spdy - http reloaded - webtechconference 2012
DESCRIPTION
The SPDY Protocol is likely going to be the successor of http. This short talk summarizes the most important points and includes a demo on how to migrate a Wordpress blog on httpd.TRANSCRIPT
Fabian Lange
SPDY - http reloaded
(WILL BE) PART OF HTTP/2.0
HTTP Problems • Single request per connection. Because HTTP can only fetch one resource at a time (HTTP
pipelining helps, but still enforces only a FIFO queue), a server delay of 500 ms prevents reuse of the TCP channel for additional requests. Browsers work around this problem by using multiple connections. Since 2008, most browsers have finally moved from 2 connections per domain to 6.
• Exclusively client-initiated requests. In HTTP, only the client can initiate a request. Even if the server knows the client needs a resource, it has no mechanism to inform the client and must instead wait to receive a request for the resource from the client.
• Uncompressed request and response headers. Request headers today vary in size from ~200 bytes to over 2KB. As applications use more cookies and user agents expand features, typical header sizes of 700-800 bytes is common. For modems or ADSL connections, in which the uplink bandwidth is fairly low, this latency can be significant. Reducing the data in headers could directly improve the serialization latency to send requests.
• Redundant headers. In addition, several headers are repeatedly sent across requests on the same channel. However, headers such as the User-Agent, Host, and Accept* are generally static and do not need to be resent.
• Optional data compression. HTTP uses optional compression encodings for data. Content should always be sent in a compressed format.
Source: http://dev.chromium.org/spdy/spdy-whitepaper
Web Requests Are Simple
• Open a connection
• Send a request
• Receive a response
• Done
How to Avoid Requests
• Caching
• Domain Sharding
– Browser Limits
• Keep Alive
– Dedicated Connections
– Waste Ressources
• Pipelining
TCP Handshake 0ms 1) Host A sends a TCP SYNchronize packet to Host B
25ms 2) Host B receives A's SYN
25ms 3) Host B sends a SYNchronize-ACKnowledgement
50ms 4) Host A receives B's SYN-ACK
75ms 5) Host A sends ACKnowledge and data
75ms 6) Host B receives ACK and data.
• With a "distance" of just 25ms, this takes
us 75ms until data arrives at server
Initial Window
• Congestion Control Mechanism
• Avoid overloading clients
• Each ACK of the client increases window
• RFC 3390
– Increasing icwnd
– Small Resonses are complete without ACK
– Avoid the ACK RTT
Pushing over http
• Push === Long Polling
• Consumes one connection on clients
• On server
– Used to be expensive to hold
– Modern servers have evented I/O
• WebSockets
Headers
Accept text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Encoding gzip, deflate
Accept-Language de-de,de;q=0.8,en-us;q=0.5,en;q=0.3
Connection keep-alive
Cookie
__utma=40497137.1800912468.1315901303.1328525769.1328537171.234;
__utmz=40497137.1326462670.198.110.utmcsr=twitterfeed|utmccn=blogfee
d_de|utmcmd=twitter; wp-settings-
3=editor%3Dhtml%26m0%3Do%26m1%3Do%26m2%3Do%26m3%3Dc%2
6m4%3Do%26m5%3Do%26m6%3Do%26m7%3Do%26m8%3Do%26m9%3
Do%26m10%3Do%26m11%3Do%26align%3Dcenter%26imgsize%3Dfull%2
6urlbutton%3Dnone%26hidetb%3D0; wp-settings-time-3=1328519940;
__utma=162617902.1417890302.1315914276.1328537194.1328541774.63;
__utmz=162617902.1328537194.62.41.utmcsr=blog.codecentric.de|utmccn
=(referral)|utmcmd=referral|utmcct=/; wp-settings-time-81=1321966374
Host blog.codecentric.de
User-Agent Mozilla/5.0 (Windows NT 6.1; WOW64; rv:10.0) Gecko/20100101
Firefox/10.0
http://blog.codecentric.de/
http://blog.codecentric.de/files/2012/02/adlite.png
Headers
Accept image/png,image/*;q=0.8,*/*;q=0.5
Accept-Encoding gzip, deflate
Accept-Language de-de,de;q=0.8,en-us;q=0.5,en;q=0.3
Connection keep-alive
Cookie
__utma=162617902.1417890302.1315914276.1328537194.1328541774.63;
__utmz=162617902.1328537194.62.41.utmcsr=blog.codecentric.de|utmccn=(referral)
|utmcmd=referral|utmcct=/; wp-settings-
3=m0%3Do%26m1%3Do%26m5%3Do%26m4%3Do%26editor%3Dhtml%26wplink%
3D1%26align%3Dcenter%26imgsize%3Dfull%26hidetb%3D1%26m7%3Do%26m9%
3Do; wp-settings-time-3=1326290899
Host blog.codecentric.de
Referer http://blog.codecentric.de/
User-Agent Mozilla/5.0 (Windows NT 6.1; WOW64; rv:10.0) Gecko/20100101 Firefox/10.0
Content Compression
• Gzip is optional
• But generally best practice
LoadModule deflate_module /usr/lib/httpd/modules/mod_deflate.so
SPDY TO THE RESCUE
SPDY Solutions • Allow many concurrent HTTP requests to run across a
single TCP session.
