attempt to auto-detect path of pid file (fixes sosedoff#7)

NEWS.md

@@ -14,6 +14,9 @@ Significant changes since 0.1.10.  Backwards-incompatible changes are *in bold*.
     *   Add `unicorn_options` variable which allows passing of arbitrary options to unicorn.
     *   Added `app_subdir` to support app running in a subdirectory.
     *   Updated documentation in [README](README.md) to fix inaccuracies and ambiguities.
+    *   `unicorn_pid` defaults to attempting to auto-detect from unicorn config file.
+        This avoids having to keep two paths in sync.
+        https://github.com/sosedoff/capistrano-unicorn/issues/7
     *   Also added the `unicorn:show_vars` task to make it easier to debug
         config variable values client-side.
 *   Defer calculation of `unicorn~roles`.

README.md

@@ -87,7 +87,8 @@ You can modify any of the following Capistrano variables in your `deploy.rb` con
 ### Absolute path parameters
 
 - `app_path`                - Set path to app root. Default to `current_path + app_subdir`.
-- `unicorn_pid`             - Set unicorn PID file path. Default to `#{current_path}/tmp/pids/unicorn.pid`
+- `unicorn_pid`             - Set unicorn PID file path. By default, attempts to auto-detect from unicorn config file. On failure, falls back to value in `unicorn_default_pid`
+- `unicorn_default_pid`     - See above. Default to `current_path/tmp/pids/unicorn.pid`
 - `bundle_gemfile`          - Set path to Gemfile. Default to `#{app_path}/Gemfile`
 - `unicorn_config_path`     - Set the directory where unicorn config files reside. Default to `#{current_path}/config`.
 

lib/capistrano-unicorn/capistrano_integration.rb

@@ -1,3 +1,5 @@
+require 'tempfile'
+
 require 'capistrano'
 require 'capistrano/version'
 
@@ -46,12 +48,54 @@ def self.load_into(capistrano_config)
           # If you find the following confusing, try running 'cap unicorn:show_vars' -
           # it might help :-)
           _cset(:app_path)                   { current_path + app_subdir }
-          _cset(:unicorn_pid)                { app_path + "/tmp/pids/unicorn.pid" }
           _cset(:bundle_gemfile)             { app_path + '/Gemfile' }
           _cset(:unicorn_config_path)        { app_path + '/' + unicorn_config_rel_path }
           _cset(:unicorn_config_file_path)   { app_path + '/' + unicorn_config_rel_file_path }
           _cset(:unicorn_config_stage_file_path) \
                                              { app_path + '/' + unicorn_config_stage_rel_file_path }
+          _cset(:unicorn_default_pid)        { app_path + "/tmp/pids/unicorn.pid" }
+          _cset(:unicorn_pid) do
+            extracted_pid = extract_pid_file
+            if extracted_pid
+              extracted_pid
+            else
+              logger.important "err :: failed to auto-detect pid from #{local_unicorn_config}"
+              logger.important "err :: falling back to default: #{unicorn_default_pid}"
+              unicorn_default_pid
+            end
+          end
+        end
+
+        def local_unicorn_config
+          File.exist?(unicorn_config_rel_file_path) ?
+              unicorn_config_rel_file_path
+            : unicorn_config_stage_rel_file_path
+        end
+
+        def extract_pid_file
+          tmp = Tempfile.new('unicorn.rb')
+          begin
+            conf = local_unicorn_config
+            tmp.write <<-EOF.gsub(/^ */, '')
+              config_file = "#{conf}"
+
+              # stub working_directory to avoid chdir failure since this will
+              # run client-side:
+              def working_directory(path); end
+
+              instance_eval(File.read(config_file), config_file) if config_file
+              puts set[:pid]
+              exit 0
+            EOF
+            tmp.close
+            extracted_pid = `unicorn -c "#{tmp.path}"`.rstrip
+            $?.success? ? extracted_pid : nil
+          rescue
+            return nil
+          ensure
+            tmp.close
+            tmp.unlink
+          end
         end
 
         # Check if a remote process exists using its pid file