Thola ukufinyelela kwangaphakathi kwe-Consistency, Availability, ne-Partition Tolerance okwenziwe ngokuvamile emakheni yokukhiqiza. Hey abantu, ngiye lokufaka. Ngizokuthunyelwe isikhathi eside, ngazi, ngazi. Phakathi nenkqubo yokusebenza, ukuphila, kanye nesikhathi esivamile "ukuba umuntu ushiye lokhu?" isibambisane spiral, ngithumela le blog ukuthatha ipuleti. Kodwa ngifike ngezindlela ezintsha. Ngaphandle kwezindaba ezivamile ezivela emathemikhali ezivamile, ngitholela izigaba ezihlangene nezinhlelo zokusebenza eziyinhloko ukuthi ngitholile ngokuphathelene ngempumelelo emzimbeni yami. I-content yobuchwepheshe engaphezu kwe-interview answer futhi ku-production real trade-offs. U-CAP ye-theorem ye-catalogue ye-catalogue ye-catalogue ye-catalogue ye-catalogue ye-catalogue ye-catalogue ye-catalogue ye-catalogue ye-catalogue ye-catalogue ye-catalogue ye-catalogue ye-catalogue ye-catalogue ye-catalogue. Thank you for sticking around (noma for just discovering this blog). Thola ucwaningo pamoja. Thola i-series ephelele ye-4-part ngqo ku-inbox yakho. 
 
