# sigdump

Server applications (like Rails app) cause performance problems, deadlock or memory swapping from time to time. But it's painful to reproduce such kind of problems. If we can get information from a running process without restarting it, it's really helpful.

`sigdump` gem installs a signal handler which dumps backtrace of running threads and number of allocated objects per class.

If GC profiler is enabled (`GC::Profiler.enable` is called), it also dumps GC statistics.

## Install

Just install one gem `sigdump` and require `sigdump/setup`:

    gem 'sigdump', :require => 'sigdump/setup'

## Usage

Send `SIGCONT` signal to dump backtrace and heap status to `/tmp/sigdump-<pid>.log`:

    $ kill -CONT <pid>

Set `SIGDUMP_SIGNAL` environment variable to change the signal (default: SIGCONT).

Set `SIGDUMP_PATH` environment variable to change the output path (default: /tmp/sigdump-\<pid\>.log). You can set "-" here to dump to STDOUT, "+" to dump to STDERR.

## Sample outout

    $ cat /tmp/sigdump-9218.log
    Sigdump at 2013-04-24 16:57:12 +0000 process 9218 (unicorn worker[3] -E staging -c /etc/unicorn/staging.rb -E staging)
      Thread #<Thread:0x00000001424518> status=run priority=0
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/sigdump-0.1.0/lib/sigdump.rb:32:in `dump_backtrace'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/sigdump-0.1.0/lib/sigdump.rb:19:in `block in dump_all_thread_backtrace'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/sigdump-0.1.0/lib/sigdump.rb:18:in `each'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/sigdump-0.1.0/lib/sigdump.rb:18:in `dump_all_thread_backtrace'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/sigdump-0.1.0/lib/sigdump.rb:9:in `block (2 levels) in install_thread_dump_handler'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/sigdump-0.1.0/lib/sigdump.rb:91:in `open'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/sigdump-0.1.0/lib/sigdump.rb:91:in `_open_dump_path'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/sigdump-0.1.0/lib/sigdump.rb:7:in `block in install_thread_dump_handler'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/unicorn-4.3.1/lib/unicorn/http_server.rb:626:in `call'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/unicorn-4.3.1/lib/unicorn/http_server.rb:626:in `select'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/unicorn-4.3.1/lib/unicorn/http_server.rb:626:in `worker_loop'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/unicorn-4.3.1/lib/unicorn/http_server.rb:487:in `spawn_missing_workers'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/unicorn-4.3.1/lib/unicorn/http_server.rb:137:in `start'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/gems/unicorn-4.3.1/bin/unicorn:121:in `<top (required)>'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/bin/unicorn:23:in `load'
          /srv/staging/current/vendor/bundle/ruby/1.9.1/bin/unicorn:23:in `<main>'
      Built-in objects:
       367,492: TOTAL
       208,193: T_STRING
        61,817: T_ARRAY
        37,343: T_DATA
        28,293: T_NODE
        10,678: T_OBJECT
         6,385: T_HASH
         5,957: T_CLASS
         2,300: T_ICLASS
         2,184: T_REGEXP
         1,547: T_MODULE
           900: T_FLOAT
           677: T_STRUCT
           497: T_BIGNUM
           432: T_MATCH
           251: T_RATIONAL
            29: T_FILE
             8: FREE
             1: T_COMPLEX
      All objects:
       207,335: String
        32,987: Array
        28,665: RubyVM::InstructionSequence
         5,863: Hash
         3,759: RubyVM::Env
         3,680: Proc
         2,338: Class
         2,184: Regexp
         1,632: MIME::Type
         1,547: Module
         1,040: Gem::Version
           982: Gem::Requirement
           945: Float
           920: Journey::Nodes::Cat
           804: Time
           660: Gem::Dependency
           497: Bignum
      ...
      String 7,556,137 bytes
       Array 821 elements
        Hash 90 pairs