Contextアンチパターン

golang.tokyo#5でのLT資料です。

Transcript

1. ContextΞϯνύλʔϯ @__timakin__ golang.tokyo#5
2. ࣗݾ঺հ
3. ࣗݾ঺հ • twitter: @__timakin__ • github: timakin • גࣜձࣾGunosy ৽نࣄۀ։ൃࣨ(Go/Swift) • ओͳGoϥΠϒϥϦ։ൃ෺ • gopli (DBϨϓϦέʔγϣϯπʔϧ) • gonvert (จࣈίʔυม׵ϥΠϒϥϦ) • octop (githubͷissue, PRϏϡʔ༻CLIπʔϧ) • ts (ٕज़ɾϏδωεܥχϡʔε८ճCLIπʔϧ) • ϓϥΠϕʔτͰΫϩʔϥʔ࡞੒ɺ࠷ۙಈը഑৴पΓ͕ؾʹͳͬͯ·͢ɻ
4. Copyright© Gunosy Inc. All Rights Reserved 4 Go / Python ΤϯδχΞืूத ▶https://gunosy.co.jp/recruit/ Gunosy͸ɺ౦ژେֶʹ௨͏3ਓͷֶੜͷ
 ʮ৘ใΛੈքதͷਓʹ࠷దʹಧ͚͍ͨʯͱ͍͏૝͍͔Β࢝·Γ·ͨ͠ɻ ౦ূϚβʔζ্৔ɺ࿡ຊ໦ώϧζ΁ͷΦϑΟεҠసΛܦͯɺ
 େ͖͘੒௕͍ͯ͠ΔձࣾͰ׆༂͍ͨ͠ϝϯόʔΛืू͍ͯ͠·͢ɻ
5. ຊ೔ͷओࢫ
6. ContextΛ͋͋ͯ͜͠͏ͯͨ͠Β
 ΰουΦϒδΣΫτͰ͖ͨ ͢·Μ
7. Զ͕Ξϯνύλʔϯͩ ٩( ᐛ )و
8. ΞδΣϯμ • context.ContextͷऔΓѻ͍ʹ͍ͭͯ • Ξϯνύλʔϯͷ࣮ྫʢ΍ͬͪΌͬͨʂ٩( ᐛ )وʣ • ެࣜͷGoDocͰਪ঑͞ΕΔίϯηϓτ • ൓লͱվળ
9. Ξϯνύλʔϯͷ࣮ྫ
10. @GoConference 2017
11. ͍ͭ͜Λݟͯ͘ΕɺͲ͏ࢥ͏ʁ
13. <- echoͷcustom context <- context in context (!!)
14. ͞Βʹ͍ͭ͜Λݟͯ͘Εʂ
15. ͍ͭ͜Λݟͯ͘ΕɺͲ͏ࢥ͏ʁ
16. ͍ͭ͜Λݟͯ͘ΕɺͲ͏ࢥ͏ʁ <- repository in context (!?)
17. ͏͢͏͢ײ͍ͮͯ͸͍ͨΑʂʂ ̍̍
18. ͢·ΜͱࢥͬͯΔ ٩( ᐛ )و
19. ݴ͍༁
20. context(context.Context) in context(ϑϨʔϜϫʔΫͷContext) • echoͷϑϨʔϜϫʔΫͷcontextͰ͸ͳ͘ඪ४ύοέʔδ ͷcontextΛ࢖ͬͯɺ಺෦ͷϩδοΫͰར༻͍ͯ͠Δ
 goroutineͷλΠϜΞ΢τ੍ޚΛ͍ͨ͠ • ͕ɺϦΫΤετϋϯυϥʹ౉ͬͯ͘Δͷ͸
 echo.Contextͩ͠ɺGAEͩͱhttp.Request͔Β
 contextΛऔΓग़ͤͳ͍ɻ • ϋϯυϥʹcontextΛ౉͢ʹ͸echo.Contextʹ
 context.ContextΛؚΊɺͦΕΛϋϯυϥҎԼͷ
 ϨΠϠʔͰར༻͢Δඞཁ͕͋Δ
21. <- echoͷcustom context <- context in context (!!)
22. repository in context • ਃ͠։͖͍͟͝·ͤΜʂʂ̍̍
 ͍͕ͭ͜ਆͩʂ • ·͊ͿͬͪΌ͚طଘͷ࣮૷(or ࢿྉ)ࢀߟʹ
 ࡞ͬͨΜͰ͕͢ɺέʔεόΠέʔεͰɺ
 ΘΓͱ͜͏͍͏globalͳΦϒδΣΫτΛೖΕͯΔ
 ݹ͍࣮૷ͱ͔͋ͬͯɺਅࣅͪΌͬͨɻ • ඪ४ύοέʔδͱͯ͠૊Έࠐ·ΕΔલͷ࣮૷Ͱ͸
 ͜͏͍͏ͷ΋͋ͬͨΑɺ͋ͬͨ͸ͣͳΜͩɻ • ਖ਼௚repository͚ͩ͡Όͳ͘configͱ͔΋٧ΊͪΌͬͨ
23. Ҏ্ʹରͯ͠օ͞Μौ͍൓Ԡ
25. ͦ͏͍͑͹GoDocͰ͸
26. GoDoc • Package context defines the Context type, 
 which carries deadlines, cancelation signals, and other request-scoped values across API boundaries and between processes. • Use context Values only for request-scoped data that transits processes and APIs, not for passing optional parameters to functions. • Do not store Contexts inside a struct type; instead, pass a Context explicitly to each function that needs it. • ͢·Μͯɻ
27. GoDoc • ओʹgoroutine͕བྷΉॲཧɺAPIΛ·͙ͨॲཧΛߦ͏࣌ɺ
 λΠϜΞ΢τ੍ޚΛద੾ʹߦ͏ͨΊʹ࢖͏ • UserIDɺଞJWT౳ͷɺͦͷϦΫΤετʹݶఆ͞ΕΔ஋ΛGet/Set͢Δ ͱ͖ʹͷΈValueΛ࢖͏ • Go1.7Ҏલ(ࠓͷGAEͱ͔)
 func GetHandler(ctx context.Context, 
 w http.ResponseWriter, r *http.Request)
 
