: so things like single user mode would be done by just specifying which set of enabled services you want on the command line (out of a series of configured choices). start/stop would affect whichever was active | 22:28 |
| sadmac2 | so its just a matter of making /etc/init/enabled_services_foo-mode /var/lib/*/enabled_services_foo-mode | 22:29 |
| Keybuk | well | 22:29 |
| Keybuk | that's basically what I was thinking | 22:30 |
| Keybuk | start <instance> would add a file in /var/lib/init that morally said that the particular instance should be auto-started | 22:30 |
| Keybuk | (assumedly it was manual before) | 22:30 |
| Keybuk | stop <instance> would add a file saying that it should not be auto-started | 22:30 |
| Keybuk | start <creating a new instance> would create a new job file in /var/lib/init for the new instance, specifying the conditions in which it runs (from the cmdline) | 22:30 |
| sadmac2 | I assume one would add and one would remove :) | 22:31 |
| MarcWeber | What actually happens when a child of a daemon exits? | 22:42 |
| sadmac2 | MarcWeber: if the daemon is still running, then nothing. | 22:43 |
| sadmac2 | MarcWeber: if the daemon dies, then its children get inherited by pid 1 (always pid 1, whatever that may be). | 22:45 |
| MarcWeber | sadmac2: Example: mysqld dies but has still one serving process. What should happen? (same for apache or such) | 22:46 |
| MarcWeber | of course the daemon should be restarted. | 22:46 |
| sadmac2 | MarcWeber: they get reparented to pid 1, which may then wait on them | 22:47 |
| MarcWeber | When does upstart get to know about them? Whet those daemon child processes are created or when the daemon dies? | 22:48 |
| MarcWeber | I'm trying to figure out wether I neet this upstart feature or not. I mean a lot of distributions still do use a traditional init.. | 22:49 |
| sadmac2 | at the moment never :) upstart just sees them as wayward userspace processes when it inherits them. Working with kernel folks on a solution (0.5.* uses ptrace to monitor the daemon as it runs and capture its calls to fork() thus finding out that way) | 22:49 |
| sadmac2 | a service is considered dead by upstart when it has no more processes. | 22:50 |
| MarcWeber | so a traditional init does restart services to early. | 22:51 |
| sadmac2 | a traditional init doesn't restart them at all :) | 22:52 |
| sadmac2 | well it can, but for most larger things it doesn't | 22:52 |
| MarcWeber | sadmac2: I've tried it. apache is not restarted if you kill it. However writing a wget /curl cron job test running apachectl {stop,start} would take me less than a minute. | 23:12 |
| sadmac | Keybuk: I'm at home now. still interested in this code/having mad ideas? | 23:12 |
| Keybuk | sadmac: sure | 23:26 |
| sadmac | Keybuk: http://sadmac.fedorapeople.org/parse_job.y | 23:31 |
| sadmac | I don't seem to have the ignore rules right to get it to not look at generated files and otherwise do what it should, but basically that replaces parse_job.c | 23:31 |
| sadmac | then we get some makefile.am changes and some changes to the test cases to account for the slightly altered error reporting. | 23:32 |
| Keybuk | slightly altered? | 23:32 |
| sadmac | most errors end up turning into UNEXPECTED_TOKEN the way things are written. This can change though. | 23:33 |
| sadmac | (unfortunate part about that error, when isn't it true?) | 23:33 |
| Keybuk | right, I think I ran across that before with bison | 23:35 |
| Keybuk | I notice you're having token issues there | 23:35 |
| Keybuk | isn't it normal to use flex to write the lexer/tokeniser then pass that to bison? | 23:35 |
| sadmac | I kinda figured the lexer would be too simple to bother. Oops. :) | 23:36 |
| Keybuk | is there any bits of syntax that are "hard" to do this wya? | 23:36 |
| sadmac | context-sensitive keywords | 23:36 |
| Keybuk | how so? | 23:37 |
| sadmac | for example, with nih_config "start on start" is valid. the second start isn't a keyword anymore, it becomes an event name. | 23:37 |
| Keybuk | isn't that just | 23:37 |
| sadmac | its very doable, the problem is it can't be done categorically. every keyword needs a (one line) mention that it promotes to string when asked. | 23:38 |
| Keybuk | start_on := "start" "on" EVENTTREE | 23:38 |
| Keybuk | EVENTTREE := "event" | EVENTTREE "or" EVENTTREE | EVENTTREE "and" EVENTTREE | 23:38 |
| sadmac | the other thing that was hard was allowing event operators to have linebreaks BUT only inside parenthesis. My solution to that isn't final | 23:38 |
| Keybuk | err s/"event"/EVENT/ | 23:38 |
| Keybuk | EVENT := NAME ARG* | 23:38 |
| Keybuk | heh, pythonic parens ;) | 23:39 |
| Keybuk | randomly | 23:39 |
| Keybuk | it's probably quite easy to parse the syntax in lua ;) | 23:39 |
| sadmac | ugh. lua is scary. | 23:39 |
| sadmac | that doesn't solve it | 23:39 |
| sadmac | what type is NAME? | 23:39 |
| Keybuk | that's a type | 23:40 |
| sadmac | when you say "start" in bison, you declare a new type. a token with name "start" is of type "start" | 23:40 |
| Keybuk | it can be a bare word, or a single or double-quoted string | 23:40 |
| Keybuk | ARG is the same | 23:40 |
| sadmac | so what we | 23:40 |
| sadmac | what we'd need is a line like this | 23:40 |
| sadmac | STR := LITERAL_TOKEN | "start" { $$ = "start" } | "on" { $$ = "on" } | "stop"..... | 23:41 |
| sadmac | the easier, and better option is to just say "keywords are keywords" and make users quote them. | 23:42 |
| Keybuk | how do you mean? | 23:42 |
| sadmac | start on start --> syntax error | 23:42 |
| sadmac | start on "start" --> ok | 23:42 |
| Keybuk | that third one can't be start | 23:42 |
| Keybuk | it's not at the start of a line | 23:42 |
| Keybuk | keywords only appear at the beginning of a line | 23:43 |
| sadmac | Keybuk: the problem is the type | 23:43 |
| sadmac | Keybuk: when "start" appears in the bison grammar, that isn't a string | 23:43 |
| sadmac | that is a "start". | 23:43 |
| sadmac | its its own type | 23:43 |
| Keybuk | surely type depends on context? | 23:43 |
| sadmac | not for tokens | 23:44 |
| sadmac | not for the output of the lexer | 23:44 |
| sadmac | you can create the hierarchy, but its a lot of text. | 23:44 |
| sadmac | because each keyword is a different type. There's no way to apply the promotion to them categorically. | 23:44 |
| sadmac | remember, when the lexer sees "start" it has to decide what type it is | 23:45 |
| Keybuk | that sucks ;) | 23:45 |
| sadmac | and the lexer doesn't maintain state other than file position. it has no idea what came before | 23:45 |
| sadmac | Keybuk: it does... but then I could put that in and several other things and all this would still be less code than the old parse_job.c. AND there'd be no more nih_config | 23:46 |
| Keybuk | what's the difference in resulting code though? | 23:46 |
| Keybuk | and any difference in speed? | 23:47 |
| sadmac | didn't look in difference in resulting code. speed seems uncanny. tests run faster than my terminal can write the results. | 23:47 |
| sadmac | the resulting code isn't that interesting here, since you never read it. they put in all the #line macros so the errors are reported against the original .y | 23:49 |
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