• Reduce the bandwidth currently used by HTTP by compressing headers and eliminating unnecessary headers.
• Make SSL the underlying transport protocol, for better security and compatibility with existing network infrastructure. Although SSL does introduce a latency penalty, we believe that the long-term future of the web depends on a secure network connection. In addition, the use of SSL is necessary to ensure that communication across existing proxies is not broken.
• Enable the server to initiate communications with the client and push data to the client whenever possible.
Source: http://dev.chromium.org/spdy/spdy-whitepaper
Connection Multiplexing
• Single TCP Connection transports all
requests
• TCP Handshake still exists
• Inital cwnd should be 16
Compression
• All data is compressed
• Includes headers
• Redundand data is removed
– User Agent of second request is known to
be same as on first
CRIME
• Compression Ratio Info-leak Made
Easy
• Cookie value can be detected when
compression is effective
Sources:
threatpost.com/en_us/blogs/new-attack-uses-ssltls-information-leak-hijack-https-sessions-090512
security.stackexchange.com/questions/19911/crime-how-to-beat-the-beast-successor/19914
Cookie: JSESSIONID=1234
c: jid=1234
d: kje=2345
Cookie: JSESSIONID=1234 Cookie: JSESSIONID=9876
X[i] = c: jid=
[i]1234 [i]9876
Y[j] = d: kje=
[j]2345 [j]0987
Cookie: JSESSIONID=1234 Cookie: JSESSIONID=1235
X[i] = c: jid=123
[i]4 [i]5
Y[j] = d: kje=234
[j]5 [j]6
Fixes
• Don't compress headers
• Use a compressor that is not affected
SSL
• Not said to be a problem with HTTP
• SSL should be default
– But actually expensive
• SSL hides SPDY traffic, so that proxies
don't break it
Pushing
• Long Lasting Connection By Design
• Send does not close the "request"
• Two flavors
– Server push
– Server hint
Compatibility
• SPDY is backwards compatible
• Uses Next Protocol Negotiation
– tools.ietf.org/html/draft-agl-tls-
nextprotoneg-02
Adoption
• Facebook implements and favors SPDY http://lists.w3.org/Archives/Public/ietf-http-wg/2012JulSep/0251.html
• Twitter implements and favors SPDY http://lists.w3.org/Archives/Public/ietf-http-wg/2012JulSep/0250.html
• Google implements and favors SPDY http://lists.w3.org/Archives/Public/ietf-http-wg/2012JulSep/0219.html
• Mozilla implements and favors SPDY http://lists.w3.org/Archives/Public/ietf-http-wg/2012JulSep/0156.html
• Wordpress.com uses SPDY https://twitter.com/wordpressdotcom/statuses/238741078172389377
Concerns
• Encryption by default renders network
caching useless
SPDY Support Clients
• Chrome
– since 11
– Ice Cream Sandwich
• Amazon Silk
– Kindle Fire
• Firefox
– Since 13
• Opera
– Since 12.1
Server
• Apache mod_spdy
• erlang-spdy
• node-spdy
• Netty 3.3.1
– Means JBoss
• Jetty 7.6.2
• Ngnix 1.3
• Tomcat 8.0.0-dev
SPDY Drafts
• dev.chromium.org/spdy/spdy-protocol/spdy-protocol-
draft1
– First draft 2009
• dev.chromium.org/spdy/spdy-protocol/spdy-protocol-
draft2
– Changes to server push
• dev.chromium.org/spdy/spdy-protocol/spdy-protocol-
draft3
– Flow control
• Draft 4 will feature compression and QoS changes
DEMO: MIGRATING PHP ON
APACHE TO SUPPORT SPDY
PHP is not Threadsafe
• The way SPDY works is incompatible
with non threadsafe implementations
– one connection one httpd worker
– But multiple requests
• Zend Threadsafe does not support
some features (mysql!)
