{"id":30782,"date":"2019-10-31T21:37:25","date_gmt":"2019-10-31T18:37:25","guid":{"rendered":"https:\/\/prohoster.info\/blog\/razrabotka-veb-serverov-na-golang-ot-prostogo-k-slozhnomu\/"},"modified":"2019-10-31T21:37:25","modified_gmt":"2019-10-31T18:37:25","slug":"razrabotka-veb-serverov-na-golang-ot-prostogo-k-slozhnomu","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sk\/blog\/news\/razrabotka-veb-serverov-na-golang-ot-prostogo-k-slozhnomu","title":{"rendered":"V\u00fdvoj webov\u00fdch serverov v Golangu \u2014 od jednoduch\u00e9ho k zlo\u017eit\u00fdm","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

\"V\u00fdvoj
\n
\nPred piatimi rokmi som za\u010dal vyv\u00edja\u0165 Gophish<\/a><\/noindex>, to mi umo\u017enilo \u0161tudova\u0165 Golang. Pochopil som, \u017ee Go je mocn\u00fd jazyk, ktor\u00e9ho mo\u017enosti s\u00fa doplnen\u00e9 mnoh\u00fdmi kni\u017enicami. Go je univerz\u00e1lny: konkr\u00e9tne, s jeho pomocou je mo\u017en\u00e9 bez probl\u00e9mov vyv\u00edja\u0165 serverov\u00e9 aplik\u00e1cie.<\/p>\n

Tento \u010dl\u00e1nok sa venuje p\u00edsaniu servera v Go. Za\u010dneme od jednoduch\u00fdch vec\u00ed, ako je \u201eHello world!\u201c, a skon\u010d\u00edme aplik\u00e1ciou s tak\u00fdmito mo\u017enos\u0165ami:<\/p>\n

\u2014 Pou\u017e\u00edvanie Let\u2019s Encrypt pre HTTPS.
\n\u2014 Pr\u00e1ca ako API-router.
\n\u2014 Pr\u00e1ca s middleware.
\n\u2014 Spracovanie statick\u00fdch s\u00faborov.
\n\u2014 Spr\u00e1vne ukon\u010denie.
\n<\/a><\/noindex><\/p>\n

Skillbox odpor\u00fa\u010da:<\/b> Praktick\u00fd kurz \u201ePython-developer od nuly\u201c<\/a><\/noindex>.<\/p>\n

Pripom\u00edname:<\/b> pre v\u0161etk\u00fdch \u010ditate\u013eov \u201eHabr\u201c \u2014 z\u013eava 10 000 rub\u013eov pri zap\u00edsan\u00ed na ak\u00fdko\u013evek kurz Skillbox s promo k\u00f3dom \u201eHabr\u201c.<\/i>\n<\/p><\/blockquote>\n

Ahoj, svete!<\/h3>\n

\nVytvorenie webov\u00e9ho servera na Go je ve\u013emi r\u00fdchle. Tu je pr\u00edklad pou\u017eitia obsluhy, ktor\u00e1 vracia s\u013e\u00faben\u00e9 \u201eAhoj, svete!\u201c.<\/p>\n

package main\n \nimport (\n\"fmt\"\n\"net\/http\"\n)\n \nfunc main() {\nhttp.HandleFunc(\"\/\", func(w http.ResponseWriter, r *http.Request) {\nfmt.Fprintf(w, \"Hello World!\")\n})\nhttp.ListenAndServe(\":80\", nil)\n}<\/code><\/pre>\n
\nPotom, ak spust\u00edte aplik\u00e1ciu a otvor\u00edte str\u00e1nku localhost<\/noindex>, okam\u017eite uvid\u00edte text \u201eAhoj, svete!\u201c (samozrejme, ak to v\u0161etko funguje spr\u00e1vne).<\/p>\n
Potom budeme opakovane pou\u017e\u00edva\u0165 obsluhu, ale najprv pochop\u00edme, ako to v\u0161etko funguje.<\/p>\n
net\/http<\/h4>\n
