[PDF] Apache Server Architecture This is usually in terms

View - Download Apache Server Architecture

Previous PDF

Next PDF

`Initially started in 1996 by Robert McCool. `Since 1996, Apache web server has been the most popular

HTTP Verver in WUe markeW on WUe PorlT PiTe Peb.

`The Apache was the first web server architecture that was uVeT by WUe NeWVcape CommunicaWion CorporaWion. `Apache has evolved with the years of the internet. Server is uVeT Wo VupporW boWU VWaWic anT Tynamic pageV online. Óany programming languageV are VupporWeT by WUe ApacUe Server are aV followVJ PHPH PerlH PyWUon anT alongViTe wiWU ÓySql. AV of April 2008H WUe ApacUe Server VerveV approximaWely 50% of

WUe currenW web pageV.

`Apache is a open source HTTP web server. It handles HTTP

Requests sent to it and then it is able to them

`Apache is Open source and is built and maintained over at

ApacUe.org

`Apache is comprised of Two main building Blocks with the Latter being comprised of many other little building blocks. The Building Blocks are the Apache Core and then the Apache ÓoTuleV WUaW in a VenVe exWenT WUe ApacUe core. Óore TeWail on WUiV on nexW couple of VliTeV. `Very easy to implement and very easy to add extend its abilities by the adding of different modules. This is why this server has become so popular.

AV you can Vee

WUe TeVignerV of

Apache decided

to take a modular approacU Vo WUaW anyone can aTT Wo

WUe baVic

funcWionaliWy of

WUe Verver wiWUouW

TiVWurbing WUe

baVic Core implemenWaWion.

yA Web Server is any Machine that receives requests from a client machine and is able to turn around process the requests and VenT back a reVponVe. TUiV iV uVually in WermV of a Peb Server Wo VenT back a Peb pageV wUen people wUaW Wo go navigaWe Wo a webpage WUaW iV UoVWeT on WUaW Verver now one may aVk Uow To you VenT anT receive WUe informaWion Wo anT from WUe Verver. TUiV iV wUere HTTP beginV Wo play a role inWo Uow WUiV all goeV abouW.

yHTTP Protocol: HTTP VWanTV for Hyper-TexW-TranVfer-ProWocol `Multithreaded and Multi-processed Web Servers `When an HTTP request arrives, the Web server starts fetching WUe reVource aV requeVWeT by WUe clienW. PUile WUe Peb Verver iV buVy feWcUing reVourceVH WUe clienW compuWerV migUW VenT more requeVWV. TUiV WoWal of requeVWV are neeTeT for processing. These requests are either ignored or handled simultaneously by the Web server. `Web servers that ignore other requests or they will even queue WUem wUile WUe VerverV are buVy. TUiV proceVV iV calleT Vingle-WUreaTeT Peb VerverV. TUiV meanV WUaW WUey are incapable of handling high Web server traffic. However, these types of Web servers are ideal for Web sites that encounter low or moTeraWe Wraffic. `Web servers that can handle simultaneous requeVWVH manage WUe requeVWV in Wwo wayV.

NiWUer WUey VWarW a new proceVV or WUey VWarW a

new WUreaT wiWUin a proceVV. Peb VerverV WUaW

VWarW a new proceVV on eacU requeVW are calleT

multi-proceVVeT Peb VerverVH wUile WUoVe WUaW start a new thread within the main process are calleT mulWiWUreaTeT Peb VerverV. TUe iV a

VligUW Tifference among WUoVe Werminology.

