How to properly diagnose a 500 error (Rails, Passenger, Nginx, Postgres) - ruby-on-rails

I'm having a real tough time diagnosing a 500 error from my application running in production. I've had it working before, but after re-deploying via Capastrano I am unable to get it going.
Here are the facts:
The server is setup with nginx + passenger, and I'm using
PostgreSQL.
Static assets are working properly, as in I'm able to access them just fine in a browser.
I can access the rails console via RAILS_ENV=production bundle exec rails console and perform Active Record actions (like
retrieving data from the db).
Within console, I can run app.get("/"), which returns a 500 error as well (after first showing the query that was run to load
the model).
The production.log file is never written to. I've set permissions 777 on it just for the hell of it. I've also set the log level to
:debug with nothing to show for it.
The nginx log (which passenger also uses) shows no indication of errors, it just notifies about cache misses.
Because nothing of use is being logged, I have no idea what to do here. I've tried setting full permission on the entire app directory with no help. Restarted the server multiple times, nothing. The database is there and rails can clearly communicate with it. I'm not sure what I did to get it to run the first time around. I just don't know why rails isn't outputting anything to the log.

Okay, I figured this out. The app ran fine in development mode, so I knew something production-specific was screwing it up. I went into config/environments/production.rb and changes these settings:
# Full error reports are disabled and caching is turned on
config.consider_all_requests_local = false # changed from true
config.action_controller.perform_caching = true # changed from false
And then after restarting passenger, rails showed me the error w/ stacktrace. Turns out I was forgetting to precompile the asset pipeline!

Things to check
1) Are you sure you are running in production environment?
Check to see if any entries are in the development.log file
2) Set up your app to email you when a 500 error occurs with a full stack trace. I use the Exception Notifier gem but there are plenty of other solutions for this.
3) When checking your app in the console are you sure you are starting the console in production mode? It is possible that the app is not starting up at all and you just forgot to set the production param thereby thinking that the app runs fine when it doesn't.
4) Are you getting an nginx 500 error or the Rails 500 error? If nginx then it is likely that your app is not starting at all and highly unlikely that you will get any rails error in your log file. The assets are static files and navigating to them proves nothing other than that they exist.
5) Are you sure you are checking the right folder on the server? Sounds really stupid but capistrano could be deploying the app to a folder that is different to the folder that nginx is looking for for your app so double check both the folder capistrano is deploying to and the folder that nginx is looking for are the same.
Just a suggestion, I would use puma rather than passenger. It's awesome with nginx.

My problem is passenger's log file (error.log) has nothing. Then it's a rotation log issue. Run
passenger-config reopen-logs
solved my problem. More.

Have you tried running in development mode to see if the error reports itself?

Related

rails 4.2 capistrano 3 Ubuntu nginx puma, getting routing error/no assets shows up

After following this tutorial, I tried was able to set up a rails application on an ec2 Ubuntu instance, running nginx web server and puma app server, deployed with capistrano 3. However, none of my assets are showing up, and I'm getting routing errors for basic functions of the Devise gem such as logging out. The chrome dev tool console shows 404 errors for the compiled application.css and application.js files.
I think the assets are there because if I ssh into the instance and go to the folder where my app is, I can see a bunch of files under public/assets. Also, if I check the capistrano logs, I can find the line bundle exec rake assets:precompile, and the status for that is successful. I tried things like going into the production.rb file and changing config.serve_static_files = ENV['RAILS_SERVE_STATIC_FILES'].present? to config.serve_static_files = true
but still no assets. I think the biggest suspect is that there is some sort of routing error, because I don't really understand how web servers, app servers, and aws instances interact with each other. Could anyone point me in the right direction on debugging this? If you need to see a specific config file please comment below.
Ok it turns out all I had to do is copy the secrets.yml from the local repo for my app to the shared folder that is in [my_app_name]/shared/config. So my app didn't know where to look for the secret key base.
Although I'm still confused on why not having the secret.yml would prevent assets from served...

