[rrd-users] Re: RRDs::graph and mod_perl

[Todd Caine]

Philip,

I've been working on doing the same thing.  I wanted to have a mod_cgi or
mod_perl script generate images based on the arguments passed to it so that
I could use the script in the <IMG SRC=script.cgi?args> tags.  I actually
tried it with FastCGI and Apache first with no success.  I could run it from
the command line and it would send the output in binary format to stdout.
When I tried to run it under Apache, the output would get sent to my
error_log file.  Weird.  I then tried a mod_perl script to do that same
thing but this time there was no data at all.  I went the open source
conference in Monterey, CA and spoke with Doug MacEachern, the man behind
mod_perl, and he said that I should try to build Perl with the sfio
library.  I haven't had the chance to try it yet, but it's worth a shot.
Here is exactly what I was told:

The output of system(), exec(), and open(PIPE, "|program") calls will not be
sent to the browser unless you Perl was configured with sfio.  You can use
backticks as a possible workaround, but you're throwing performance out the
window either way.

Hope this helps.  Let me know if you try the sfio route.  I would greatly
appreciate it.

Ciao,
TOdd


Philip Molter wrote:

> I'm using RRDs with mod_perl on a Solaris 8 box with
> Apache/mod_perl and perl 5.6.0.  The call to RRDs::graph is made
> with various arguments to print to a file on STDOUT.  RRDs reports
> no error, but no graph information is sent to STDOUT.  This process
> works fine without mod_perl.  I've attached the part of a truss
> output where the problem appears to be occurring.  Any ideas?  I
> know I could output to a temporary file, print the contents of the
> temporary file, and then unlink the file (how Bronc does it), but
> that's extremely inefficient.
>
> Any ideas?
>
> Philip
>
> ps. filenames have been changed to protect the innocent
>
> -----TRUSS OUTPUT-----
> # Printing out debug before the graph call begins
> 10909:  write(2, " -\n - a P N G\n - h   1".., 1140)    = 1140
> 10909:  write(2, "\n", 1)                               = 1
> 10909:  time()                                          = 965141926
> 10909:  time()                                          = 965141926
> 10909:  time()                                          = 965141926
> 10909:  open("CPU-cpu.rrd", O_RDONLY)  = 6
> 10909:  fstat64(6, 0xFFBEE220)                          = 0
> 10909:  ioctl(6, TCGETA, 0xFFBEE1AC)                    Err#25 ENOTTY
> 10909:  read(6, " R R D\0 0 0 0 1\0\0\0\0".., 8192)     = 8192
> 10909:  llseek(6, 0, SEEK_CUR)                          = 8192
> 10909:  lseek(6, 3569352, SEEK_SET)                     = 3569352
> 10909:  lseek(6, 196296, SEEK_SET)                      = 196296
> 10909:  read(6, " @ %A6AE9A06 0F8 @  87BB".., 8192)     = 8192
> 10909:  read(6, " @11BE z v\b E ` @10FC m".., 8192)     = 8192
> 10909:  llseek(6, 0xFFFFFFFFFFFFE420, SEEK_CUR)         = 205544
> 10909:  close(6)                                        = 0
> 10909:  brk(0x0060B000)                                 = 0
> 10909:  brk(0x00625800)                                 = 0
> 10909:  ioctl(1, TCGETA, 0xFFBEDFDC)                    Err#6 ENXIO
> 10909:  fstat64(1, 0xFFBEE050)                          = 0
> 10909:  brk(0x00641000)                                 = 0
> 10909:  brk(0x0065D800)                                 = 0
> 10909:  write(2, " g r a p h :   W e   p r".., 31)      = 31
> 10909:  write(2, "\n", 1)                               = 1
> # Printing out debug after the graph call finishes
>
> * Philip Molter
> * Data Foundry International
> * http://www.datafoundry.net/
> * philip at datafoundry.net
>
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 <!-- Todd Caine - tcaine at eli.net
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