[9front] plumber: remove $plumbsrv, add optional srvname, usage check

[9front] plumber: remove $plumbsrv, add optional srvname, usage check

[qwx]

Plumber both posts a service to /srv and sets a $plumbsrv environment
variable.  Our libplumb no longer uses $plumbsrv and nothing else
does.  It's a silly hack;  rc doesn't update /env immediately, and
scripts, which for instance set up subrios, cannot rely on it to
clean up the plumber at the end.

Instead, add the option to specify a srvname, actually check for some
common errors and print a usage string.

Thanks to Ori for input and a preliminary patch.  Thoughts?

Cheers,
qwx

diff 87a823332f9eaa4ff1e72f8524f6e59d1cc4f407 uncommitted
--- a//sys/man/4/plumber
+++ b//sys/man/4/plumber
@@ -6,6 +6,9 @@
 [
 .B -p
 .I plumbing
+] [
+.B -s
+.I srvname
 ]
 .SH DESCRIPTION
 The
@@ -31,11 +34,17 @@
 and a set of output
 .I ports
 for dispatching messages to applications.
+.PP
 The service is also published as a
 .IR srv (4)
-file, named in
-.BR $plumbsrv ,
+file,
+.IR srvname ,
 for mounting elsewhere.
+By default, its name is a dot-separated concatenation
+of the program's name and a process id.
+A different one can be specified via the
+.B -s
+option.
 .PP
 Programs use
 .B write
--- a//sys/src/cmd/plumb/fsys.c
+++ b//sys/src/cmd/plumb/fsys.c
@@ -218,9 +218,10 @@
 	clock = getclock();
 	if(cexecpipe(&mntfd, &srvfd) < 0)
 		error("can't create pipe: %r");
-	sprint(srvfile, "/srv/plumb.%s.%d", user, getpid());
-	if(putenv("plumbsrv", srvfile) < 0)
-		error("can't write $plumbsrv: %r");
+	if(srvname == nil)
+		snprint(srvfile, sizeof(srvfile), "/srv/plumb.%s.%d", user, getpid());
+	else
+		snprint(srvfile, sizeof(srvfile), "/srv/%s", srvname);
 	fd = create(srvfile, OWRITE|OCEXEC|ORCLOSE, 0600);
 	if(fd < 0)
 		error("can't create /srv file: %r");
--- a//sys/src/cmd/plumb/plumber.c
+++ b//sys/src/cmd/plumb/plumber.c
@@ -15,6 +15,7 @@
 int	printerrors=1;
 jmp_buf	parsejmp;
 char	*lasterror;
+char	*srvname;
 
 void
 makeports(Ruleset *rules[])
@@ -38,6 +39,13 @@
 }
 
 void
+usage(void)
+{
+	fprint(2, "usage: %s [-p plumbfile] [-s srvname]\n", argv0);
+	exits("usage");
+}
+
+void
 threadmain(int argc, char *argv[])
 {
 	char buf[512];
@@ -48,7 +56,13 @@
 
 	ARGBEGIN{
 	case 'p':
-		plumbfile = ARGF();
+		plumbfile = EARGF(usage());
+		break;
+	case 's':
+		srvname = EARGF(usage());
+		break;
+	default:
+		usage();
 		break;
 	}ARGEND
 
--- a//sys/src/cmd/plumb/plumber.h
+++ b//sys/src/cmd/plumb/plumber.h
@@ -92,3 +92,4 @@
 char		*lasterror;
 char		**ports;
 int		nports;
+char		*srvname;

Re: [9front] plumber: remove $plumbsrv, add optional srvname, usage check

[umbraticus]

yes, please. named srv has long been needed

Re: [9front] plumber: remove $plumbsrv, add optional srvname, usage check

[sirjofri]

I didn't look at the patch, but yes, please do this.

In the past I sometimes had to rename the srv file...