 Kuyinto Part 1 ye-4-part series ku-CAP theorem kanye ne-distributed systems trade-offs. Kuyinto Part 1 ye-4-part series ku-CAP theorem kanye ne-distributed systems trade-offs. Uma ubhaliswe ngezinombolo ezingenalutho noma zezinombolo ezingenalutho ezingenalutho ngaphakathi kweminyaka eminingi edlule, sicela ubhaliswe imibuzo yokwakha izinhlelo okuyinto ekugcineni kuholele ku-version ye-CAP theorem. Futhi ungacebisa ngezinye izinto ezivela eminyakeni se-"ingaba ukhethe kuphela ezimbili kusuka ku-three". Umehlile...kinda. Nangona kungcono ubuchwepheshe, inkulumo emzimbeni kuyinto grotesquely over-simplified. Lezi oversimplification ivela kwangena wena lapho uxhumane ukuthi isitoreji yakho yedatha esithathwe. Ikhono yami kuyinto ukunciphisa ukuthi i-CAP i-theorem inikeza nathi futhi inikeza indlela izinhlelo zokukhiqiza zithintela le "pick two" iholide. Yini i-CAP Theorem? Thina ukuguqulwa kwelanga, ngo-2000, I-Inktomi Corporation, emzimbeni we-PODC symposium ye-ACM, wabhala isivumelwano esithakazelisayo ama-developers iminyaka eminyakeni: isitoreji se-distributed data angakwazi ukugcina kuphela amabili angu-2 of the three of the following: Consistency, Availability, and Partition Tolerance. U-Eric Brewer Emva kweminyaka embalwa, i-theorem ye-Briewer yasungulwa ngokuvumelana ne-proof ngu-Seth Gilbert no-Nancy Lynch. I-theorem, i-idea etholakalayo, yonke into etholakalayo. Kodwa eminye eminyakeni embalwa embalwa embalwa embalwa embalwa embalwa embalwa embalwa. Okwamanje, wonke umuntu uyazi i-"pick two" ingxenye ye-hypothesis, kodwa ngokuvamile zihlanganisa indawo enhle kakhulu: . you only have to pick two   a network partition during Kwangathi Uma inethiwekhi kuyinto enhle, ungakwazi ukufinyelela yonke ezintathu. I-theorem inikeza ukulawula kuphela lapho izimo zihlukile - lapho uqala ukuphazamiseka ama-network packets, noma ama-switches zihlukile, noma lapho umgogodla uxuba umugqa we-fiber (eye kwenziwa Amazon). I-CAP Theorem: Consistency, Availability, and Partition Tolerance Sishayele kakhulu mayelana ne-C, i-A, ne-P ngokwenene ne-imeyili zabo, ngoba izici ezivamile zihlanganisa ngezifiso. What Is Consistency ku-CAP Theorem? (Linearizability) Uma i-CAP i-theorem ibizwa ku-consistency, ibizwa ku-highest form of consistency. . Uma usuka emkhakheni yebhizinisi, uye wabhala umugqa we-strength and weakly. I-atomic consistency iyiphi isinyathelo ephakeme kakhulu. I-atomic consistency iyaziwa nangokuthi . Ukusebenza kwe-atomic Ukuhlobisa Ukuhlobisa Linearizability kuyinto lapho zonke izinhlelo zokusebenza Ngokwesibonelo, uma isebenze isebenze A ngaphambi isebenze B, then operation B should logically take effect after operation A. Ngokwesibonelo, uma isebenze A isebenze ngaphambi isebenze B, then operation B should logically take effect after operation A. Ukuhlobisa Thola usebenzisa isibonelo yomhlaba real ukuze kusiza ukucubungula lokhu umqondo. Qinisekisa ukuthi uxhumane isilinganiso yakho yebhanki futhi uzobona $5,000. Ungayifaka ukuthi uxhumane $1000 kusuka ku-akhawunti. Ngemuva kwalokho uxhumane isilinganiso yakho. Linearizability I-$4000 (noma inguqulo), kodwa akuyona i-$5000 embalwa. I-transfer iye kwenziwa noma akuyona. Akukho isimo lapho uzothola i-value esidala ngemuva kokufaka i-value entsha. Izinzuzo Izinzuzo Ngena ngemva Kuyinto amandla kunazo zonke ama-nodes ngempumelelo ukubonisa idatha efanayo” – lokhu kubizwa ngokuthi Ngiya Yini i-CAP Theorem ibizwa. a lot Ukulungiselela is NOT Ngenxa yokuba kukhona izinhlelo eziningana ezinzima imodeli ukuxhumana, ezifana: ukulayishwa monotonous, ukulayishwa-your-writes, futhi ukuxhumana kwe-causal, ngenkathi kubalulekile kakhulu. Kodwa zonke lezi amamodeli zangaphakeme kunoma linearizability, okwenza ukuthi izinhlelo zingatholakala I-CAP i-theorem ayidinga izinhlelo ezisebenzisa lezi zibonelelo, kuphela i-linearizability. Ngaphansi kakhulu Yini i-Accessibility ku-CAP Theorem? I-CAP ye-definition ye-availability iyatholakala kakhulu, ithi: "Uma wonke isicelo ku-non-failing node Thola impendulo » ikhaya Qaphela ukuthi lokhu akuzodinga noma enye yezinto ezilandelayo: 
 
 
 
 Ukusabela kufanele kube ngokushesha. Ukubuyekezwa ukuthi imibuzo kufuneka kuyinto elula. Kuyinto ezininzi ama-nodes kufuneka ukuguqulwa. Ngokwesibonelo, uma unayo i-cluster ye-10 ye-nodes futhi ama-nodes ezine ze-4 zihlanganisa, ama-nodes ezine ze-4 zihlanganisa Ukuphendula izivakashi ziye zihlanganiswe ngokuthi "kuhambelana" ngaphansi kwe-CAP ye-definition ye-"availability". Kulesi isibonelo, isithombe se-4xx noma isibuyekezo se-stable kusebenza ngokuthi "kuhambelana". must Ngiyazi lwezimfihlo: Phakathi ne-network partition, i-MongoDB primary replica set okuyinto angakwazi ukufinyelela zonke ama-replicas angu-secondary ngeke "ukuguqula" futhi zixazulwe ngokugcwele. Lezi zithombe zithole isikhathi. Ngokusho i-CAP theorem. , nangokuthi inqubo ye-MongoDB isebenza njenge-anticipated. unavailability Yini I-Partition Tolerance? (Why You Can't Avoid It) Kuyinto lapho i-”pick two” umkhakha umkhakha. I-Partition Tolerance inikeza ukuthi uhlelo yakho isebenza njengokuthunyelwe nangokuthi inethiwekhi iveza ama-nodes akho ku-groups angakwazi ukuxhumana. Khona-ke ukuthi? Lokhu akuyona wena. I-network partitions iyona inqubo ezihlangeneyo. I-internet etholakalayo ngosuku, i-data centers ezihlangene izicelo zethu zihlanganisa lokhu. Ama-switches zihlanganisa, ama-fiber zihlanganisa, ama-cloud providers zihlanganisa i-accessibility zone, ama-packages zihlanganisa, ngisho ngaphakathi kwe-datacenter, kukhona izimo zebhizinisi ezihlangeneyo. Kuyinto engatholakali. Ukubuyekezwa kwe-Reality Ngaba ushiye phakathi kwe-C, i-A, ne-P. Ngaba ushiye phakathi kwe-C kanye ne-A lapho i-P akukwazi ukufinyelela. partition tolerance is absolutely mandatory I-trade-off yokuqala Okay, thina siphinde ukuthi kungenzeka lapho inethiwekhi ngempumelelo. Ngaphambi kokwenza lokhu, sicela ukuguqulwa kwegama le-CAP kanye nemikhiqizo yayo uma P (Partition Tolerance) iyadingeka ngokuphelele: 
 