\nVo vzore bol pou\u017eit\u00fd bal\u00edk net\/http<\/code><\/a><\/noindex>, je to z\u00e1kladn\u00fd prostriedok v Go na v\u00fdvoj serverov a HTTP klientov. Aby sme porozumeli k\u00f3du, po\u010fme sa pozrie\u0165 na v\u00fdznam troch d\u00f4le\u017eit\u00fdch prvkov: http.Handler, http.ServeMux a http.Server.<\/p>\n
HTTP spracovatelia<\/h4>\n
\nKe\u010f dostaneme po\u017eiadavku, spracovate\u013e ju analyzuje a vytv\u00e1ra odpove\u010f. Spracovatelia v Go s\u00fa implementovan\u00ed nasledovne:<\/p>\n
type Handler interface {\n        ServeHTTP(ResponseWriter, *Request)\n}<\/code><\/pre>\n
\nV prvom pr\u00edklade sa pou\u017e\u00edva pomocn\u00e1 funkcia http.HandleFunc. Obaluje in\u00fa funkciu, ktor\u00e1 na druhej strane prij\u00edma http.ResponseWriter a http.Request v ServeHTTP.<\/p>\n
In\u00fdmi slovami, spracovatelia v Golangu s\u00fa reprezentovan\u00ed jedn\u00fdm rozhran\u00edm, \u010do pon\u00faka mno\u017estvo mo\u017enost\u00ed pre program\u00e1tora. Napr\u00edklad, middleware je implementovan\u00e9 pomocou spracovate\u013ea, kde ServeHTTP najprv nie\u010do rob\u00ed a potom vol\u00e1 met\u00f3du ServeHTTP in\u00e9ho spracovate\u013ea.<\/p>\n
Ako u\u017e bolo spomenut\u00e9, spracovatelia jednoducho vytv\u00e1raj\u00fa odpovede na po\u017eiadavky. Ale ktor\u00fd konkr\u00e9tny spracovate\u013e treba pou\u017ei\u0165 v konkr\u00e9tnom \u010dase?<\/p>\n
Smerovanie po\u017eiadaviek<\/h4>\n
\nAby ste si spr\u00e1vne vybrali, vyu\u017eite HTTP multiplexer. V niektor\u00fdch kni\u017eniciach sa naz\u00fdva muxer alebo router, ale v\u0161etko je to rovnak\u00e9. Funkcia multiplexeru spo\u010d\u00edva v anal\u00fdze cesty po\u017eiadavky a vo v\u00fdbere vhodn\u00e9ho spracovate\u013ea.<\/p>\n
Ak je potrebn\u00e1 podpora zlo\u017eit\u00e9ho smerovania, je lep\u0161ie vyu\u017ei\u0165 extern\u00e9 kni\u017enice. Niektor\u00e9 z najpokro\u010dilej\u0161\u00edch s\u00fa gorilla\/mux<\/a><\/noindex> a go-chi\/chi<\/a><\/noindex>, tieto kni\u017enice umo\u017e\u0148uj\u00fa realizova\u0165 medzi spracovanie bez v\u00e4\u010d\u0161\u00edch probl\u00e9mov. S ich pomocou m\u00f4\u017eete nastavi\u0165 wildcard smerovanie a vykona\u0165 mno\u017estvo in\u00fdch \u00faloh. Ich v\u00fdhodou je kompatibilita so \u0161tandardn\u00fdmi HTTP spracovate\u013emi. V\u00fdsledkom je, \u017ee m\u00f4\u017eete nap\u00edsa\u0165 jednoduch\u00fd k\u00f3d s mo\u017enos\u0165ou jeho modifik\u00e1cie v bud\u00facnosti.<\/p>\n
Pr\u00e1ca so zlo\u017eit\u00fdmi frameworkami v be\u017en\u00fdch situ\u00e1ci\u00e1ch si vy\u017eaduje nie \u00faplne \u0161tandardn\u00e9 rie\u0161enia, \u010do zna\u010dne s\u0165a\u017euje pou\u017e\u00edvanie predvolen\u00fdch spracovate\u013eov. Na vytvorenie drvivej v\u00e4\u010d\u0161iny aplik\u00e1ci\u00ed sta\u010d\u00ed kombin\u00e1cia kni\u017enice predvolenej a jednoduch\u00e9ho smerova\u010da.<\/p>\n