Re: [9front] plumber: remove $plumbsrv, add optional srvname, usage check

[ori]

Quoth qwx@sciops.net:
> Plumber both posts a service to /srv and sets a $plumbsrv environment
> variable.  Our libplumb no longer uses $plumbsrv and nothing else
> does.  It's a silly hack;  rc doesn't update /env immediately, and
> scripts, which for instance set up subrios, cannot rely on it to
> clean up the plumber at the end.
> 
> Instead, add the option to specify a srvname, actually check for some
> common errors and print a usage string.
> 
> Thanks to Ori for input and a preliminary patch.  Thoughts?
> 
> Cheers,
> qwx
> 

Since this removes '$srvname': is anyone using it at the moment?


otherwise, this looks good to me.

Re: [9front] plumber: remove $plumbsrv, add optional srvname, usage check

[kvik]

Quoth qwx@sciops.net:
> It's a silly hack;  rc doesn't update /env immediately, and
> scripts, which for instance set up subrios, cannot rely on it to
> clean up the plumber at the end.

Adding also the usual -m mount flag to plumber would perhaps solve
this problem for you more naturally.

Re: [9front] plumber: remove $plumbsrv, add optional srvname, usage check

[qwx]

> Quoth qwx@sciops.net:
> > It's a silly hack;  rc doesn't update /env immediately, and
> > scripts, which for instance set up subrios, cannot rely on it to
> > clean up the plumber at the end.
> 
> Adding also the usual -m mount flag to plumber would perhaps solve
> this problem for you more naturally.

I'm not sure I understand what you mean.  My problem is that a
service file is posted which I can't remove if I don't know its
name.  The mount point on the other hand is always /mnt/plumb.

Did I understand you correctly?

Thanks,
qwx

Re: [9front] plumber: remove $plumbsrv, add optional srvname, usage check

[kvik]

Quoth qwx@sciops.net:
> My problem is that a service file is posted which I can't remove
> if I don't know its name.

My point is that with the -m flag you might not need to post the
srv file to start with and the plumber process would go away
together with the namespace.

This assumes you don't need the srv file.
You might.
I usually don't.

Re: [9front] plumber: remove $plumbsrv, add optional srvname, usage check

[kvik]

> Quoth qwx@sciops.net:
The mount point on the other hand is always /mnt/plumb.

Wow, I'm drunk and dumb and stupid. Yes, of course the -m flag
alone doesn't change anything.

The option I implied is only posting the srv file when requested
whence you wouldn't need to clean it up afterwards in the usual
case.

Sorry for confusion.

Re: [9front] plumber: remove $plumbsrv, add optional srvname, usage check

[qwx]

> My point is that with the -m flag you might not need to post the
> srv file to start with and the plumber process would go away
> together with the namespace.
[...]
> The option I implied is only posting the srv file when requested
> whence you wouldn't need to clean it up afterwards in the usual
> case.

Yeah, I see what you mean.  Right now, the plumber doesn't have an
option not to post a srv file, and I'm not sure -m will work nicely
because libplumb relies on it being mounted there.

It makes sense that $plumbsrv be ejected, and I don't see anyone
or anything using it;  on the other hand, I'm not sure we can only
optionally post a service file without breaking people's setups.
I think being able to specify another name is enough.  The program
doesn't use postmountsrv(2) or other srv(2) shit, so we'd have to
add more code for an option to disable this or refactor or
something, I don't know.

I propose that we just push the patch as is unless someone sees a
better solution.

Thanks!
qwx

Re: [9front] plumber: remove $plumbsrv, add optional srvname, usage check

[qwx]

> Yeah, I see what you mean.  Right now, the plumber doesn't have an
> option not to post a srv file, and I'm not sure -m will work nicely
> because libplumb relies on it being mounted there.

That's bullshit, it's only the default (cf. plumb(2)).  Sorry!

qwx

Re: [9front] plumber: remove $plumbsrv, add optional srvname, usage check

[qwx]

Pushed as is.

Thanks for the input, everyone!

qwx