`IIS (Internet Information Services) on the

Windows platform is an example of a

multithreaded Web server. Apache on a Unix plaWform iV a mulWi-proceVVeT Peb Verver. `Windows platform lack forking for server client requeVW inWeracWion wUicU puW ApacUe on a

Unix plaWform more efficienW. Unix iV WUe

software for the hardware architecture of a web based server. `As we stated before the Client makes an HTTP request to the server in this case the Apache Web

Verver WUen WUe Verver UanTleV WUe

Verver poolV WUe connecWionV Wo iWH

by WUe baVic inVWrucWionV wiWUin WUe

ApacUe Core WUen WUe Verver VenTV

back a reVponVe. Óany people To noW realiYe WUaW WUey be uWiliYing an

ApacUe web Verver everyTay Vince

iW iV WUe moVW popular web Verver ouW rigUW now. PUen you go online and request a webpage. Most likely an Apache Web server is proceVVing your requeVW anT WUen iW iV VenTing you back WUe webpage you requeVWeT. `As I mentioned Before The overall overview of the Apache Web Server is comprised of a Modular approach to the way WUe VyVWem iV builW inVWeaT of juVW Uaving WUe Verver juVW be one piece of coTe UanTling everyWUing. TUiV in Wurn allowV for more robuVWneVV anT allow for beWWer cuVWomiYaWion wiWUouW geWWing riT of WUe VecuriWy WUaW iV implemenWeT wiWUin WUe

ApacUe Core.

`In order to achieve this Modular Approach the Apache MeVignerV TeciTeT Wo break Town WUe Verver inWo Wwo main

ComponenWV.

Server. Such as allocating requests and maintaining and pooling all WUe connecWionV. ŃThe Apache Modules: PUicU are in a VenVe WUe aTTeT exWenVionV Wo WUe Verver wUicU UanTle a loW of WUe oWUer WypeV of proceVVing WUe Verver muVW acUieve VucU aV Toing uVer AuWUenWicaWion. `This is what usually occurs in the Apache Core in a sense an overview of the flow that happens in the Apache Core. This is the Apache Core interacting with all the other components that VurrounT iW. TUeVe are WUe core componenWV of WUe ApacUe arcUiWecWure. TUe purpoVe for WUiV waV WUaW WUe TeVignerV wanWeT PR NHHS HYHU\ ŃRPSRQHQP POMP GLGQ·P QHHG HMŃO RPOHU VHSMUMPH so they made them into modules. So this is what was left after HYHU\POLQJ RMV OHIPB 6R POLV LV POH %MVLŃ ´NUMLQµ RI POH $SMŃOH

Web Server.