 
 I-Consistency: Ukukhuthaza imibuzo enokuthumela idatha enhle (ukukhuthaza ukufikelela) Ukubuyekezwa: Ukubuyekeza zonke imibuzo, ngisho uma idatha kuyimfuneko (ukubuyekeza ukuxhaswa) Okokuqala, sicela ukuthatha isicelo esifundeni: " inethiwekhi isikhwama”. Uma inethiwekhi iyatholakala, singatholakala kanye nokufinyelela. Uma akukho partition? Ungatholakala futhi. I-app yakho yebhanki yebhanki inikeza izilinganiso ezingenalutho, zokusebenza ngokushesha nangokufinyelela kakhulu – ngoba isikhathi eside, inethiwekhi isebenza ngokushesha. Ungathola inethiwekhi yakho, ukuhambisa imali, futhi ukubonisa inani olushintsha ngokushesha. Kwangathi Umbuzo ukuthi i-CAP i-theorem inikeza wena ukufinyelela: What should your system do when the network eventually fails? I-core trade-off: Phakathi ne-partition, izinhlelo ze-CP zihlanganisa ukubonisa idatha ebuthakathaka ngokuvumelana. Ama-AP izinhlelo zihlanganisa ku-stoptime ngokuvimbela idatha ebuthakathaka. Akukho iyiphi isizukulwane esihle noma ebuthakathaka, konke kuxhomekeke ukuthi kungcono isistimu yakho. I-CP Systems: Ukukhetha I-Consistency Ngaphezulu Kwama-availability I-CP systems ivame ukuthi ngexesha le-network partition, izivakashi zixazulule ngaphandle kokufaka idatha eyenziwe. Yini, lapho lokhu kubalulekile? 
 
 
 Banks: Uma umsebenzisi ivumela i-transaction, kungcono ukuba isithombe kancane noma ingozi ukuthi i-transaction ivela ezimbini? Okungenani okokuqala, okungenani? Thina ngokuvamile akuyona abathengi ukuthi i-transaction iyatholakala lapho akuyona. Thina akuyona ngokuvamile i-30 amaminithi kuncike ukuthi. Ukulawula I-Inventory: Uma akufanele ukuba imikhiqizo iyatholakala, kungcono ukunciphisa inkonzo noma ukunceda amathuba yokuthengisa okungenani? Thola uchofoza uhlelo yomhlaba real, Ukusuka kwebhizinisi yabo: "etcd kuyinto enhle kakhulu, ibhizinisi key-value eyenziwe ... It ukulawula ukwahlukanisa umongameli ngesikhathi imisindo yebhizinisi futhi ingatholela isixazululo machine, ngisho node umongameli." etcd Kubernetes isebenzisa etcd njenge-backup store yayo kuzo zonke izakhiwo ze-cluster. Uma usebenzisa Kubernetes ngaphambi kwalokho, ubona I-command isizukulwane. Isikhathi esisodwa: etcd ayikwazi ukufinyelela ama-nodes emininzi, kuvimbela ukufinyelela ( iziphumo) ukuze linearizability. kubectl kubectl I-AP Systems: Ukukhetha Ukuphepha Ngaphezulu kokusebenza Izinkqubo ze-AP zihlanganisa ukuthi ngesikhathi kokuhlanganisa inethiwekhi, zihlanganisa ukunikela idatha ebuthakathaka kunoma ukunciphisa imibuzo. Izindlela ezimbalwa lapho lokhu kusetshenziselwa: 
 