Spracovanie po\u017eiadaviek<\/h4>\n
\nOkrem toho potrebujeme komponent, ktor\u00fd bude \"po\u010d\u00fava\u0165\" prich\u00e1dzaj\u00face pripojenia a presmeruje v\u0161etky po\u017eiadavky spr\u00e1vnemu spracovate\u013eovi. S touto \u00falohou si bez probl\u00e9mov porad\u00ed http.Server.<\/p>\n
Ni\u017e\u0161ie je uveden\u00e9, \u017ee server je zodpovedn\u00fd za v\u0161etky \u00falohy, ktor\u00e9 s\u00favisia so spracovan\u00edm pripojen\u00ed. Napr\u00edklad prev\u00e1dzka cez protokol TLS. Na implement\u00e1ciu volania http.ListenAndServer sa pou\u017e\u00edva \u0161tandardn\u00fd HTTP server.<\/p>\n
Teraz sa pozrime na zlo\u017eitej\u0161ie pr\u00edklady.<\/p>\n
Pridanie Let\u2019s Encrypt<\/h3>\n
\nPredvolene na\u0161a aplik\u00e1cia funguje cez HTTP protokol, av\u0161ak odpor\u00fa\u010da sa pou\u017e\u00edva\u0165 protokol HTTPS. V Go to mo\u017eno urobi\u0165 bez probl\u00e9mov. Ak ste z\u00edskali certifik\u00e1t a s\u00fakromn\u00fd k\u013e\u00fa\u010d, sta\u010d\u00ed uvies\u0165 ListenAndServeTLS so spr\u00e1vnymi s\u00fabormi certifik\u00e1tu a k\u013e\u00fa\u010da.<\/p>\n
http.ListenAndServeTLS(\":443\", \"cert.pem\", \"key.pem\", nil)<\/code><\/pre>\n
\nV\u017edy je mo\u017en\u00e9 to urobi\u0165 lep\u0161ie.<\/p>\n
Let\u2019s Encrypt<\/a><\/noindex> poskytuje bezplatn\u00e9 certifik\u00e1ty s mo\u017enos\u0165ou automatickej aktualiz\u00e1cie. Na vyu\u017eitie slu\u017eby je potrebn\u00fd bal\u00edk autocert<\/code>.<\/p>\n
Najjednoduch\u0161\u00ed sp\u00f4sob, ako ho nastavi\u0165, je vyu\u017ei\u0165 met\u00f3du autocert.NewListener v kombin\u00e1cii s http.Serve. Met\u00f3da umo\u017e\u0148uje z\u00edskava\u0165 a aktualizova\u0165 TLS certifik\u00e1ty, zatia\u013e \u010do HTTP server spracov\u00e1va po\u017eiadavky:<\/p>\n
http.Serve(autocert.NewListener(\"example.com\"), nil)<\/code><\/pre>\n
\nAk otvor\u00edme v prehliada\u010di example.com<\/a><\/noindex>, dostaneme HTTPS odpove\u010f \u201eAhoj, svet!\u201c.<\/p>\n
Ak potrebujete podrobnej\u0161ie nastavenie, mali by ste vyu\u017ei\u0165 mana\u017e\u00e9r autocert.Manager. Potom vytvor\u00edme vlastn\u00fd in\u0161tanciu http.Server (do tejto chv\u00edle sme ho pou\u017e\u00edvali predvolene) a prid\u00e1me mana\u017e\u00e9r do servera TLSConfig:<\/p>\n
m := &autocert.Manager{\nCache:      autocert.DirCache(\"golang-autocert\"),\nPrompt:     autocert.AcceptTOS,\nHostPolicy: autocert.HostWhitelist(\"example.org\", \"www.example.org\"),\n}\nserver := &http.Server{\n    Addr:      \":443\",\n    TLSConfig: m.TLSConfig(),\n}\nserver.ListenAndServeTLS(\"\", \"\")<\/code><\/pre>\n
\nTo je jednoduch\u00fd sp\u00f4sob, ako implementova\u0165 pln\u00fa podporu HTTPS s automatickou aktualiz\u00e1ciou certifik\u00e1tu.<\/p>\n
