Presentation (PowerPoint File)

Web Servers: Implementation and Performance Erich Nahum IBM T.J. Watson Research Center www.research.ibm.com/people/n/nahum [email_address]

Contents and Timeline: ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Things Not Covered in Tutorial ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Assumptions and Expectations ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Objectives and Takeaways ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],After this tutorial, hopefully we will all know: Many lessons should be applicable to any networked server, e.g., files, mail, news, DNS, LDAP, etc.

Acknowledgements Many people contributed comments and suggestions to this tutorial, including: Abhishek Chandra Mark Crovella Suresh Chari Peter Druschel Jim Kurose Balachander Krishnamurthy Vivek Pai Jennifer Rexford Anees Shaikh Srinivasan Seshan Errors are all mine, of course.

Chapter 1: Introduction to the World-Wide Web (WWW)

Introduction to the WWW ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Client Proxy Server http request http request http response http response

How are Requests Generated? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Most browser requests are HTTP requests.

How are DNS names resolved? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

DNS in Action myclient.watson.ibm.com ns.watson.ibm.com (name server) A.GTLD-SERVER.NET (name server for .edu) ns.ucla.edu (name server) 12.100.104.5 www.ipam.ucla.edu www.ipam.ucla.edu? www.ipam.ucla.edu? ns.ucla.edu (TTL = 1d) 12.100.104.5 (TTL = 10 min) 12.100.104.5 www.ipam.ucla.edu? GET /index.html 200 OK index.html

What Happens Then? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],<html> <head> <meta name=“Author” content=“Erich Nahum”> <title> Linux Web Server Performance </title> </head> <body text=“#00000”> <img width=31 height=11 src=“ibmlogo.gif”> <img src=“images/new.gif> <h1>Hi There!</h1> Here’s lots of cool linux stuff! <a href=“more.html”> Click here</a> for more! </body> </html> sample html file

So What’s a Web Server Do? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Server capacity planning is non-trivial.

What do HTTP Requests Look Like? GET /images/penguin.gif HTTP/1.0 User-Agent: Mozilla/0.9.4 (Linux 2.2.19) Host: www.kernel.org Accept: text/html, image/gif, image/jpeg Accept-Encoding: gzip Accept-Language: en Accept-Charset: iso-8859-1,*,utf-8 Cookie: B=xh203jfsf; Y=3sdkfjej <cr><lf> ,[object Object],[object Object],[object Object],[object Object]

What Kind of Requests are there? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

What Do Responses Look Like? HTTP/1.0 200 OK Server: Tux 2.0 Content-Type: image/gif Content-Length: 43 Last-Modified: Fri, 15 Apr 1994 02:36:21 GMT Expires: Wed, 20 Feb 2002 18:54:46 GMT Date: Mon, 12 Nov 2001 14:29:48 GMT Cache-Control: no-cache Pragma: no-cache Connection: close Set-Cookie: PA=wefj2we0-jfjf <cr><lf> <data follows…> ,[object Object]

What Responses are There? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

What are all these Headers? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Specify capabilities and properties: Server must pay attention to respond properly.

The Role of Proxies clients servers proxy Internet ,[object Object],[object Object],[object Object]

Why have a Proxy? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Proxy Placement in the Web clients servers proxy Internet proxy proxy “ reverse” proxy ,[object Object],[object Object],[object Object],[object Object]

Content Distribution Networks origin servers proxy Internet proxy proxy ,[object Object],[object Object],[object Object],[object Object]

Mechanisms for CDN’s ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

DNS Based Request-Routing local nameserver client request- routing DNS name server www.service.com cdn 2 cdn 4 cdn 3 cdn 1 cdn 5 service.com? service.com? cdn 3 cdn 3

Summary: Introduction to WWW ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Chapter 2: Outline of a Typical Web Server Transaction

Outline of an HTTP Transaction ,[object Object],[object Object],[object Object],[object Object],[object Object],initialize; forever do { get request; process; send response; log request; } server in a nutshell

