{"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\/cs\/blog\/news\/razrabotka-veb-serverov-na-golang-ot-prostogo-k-slozhnomu","title":{"rendered":"V\u00fdvoj webov\u00fdch server\u016f na Golangu \u2014 od jednoduch\u00e9ho k slo\u017eit\u00e9mu","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

\"V\u00fdvoj
\n
\nP\u0159ed p\u011bti lety jsem za\u010dal vyv\u00edjet Gophish<\/a><\/noindex>, co\u017e mi umo\u017enilo se sezn\u00e1mit s Golangem. Uv\u011bdomil jsem si, \u017ee Go je mocn\u00fd jazyk, jeho\u017e mo\u017enosti dopl\u0148uj\u00ed mno\u017estv\u00ed knihoven. Go je univerz\u00e1ln\u00ed: zejm\u00e9na d\u00edky n\u011bmu je mo\u017en\u00e9 bez probl\u00e9m\u016f vyv\u00edjet serverov\u00e9 aplikace.<\/p>\n

Tento \u010dl\u00e1nek je v\u011bnov\u00e1n psan\u00ed serveru v Go. Za\u010dneme s jednoduch\u00fdmi v\u011bcmi, jako je \u201eHello world!\u201c, a skon\u010d\u00edme aplikac\u00ed s n\u00e1sleduj\u00edc\u00edmi funkcemi:<\/p>\n

\u2014 Pou\u017eit\u00ed Let\u2019s Encrypt pro HTTPS.
\n\u2014 Pr\u00e1ce jako API router.
\n\u2014 Pr\u00e1ce s middleware.
\n\u2014 Zpracov\u00e1n\u00ed statick\u00fdch soubor\u016f.
\n\u2014 Spr\u00e1vn\u00e9 ukon\u010den\u00ed aplikace.
\n<\/a><\/noindex><\/p>\n

Skillbox doporu\u010duje:<\/b> Praktick\u00fd kurz \u201ePython developer z nuly\u201c<\/a><\/noindex>.<\/p>\n

P\u0159ipom\u00edn\u00e1me:<\/b> pro v\u0161echny \u010dten\u00e1\u0159e \"Habra\" \u2013 sleva 10 000 korun p\u0159i registraci na jak\u00fdkoli kurz Skillbox s promok\u00f3dem \"Habr\".<\/i>\n<\/p><\/blockquote>\n