 
 I-Social Media Feeds: Abasebenzisi akugqithisa kakhulu ukuthi isicelo ivumela impendulo ebuthakayo / ebuthakayo kunokwenzeka ngokuphelele. Ngaphezu kwalokho, kubalulekile ukuba umdlali awukwazi ukubonisa imiphumela emkhatsini yayo eminyakeni embalwa? Akukho kakhulu. Isithombe se-user ye-app ebuthakayo kunzima kakhulu kunamaxesha lokuphendula ebuthakayo. I-Shopping Carts: Umzekelo enhle kakhulu kulokhu i-Amazon's DynamoDB, okuyinto ngokuvamile yasungulwa ukuhlangabezana ne-shopping cart problem yayo; kuyinto "ngokusebenza njalo" imijikelezo. Ungafaka njalo ku-shopping cart. Akunemibala ukuba umuntu omunye uhamba nge-shopping cart yakho (i-Amazon izixazulule izinguquko), uzothola njalo "ngafaka ku-shopping cart". Ukuze i-real-world AP system, ungathanda kakhulu, i-AP system enhle kuphela i-DNS ngokuvamile. I-DNS, i-Domain Name System, iyisisombululo enhle ye-AP system, futhi bonke sinasebenzisa amakhulu amahora ngosuku ngaphandle kokufunda. Uma idivayisi ye-DNS iyahlaziywa, idivayisi asebenzayo ayihlaziywa ngamazwe ngamazwe ngamazwe ngamazwe ngamazwe ngamazwe ngamazwe ngamazwe ngamazwe ngamazwe ngamazwe ngamazwe ngamazwe ngamazwe ngamazwe ngamazwe ngamazwe. , I-DNS ayizange "ukukwazi ukufinyelela". It uzothola impendulo, ngisho uma lesi impendulo uxhumane. Lokhu kubalulekile ukuthi izibuyekezo ze-DNS zihlanganisa isikhathi futhi ukuthi izindawo ezithile zihlanganisa engatholakala kumadoda lapho akuyona izibuyekezo. Ngokusho kwe-DNS, ukuxhaswa kokuphumelela kuyinto engcono kakhulu kunesikhathi sokuphumelela, okuyinto angacindezela inthanethi. however Okulandelayo Up: I-Cost Hidden Of Choosing I-Consistency Kuhlolwe kulandelayo kulesi sethu, siphinde emangalisayo emakhemikhali CP-databases kanye namasevisi eziholela ukuxhaswa kunomthelela ngesikhathi isixazululo webhizinisi. Sihlola: 
 
 
 
 Ungayifaka kanjani izinhlelo ze-CP zibonisa ukuxhumana okuqinile. Izindleko zokuxhumana. Uma ukhethe ukuzinza phezu ukufinyelela kubalulekile. I-"pick two" inikeza i-illusion of being stuck with your choice for the entire lifetime of the system, lapho ngokwenene, ngokwemvelo kuyinto enhle kakhulu. I-Subscribe to get Part 2 lapho ivuliwe. Ngiyaxolisa. Uma ungenza le post, sicela ubhalisele, njengoba inikeza nami ukujabulela. Uluhlu Ukuhlobisa 
 
 
 
 U-Eric Brewer's 2000 Podc Ukubonisa I-Briewer's Conjecture ne-Feasibility of Consistent, Available, Partition-Tolerant Web Services ngu-Nancy Lynch noSeth Gilbert Waze

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