Cloned a RoR server and now getting "we're sorry, but something went wrong error"

I have a working RoR app that's running on Ubuntu Server, served by Nginx and Unicorn. It's using a local postgres database. I also think it's running on Sinatra instead of rails, but I'm too new to RoR to be able to say for certain.
I am attempting to create a development copy of the app to do some testing with. I'm able to do so using the source code, bundle install, and then running webbrick on my desktop. However, my developer wants to duplicate the environment that the actual production copy is running in. I cloned the server hosting the application, but when I browse to the server I get the dreaded "We're sorry, but something went wrong" error.
Here's what I've checked so for. I looked at the log files in the app/logs directory, and those haven't been updated in the last 6 days, so I suspect nothing relevant will be in them. If I run "service nginx status", it appears to be started. The database is running, and I can access it through the psql interface. Again, I'm pretty much an RoR newb... I was hoping one of you kind folks might give me some advice. Where should I look next? I'm sure it's something simple that I'm just overlooking. Thanks in advance!
In your config > environments > production.rb file change the consider_all_requests_local variable to true.
config.consider_all_requests_local = true
FYI, unicorn was not starting along with NGINX. I was able to script unicorn to start on boot, and this fixed my problem.

check 500 internal server error in production mode in rails 3.2

I have my app in production mode in my linode account and I get in one page a 500 internal server error the message:
We're sorry, but something went wrong.
However in my development environment works fine this page.
How can I debug this error?
How can I see the error origin in my production mode?
I want that rails show errors in production mode.
How can I do it?
Thank you!
If you have access to ssh, log in to your server via ssh and go to your rails log directory, which is inside your rails directory.
Once you are there run the command tail production.log . If this doesn't give you enough information you can also do a tail -n100 production.log (gives you last hundred lines of the production log).
If you have deployed via heroku, then you can access the logs by running heroku logs in your local console. (more information here https://devcenter.heroku.com/articles/logging)
I also find it helpful to use the exception_notification gem https://github.com/rails/exception_notification when running in production, as it emails you a stacktrace when an error occurs. Plenty of others also use Hoptoad (http://hoptoadapp.com/) or Exceptional (http://www.exceptional.io/) however i prefer the simple exception_notification gem.
Also, in some rare occasions when i can't trace the error as a final measure i sometimes open up port 3000 temporarily on the remote server firewall and cd to the rails project and run rails server production with the log level set to debug in config/environments/production.rb so i can see the error in the console, and then close off the port when i have finished.
Hope that helps.
tail -n100 production.log
will only show the last 100 lines of the log file. Just in case you want to see the log running in real time.
use this
tail -1000f log/production.log

No log messages in production.log

I wrote a demo HelloWorld Rails app and tested it with WEBrick (it doesn't even use a DB, it's just a controller which prints "hello world"). Then I tried to deploy it to a local Apache powered with Passenger. In fact this test is just to get Passenger working (it's my first deploy on Apache). Now I'm not even sure that Passenger works, but I don't get any error on the Apache side.
When I fire http://rails.test/ the browser shows the Rails 500 error page - so I assume that Passenger works. I want to investigate the logs, but it happens that production.log is empty! I don't think it's a permission problem, because if I delete the file, it is recreated when I reload the page. I tried to change the log level in conf/environments/production.rb, tried to manually write to log file with Rails console production and
Rails.logger.error('asdf')
it returns true but nothing gets written to production.log. The path (obtained per Rails.logger.inspect) is correct, and I remark that the file is recreated if I manually remove it. How can I know what's going on?
(I already checked the Apache logs, plus I set the highest debug level for Passenger but it seems a Rails problem, so is not logged by the server)
Assuming you're running Rails 3.2.1, this is a bug. It was patched in 3.2.2.
If you can't upgrade to 3.2.2 for any reason, this comment on GitHub has a workaround:
# config/initializers/patch_rails_production_logging.rb
Rails.logger.instance_variable_get(:#logger).instance_variable_get(:#log_dest).sync = true if Rails.logger
Setting this works on Rails 3.2.11:
Rails.logger = ActiveSupport::BufferedLogger.new(Rails.root.join("log","production.log"))

My Rails app is returning HTTP 500 for all its URLs, but nothing shows up in the log file. How can I diagnose the problem?