Ahoj, sv\u011bte!<\/h3>\n

\nVytvo\u0159it webov\u00fd server v Go lze velmi rychle. Zde je p\u0159\u00edklad pou\u017eit\u00ed zpracovatele, kter\u00fd vrac\u00ed sl\u00edben\u00e9 \u201eAhoj, sv\u011bte!\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, \"Ahoj sv\u011bte!\")\n})\nhttp.ListenAndServe(\":80\", nil)\n}<\/code><\/pre>\n
\nPot\u00e9, co aplikaci spust\u00edte a otev\u0159ete str\u00e1nku localhost<\/noindex>, uvid\u00edte okam\u017eit\u011b text \u201eAhoj, sv\u011bte!\u201c (samoz\u0159ejm\u011b, pokud v\u0161echno funguje spr\u00e1vn\u011b).<\/p>\n
D\u00e1le budeme opakovan\u011b pou\u017e\u00edvat zpracovatele, ale nejprve si poj\u010fme objasnit, jak v\u0161echno funguje.<\/p>\n
net\/http<\/h4>\n
\nV p\u0159\u00edkladu byl pou\u017eit bal\u00ed\u010dek net\/http<\/code><\/a><\/noindex>, co\u017e je hlavn\u00ed n\u00e1stroj v Go pro v\u00fdvoj jak server\u016f, tak HTTP klient\u016f. Abychom porozum\u011bli k\u00f3du, poj\u010fme si vysv\u011btlit v\u00fdznam t\u0159\u00ed d\u016fle\u017eit\u00fdch prvk\u016f: http.Handler, http.ServeMux a http.Server.<\/p>\n
HTTP zpracovatel\u00e9<\/h4>\n
\nKdy\u017e obdr\u017e\u00edme po\u017eadavek, zpracovatel jej analyzuje a vytvo\u0159\u00ed odpov\u011b\u010f. Zpracovatel\u00e9 v Go jsou implementov\u00e1ni n\u00e1sleduj\u00edc\u00edm zp\u016fsobem:<\/p>\n
type Handler interface {\n        ServeHTTP(ResponseWriter, *Request)\n}<\/code><\/pre>\n
\nV prvn\u00edm p\u0159\u00edkladu se pou\u017e\u00edv\u00e1 pomocn\u00e1 funkce http.HandleFunc. Ta obaluje jinou funkci, kter\u00e1 naopak p\u0159ij\u00edm\u00e1 http.ResponseWriter a http.Request v ServeHTTP.<\/p>\n
Jin\u00fdmi slovy, zpracovatel\u00e9 v Golangu jsou prezentov\u00e1ny jednotn\u00fdm rozhran\u00edm, co\u017e program\u00e1torovi poskytuje mnoho mo\u017enost\u00ed. Nap\u0159\u00edklad middleware je realizov\u00e1no pomoc\u00ed zpracovatele, kde ServeHTTP nejprve n\u011bco ud\u011bl\u00e1 a pot\u00e9 zavol\u00e1 metodu ServeHTTP jin\u00e9ho zpracovatele.<\/p>\n
Jak bylo uvedeno v\u00fd\u0161e, zpracovatel\u00e9 jednodu\u0161e vytv\u00e1\u0159ej\u00ed odpov\u011bdi na po\u017eadavky. Ale kter\u00fd konkr\u00e9tn\u00ed zpracovatel by m\u011bl b\u00fdt pou\u017eit v dan\u00e9m okam\u017eiku?<\/p>\n
Sm\u011brov\u00e1n\u00ed po\u017eadavk\u016f<\/h4>\n
\nAby u\u010dinili spr\u00e1vnou volbu, vyu\u017eijte HTTP multiplexor. V n\u011bkter\u00fdch knihovn\u00e1ch se mu \u0159\u00edk\u00e1 muxer nebo router, ale v\u0161echny tyto term\u00edny ozna\u010duj\u00ed tot\u00e9\u017e. Funkce multiplexoru spo\u010d\u00edv\u00e1 v anal\u00fdze cesty po\u017eadavku a v\u00fdb\u011bru odpov\u00eddaj\u00edc\u00edho zpracovatele.<\/p>\n
Pokud pot\u0159ebujete podporu slo\u017eit\u00e9ho sm\u011brov\u00e1n\u00ed, je lep\u0161\u00ed vyu\u017e\u00edt specializovan\u00e9 knihovny. N\u011bkter\u00e9 z nejpokro\u010dilej\u0161\u00edch jsou gorilla\/mux<\/a><\/noindex> a go-chi\/chi<\/a><\/noindex>, tyto knihovny umo\u017e\u0148uj\u00ed implementaci mezisouborov\u00e9ho zpracov\u00e1n\u00ed bez v\u011bt\u0161\u00edch probl\u00e9m\u016f. D\u00edky nim lze nastavit wildcard sm\u011brov\u00e1n\u00ed a prov\u00e9st dal\u0161\u00ed \u00fakoly. Jejich v\u00fdhodou je kompatibilita se standardn\u00edmi HTTP zpracovateli. V\u00fdsledkem je, \u017ee m\u016f\u017eete napsat jednoduch\u00fd k\u00f3d s mo\u017enost\u00ed jeho budouc\u00ed modifikace.<\/p>\n
Pr\u00e1ce se slo\u017eit\u00fdmi frameworky v b\u011b\u017en\u00e9 situaci vy\u017eaduje nestandardn\u00ed \u0159e\u0161en\u00ed, co\u017e zna\u010dn\u011b zt\u011b\u017euje pou\u017eit\u00ed v\u00fdchoz\u00edch zpracovatel\u016f. Pro v\u011bt\u0161inu aplikac\u00ed posta\u010d\u00ed kombinace v\u00fdchoz\u00ed knihovny a jednoduch\u00e9ho routeru.<\/p>\n
