paste.httpserver并使用HTTP/1.1 Keep-alive减慢速度；用httperf和ab测试 [英] paste.httpserver and slowdown with HTTP/1.1 Keep-alive; tested with httperf and ab
问题描述
我有一个基于paste.httpserver的Web服务器，作为HTTP和WSGI之间的适配器.当我使用httperf进行性能评估时，如果每次使用--num-conn发出一个新请求，我每秒都可以执行1,000个以上的请求.如果我改用--num-call重用连接，那么我每秒会收到大约11个请求，速度的1/100.
如果我尝试ab会超时.
我的测试是
% ./httperf --server localhost --port 8080 --num-conn 100
...
Request rate: 1320.4 req/s (0.8 ms/req)
...
和
% ./httperf --server localhost --port 8080 --num-call 100
...
Request rate: 11.2 req/s (89.4 ms/req)
...
这是一个简单的可复制服务器
from paste import httpserver
def echo_app(environ, start_response):
n = 10000
start_response("200 Ok", [("Content-Type", "text/plain"),
("Content-Length", str(n))])
return ["*" * n]
httpserver.serve(echo_app, protocol_version="HTTP/1.1")
这是一个多线程服务器，很难配置.这是一个单线程的变体:
from paste import httpserver
class MyHandler(httpserver.WSGIHandler):
sys_version = None
server_version = "MyServer/0.0"
protocol_version = "HTTP/1.1"
def log_request(self, *args, **kwargs):
pass
def echo_app(environ, start_response):
n = 10000
start_response("200 Ok", [("Content-Type", "text/plain"),
("Content-Length", str(n))])
return ["*" * n]
# WSGIServerBase is single-threaded
server = httpserver.WSGIServerBase(echo_app, ("localhost", 8080), MyHandler)
server.handle_request()
使用
进行分析% python2.6 -m cProfile -o paste.prof paste_slowdown.py
然后点击
%httperf --client=0/1 --server=localhost --port=8080 --uri=/ \
--send-buffer=4096 --recv-buffer=16384 --num-conns=1 --num-calls=500
我得到一个类似的个人资料
>>> p=pstats.Stats("paste.prof")
>>> p.strip_dirs().sort_stats("cumulative").print_stats()
Sun Nov 22 21:31:57 2009 paste.prof
109749 function calls in 46.570 CPU seconds
Ordered by: cumulative time
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 46.571 46.571 {execfile}
1 0.001 0.001 46.570 46.570 paste_slowdown.py:2(<module>)
1 0.000 0.000 46.115 46.115 SocketServer.py:250(handle_request)
1 0.000 0.000 44.675 44.675 SocketServer.py:268(_handle_request_noblock)
1 0.000 0.000 44.675 44.675 SocketServer.py:301(process_request)
1 0.000 0.000 44.675 44.675 SocketServer.py:318(finish_request)
1 0.000 0.000 44.675 44.675 SocketServer.py:609(__init__)
1 0.000 0.000 44.675 44.675 httpserver.py:456(handle)
1 0.001 0.001 44.675 44.675 BaseHTTPServer.py:325(handle)
501 0.006 0.000 44.674 0.089 httpserver.py:440(handle_one_request)
2001 0.020 0.000 44.383 0.022 socket.py:373(readline)
501 44.354 0.089 44.354 0.089 {method 'recv' of '_socket.socket' objects}
1 1.440 1.440 1.440 1.440 {select.select}
....
您可以看到几乎所有时间都在录制中.
我决定在httpref上保释并编写我自己的HTTP/1.1-with-keep-alive请求并使用netcat发送该请求:
GET / HTTP/1.1
Location: localhost
Connection: Keep-Alive
Content-Length: 0
GET / HTTP/1.1
Location: localhost
Connection: Keep-Alive
Content-Length: 0
... repeat 97 more times, to have 99 keep-alives in total ...
GET / HTTP/1.1
Location: localhost
Connection: Close
Content-Length: 0
我发给的
nc localhost 8080 < ~/src/send_to_paste.txt
100个请求的总时间为0.03秒，因此性能非常好.
这表明httperf做错了什么(但这是一个被广泛使用和尊重的代码)，所以我尝试了'ab'
% ab -n 100 -k localhost:8080/
This is ApacheBench, Version 1.3d <$Revision: 1.73 $> apache-1.3
Copyright (c) 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Copyright (c) 2006 The Apache Software Foundation, http://www.apache.org/
Benchmarking localhost (be patient)...
Server timed out
: Operation now in progress
安装服务器，它可以处理一个请求，并正在等待第二个请求.
有什么想法吗?
经过一番努力，似乎是一个朋友提出了明显的建议，我搜索了"200ms套接字延迟"，并找到了对此问题的描述.
粘贴跟踪报告位于 http://trac.pythonpaste.org/pythonpaste/ticket/392 以及一个在处理程序使用HTTP/1.1时启用TCP_NODELAY的补丁.