Pridanie vlastn\u00fdch tr\u00e1s<\/h3>\n
\nPredvolen\u00fd router zahrnut\u00fd v \u0161tandardnej kni\u017enici je dobr\u00fd, ale je ve\u013emi jednoduch\u00fd. V v\u00e4\u010d\u0161ine aplik\u00e1ci\u00ed je potrebn\u00e1 zlo\u017eitej\u0161ia smerovanie, vr\u00e1tane vnoren\u00fdch a wildcard tr\u00e1s alebo proced\u00fary nastavenia \u0161abl\u00f3n a parametrov tr\u00e1s.<\/p>\n
V tomto pr\u00edpade by malo by\u0165 rozumn\u00e9 pou\u017ei\u0165 bal\u00edky gorilla\/mux<\/a><\/noindex> a go-chi\/chi<\/a><\/noindex>. S posledn\u00fdm sa nau\u010d\u00edme pracova\u0165 \u2014 ni\u017e\u0161ie je uveden\u00fd pr\u00edklad.<\/p>\n
M\u00e1me s\u00fabor api\/v1\/api.go, ktor\u00fd obsahuje trasy pre na\u0161e API:<\/p>\n
\/ HelloResponse is the JSON representation for a customized message\ntype HelloResponse struct {\nMessage string `json:\"message\"`\n}\n \n\/\/ HelloName returns a personalized JSON message\nfunc HelloName(w http.ResponseWriter, r *http.Request) {\nname := chi.URLParam(r, \"name\")\nresponse := HelloResponse{\nMessage: fmt.Sprintf(\"Hello %s!\", name),\n}\njsonResponse(w, response, http.StatusOK)\n}\n \n\/\/ NewRouter returns an HTTP handler that implements the routes for the API\nfunc NewRouter() http.Handler {\nr := chi.NewRouter()\nr.Get(\"\/{name}\", HelloName)\nreturn r\n}<\/code><\/pre>\n
\nNastav\u00edme predponu pre trasy api\/vq v hlavnom s\u00fabore.<\/p>\n
Potom to m\u00f4\u017eeme pripoji\u0165 k n\u00e1\u0161mu hlavn\u00e9mu routeru pod prefixom api\/v1 vo na\u0161ej hlavnej aplik\u00e1cii:<\/p>\n
\/\/ NewRouter returns a new HTTP handler that implements the main server routes\nfunc NewRouter() http.Handler {\nrouter := chi.NewRouter()\n    router.Mount(\"\/api\/v1\/\", v1.NewRouter())\n    return router\n}\nhttp.Serve(autocert.NewListener(\"example.com\"), NewRouter())<\/code><\/pre>\n
\nJednoduchos\u0165 pr\u00e1ce so zlo\u017eit\u00fdmi trasami v Go umo\u017e\u0148uje zjednodu\u0161i\u0165 \u0161trukt\u00farovanie pri spr\u00e1ve ve\u013ek\u00fdch komplexn\u00fdch aplik\u00e1ci\u00ed.<\/p>\n
Pr\u00e1ca s middleware<\/h3>\n
\nPri medziobslu\u017enom spracovan\u00ed sa pou\u017e\u00edva obalenie jedn\u00e9ho HTTP spracovate\u013ea \u010fal\u0161\u00edm, \u010do umo\u017e\u0148uje r\u00fdchlo vykon\u00e1va\u0165 autentifik\u00e1ciu, kompresiu, logovanie a niektor\u00e9 \u010fal\u0161ie funkcie.<\/p>\n
Ako pr\u00edklad si vezmime rozhranie http.Handler, pomocou ktor\u00e9ho nap\u00ed\u0161eme spracovate\u013ea s autentifik\u00e1ciou pou\u017e\u00edvate\u013eov slu\u017eby.<\/p>\n