I have a Rails app that is running on a production server with Apache and Phusion Passenger. The app works fine locally when using Mongrel, but whenever I try to load a URL on the production server, it returns HTTP 500. I know the server is working properly, because I can get the static elements of the application (e.g., JavaScript files, stylesheets, images) just fine. I've also checked the Passenger status and it is loading the app (it must be, since the app's 500 Internal Server Error page is returned, not just the default Apache one). Also, when I load the app via script/console production and do something like app.get("/"), 500 is also returned.
The problem is that there is nothing in the log files to indicate the problem. production.log is empty. The Apache error logs show no problems with Apache, either. I'm stumped as to what's going on and I'm not sure how to diagnose the problem.
I know I may have been a bit vague, but can anyone give a suggestion on what the problem may be? Or at least a way I can go about diagnosing it?
The answer for this specific situation was a problem with my app. One of the model classes used a different database connection than the rest of the app. This database connection was not configured properly. I think the reason why nothing was written to the log files is that Rails bailed out without having any idea what to do.
Since it may be helpful for others to see how I diagnosed this problem, here was my thought process:
The issue couldn't be with Apache: no errors were written into the Apache log files.
The issue probably wasn't with Passenger: Passenger wasn't writing any errors to the Apache log file, and it seemed to be loading my app properly, since passenger-status showed it as loaded and it was display my app's 500 Internal Server Error page (not the default Apache one).
From there I surmised that it must be something broken in my app that happened very early on in the initialization phase, but wasn't something that caused the app to completely bail and throw an exception. I poked around in the Phusion Passenger Google Group, and ultimately stumbled upon this helpful post, which suggested that the error may be a database connectivity issue. Sure enough, removing this misconfigured database and all references to it made the app work!
Have you tried running the app locally using Passenger?
Try running the application locally on Mongrel in Production mode, to make sure that there's no weird issues with that particular environment. If that works, then you know that it's not an issue with your codebase. Since your static components are being served properly, that tells me that Apache is working fine. The only gear in the system left is Passenger. At this point, I would say it's an improperly configured Passenger. You should post up your Passenger config file, and ask the question on ServerFault.
A couple of things to try :
Have you gone though the following from the docs:
6.3.7. My Rails application’s log file is not being written to
There are a couple things that you
should be aware of:
By default, Phusion Passenger runs Rails applications in production
mode, so please be sure to check
production.log instead of
development.log. See RailsEnv for
configuration.
*
By default, Phusion Passenger runs Rails applications as the owner
of environment.rb. So the log file can
only be written to if that user has
write permission to the log file.
Please chmod or chown your log file
accordingly.
See User switching (security) for details.
If you’re using a RedHat-derived Linux
distribution (such as Fedora or
CentOS) then it is possible that
SELinux is interfering. RedHat’s
SELinux policy only allows Apache to
read/write directories that have the
httpd_sys_content_t security context.
Please run the following command to
give your Rails application folder
that context:
Have you checked your vhost or httpf.conf file ? Do you have any logging directives ?
Check the top level apache log file
Try setting PassengerLogLevel to 1 or 2 or 3, as shown here http://www.modrails.com/documentation/Users%20guide.html#_passengerloglevel_lt_integer_gt
Do you have any rack apps installed ?
My suggestion would be to go right back to "Hello World" land and create the smallest possible Ruby example application and upload it to see if there is a problem with Passenger or Ruby on the server.
May be a silly suggestion but I suggest you start by increasing the logging levels on production while you are testing. Do this in config/environments/production.rb and use:
config.log_level = :debug
This should at least get you some sort of backtrace so you can start to find the problem.
If you still get nothing - you may find that you have an issue with something as simple as a missing gem/plugin on your production server. That sort of thing may well manifest as a "500" error and just not be very verbose for you.
Can you run the test suite on your production server?

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