`The Apache Core is comprised of many different little ŃRPSRQHQPV POMP·V OMQGOH POH %MVLŃ LPSOHPHQPMPLRQ RI ROMP M web server should be doing. `The core components are a series of classes that handle Vpecific WaVkV. TUeVe VUoulT noW be confuVeT wiWU moTuleVH which are just add on implementations of different things that Apache can be customized to do. Modules will be explaineT more in TeWail in WUe furWUer VliTeV. `The Apache Core provides us with the Main functionality of a HTTP web Verver. PiWUouW iW or allowing a cUange Wo iW will remove its modularity, but also remove some of the security. This is why Modules are needed in order to extend the core funcWionaliWy of ApacUe. `The core components of make up the Apache core are as follows: Ńhttp_protocol.c: TUiV iV WUe componenW WUaW UanTleV all of WUe rouWineV WUaW communicaWe TirecWly wiWU WUe clienW by uVing WUe HTTP proWocol. TUiV iV WUe componenW WUaW knowV Uow Wo alVo UanTle WUe VockeW connecWionV WUrougU wUicU WUe clienW connecWV Wo WUe Verver. All TaWa WranVfer iV Tone WUrougU WUiV componenW. Ńhttp_main.c: WUiV componenW iV reVponVible for WUe VWarWup of WUe Verver anT conWainV WUe main Verver loop WUaW waiWV for anT accepWV connecWionV. IW iV alVo in cUarge of managing WimeouWV. Ńhttp_request.c: TUiV componenW UanTleV WUe flow of requeVW processing, passing control to the modules as needed in the right order. It is also in charge of error handling. Ńhttp_core.c: WUe componenW implemenWing WUe moVW baVic functionality, it just bairly serves documents. Ńalloc.c: WUe componenW WUaW WakeV care of allocaWing reVource poolVH anT keeping Wrack of WUem. Ńhttp_config.c : WUiV componenW proviTeV funcWionV for oWUer uWiliWieVH incluTing reaTing configuraWion fileV anT managing WUe informaWion gaWUereT from WUoVe fileV ()H aV well aV VupporW for WUe liVW of moTuleV WUaW will be calleT Wo Vervice Turing TifferenW pUaVeV of WUe requeVWV WUaW are going on wiWUin WUe Verver. `As you can see apache has many different components within WUe Core WUeVe all allow WUe Verver Wo be more Vecure anT more robuVWH buW alVo Tue Wo WUe implemenWaWion of WUe arcUiWecWure raiVeV VecuriWy Vince anyone WUaW wanWV Wo aTT funcWionaliWy Wo WUe Verver muVW To Vo by WUe uVe of moTuleV. `Before we can continue to talk about the Apache Modules we must be able to talk about what are the request phases that are going on wiWUin WUe core. In oWUer worTV Uow ToeV ApacUe know wUaW Wo To wiWU a requeVW WUaW iW receiveT from WUe clienW buW alVo wUaW Vo iW ToeV afWer iW UaV receiveT WUe requeVW anT wUere ToeV iW go from WUere in orTer Wo UanTle WUe requeVW WUaW waV maTe Wo iW. TUiV iV wUere requeVW PUaVeV come inWo play. `Modules due to the architecture of Apache do not know TirecWly abouW eacU oWUer anT noW one moTule alone can completely fill or process the request that is made to the Apache server. Most requests are processes by sending the informaWion from one moTule back Wo WUe core WUen back Wo anoWUer moTule unWil WUe requeVW iV compleWely UanTleT anT WUen iW iV VenW back Wo WUe clienW. ApacUe UaV VomeWUing calleT componenW of WUe core. `The phases or the logic that the HTTP_REQUEST Module of the Apache core controls are as follows:

ŃURI to filename translation;

ŃCheck access based on host address, and other available informaWion; ŃGet an user id from the HTTP request and validate it;

ŃAuthorize the user;

ŃDetermine the MIME type of the requested object (the conWenW WypeH WUe encoTing anT WUe language); ŃFix-upV (for example replace aliaVeV by WUe acWual paWU);

ŃSend the actual data back to the client;

ŃLog the request;

`Modules were made to extend/overwrite and implement the functionality of the Apache web server. `+RRHYHU PRGXOHV GR QRP GLUHŃPO\ H[PHQG HMŃO RPOHU RU ´NQRRµ directly about each other. `So in turn Modules are connected to the Apache core all the same way. `Modules since they do not know directly about each other muVW paVV all in formaWion back Wo WUe core anT WUen WUe core VenTV WUaW informaWion Wo anoWUer appropriaWe moTule Apache Core. This in turn does not allow any changing of the stable Apache Core, but also implements a layer of security, becauVe no proceVV can move on wiWUouW paVVing WUe in formaWion Wo WUe Core anT WUe core cUeckV anT UanTleV errorV `Apache web server has a modular architecture with a core componenW WUaW TefineV WUe moVW baVic funcWionaliWy of a web Verver anT a number of moTuleV wUicU implemenWV WUe VWepV of proceVVing a HTTP requeVWH offering UanTlerV for one or more of the phases. The core is the one that accepts and manages HTTP connections and calls the handlers in modules in WUe appropriaWe orTer Wo Vervice WUe currenW requeVW by parenW anT cUilT. `Concurrency exists only between a number of persistent identical processes that service incoming HTTP requests on the same port. Modules are not implemented as separate proceVV alWUougU iW iV poVVible Wo fork cUilTren or Wo cooperaWe wiWU oWUer inTepenTenW proceVV Wo UanTle a pUaVe of proceVVing a requeVW. `The functionality of Apache can be easily changed by writing new modules which complements or replace the existing one. TUe Verver iV alVo UigUly configurableH aW TifferenW levelV anT moTuleV can Tefine WUeir own configuraWion commanTV. `One cool thing about Apache that makes it robust and allows for beWWer VpeeT iV WUe facW WUaWH ApacUe allowV for iniWialiYaWion of moTuleV Mynamically. So noW every moTule iV started when the server starts up which really allows for a giant speed boost. `So what this allows is Apache to only initialize the modules WUaW iW neeTV aW WUaW momenW. PUicU allowV requeVWV Wo be proceVVeT a loW faVWer WUan uVual. `Modules have something inside them that are called