 Go1.7Ҏ߱
 ctx := r.Context() • ଞͷ༻్ɺड͚౉͠ํͰ࢖Θͳ͍ɻ
 ઈରͩͧɻ
28. ൓লͱվળ
29. GoDoc • ແବʹߏ଄ମʹcontextೖΕͳ͍ • echo -> net/http • ContextΛద੾ʹϋϯυϥʹ౉͢ • λΠϜΞ΢τઃఆ͸ServeHTTPͰߦ͏ʢMiddlewareͰ΋Մʣ • func Handler(ctx context.Context, w http.ResponseWriter, r *http.Request) • request-scopedͳ஋ʹݶఆ • repository.FromContextͱ͔શ෦ফ͢ • ϋϯυϥͰ౎౓ctxΛ౉ͯ͠ੜ੒ • ֤छΫϥΠΞϯτ΍Βlogger͸HandlerͷϨγʔόΛఆٛͯͦ͠ͷதʹೖΕΔ • function (app *App) GetItemHandler(ctx context.Context, …)
30. ແବʹߏ଄ମʹcontextೖΕͳ͍ • echoΛnet/httpʹશஔ͖׵͑ • GAE(SE)ͩͱrequestʹContext͕ೖͬͯͳ͍ɻ
 ͞Βʹɺecho.ContextͷͲ͔͜Β΋context.Context͕ͱ Γͩͤͳ͍ɻ • ͦ΋ͦ΋GAEΛ࢖͍ͬͯͨͷͰɺechoඋ͑෇͚ͷϩΨʔ ͱ͔࢖Θͳ͍͠ɺrouting͘Β͍Ͱ͔͠Ըܙͳ͍ • ϑϨʔϜϫʔΫ͕଍͔ͤʹͳ͍ͬͯͨͷͰɺ֎͢ɻ • ϋϯυϥʹඪ४ͷcontext͚ͩ౉͢Լ४උɻ
31. ContextΛద੾ʹϋϯυϥʹ౉͢ • λΠϜΞ΢τઃఆ͸ServeHTTPͰߦ͏ʢMiddleware Ͱ΋Մʣ ServeHTTPΛ࣮૷ͨ͠AppHandlerΛఆٛͯ͠ɺ
 தͰappengineͷContext(context.Context)Λ λΠϜΞ΢τઃఆ෇͖Ͱϋϯυϥʹ౉͢
32. request-scopedͳ஋ʹݶఆ • ͔ͯrequest-scopedͳ஋ͱ͔ಛʹͳ͍APIͩͬͨɻ • ͳͷͰWithValueશ෦ফͨ͠ɻ • repository.FromContextͱ͔શ෦ফ͢ • ϋϯυϥͰ౎౓ctxΛ౉ͯ͠ੜ੒ • GAEͩͱloggerͱ͔datastoreͰcontext͕ඞཁ • ͳͷͰɺglobalʹѻ͍͍ͨ஋ͩͱͯ͠΋ɺ
 ϋϯυϥҎ߱Ͱຖճݺͼग़ͯ͠·͢ɻ
 ʢ͜Ε͸ϕετϓϥΫςΟε͋Δͷ͔ʁʣ
33. Ϩγʔόʹglobalͳ஋ΛೖΕΔ
34. • (app *App)ΛϨγʔόͱͯ͠ઃఆ͢Δʹ͸handlerʹ ౰ͨΔϝιου͸શͯಉҰpackageͱͯ͠ఆٛ͞ΕΔ ඞཁ͕͋Δ • cannot define new methods on non-local type • ͳͷͰɺݸผͷυϝΠϯϩδοΫΛ࣋ͭσΟϨΫτϦ ͱ͸ผʹɺhandlerσΟϨΫτϦΛஔ͖ɺͦ͜ʹApp ͷఆٛͱݸผͷϦΫΤετϋϯυϥΛ࣋ͨͤΔɻ Ϩγʔόʹglobalͳ஋ΛೖΕΔ
35. app.go
36. main.go handler.AppHandler{Impl: app.HogeHandler}
 ͱ͍͏ܗࣜͰɺServeHTTPΛ࣋ͭAppHandlerʹ App structΛ࣋ͭHogeHandlerΛ౉͢ɻ
37. ·ͱΊ • ਆ͸ࢮΜͩɻcontextড়Խ׬ྃɻ • request-scopedͳ஋ͱɺλΠϜΞ΢τҎ֎࢖Θͳ͍ɻ • άϩʔόϧͳΦϒδΣΫτΛར༻͢ΔͨΊʹ
 ϋϯυϥڞ௨ͷstructΛ༻ҙ͢Δɻ
 ͦͷӨڹͰϋϯυϥ͸ಉҰpackageʹ·ͱΊΔɻ