Re: Combating nginx 499 HTTP responses during flash traffic scenario

[Eric Wong <normalperson@yhbt.net>]

Eric Wong <normalperson@yhbt.net> wrote:
> I fixed up some minor line-wrapping, signed-off, and added your
> quote above to the commit message.  Pushed as
> commit 5c700fc2cf398848ddcf71a2aa3f0f2a6563e87b
> to git://bogomips.org/unicorn.git

One more fix/cleanup to maintain compatibility with Rainbows!

>From 69e6a793d34ff71da7c8ca59962d627e2fb508d8 Mon Sep 17 00:00:00 2001
From: Eric Wong <normalperson@yhbt.net>
Date: Tue, 4 Dec 2012 02:35:26 +0000
Subject: [PATCH] fix const error responses for Rainbows!

Rainbows! relies on the ERROR_XXX_RESPONSE constants of unicorn
4.x.  Changing the constants in unicorn 4.x will break existing
versions of Rainbows!, so remove the dependency on the constants
and generate the error response dynamically.

Unlike Mongrel, unicorn is unlikely to see malicious traffic and
thus unlikely to benefit from making error messages constant.

For unicorn 5.x, we will drop these constants entirely.

(Rainbows! most likely cannot support check_client_connection
 consistently across all concurrency models since some of them
 pessimistically buffer all writes in userspace.  However, the
 extra concurrency of Rainbows! makes it less likely to be
 overloaded than unicorn, so this feature is likely less useful
 for Rainbows!)
---
 lib/unicorn/const.rb         | 10 ++++++----
 lib/unicorn/http_response.rb |  4 ++++
 lib/unicorn/http_server.rb   | 15 +++++++--------
 3 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/lib/unicorn/const.rb b/lib/unicorn/const.rb
index 60a63b1..02e29c7 100644
--- a/lib/unicorn/const.rb
+++ b/lib/unicorn/const.rb
@@ -29,10 +29,12 @@ module Unicorn::Const
 
   # :stopdoc:
   # common errors we'll send back
-  ERROR_400_RESPONSE = "400 Bad Request\r\n\r\n"
-  ERROR_414_RESPONSE = "414 Request-URI Too Long\r\n\r\n"
-  ERROR_413_RESPONSE = "413 Request Entity Too Large\r\n\r\n"
-  ERROR_500_RESPONSE = "500 Internal Server Error\r\n\r\n"
+  # (N.B. these are not used by unicorn, but we won't drop them until
+  #  unicorn 5.x to avoid breaking Rainbows!).
+  ERROR_400_RESPONSE = "HTTP/1.1 400 Bad Request\r\n\r\n"
+  ERROR_414_RESPONSE = "HTTP/1.1 414 Request-URI Too Long\r\n\r\n"
+  ERROR_413_RESPONSE = "HTTP/1.1 413 Request Entity Too Large\r\n\r\n"
+  ERROR_500_RESPONSE = "HTTP/1.1 500 Internal Server Error\r\n\r\n"
 
   EXPECT_100_RESPONSE = "HTTP/1.1 100 Continue\r\n\r\n"
   EXPECT_100_RESPONSE_SUFFIXED = "100 Continue\r\n\r\nHTTP/1.1 "
diff --git a/lib/unicorn/http_response.rb b/lib/unicorn/http_response.rb
index 61563cd..579d957 100644
--- a/lib/unicorn/http_response.rb
+++ b/lib/unicorn/http_response.rb
@@ -17,6 +17,10 @@ module Unicorn::HttpResponse
   }
   CRLF = "\r\n"
 
+  def err_response(code, response_start_sent)
+    "#{response_start_sent ? '' : 'HTTP/1.1 '}#{CODES[code]}\r\n\r\n"
+  end
+
   # writes the rack_response to socket as an HTTP response
   def http_response_write(socket, status, headers, body,
                           response_start_sent=false)
diff --git a/lib/unicorn/http_server.rb b/lib/unicorn/http_server.rb
index ef1ea58..aa98aeb 100644
--- a/lib/unicorn/http_server.rb
+++ b/lib/unicorn/http_server.rb
@@ -519,22 +519,21 @@ class Unicorn::HttpServer
   # if the socket is already closed or broken.  We'll always ensure
   # the socket is closed at the end of this function
   def handle_error(client, e)
-    msg = case e
+    code = case e
     when EOFError,Errno::ECONNRESET,Errno::EPIPE,Errno::EINVAL,Errno::EBADF,
          Errno::ENOTCONN
-      Unicorn::Const::ERROR_500_RESPONSE
+      500
     when Unicorn::RequestURITooLongError
-      Unicorn::Const::ERROR_414_RESPONSE
+      414
     when Unicorn::RequestEntityTooLargeError
-      Unicorn::Const::ERROR_413_RESPONSE
+      413
     when Unicorn::HttpParserError # try to tell the client they're bad
-      Unicorn::Const::ERROR_400_RESPONSE
+      400
     else
       Unicorn.log_error(@logger, "app error", e)
-      Unicorn::Const::ERROR_500_RESPONSE
+      500
     end
-    msg = "HTTP/1.1 #{msg}" unless @request.response_start_sent
-    client.kgio_trywrite(msg)
+    client.kgio_trywrite(err_response(code, @request.response_start_sent))
     client.close
     rescue
   end
-- 
Eric Wong
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