Readying a Server ,[object Object],[object Object],[object Object],[object Object],[object Object],s = socket(); /* allocate listen socket */ bind(s, 80); /* bind to TCP port 80 */ listen(s); /* indicate willingness to accept */ while (1) { newconn = accept(s); /* accept new connection */b

Processing a Request ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],remoteIP = getsockname(newconn); remoteHost = gethostbyname(remoteIP); gettimeofday(currentTime); read(newconn, reqBuffer, sizeof(reqBuffer)); reqInfo = serverParse(reqBuffer);

Processing a Request (cont) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],fileName = parseOutFileName(requestBuffer); fileAttr = stat(fileName); serverCheckFileStuff(fileName, fileAttr); open(fileName);

Responding to a Request ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],read(fileName, fileBuffer); headerBuffer = serverFigureHeaders(fileName, reqInfo); write(newSock, headerBuffer); write(newSock, fileBuffer); close(newSock); close(fileName); write(logFile, requestInfo);

Optimizing the Basic Structure ,[object Object],[object Object],[object Object]

Optimizations: Caching ,[object Object],fileDescriptor = lookInFDCache(fileName); metaInfo = lookInMetaInfoCache(fileName); headerBuffer = lookInHTTPHeaderCache(fileName); Idea is to exploit locality in client requests. Many files are requested over and over (e.g., index.html). ,[object Object],[object Object]

Optimizations: Caching (cont) ,[object Object],fileData = lookInFileDataCache(fileName); fileData = lookInMMapCache(fileName); remoteHostName = lookRemoteHostCache(fileName); ,[object Object],[object Object]

Optimizations: OS Primitives ,[object Object],acceptExtended(listenSock, &newSock, readBuffer, &remoteInfo); currentTime = *mappedTimePointer; buffer[0] = firstHTTPHeader; buffer[1] = secondHTTPHeader; buffer[2] = fileDataBuffer; writev(newSock, buffer, 3); ,[object Object],[object Object]

OS Primitives (cont) ,[object Object],httpInfo = cacheLookup(reqBuffer); sendfile(newConn, httpInfo->headers, httpInfo->fileDescriptor, OPT_CLOSE_WHEN_DONE); ,[object Object],[object Object],All this assumes proper OS support. Most have it these days.

An Accelerated Server Example ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],That’s it! acceptex(socket, newConn, reqBuffer, remoteHostInfo); httpInfo = cacheLookup(reqBuffer); sendfile(newConn, httpInfo->headers, httpInfo->fileDescriptor, OPT_CLOSE_WHEN_DONE); write(logFile, requestInfo);

Complications ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Complications (cont) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Summary: Outline of a Typical HTTP Transaction ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Chapter 3: Server Architectural Models

Server Architectural Models ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Process Model (ex: Apache) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Process Model: Pros and Cons ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Thread Model (Ex: JAWS) ,[object Object],[object Object],[object Object]

Thread Model: Pros and Cons ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Event Model (Ex: Flash) ,[object Object],[object Object],while (1) { accept new connections until none remaining; call select() on all active file descriptors; for each FD: if (fd ready for reading) call read(); if (fd ready for writing) call write(); }

Event-Driven: Pros and Cons ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

In-Kernel Model (Ex: Tux) ,[object Object],[object Object],[object Object],[object Object],user/ kernel boundary user-space server kernel-space server user/ kernel boundary TCP HTTP IP ETH SOCK TCP IP ETH HTTP

In-Kernel Model: Pros and Cons ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

So What’s the Performance? ,[object Object],[object Object],[object Object]

Summary: Server Architectures ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Chapter 5: Workload Characterization

Workload Characterization ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Factors to Consider ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],client? proxy? server?