Zpracov\u00e1n\u00ed po\u017eadavk\u016f<\/h4>\n
\nD\u00e1le pot\u0159ebujeme komponent, kter\u00fd bude 'poslouchat' p\u0159\u00edchoz\u00ed spojen\u00ed a sm\u011brovat v\u0161echny po\u017eadavky spr\u00e1vn\u00e9mu zpracovateli. Tento \u00fakol snadno zvl\u00e1dne http.Server.<\/p>\n
N\u00ed\u017ee je uvedeno, \u017ee server odpov\u00edd\u00e1 za v\u0161echny \u00fakoly, kter\u00e9 se t\u00fdkaj\u00ed zpracov\u00e1n\u00ed spojen\u00ed. To zahrnuje nap\u0159\u00edklad pr\u00e1ci s protokolem TLS. Pro realizaci vol\u00e1n\u00ed http.ListenAndServer se pou\u017e\u00edv\u00e1 standardn\u00ed HTTP server.<\/p>\n
Nyn\u00ed se pod\u00edvejme na slo\u017eit\u011bj\u0161\u00ed p\u0159\u00edklady.<\/p>\n
P\u0159id\u00e1n\u00ed Let\u2019s Encrypt<\/h3>\n
\nVe v\u00fdchoz\u00edm nastaven\u00ed na\u0161e aplikace funguje na HTTP protokolu, av\u0161ak doporu\u010duje se pou\u017e\u00edvat HTTPS protokol. V Go to lze snadno prov\u00e9st. Pokud jste obdr\u017eeli certifik\u00e1t a soukrom\u00fd kl\u00ed\u010d, sta\u010d\u00ed napsat ListenAndServeTLS s uveden\u00edm spr\u00e1vn\u00fdch soubor\u016f certifik\u00e1tu a kl\u00ed\u010de.<\/p>\n
http.ListenAndServeTLS(\":443\", \"cert.pem\", \"key.pem\", nil)<\/code><\/pre>\n
\nV\u017edy je mo\u017en\u00e9 ud\u011blat to l\u00e9pe.<\/p>\n
Let\u2019s Encrypt<\/a><\/noindex> nab\u00edz\u00ed bezplatn\u00e9 certifik\u00e1ty s mo\u017enost\u00ed automatick\u00e9 obnovy. K vyu\u017eit\u00ed t\u00e9to slu\u017eby je pot\u0159eba bal\u00ed\u010dek autocert<\/code>.<\/p>\n
Nejjednodu\u0161\u0161\u00ed zp\u016fsob, jak ho nastavit, je pou\u017e\u00edt metodu autocert.NewListener v kombinaci s http.Serve. Tato metoda umo\u017e\u0148uje z\u00edsk\u00e1vat a obnovovat TLS certifik\u00e1ty, zat\u00edmco HTTP server zpracov\u00e1v\u00e1 po\u017eadavky:<\/p>\n
http.Serve(autocert.NewListener(\"example.com\"), nil)<\/code><\/pre>\n
\nPokud to otev\u0159eme v prohl\u00ed\u017ee\u010di example.com<\/a><\/noindex>, dostaneme HTTPS-odpov\u011b\u010f \u201eHello, world!\u201c.<\/p>\n
Pokud pot\u0159ebujete podrobn\u011bj\u0161\u00ed nastaven\u00ed, je dobr\u00e9 pou\u017e\u00edt spr\u00e1vce autocert.Manager. Pot\u00e9 vytvo\u0159\u00edme vlastn\u00ed instanci http.Server (dosud jsme pou\u017e\u00edvali v\u00fdchoz\u00ed) a p\u0159id\u00e1me spr\u00e1vce do serveru 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 zp\u016fsob, jak implementovat plnou podporu HTTPS s automatickou obnovou certifik\u00e1tu.<\/p>\n
P\u0159id\u00e1n\u00ed nestandardn\u00edch tras<\/h3>\n
\nV\u00fdchoz\u00ed sm\u011brova\u010d, kter\u00fd je sou\u010d\u00e1st\u00ed standardn\u00ed knihovny, je dobr\u00fd, ale velmi jednoduch\u00fd. V\u011bt\u0161ina aplikac\u00ed pot\u0159ebuje slo\u017eit\u011bj\u0161\u00ed sm\u011brov\u00e1n\u00ed, v\u010detn\u011b vno\u0159en\u00fdch a wildcard tras nebo procedury pro nastavov\u00e1n\u00ed \u0161ablon a parametr\u016f cest.<\/p>\n
V tomto p\u0159\u00edpad\u011b stoj\u00ed za to pou\u017e\u00edt bal\u00ed\u010dky gorilla\/mux<\/a><\/noindex> a go-chi\/chi<\/a><\/noindex>. S t\u00edm posledn\u00edm se nau\u010d\u00edme pracovat \u2014 n\u00ed\u017ee je uveden p\u0159\u00edklad.<\/p>\n
D\u00e1no \u2014 soubor api\/v1\/api.go, kter\u00fd obsahuje trasy pro 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 pro trasy prefix api\/vq v hlavn\u00edm souboru.<\/p>\n
