Use SIGHUP to dynamically reload an fcgi process without restarting it. Refactored dispatch.fcgi so that the RailsFCGIHandler is in the lib dir.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@1565 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

1 files changed, 112 insertions, 0 deletions

diff --git a/railties/lib/fcgi_handler.rb b/railties/lib/fcgi_handler.rb
new file mode 100644
index 0000000000..f615ff6d34
--- /dev/null
+++ b/railties/lib/fcgi_handler.rb
@@ -0,0 +1,112 @@
+require 'fcgi'
+require 'logger'
+require 'dispatcher'
+
+class RailsFCGIHandler
+  attr_reader :when_ready
+  attr_reader :processing
+
+  def self.process!
+    new.process!
+  end
+
+  def initialize(log_file_path = "#{RAILS_ROOT}/log/fastcgi.crash.log")
+    @when_ready = nil
+    @processing = false
+
+    trap("HUP",  method(:restart_handler).to_proc)
+    trap("USR1", method(:trap_handler).to_proc)
+
+    # initialize to 11 seconds ago to minimize special cases
+    @last_error_on = Time.now - 11
+
+    @log_file_path = log_file_path
+    dispatcher_log(:info, "starting")
+  end
+
+  def process!
+    mark!
+
+    FCGI.each_cgi do |cgi| 
+      if when_ready == :restart
+        restore!
+        @when_ready = nil
+        dispatcher_log(:info, "restarted")
+      end
+
+      process_request(cgi)
+      break if when_ready == :exit
+    end
+
+    dispatcher_log(:info, "terminated gracefully")
+
+  rescue SystemExit => exit_error
+    dispatcher_log(:info, "terminated by explicit exit")
+
+  rescue Object => fcgi_error
+    # retry on errors that would otherwise have terminated the FCGI process,
+    # but only if they occur more than 10 seconds apart.
+    if !(SignalException === fcgi_error) && Time.now - @last_error_on > 10
+      @last_error_on = Time.now
+      dispatcher_error(fcgi_error, "almost killed by this error")
+      retry
+    else
+      dispatcher_error(fcgi_error, "killed by this error")
+    end
+  end
+
+  private
+    def logger
+      @logger ||= Logger.new(@log_file_path)
+    end
+
+    def dispatcher_log(level, msg)
+      time_str = Time.now.strftime("%d/%b/%Y:%H:%M:%S")
+      logger.send(level, "[#{time_str} :: #{$$}] #{msg}")
+    rescue Object => log_error
+      STDERR << "Couldn't write to #{@log_file_path.inspect}: #{msg}\n"
+      STDERR << "  #{log_error.class}: #{log_error.message}\n"
+    end
+
+    def dispatcher_error(e,msg="")
+      error_message =
+        "Dispatcher failed to catch: #{e} (#{e.class})\n" +
+        "  #{e.backtrace.join("\n  ")}\n#{msg}"
+      dispatcher_log(:error, error_message)
+    end
+
+    def trap_handler(signal)
+      if processing
+        dispatcher_log :info, "asked to terminate ASAP"
+        @when_ready = :exit
+      else
+        dispatcher_log :info, "told to terminate NOW"
+        exit
+      end
+    end
+
+    def restart_handler(signal)
+      @when_ready = :restart
+      dispatcher_log :info, "asked to restart ASAP"
+    end
+
+    def process_request(cgi)
+      @processing = true
+      Dispatcher.dispatch(cgi)
+    rescue Object => e
+      raise if SignalException === e
+      dispatcher_error(e)
+    ensure
+      @processing = false
+    end
+
+    def mark!
+      @features = $".clone
+    end
+
+    def restore!
+      $".replace @features
+      Dispatcher.reset_application!
+      ActionController::Routing::Routes.reload
+    end
+end