Probability Refresher ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Important Distributions ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

More Probability ,[object Object],[object Object],[object Object]

What Info is Useful? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Sample Logs for Illustration We’ll use statistics generated from these logs as examples. 12,445,739 11,485,600 5,800,000 1,586,667 Hits: 28,804,852 54,697,108 10,515,507 14,171,711 Bytes: 319,698 86,0211 80,921 256,382 Clients: Corporate Presence Corporate Presence Nagano 1998 Olympics Event Site Kasparov-Deep Blue Event Site Description: 1 day in Feb 2001 1 day in June 1998 2 days in Feb 1998 2 weeks in May 1997 Period: 42,874 15,788 30,465 2,293 URLS: IBM 2001 IBM 1998 Olympics 1998 Chess 1997 Name:

Request Methods ,[object Object],[object Object],noise noise noise noise Others: 00.2% 00.02% 00.04 % 00.007% POST 02% 00.08% 00.3 % 04% HEAD 97% 99.3% 99.6% 96% GET IBM 2001 IBM 1998 Olympics 1998 Chess 1997

Response Codes ,[object Object],[object Object],[object Object],67.72 --.-- --.-- --.-- 15.11 16.26 00.001 00.001 00.009 00.79 00.002 00.07 00.006 00.0003 00.0004 75.28 00.00001 --.-- --.-- 01.18 22.84 00.003 00.0001 00.01 00.65 --.-- 00.006 00.0005 00.0001 00.005 76.02 --.-- --.-- --.-- 00.05 23.24 00.0001 00.001 00.02 00.64 --.-- 00.003 00.0001 --.-- 00.00004 85.32 --.-- 00.25 00.05 00.05 13.73 00.001 --.—- 00.01 00.55 --.-- --.-- --.-- --.-- 00.0003 OK NO_CONTENT PARTIAL_CONTENT MOVED_PERMANENTLY MOVED_TEMPORARILY NOT_MODIFIED BAD_REQUEST UNAUTHORIZED FORBIDDEN NOT_FOUND PROXY_AUTH SERVER_ERROR NOT_IMPLEMENTED SERVICE_UNAVAIL UNKNOWN 200 204 206 301 302 304 400 401 403 404 407 500 501 503 ??? IBM 2001 IBM 1998 Olympics 1998 Chess 1997 Meaning Code

Resource (File) Sizes ,[object Object],[object Object],[object Object]

Tails from the File Size ,[object Object],[object Object]

Response (Transfer) Sizes ,[object Object],[object Object]

Tails of Transfer Size ,[object Object],[object Object]

Resource Popularity ,[object Object],[object Object],[object Object],[object Object]

Number of Embedded Objects ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Trend seems to be that number is increasing over time.

Session Inter-Arrivals ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Protocol Support ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Appears that we are in the middle of a slow transition to 1.1

Summary: Workload Characterization ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Chapter 6: Workload Generators

Why Workload Generators? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Measure Reproduce Find Problem Fix and/or improve The Performance Debugging Cycle

Problems with Workload Generators ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

How does W. Generation Work? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Responses Requests

Evolution: WebStone ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],www.mindcraft.com/webstone 5 MB 0.10 500 KB 0.90 50 KB 14.00 5 KB 50.00 500 B 35.00 Size Percentage

Evolution: SPECWeb96 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],100 KB – 1 MB 1.00 10-100 KB 14.00 1-10 KB 50.00 0-1 KB 35.00 Size Percentage

SPECWeb96 (cont) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Evolution: SURGE ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

SURGE (cont) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Evolution: S-client ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

S-Client (cont) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Evolution: SPECWeb99 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

SPECWeb99 (cont) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

SPECWeb99 (cont) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

SpecWeb99 vs. File Sizes ,[object Object]

SpecWeb99 vs. File Size Tail ,[object Object]

SpecWeb99 vs.Transfer Sizes ,[object Object],[object Object]

Spec99 vs.Transfer Size Tails ,[object Object]

Spec99 vs. Resource Popularity ,[object Object]

Evolution: TPC-W ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

TPC-W (cont) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Summary: Workload Generators ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

End of this tutorial… ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],www.sigmetrics.org

Chapter: Event Notification ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Chapter: Introduction to TCP ,[object Object],[object Object],[object Object],[object Object],[object Object],application transport network link physical

Chapter: TCP Dynamics ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Chapter: Server TCP Implementation ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

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