Pak to m\u016f\u017eeme p\u0159ipojit k na\u0161emu hlavn\u00edmu sm\u011brova\u010di pod prefixem api\/v1 zp\u011bt v na\u0161\u00ed hlavn\u00ed aplikaci:<\/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
\nJednoduchost pr\u00e1ce se slo\u017eit\u00fdmi trasami v Go umo\u017e\u0148uje zjednodu\u0161it strukturov\u00e1n\u00ed s \u00fadr\u017ebou velk\u00fdch komplexn\u00edch aplikac\u00ed.<\/p>\n
Pr\u00e1ce s middlewarem<\/h3>\n
\nP\u0159i zpracov\u00e1n\u00ed prost\u0159ednictv\u00edm middleware se pou\u017e\u00edv\u00e1 obalov\u00e1n\u00ed jednoho HTTP zpracovatele jin\u00fdm, co\u017e umo\u017e\u0148uje rychl\u00e9 prov\u00e1d\u011bn\u00ed ov\u011b\u0159ov\u00e1n\u00ed, komprese, protokolov\u00e1n\u00ed a n\u011bkter\u00fdch dal\u0161\u00edch funkc\u00ed.<\/p>\n
Jako p\u0159\u00edklad si vezmeme rozhran\u00ed http.Handler, s jeho\u017e pomoc\u00ed nap\u00ed\u0161eme zpracovatele s ov\u011b\u0159ov\u00e1n\u00edm u\u017eivatel\u016f 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        \/\/ P\u0159edpokl\u00e1d\u00e1me, \u017ee ov\u011b\u0159en\u00ed pro\u0161lo, spus\u0165te p\u016fvodn\u00ed zpracovatele\n        next.ServeHTTP(w, r)\n    })\n}<\/code><\/pre>\n
\nExistuj\u00ed extern\u00ed sm\u011brova\u010de, nap\u0159\u00edklad chi, kter\u00e9 umo\u017e\u0148uj\u00ed roz\u0161\u00ed\u0159it funk\u010dnost middleware.<\/p>\n
Pr\u00e1ce se statick\u00fdmi soubory<\/h3>\n
\nStandardn\u00ed knihovna Go obsahuje mo\u017enosti pro pr\u00e1ci se statick\u00fdm obsahem, v\u010detn\u011b obr\u00e1zk\u016f a soubor\u016f JavaScript a CSS. P\u0159\u00edstup k nim je mo\u017en\u00e9 z\u00edskat prost\u0159ednictv\u00edm funkce http.FileServer. Ta vrac\u00ed zpracovatele, kter\u00fd distribuuje soubory z ur\u010den\u00e9ho adres\u00e1\u0159e.<\/p>\n
func NewRouter() http.Handler {\n    router := chi.NewRouter()\n    r.Get(\"\/{name}\", HelloName)\n \n\/\/ Nastaven\u00ed statick\u00e9ho souboru\nstaticPath, _ := filepath.Abs(\"..\/..\/static\/\")\nfs := http.FileServer(http.Dir(staticPath))\n    router.Handle(\"\/*\", fs)\n    \n    return r<\/code><\/pre>\n
\nJe d\u016fle\u017eit\u00e9 si pamatovat, \u017ee http.Dir zobrazuje obsah adres\u00e1\u0159e pouze v p\u0159\u00edpad\u011b, \u017ee neobsahuje hlavn\u00ed soubor index.html. V tomto p\u0159\u00edpad\u011b, abychom zabr\u00e1nili kompromitaci adres\u00e1\u0159e, je dobr\u00e9 pou\u017e\u00edt bal\u00ed\u010dek neindexovan\u00fd<\/code><\/a><\/noindex>.<\/p>\n
Spr\u00e1vn\u00e9 ukon\u010den\u00ed pr\u00e1ce<\/h3>\n
\nV Go existuje funkce pro spr\u00e1vn\u00e9 ukon\u010den\u00ed HTTP serveru. To lze prov\u00e9st pomoc\u00ed metody Shutdown(). Server b\u011b\u017e\u00ed v gorutin\u011b a n\u00e1sledn\u011b se naslouch\u00e1 kan\u00e1lu pro p\u0159\u00edjem sign\u00e1lu p\u0159eru\u0161en\u00ed. Jakmile je sign\u00e1l p\u0159ijat, server se neza\u010dne okam\u017eit\u011b vyp\u00ednat, ale a\u017e po n\u011bkolika 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\/\/ \u010cek\u00e1n\u00ed na p\u0159eru\u0161en\u00ed\nc := make(chan os.Signal, 1)\nsignal.Notify(c, os.Interrupt)\n<-c\n \n\/\/ Pokus o spr\u00e1vn\u00e9 ukon\u010den\u00ed\nctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)\ndefer cancel()\nsrv.Shutdown(ctx)<\/code><\/pre>\n
<\/p>\n
Na z\u00e1v\u011br<\/h3>\n
\nGo je mocn\u00fd jazyk s prakticky univerz\u00e1ln\u00ed standardn\u00ed knihovnou. Jeho v\u00fdchoz\u00ed vlastnosti jsou velmi \u0161irok\u00e9, a ty lze pos\u00edlit pomoc\u00ed rozhran\u00ed \u2014 co\u017e umo\u017e\u0148uje skute\u010dn\u011b spolehliv\u00fd v\u00fdvoj HTTP server\u016f.<\/p>\n
Skillbox doporu\u010duje:<\/b><\/p>\n