Handlers.

ŃHandlers: A UanTler iV for ApacUe WUe acWion WUaW muVW be performeT in Vome pUaVe of Vervicing a requeVW. Ńor example a UanTler WUaW requeVWV a file muVW open WUe file WUen reaT WUe file then send it to the Apache core to then be sent to the client. Handlers are defined by the modules depending on when they are neeTeT Wo fulfill a requeVW WUen WUe HanTlerV are WUe oneV WUaW VenT back WUe proceVVing from WUe ApacUe ÓoTule Wo WUe ApacUe `Overview of the

Handler system within

an Apache Module. As you can Vee WUe

HanTler ToeV wUaW iW

neeTV Wo To Wo fulfill a requeVW WUen WUe VenTV

WUaW proceVV back Wo

componenW of WUe

ApacUe core in orTer

Wo be VenW Wo anoWUer

module for processing or back to the client. `Module Configuration `If you are using a static configuration of Apache, choose the moTuleV you wiVU Wo incorporaWe wiWU care. UVing VWaWic moTe comeV aW a price ³ WUe more moTuleVH WUe more memory you uVe. TUuVH a forkeT mulWi-proceVVing moTule can Uave a VignificanW effecW on WUe macUineGV memory requiremenWV. `Note that some items are automatically included, so you'll neeT Wo expliciWly enable anT TiVable neeTeT moTuleV. AlVo remember Wo incluTe any WUirT-parWy moTuleV (e.g.H UVe configure --Uelp Wo geW a liVW of WUe available opWionV. Apache provides access to two levels of concurrency. The concurrent processes executing truly simultaneously, in the case WUaW WUey run on VeparaWe proceVVorVH aV in WUe caVe of VeparaWe proceVVeV running on a mulWiWaVking VyVWem. AV wellH if mulWi- WUreaTing iV VupporWeT by WUe operaWing VyVWemH a TefaulW of up Wo

50 WUreaTV iV alloweT for eacU proceVV.

`Each request that the server receives is actually handled by a copy of WUe UWWp program. So raWUer WUan creaWing a new inVWance copy wUen iW iV neeTeTH anT TeVWroying iW wUen a request is finished, Apache maintains at least 5 and at most

10 inactive children at any given time. The parent process

runV a perioTic cUeck on a VWrucWure calleT WUe VcoreboarTH wUicU keepV Wrack of all exiVWing Verver proceVVeV anT WUeir

VWaWuV.

`If the scoreboard lists is ever less than the minimum number of idle servers, then the parent will spawn more. `If the scoreboard lists more than the maximum number of iTle VerverVH WUen WUe parenW will proceeT Wo kill off WUe exWra cUilTren. `When it receives a request, the parent process passes it along to the next idle child on the scoreboard. Then the parent goeV back Wo liVWening for WUe nexW requeVW. `When doing the parent and child request there is a limit which by default is set to 256 of the total number request at one time. The default settings was programmed by the creaWorV for WUe Verver waV Wo pick in orTer Wo keep WUe VcoreboarT file Vmall enougU Vo WUaW iW can be VcanneT by WUe proceVVeV wiWUouW cauVing overUeaT concernV. `Since the number of requests that can be processed at any one time is limited by the number of processes that can exist, WUere iV a queue proviTeT for waiWing requeVWV. TUe queue waiWing liVW waV menWioneT Wo be wUen WUe parenW paVVeV a requeVW Wo a cUilTH wUicU waV iTleH WUen WUe parenW reWurnV Wo receive next request. The maximum number of pending requests that can sit on the queue can reach somewhere in

WUe 400-600.

