Rails: Finding a bug that occurs in a Resque worker. No logs to Rollbar

Question

I'm using Rails and Rollbar to track errors and Resque to handle delayed tasks. One of my workers is failing with below error in the resque GUI:

Net::ReadTimeout
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/protocol.rb:158:in `rescue in rbuf_fill'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/protocol.rb:152:in `rbuf_fill'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/protocol.rb:134:in `readuntil'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/protocol.rb:144:in `readline'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/http/response.rb:39:in `read_status_line'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/http/response.rb:28:in `read_new'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/http.rb:1412:in `block in transport_request'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/http.rb:1409:in `catch'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/http.rb:1409:in `transport_request'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/http.rb:1382:in `request'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/http.rb:1283:in `request_get'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/http.rb:479:in `block in get_response'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/http.rb:852:in `start'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/http.rb:582:in `start'
/app/vendor/ruby-2.0.0/lib/ruby/2.0.0/net/http.rb:477:in `get_response'
/app/app/services/get_json.rb:4:in `call'
/app/app/models/imdb.rb:9:in `data'
/app/app/models/customer.rb:92:in `imdb_data'
/app/app/models/customer.rb:60:in `get_external_data'
/app/app/models/customer.rb:13:in `scan'
/app/app/models/shop.rb:110:in `block in bulk_scan'
/app/app/models/shop.rb:101:in `each'
/app/app/models/shop.rb:101:in `bulk_scan'
/app/app/workers/bulk_scanner.rb:9:in `perform'

But it would be really helpful to see more robust information about the failure. Eg what were the parameters. Usually I use Rollbar for this type of thing, but it doesn't seem to be logging this error for some reason.

How would I go about fixing this bug? Because I don't really know what's triggering it? (my worker is basically looping through a whole bunch of API calls with different users, and I don't know which one is failing)

Answer 1

You can create a custom logger, and use it to record useful information to trace your problem. In your worker, add debug statements that dump out variable contents, etc.

my_log = Logger.new("log/worker.log")

def do_stuff
  my_log.info "#do_stuff"
end

Another option is to put a breakpoint in your code. You'll get an interactive shell that you can use to fiddle around.

debugger