Made dispatch.fcgi more robust by catching fluke errors and retrying unless its a permanent condition. [Jamis Buck] Allow graceful exits for dispatch.fcgi processes by sending a SIGUSR1. If the process is currently handling a request, the request will be allowed to complete and then will terminate itself. If a request is not being handled, the process is terminated immediately (via #exit). This basically works like restart graceful on Apache. [Jamis Buck]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@1284 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

2 files changed, 53 insertions, 6 deletions

diff --git a/railties/CHANGELOG b/railties/CHANGELOG
index 5664206ed0..f98c57459d 100644
--- a/railties/CHANGELOG
+++ b/railties/CHANGELOG
@@ -1,5 +1,10 @@
 *SVN*
 
+
+* Allow graceful exits for dispatch.fcgi processes by sending a SIGUSR1. If the process is currently handling a request, the request will be allowed to complete and then will terminate itself. If a request is not being handled, the process is terminated immediately (via #exit). This basically works like restart graceful on Apache. [Jamis Buck]
+
+* Made dispatch.fcgi more robust by catching fluke errors and retrying unless its a permanent condition. [Jamis Buck]
+
 * Added console --profile for profiling an IRB session #1154 [bitsweat]
 
 * Changed console_sandbox into console --sandbox #1154 [bitsweat]
diff --git a/railties/dispatches/dispatch.fcgi b/railties/dispatches/dispatch.fcgi
index 683a61f4c9..34a99a7105 100755
--- a/railties/dispatches/dispatch.fcgi
+++ b/railties/dispatches/dispatch.fcgi
@@ -1,27 +1,69 @@
 #!/usr/local/bin/ruby
 
+def dispatcher_log(level, path,msg)
+  Logger.new(path).send(level, msg)
+rescue Object => log_error
+  STDERR << "Couldn't write to #{path}: #{msg}"
+end
+
 def dispatcher_error(path,e,msg="")
   error_message =
     "[#{Time.now}] Dispatcher failed to catch: #{e} (#{e.class})\n  #{e.backtrace.join("\n  ")}\n#{msg}"
-  Logger.new(path).fatal(error_message)
-rescue Object => log_error
-  STDERR << "Couldn't write to #{path} (#{e} [#{e.class}])\n" << error_message
+  dispatcher_log(:error, path, error_message)
 end
 
+last_error_on = nil
 begin
   require File.dirname(__FILE__) + "/../config/environment"
   require 'dispatcher'
   require 'fcgi'
 
   log_file_path = "#{RAILS_ROOT}/log/fastcgi.crash.log"
+  dispatcher_log(:info, log_file_path, "fcgi #{$$} starting")
+
+  # Allow graceful exits by sending the process SIGUSR1. If the process is
+  # currently handling a request, the request will be allowed to complete and
+  # then will terminate itself. If a request is not being handled, the
+  # process is terminated immediately (via #exit).
+
+  $please_exit_at_your_earliest_convenience = false
+  $i_am_currently_processing_a_request = false
+  trap("USR1") do
+    if $i_am_currently_processing_a_request
+      dispatcher_log(:info, log_file_path, "asking #{$$} to terminate ASAP")
+      $please_exit_at_your_earliest_convenience = true
+    else
+      dispatcher_log(:info, log_file_path, "telling #{$$} to terminate NOW")
+      exit
+    end
+  end
+
+  # Process each request as it comes in, as a pseudo-CGI.
 
   FCGI.each_cgi do |cgi| 
     begin
+      $i_am_currently_processing_a_request = true
       Dispatcher.dispatch(cgi)
-    rescue Object => rails_error
-      dispatcher_error(log_file_path, rails_error)
+    rescue Object => e
+      dispatcher_error(log_file_path, e)
+    ensure
+      $stdout.flush
+      $i_am_currently_processing_a_request = false
+      break if $please_exit_at_your_earliest_convenience
     end
   end
+
+  dispatcher_log(:info, log_file_path, "fcgi #{$$} terminated gracefully")
+rescue SystemExit => exit_error
+  dispatcher_log(:info, log_file_path, "fcgi #{$$} terminated by explicit exit")
 rescue Object => fcgi_error
-  dispatcher_error(log_file_path, fcgi_error, "FCGI process #{$$} killed by this error\n")
+  # retry on errors that would otherwise have terminated the FCGI process, but
+  # only if they occur more than 10 seconds apart.
+  if !(SignalException === fcgi_error) && (last_error_on.nil? || last_error_on - Time.now > 10)
+    last_error_on = Time.now
+    dispatcher_error(log_file_path, fcgi_error, "FCGI process #{$$} almost killed by this error\n")
+    retry
+  else
+    dispatcher_error(log_file_path, fcgi_error, "FCGI process #{$$} killed by this error\n")
+  end
 end
\ No newline at end of file