I have a web server based on paste.httpserver as an adapater between HTTP and WSGI. When I do performance measurements with httperf, I can do over 1,000 requests per second if I start a new request each time using --num-conn. If I instead reuse the connection using --num-call then I get about 11 requests per second, 1/100th of the speed.
If I try ab I get a timeout.
My tests are
% ./httperf --server localhost --port 8080 --num-conn 100
...
Request rate: 1320.4 req/s (0.8 ms/req)
...
and
% ./httperf --server localhost --port 8080 --num-call 100
...
Request rate: 11.2 req/s (89.4 ms/req)
...
Here's a simple reproducible server
from paste import httpserver
def echo_app(environ, start_response):
n = 10000
start_response("200 Ok", [("Content-Type", "text/plain"),
("Content-Length", str(n))])
return ["*" * n]
httpserver.serve(echo_app, protocol_version="HTTP/1.1")
It's a multi-threaded server, which is hard to profile. Here's a variation which is single threaded:
from paste import httpserver
class MyHandler(httpserver.WSGIHandler):
sys_version = None
server_version = "MyServer/0.0"
protocol_version = "HTTP/1.1"
def log_request(self, *args, **kwargs):
pass
def echo_app(environ, start_response):
n = 10000
start_response("200 Ok", [("Content-Type", "text/plain"),
("Content-Length", str(n))])
return ["*" * n]
# WSGIServerBase is single-threaded
server = httpserver.WSGIServerBase(echo_app, ("localhost", 8080), MyHandler)
server.handle_request()
Profiling that with
% python2.6 -m cProfile -o paste.prof paste_slowdown.py
and hitting it with
%httperf --client=0/1 --server=localhost --port=8080 --uri=/ \
--send-buffer=4096 --recv-buffer=16384 --num-conns=1 --num-calls=500
I get a profile like
>>> p=pstats.Stats("paste.prof")
>>> p.strip_dirs().sort_stats("cumulative").print_stats()
Sun Nov 22 21:31:57 2009 paste.prof
109749 function calls in 46.570 CPU seconds
Ordered by: cumulative time
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.000 0.000 46.571 46.571 {execfile}
1 0.001 0.001 46.570 46.570 paste_slowdown.py:2(<module>)
1 0.000 0.000 46.115 46.115 SocketServer.py:250(handle_request)
1 0.000 0.000 44.675 44.675 SocketServer.py:268(_handle_request_noblock)
1 0.000 0.000 44.675 44.675 SocketServer.py:301(process_request)
1 0.000 0.000 44.675 44.675 SocketServer.py:318(finish_request)
1 0.000 0.000 44.675 44.675 SocketServer.py:609(__init__)
1 0.000 0.000 44.675 44.675 httpserver.py:456(handle)
1 0.001 0.001 44.675 44.675 BaseHTTPServer.py:325(handle)
501 0.006 0.000 44.674 0.089 httpserver.py:440(handle_one_request)
2001 0.020 0.000 44.383 0.022 socket.py:373(readline)
501 44.354 0.089 44.354 0.089 {method 'recv' of '_socket.socket' objects}
1 1.440 1.440 1.440 1.440 {select.select}
....
You can see that nearly all the time is in a recv.
I decided to bail on httpref and write my own HTTP/1.1-with-keep-alive request and send it using netcat:
GET / HTTP/1.1
Location: localhost
Connection: Keep-Alive
Content-Length: 0
GET / HTTP/1.1
Location: localhost
Connection: Keep-Alive
Content-Length: 0
... repeat 97 more times, to have 99 keep-alives in total ...
GET / HTTP/1.1
Location: localhost
Connection: Close
Content-Length: 0
which I sent with
nc localhost 8080 < ~/src/send_to_paste.txt
Total time for 100 requests was 0.03 seconds, so it's very good performance.
This suggests that httperf is doing something wrong (but it's a widely used and respected piece of code), so I tried 'ab'
% ab -n 100 -k localhost:8080/
This is ApacheBench, Version 1.3d <$Revision: 1.73 $> apache-1.3
Copyright (c) 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Copyright (c) 2006 The Apache Software Foundation, http://www.apache.org/
Benchmarking localhost (be patient)...
Server timed out
: Operation now in progress
Instrumenting the server, it handles one request and is waiting for the second.
Any idea of what's going on?
After some effort, it seems to be either Nagle's algorithm or the delayed ACK, or the interactions between them. It goes away if I do something like
server.socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
How did I track it down? First, I instrumented every 'recv' in socket.py, so I could figure out which recv was waiting. I would see about 5 recv's out of 11 had a delay of almost 200ms. I couldn't figure out why there was any delay. I then used Wireshark to watch the messages and noticed that the it was actually the send from the server to the client which had the delay. That meant something in the TCP layer in the outgoing messages from my client.
A friend suggested the obvious, and I searched for "200ms socket delay" and found descriptions of this problem.
The paste trac report is at http://trac.pythonpaste.org/pythonpaste/ticket/392 along with a patch which enables TCP_NODELAY when the handler uses HTTP/1.1.
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