Case studies of designing developer friendly libraries #gocon

by Masayuki Izumi

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@izumin5210 Application Engineer, Wantedly People Wantedly, Inc.

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©2019 Wantedly, Inc. `context.Context` ਖ਼͘͠࢖͓͏ context ωοτϫʔΫ*0ͳͲɺ͔͔࣌ؒΔॲཧ͕͋Δͱ͖͸ඞͣDPOUFYUΛ౉͢ʂ ωοτϫʔΫෆௐͰΊͬͪΌ͔͔࣌ؒΔ͔΋ˠλΠϜΞ΢τ͍ͨ͠ $POUFYUΛར༻ͯ͠ϝτϦΫεऩूͳͲΛߦ͏πʔϧ΁ͷରԠʢޙड़ʣ HPPHMFDMPVEHPͳͲɺίϯετϥΫλͰDPOUFYUΛ  ཁٻ͢Δύλʔϯ΋͋Δ client, err := pubsub.NewClient(ctx, "project-id") if err != nil { // ... } ڷʹै͏

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©2019 Wantedly, Inc. `context.Context`ͱܭଌ DPOUFYUʹσʔλऩू༻ͷTUSVDUΛ࢓ࠐΉύοέʔδ͕ଘࡏ͢Δ FHPQFODFOTVTHP OFXSFMJDHPBHFOU AIUUQ 3PVOE5SJQQFSA΍ATUBUT)BOEMFSAͰDPOUFYU͔Β  ΦϒδΣΫτΛऔΓग़͠ɺܭଌͨ͠σʔλΛॻ͖ࠐΉ ͜ͷ࢓૊ΈΛਖ਼͘͠ಈ࡞ͤ͞ΔͨΊʹ΋$POUFYU఻ൖ͸ॏཁ func traceHandleRPC(ctx context.Context, rs stats.RPCSt span := trace.FromContext(ctx) switch rs := rs.(type) { case *stats.Begin: span.AddAttributes( trace.BoolAttribute("Client", rs.Client), trace.BoolAttribute("FailFast", rs.FailFast)) case *stats.InPayload: // snip. case *stats.OutPayload: // snip. case *stats.End: // snip. span.End() } } https://github.com/census-instrumentation/opencensus-go/blob/v0.21.0/plugin/ocgrpc/trace_common.go#L84-L107 ڷʹै͏

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©2019 Wantedly, Inc. Interceptor / Middleware ॲཧલޙʹϑοΫͰ͖ΔػߏΛ࡞Δύλʔϯ H31$ʹ͸JOUFSDFQUPSͱ͍͏໊લͰ࣮૷͞Ε͍ͯΔ ॲཧͷલޙͰϏδωεϩδοΫʹؔ܎ͳ͍ॲཧΛ࣮ߦͰ͖Δ FHೝূ ϩΪϯά ΤϥʔϨϙʔτ ʜ * https://docs.pylonsproject.org/projects/pylons-webframework/en/latest/concepts.html#wsgi-middleware ڷʹै͏

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©2019 Wantedly, Inc. ֦ுੑΛอͭ Redigoͷྫ github.com/gomodule/redigo 3FEJTΫϥΠΞϯτ A$POOAΠϯλϑΣʔεʹίϚϯυൃߦ༻ͷ  ϝιου͕ੜ͍͑ͯΔ type Conn interface { // Close closes the connection. Close() error // Err returns a non-nil value when the connection is not usable. Err() error // Do sends a command to the server and returns the received reply. Do(commandName string, args ...interface{}) (reply interface{}, err // Send writes the command to the client's output buffer. Send(commandName string, args ...interface{}) error // Flush flushes the output buffer to the Redis server. Flush() error // Receive receives a single reply from the Redis server Receive() (reply interface{}, err error) }

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©2019 Wantedly, Inc. Redigoͷྫ github.com/gomodule/redigo ࣮ࡍͷར༻Ͱ͸ɺ͍͍ͩͨDPOOFDUJPOQPPMΛ  ࢖͏͜ͱʹͳΔ pool := &redis.Pool{ Dial: func () (redis.Conn, error) { return redis.Dial("tcp", addr) }, } conn, err := pool.GetContext(ctx) ֦ுੑΛอͭ

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©2019 Wantedly, Inc. Redigoͷྫ github.com/gomodule/redigo ࣮ࡍͷར༻Ͱ͸ɺ͍͍ͩͨ$POOFDUJPO1PPMΛ  ࢖͏͜ͱʹͳΔ pool := &redis.Pool{ DialContext: func (ctx context.Context) (redis.Conn, error) { return redis.Dial("tcp", addr) }, } conn, err := pool.GetContext(ctx) ֦ுੑΛอͭ

