From 5c700fc2cf398848ddcf71a2aa3f0f2a6563e87b Mon Sep 17 00:00:00 2001 From: Tom Burns Date: Tue, 30 Oct 2012 16:22:21 -0400 Subject: Begin writing HTTP request headers early to detect disconnected clients This patch checks incoming connections and avoids calling the application if the connection has been closed. It works by sending the beginning of the HTTP response before calling the application to see if the socket can successfully be written to. By enabling this feature users can avoid wasting application rendering time only to find the connection is closed when attempting to write, and throwing out the result. When a client disconnects while being queued or processed, Nginx will log HTTP response 499 but the application will log a 200. Enabling this feature will minimize the time window during which the problem can arise. The feature is disabled by default and can be enabled by adding 'check_client_connection true' to the unicorn config. [ew: After testing this change, Tom Burns wrote: So we just finished the US Black Friday / Cyber Monday weekend running unicorn forked with the last version of the patch I had sent you. It worked splendidly and helped us handle huge flash sales without increased response time over the weekend. Whereas in previous flash traffic scenarios we would see the number of HTTP 499 responses grow past the number of real HTTP 200 responses, over the weekend we saw no growth in 499s during flash sales. Unexpectedly the patch also helped us ward off a DoS attack where the attackers were disconnecting immediately after making a request. ref: ] Signed-off-by: Eric Wong --- examples/unicorn.conf.rb | 6 ++++++ ext/unicorn_http/unicorn_http.rl | 4 +++- lib/unicorn/configurator.rb | 25 +++++++++++++++++++++++++ lib/unicorn/const.rb | 12 ++++++++---- lib/unicorn/http_request.rb | 19 +++++++++++++++++++ lib/unicorn/http_response.rb | 6 ++++-- lib/unicorn/http_server.rb | 23 +++++++++++++++++++++-- test/exec/test_exec.rb | 7 ++++++- test/unit/test_configurator.rb | 24 ++++++++++++++++++++++++ 9 files changed, 116 insertions(+), 10 deletions(-) diff --git a/examples/unicorn.conf.rb b/examples/unicorn.conf.rb index 0238043..1f4c9c0 100644 --- a/examples/unicorn.conf.rb +++ b/examples/unicorn.conf.rb @@ -46,6 +46,12 @@ preload_app true GC.respond_to?(:copy_on_write_friendly=) and GC.copy_on_write_friendly = true +# Enable this flag to have unicorn test client connections by writing the +# beginning of the HTTP headers before calling the application. This +# prevents calling the application for connections that have disconnected +# while queued. +check_client_connection false + before_fork do |server, worker| # the following is highly recomended for Rails + "preload_app true" # as there's no need for the master process to hold a connection diff --git a/ext/unicorn_http/unicorn_http.rl b/ext/unicorn_http/unicorn_http.rl index 96dcf83..1a8003f 100644 --- a/ext/unicorn_http/unicorn_http.rl +++ b/ext/unicorn_http/unicorn_http.rl @@ -115,7 +115,7 @@ struct http_parser { } len; }; -static ID id_clear, id_set_backtrace; +static ID id_clear, id_set_backtrace, id_response_start_sent; static void finalize_header(struct http_parser *hp); @@ -626,6 +626,7 @@ static VALUE HttpParser_clear(VALUE self) http_parser_init(hp); rb_funcall(hp->env, id_clear, 0); + rb_ivar_set(self, id_response_start_sent, Qfalse); return self; } @@ -1031,6 +1032,7 @@ void Init_unicorn_http(void) SET_GLOBAL(g_http_connection, "CONNECTION"); id_clear = rb_intern("clear"); id_set_backtrace = rb_intern("set_backtrace"); + id_response_start_sent = rb_intern("@response_start_sent"); init_unicorn_httpdate(); } #undef SET_GLOBAL diff --git a/lib/unicorn/configurator.rb b/lib/unicorn/configurator.rb index 89cbf5c..9752cdd 100644 --- a/lib/unicorn/configurator.rb +++ b/lib/unicorn/configurator.rb @@ -45,6 +45,7 @@ class Unicorn::Configurator }, :pid => nil, :preload_app => false, + :check_client_connection => false, :rewindable_input => true, # for Rack 2.x: (Rack::VERSION[0] <= 1), :client_body_buffer_size => Unicorn::Const::MAX_BODY, :trust_x_forwarded => true, @@ -96,6 +97,18 @@ class Unicorn::Configurator if ready_pipe = RACKUP.delete(:ready_pipe) server.ready_pipe = ready_pipe end + if set[:check_client_connection] + set[:listeners].each do |address| + if set[:listener_opts][address][:tcp_nopush] == true + raise ArgumentError, + "check_client_connection is incompatible with tcp_nopush:true" + end + if set[:listener_opts][address][:tcp_nodelay] == true + raise ArgumentError, + "check_client_connection is incompatible with tcp_nodelay:true" + end + end + end set.each do |key, value| value == :unset and next skip.include?(key) and next @@ -454,6 +467,18 @@ class Unicorn::Configurator set_int(:client_body_buffer_size, bytes, 0) end + # When enabled, unicorn will check the client connection by writing + # the beginning of the HTTP headers before calling the application. + # + # This will prevent calling the application for clients who have + # disconnected while their connection was queued. + # + # This option cannot be used in conjunction with tcp_nodelay or + # tcp_nopush. + def check_client_connection(bool) + set_bool(:check_client_connection, bool) + end + # Allow redirecting $stderr to a given path. Unlike doing this from # the shell, this allows the unicorn process to know the path its # writing to and rotate the file if it is used for logging. The diff --git a/lib/unicorn/const.rb b/lib/unicorn/const.rb index b3d8d71..f0c4c12 100644 --- a/lib/unicorn/const.rb +++ b/lib/unicorn/const.rb @@ -29,12 +29,16 @@ module Unicorn::Const # :stopdoc: # common errors we'll send back - 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" + 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" + EXPECT_100_RESPONSE = "HTTP/1.1 100 Continue\r\n\r\n" + EXPECT_100_RESPONSE_SUFFIXED = "100 Continue\r\n\r\nHTTP/1.1 " + HTTP_RESPONSE_START = ['HTTP', '/1.1 '] HTTP_EXPECT = "HTTP_EXPECT" + # :startdoc: end diff --git a/lib/unicorn/http_request.rb b/lib/unicorn/http_request.rb index a0435d6..79ead2e 100644 --- a/lib/unicorn/http_request.rb +++ b/lib/unicorn/http_request.rb @@ -22,11 +22,14 @@ class Unicorn::HttpParser NULL_IO = StringIO.new("") + attr_accessor :response_start_sent + # :stopdoc: # A frozen format for this is about 15% faster REMOTE_ADDR = 'REMOTE_ADDR'.freeze RACK_INPUT = 'rack.input'.freeze @@input_class = Unicorn::TeeInput + @@check_client_connection = false def self.input_class @@input_class @@ -35,6 +38,15 @@ class Unicorn::HttpParser def self.input_class=(klass) @@input_class = klass end + + def self.check_client_connection + @@check_client_connection + end + + def self.check_client_connection=(bool) + @@check_client_connection = bool + end + # :startdoc: # Does the majority of the IO processing. It has been written in @@ -70,6 +82,13 @@ class Unicorn::HttpParser # an Exception thrown from the parser will throw us out of the loop false until add_parse(socket.kgio_read!(16384)) end + + # detect if the socket is valid by writing a partial response: + if @@check_client_connection && headers? + @response_start_sent = true + Unicorn::Const::HTTP_RESPONSE_START.each { |c| socket.write(c) } + end + e[RACK_INPUT] = 0 == content_length ? NULL_IO : @@input_class.new(socket, self) e.merge!(DEFAULTS) diff --git a/lib/unicorn/http_response.rb b/lib/unicorn/http_response.rb index b781e20..61563cd 100644 --- a/lib/unicorn/http_response.rb +++ b/lib/unicorn/http_response.rb @@ -18,11 +18,13 @@ module Unicorn::HttpResponse CRLF = "\r\n" # writes the rack_response to socket as an HTTP response - def http_response_write(socket, status, headers, body) + def http_response_write(socket, status, headers, body, + response_start_sent=false) status = CODES[status.to_i] || status + http_response_start = response_start_sent ? '' : 'HTTP/1.1 ' if headers - buf = "HTTP/1.1 #{status}\r\n" \ + buf = "#{http_response_start}#{status}\r\n" \ "Date: #{httpdate}\r\n" \ "Status: #{status}\r\n" \ "Connection: close\r\n" diff --git a/lib/unicorn/http_server.rb b/lib/unicorn/http_server.rb index 13df55a..ef1ea58 100644 --- a/lib/unicorn/http_server.rb +++ b/lib/unicorn/http_server.rb @@ -17,6 +17,7 @@ class Unicorn::HttpServer :listener_opts, :preload_app, :reexec_pid, :orig_app, :init_listeners, :master_pid, :config, :ready_pipe, :user + attr_reader :pid, :logger include Unicorn::SocketHelper include Unicorn::HttpResponse @@ -355,6 +356,14 @@ class Unicorn::HttpServer Unicorn::HttpParser.trust_x_forwarded = bool end + def check_client_connection + Unicorn::HttpRequest.check_client_connection + end + + def check_client_connection=(bool) + Unicorn::HttpRequest.check_client_connection = bool + end + private # wait for a signal hander to wake us up and then consume the pipe @@ -524,23 +533,33 @@ class Unicorn::HttpServer Unicorn.log_error(@logger, "app error", e) Unicorn::Const::ERROR_500_RESPONSE end + msg = "HTTP/1.1 #{msg}" unless @request.response_start_sent client.kgio_trywrite(msg) client.close rescue end + def expect_100_response + if @request.response_start_sent + Unicorn::Const::EXPECT_100_RESPONSE_SUFFIXED + else + Unicorn::Const::EXPECT_100_RESPONSE + end + end + # once a client is accepted, it is processed in its entirety here # in 3 easy steps: read request, call app, write app response def process_client(client) status, headers, body = @app.call(env = @request.read(client)) if 100 == status.to_i - client.write(Unicorn::Const::EXPECT_100_RESPONSE) + client.write(expect_100_response) env.delete(Unicorn::Const::HTTP_EXPECT) status, headers, body = @app.call(env) end @request.headers? or headers = nil - http_response_write(client, status, headers, body) + http_response_write(client, status, headers, body, + @request.response_start_sent) client.shutdown # in case of fork() in Rack app client.close # flush and uncork socket immediately, no keepalive rescue => e diff --git a/test/exec/test_exec.rb b/test/exec/test_exec.rb index b30a3d6..1cee2b7 100644 --- a/test/exec/test_exec.rb +++ b/test/exec/test_exec.rb @@ -871,13 +871,14 @@ EOF wait_for_death(pid) end - def hup_test_common(preload) + def hup_test_common(preload, check_client=false) File.open("config.ru", "wb") { |fp| fp.syswrite(HI.gsub("HI", '#$$')) } pid_file = Tempfile.new('pid') ucfg = Tempfile.new('unicorn_test_config') ucfg.syswrite("listen '#@addr:#@port'\n") ucfg.syswrite("pid '#{pid_file.path}'\n") ucfg.syswrite("preload_app true\n") if preload + ucfg.syswrite("check_client_connection true\n") if check_client ucfg.syswrite("stderr_path 'test_stderr.#$$.log'\n") ucfg.syswrite("stdout_path 'test_stdout.#$$.log'\n") pid = xfork { @@ -942,6 +943,10 @@ EOF hup_test_common(false) end + def test_check_client_hup + hup_test_common(false, true) + end + def test_default_listen_hup_holds_listener default_listen_lock do res, pid_path = default_listen_setup diff --git a/test/unit/test_configurator.rb b/test/unit/test_configurator.rb index 267eea3..1298f0e 100644 --- a/test/unit/test_configurator.rb +++ b/test/unit/test_configurator.rb @@ -132,6 +132,30 @@ class TestConfigurator < Test::Unit::TestCase Unicorn::Configurator.new(:config_file => tmp.path) end + def test_check_client_connection + tmp = Tempfile.new('unicorn_config') + test_struct = TestStruct.new + tmp.syswrite("check_client_connection true\n") + + assert_nothing_raised do + Unicorn::Configurator.new(:config_file => tmp.path).commit!(test_struct) + end + + assert test_struct.check_client_connection + end + + def test_check_client_connection_with_tcp_bad + tmp = Tempfile.new('unicorn_config') + test_struct = TestStruct.new + listener = "127.0.0.1:12345" + tmp.syswrite("check_client_connection true\n") + tmp.syswrite("listen '#{listener}', :tcp_nopush => true\n") + + assert_raises(ArgumentError) do + Unicorn::Configurator.new(:config_file => tmp.path).commit!(test_struct) + end + end + def test_after_fork_proc test_struct = TestStruct.new [ proc { |a,b| }, Proc.new { |a,b| }, lambda { |a,b| } ].each do |my_proc| -- cgit v1.2.3-24-ge0c7