func RequireAuthentication(next http.Handler) http.Handler {\n    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {\n        if !isAuthenticated(r) {\n            http.Redirect(w, r, \"\\\/login\", http.StatusTemporaryRedirect)\n            return\n        }\n        \\\/\\\/ Ak autentifik\u00e1cia pre\u0161la, spusti p\u00f4vodn\u00e9ho spracovate\u013ea\n        next.ServeHTTP(w, r)\n    })\n}<\/code><\/pre>\n
\nExistuj\u00fa aj tretie strany routery, ako napr\u00edklad chi, ktor\u00e9 umo\u017e\u0148uj\u00fa roz\u0161\u00edri\u0165 funk\u010dnos\u0165 medziobsluhy.<\/p>\n
Pr\u00e1ca so statick\u00fdmi s\u00fabormi<\/h3>\n
\n\u0160tandardn\u00e1 kni\u017enica Go obsahuje mo\u017enosti pre pr\u00e1cu so statick\u00fdm obsahom, vr\u00e1tane obr\u00e1zkov, ako aj s\u00faborov JavaScript a CSS. K nim sa d\u00e1 pristupova\u0165 cez funkciu http.FileServer. T\u00e1 vracia spracovate\u013ea, ktor\u00fd distribuuje s\u00fabory z ur\u010ditej prie\u010dinky.<\/p>\n
func NewRouter() http.Handler {\n    router := chi.NewRouter()\n    r.Get(\"\\\/ {name}\\\", HelloName)\n \n\\\/\\\/ Nastavenie distrib\u00facie statick\u00fdch s\u00faborov\nstaticPath, _ := filepath.Abs(\"..\\\/..\\\/static\\\/\\\")\nfs := http.FileServer(http.Dir(staticPath))\n    router.Handle(\"\\\/*\\\", fs)\n    \n    return r<\/code><\/pre>\n
\nJe d\u00f4le\u017eit\u00e9 pam\u00e4ta\u0165 na to, \u017ee http.Dir zobrazuje obsah prie\u010dinka, ak v \u0148om nie je hlavn\u00fd s\u00fabor index.html. V takom pr\u00edpade, aby sme predi\u0161li kompromit\u00e1cii prie\u010dinka, je dobr\u00e9 pou\u017ei\u0165 bal\u00edk unindexed<\/code><\/a><\/noindex>.<\/p>\n
Korektn\u00e9 ukon\u010denie pr\u00e1ce<\/h3>\n
\nV Go existuje aj funkcia, ako korektn\u00e9 ukon\u010denie HTTP servera. To sa d\u00e1 dosiahnu\u0165 pomocou met\u00f3dy Shutdown(). Server be\u017e\u00ed v gorutine, a n\u00e1sledne je kan\u00e1l po\u010d\u00favan\u00fd na prijatie sign\u00e1lu preru\u0161enia. Akon\u00e1hle je sign\u00e1l prijat\u00fd, server sa vypne, ale nie okam\u017eite, ale po nieko\u013ek\u00fdch sekund\u00e1ch.<\/p>\n
handler := server.NewRouter()\nsrv := &http.Server{\n    Handler: handler,\n}\n \ngo func() {\nsrv.Serve(autocert.NewListener(domains...))\n}()\n \n\\\/\\\/ \u010cakajte na preru\u0161enie\nc := make(chan os.Signal, 1)\nsignal.Notify(c, os.Interrupt)\n<-c\n \n\\\/\\\/ Pokus o korektn\u00e9 ukon\u010denie\nctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)\ndefer cancel()\nsrv.Shutdown(ctx)<\/code><\/pre>\n
<\/p>\n
Na z\u00e1ver<\/h3>\n
\nGo \u2014 mocn\u00fd jazyk s takmer univerz\u00e1lnou \u0161tandardnou kni\u017enicou. Jeho predvolen\u00e9 mo\u017enosti s\u00fa ve\u013emi \u0161irok\u00e9, a ich roz\u0161\u00edrenie je mo\u017en\u00e9 pomocou rozhran\u00ed \u2014 to umo\u017e\u0148uje vyv\u00edja\u0165 skuto\u010dne spo\u013eahliv\u00e9 HTTP servery.<\/p>\n
Skillbox odpor\u00fa\u010da:<\/b><\/p>\n