Troubleshooting tips for getting Apache/RailsApp/Dreamhost

Hi,

Background: I’m currently stuck getting my basic rails application
working on dreamhost. I have gone throught the doco. Note that I can
via my unix account run “ruby script/server” and get the application
working via webbrick. The problem I am having is that trying to go to
the app via the normal apache approach my browser just sits and spins
with nothing coming back.

Question: Are there any good trouble-shooting tips on how I can
test/prove for myself where a potential problem may lie in terms of
ensuring the dreamhost apache server is correctly picking up my config,
and then triggering ruby appropriately and runnign my rails application
(I’m not really sure how this works)

The key files from what I can gather are:

  • .htaccess: So I’m guessing this is what the dreamhost apache server
    picks up on for configuration - I’ve made the recommended adjustments
    here to get redirects to (a) dispatch.fcgi script and
    (b) make sure it’s executable
  • the “dispatch.fcgi” script

Just understanding how key flow concepts of a URL request coming into my
dreamhost domain and how it triggers things would be great, and then
pointers on how to faultfind/monitor things to try to find out at which
points things are working properly.

Thanks in advance

You’re on the right track, in that those are the most likely things
to try.

But here are lots of others. Really triple check your config files,
as small typos, line ending differences, or even extra returns (in
YAML) could be causing the problem.

http://wiki.dreamhost.com/index.php/Ruby_on_Rails

        - dan


Dan K. mailto:[email protected]
http://www.dankohn.com/ tel:+1-415-233-1000

Tks Dan - I’ll double check these things.

I was really hoping to learn more about how to do more “white box”
fault-finding rather than keep trying things until the system works. My
best guess is to start by reading up on how FastCGI is configured and
works within Apache, and then how this passes requests or kicks ruby
into gear when it needs to. This might then give me leads on where the
monitor points might be for things like (a) did the request get to
apache, (b) did apache pass it in to FastCGI, © did FastCGI try to
engage Ruby etc, if this makes sense.

Any leads/ideas on what some good monitoring points are here from anyone
would be great, or suggestions on what I shoudl be reading up on to
learn how this this stuff works for myself.

thanks & cheers
Greg

Dan K. wrote:

You’re on the right track, in that those are the most likely things
to try.

But here are lots of others. Really triple check your config files,
as small typos, line ending differences, or even extra returns (in
YAML) could be causing the problem.

http://wiki.dreamhost.com/index.php/Ruby_on_Rails

        - dan


Dan K. mailto:[email protected]
http://www.dankohn.com/ tel:+1-415-233-1000

Greg H. wrote:

…(a) did the request get to
apache, (b) did apache pass it in to FastCGI, © did FastCGI try to
engage Ruby etc, if this makes sense.

Any leads/ideas on what some good monitoring points are here from anyone
would be great, or suggestions on what I shoudl be reading up on to
learn how this this stuff works for myself.

a - look in the apache logs under ~/logs/site.name/http. If there are
entries in error.log, apache at least tried to start your fcgi process

b - look in rails_app_dir/log/ in fastcgi.crash.log. If there are
entries in there, apache started your fcgi process

c - look in rails_app_dir/log/ in production.log if there are entries in
there, your rails app tried to do something.

Hope this helps!

–Al Evans

On 7/22/06, Greg H. [email protected] wrote:

would be great, or suggestions on what I shoudl be reading up on to
learn how this this stuff works for myself.

The best way to monitor what apache is doing, aside from strace, is
its error log. Especially if you set LogLevel debug, though don’t
leave that on as your logs will grow quickly.

Which version of apache are you using? I’ve used mod_fcgid (not
mod_fastcgi) with apache 2.0 and 2.2 to good effect.

Did you enable FastCGI in the Dreamhost control panel?

https://panel.dreamhost.com/
then click Managed Domains
Web Hosting, edit

PHP Version: 5.1.2 4.4.2
Extra Web Security? (highly recommended)
FastCGI Support? (advanced)

thanks Guys - excellent tips - I’ve got things working (see below)

Jon - re “Did you enable FastCGI in the Dreamhost control panel?”
==> Yep I did this for the subdomain I’m using for the app. I did
notice that my main domain itself I HAD NOT enabled FastCGI. After I
enable this on the parent domain as well this basically got things
working :slight_smile:

Al - Thanks for the fault finding tips. This was exactly what I was
trying to find out.

Vincent - Actually I’m not exactly sure on Dreamhost how to confirm what
version of apache is actually running. Things like ps & top seemed to
be locked down so you can only see your own processes. :frowning: - but then
again I’m only a novice re unix. I can see there seems to be an apache
and a apache2 directory on the machine.

Just a point of interest I see under top there are 3 ruby processes
running. I’m guessing these might be 3 identical ruby interpretters
ready to take a request that FastCGI pools? Just guessing, I’ll have
to read up on FastCGI and ruby and how this works. I have already read
about potential zombie processes associated with FastCGI that one has to
kill off from time to time too.

Thanks again
Greg

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