`Apache server architecture was designed to maximize one connecWion. TUe uVeV WUe perViVWenW connecWion Wo allow multiple requests from a client to be handled by one connection, rather than opening and closing a connection for eacU requeVW. TUe TefaulW maximum number of requeVWV alloweT over one connecWion iV 100. TUe connecWion iV cloVeT by a WimeouW.

Security Perspective

Hopefully wiWU WUe preVenWaWion of WUe ApacUe Verver. You can now know what multi-proceVVeT Peb VerverV are anT how Apache qualifies to be one. AnoWUer imporWanW aVpecW WUaW iV worWU TiVcuVVing iV Uow proceVVeV work. Two WypeV of proceVVeV are invokeTH parenW anT cUilT. TUe parenW proceVV iV WUe main proceVV from wUicU several child processes are invoked.

Now Uow ToeV WUiV imply Wo VecuriWy rigUW?

PUenever a requeVW iV VenW Wo WUe ApacUe Peb VerverH WUe parenW proceVV receiveV WUe requeVW. TUen WUe parenW proceVV forwarTV WUe requeVW Wo one of WUe cUilT proceVVeV. TUe cUilT process then handles the request by responding to it. This behavior is supported for a valid reason: security. `The root user (SuperUser has all privileges like an Admin) initiates the parent process of the Web server in UNIX VyVWemV. TUe rooW uVerH iV WUe moVW powerful uVer on WUe UNIX VyVWem. Ńor VecuriWy reaVonVH WUe parenW proceVV ToeVnGW TirecWly proceVV WUe requeVWV VenW by WUe clienWV. `For example, if a client sends a request with malicious inWenWionV anT WUe parenW proceVV UanTleV WUe requeVW. TUe parenW proceVV will being run aV a rooW uVer (SupperUVer) will Uave all neceVVary rigUWV Wo perform any operaWion on WUe compuWerH WUereby making WUe VyVWem Verver vulnerable. However, if the request is forwarded to a process that has restricted permissions on the computer, no harm can be done wUicU iV UanTleT in WUe cUilT proceVV. TUiV iV becauVe cUilT proceVVeV are run aV uVerV wiWU reVWricWeT privilegeV. `Providing any kind of system information to a hacker could poWenWially proviTe a Uacker wiWU WUe ammuniWion WUey neeT to break into your server. The less a hacker knows about the configuration of a system, the harder it is to break into. The iVVue WUaW many buVineVV uVeV ApacUe Verver Wo UoVW webViWeV. `One of the most common exploits used by hackers is to "take over" a service running on the server and use it for their own purposes. For example, gaining access to a mail application via an HTÓL form-baVeT VcripW. Hacker woulT uVe WUe mail Verver Wo VenT ouW Vpam or acquire confiTenWial uVer informaWion. `While not a direct security threat, a poorly written application can use up a system's available resources to the point where iW becomeV almoVW compleWely unreVponVive. `Safe programming layer to prevent buffer overrun exploitsquotesdbs_dbs9.pdfusesText_15

[PDF] apache web server complete guide pdf

[PDF] apache web server configuration in linux step by step pdf

[PDF] apache web server license

[PDF] apache web server tutorial

[PDF] apache: the definitive guide

[PDF] apache: the definitive guide pdf

[PDF] apartment for rent in paris texas

[PDF] apartment for rent in paris tx

[PDF] apartment for rent near geneva switzerland

[PDF] apartment rental basel switzerland

[PDF] apartment rental bern switzerland

[PDF] apartment rental geneva switzerland

[PDF] apartment rental lake zurich switzerland

[PDF] apartment rental verification form

[PDF] apartment rental zurich switzerland