• Need to externalize it with cgi
mod_php to mod_fcgid + php
• yum install mod_fcgid
• vi /etc/httpd/conf/httpd.conf
• mv /etc/httpd/conf.d/php.conf
/etc/httpd/conf.d/php.conf.bak
• vi /etc/httpd/conf.d/fcgid.conf
<Directory "/var/www/html">
Options Indexes FollowSymLinks ExecCGI
</Directory>
DirectoryIndex index.php
AddHandler fcgid-script .fcgi .php
DefaultInitEnv PHPRC "/etc/"
MaxRequestsPerProcess 1000
MaxProcessCount 10
MaxRequestLen 209715200
IPCCommTimeout 240
IdleTimeout 240
FCGIWrapper /usr/bin/php-cgi .php
mod_prefork to mod_worker
• Needs recompilation
• Luckily we have both already – httpd -V | grep MPM
– httpd.worker -V | grep MPM
• sudo vi /etc/init.d/httpd
httpd=${HTTPD-
/usr/sbin/httpd.worker}
prog=httpd.worker
mod_ssl
• We need mod_ssl patched with NPN
• yum install subversion curl gcc-
c++ patch binutils make
• mkdir modssl; cd modssl
• svn export http://mod-
spdy.googlecode.com/svn/trunk/src/
build_modssl_with_npn.sh
• ./build_modssl_with_npn.sh
• cp /root/modssl/mod_ssl.so
/etc/httpd/modules/mod_ssl.so
[root@centos57 modssl]# ./build_modssl_with_npn.sh
Using buildroot: /tmp/tmp.CooHIy8770
Downloading http://www.openssl.org/source/openssl-1.0.1-beta2.tar.gz
######################################################################## 100.0%
Downloading http://www.apache.org/dist/httpd/httpd-2.2.21.tar.gz
######################################################################## 100.0%
Downloading https://issues.apache.org/bugzilla/attachment.cgi?id=27969context=patch
######################################################################## 100.0%
Uncompressing openssl-1.0.1-beta2.tar.gz ... done
Uncompressing httpd-2.2.21.tar.gz ... done
Applying Apache mod_ssl NPN patch ...
patching file modules/ssl/ssl_private.h
patching file modules/ssl/ssl_engine_init.c
patching file modules/ssl/ssl_engine_io.c
patching file modules/ssl/ssl_engine_kernel.c
patching file modules/ssl/mod_ssl.c
patching file modules/ssl/mod_ssl.h
done
Configuring OpenSSL ... done
Building OpenSSL (this may take a while) ... done
Configuring Apache mod_ssl ... done
Building Apache mod_ssl (this may take a while) ... done
Generated mod_ssl.so at /root/modssl/mod_ssl.so.
mod_spdy • Built from source • mkdir mod_spdy; cd mod_spdy
• svn co http://src.chromium.org/svn/trunk/tools/depot_tools
• export PATH="$PATH":`pwd`/depot_tools
• gclient config http://mod-spdy.googlecode.com/svn/trunk/src
• gclient sync --force
• cd src; make BUILDTYPE=Release
• sudo cp out/Release/libmod_spdy.so /etc/httpd/modules/mod_spdy.so
• vi /etc/httpd/conf.d/spdy.conf
LoadModule spdy_module /etc/httpd/modules/mod_spdy.so
SpdyEnabled on
chrome://net-internals/#spdy
Is it spdy?
• www.devthought.com/2012/03/10/chro
me-spdy-indicator/
• ckon.wordpress.com/2012/03/11/spdy-
indicator-for-firefox/
HTTP
2.07
seconds
HTTPS
4.94
seconds
SPDY
2.65
seconds
real HTTP
17.83
seconds
real SPDY
11.70
seconds
Online Demo
• www.modspdy.com/world-flags/
www.belshe.com/2012/08/20/visualizing-spdy-vs-http
LET'S MAKE THE WEB
FASTER