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©2019 Wantedly, Inc. Redigoͷྫ github.com/gomodule/redigo ࣮ࡍͷར༻Ͱ͸ɺ͍͍ͩͨ$POOFDUJPO1PPMΛ  ࢖͏͜ͱʹͳΔ %JBM࣮૷ΛಠࣗఆٛͰ͖ΔΑ͏ʹͳ͍ͬͯΔͷ ͰɺASFEJT$POOAΛXSBQ͢Δ͜ͱͰϩΨʔ΍ ϝτϦΫεऩूΛ࢓ࠐΊΔ ࣅͨྫͱͯ͠͸AOFUIUUQ5SBOTQPSUAͳͲ pool := &redis.Pool{ DialContext: func (ctx context.Context) (redis.Conn, error) { conn, err := redis.Dial("tcp", addr) if err != nil { return nil, err } return redis.NewLoggingConn(conn, logger, "redis") }, } conn, err := pool.GetContext(ctx) ֦ுੑΛอͭ

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©2019 Wantedly, Inc. google-cloud-go ͷྫ cloud.google.com/go $MPVE%BUBTUPSF΍$MPVE1VC4VCͳͲɺ  ($1Ͱఏڙ͞ΕΔ͋ΒΏΔαʔϏεͷΫϥΠΞ ϯτ͕ଘࡏ ͍͍ͩͨͷΫϥΠΞϯτ͸ίϯετϥΫλͰΦϓ γϣϯΛड͚औΕΔΑ͏ʹͳ͍ͬͯΔ client, err := pubsub.NewClient(ctx, "project-id") if err != nil { // ... } ֦ுੑΛอͭ

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©2019 Wantedly, Inc. google-cloud-go ͷྫ cloud.google.com/go ίϯετϥΫλʹ౉ͤΔΦϓγϣϯʹ͸ɺ௨৴ʹ ར༻͢ΔAHSQD$MJFOU$POOA΍ AIUUQ$MJFOUAͳͲ΋ؚ·ΕΔ JOUFSDFQUPS΍TUBUTIBOEMFSͳͲ͕ඞཁʹͳΔ ϩΨʔ΍ܭଌܥͳͲ͸࢓ࠐΈ์୊ * https://godoc.org/google.golang.org/api/option#ClientOption ֦ுੑΛอͭ

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©2019 Wantedly, Inc. Functional option ϥΠϒϥϦͳͲͰɺΦϓγϣϯΛࢦఆͤ͞ΔΑ͏ ʹ͢ΔͨΊͷύλʔϯ DGCVJMEFSQBUUFSO type Option func(*Config) func WithHTTPClient(client *http.Client) Option { return func(c *Config) { c.HTTPClient = client } } func NewClient(opts ...Option) Client { cfg := new(Config) for _, f := range opts { f(cfg) } // ... } ֦ுੑΛอͭ

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©2019 Wantedly, Inc. type Option func(*Config) func WithHTTPClient(client *http.Client) Option { return func(c *Config) { c.HTTPClient = client } } func NewClient(opts ...Option) Client { cfg := new(Config) for _, f := range opts { f(cfg) } // ... } func NewClientBuilder() *Builder { return &Builder{} } func (b *Builder) SetHTTPClient(client *http.Client) *Builder { b.HTTPClient = client return b } func (b *Builder) Build() Client { // ... } Builder pattern Functional option pattern

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©2019 Wantedly, Inc. ܕΛ׆͔ͨ͢Ίͷίʔυੜ੒ FH 03.42-#PJMFS YPʢ֎෦ʹ͋ΔεΩʔϚΛ(Pʹམͱ͠ࠐΉʣ %*XJSFʢܕΛݟͯґଘؔ܎ͷ%"(Λͭ͘Δʣ ͱ͘ʹ(Pͷ֎ʹܕఆ͕ٛ͋Δ৔߹ʢFH%# TXBHHFS QSPUPCVGʣʹ༗ޮ Ϣʔβ͕ੜ੒ޙͷίʔυΛฤू͢Δඞཁ͕ͳ͍Α͏ʹੜ੒ͯ͋͛͠Δͱྑ͍ ੜ੒πʔϧ͕Ξοϓσʔτ͞Εͨͱ͖ʹ௥ैͰ͖ΔΑ͏ʹ // Code generated by protoc-gen-go. DO NOT EDIT. // source: content.proto package api_pb import ( context "context" fmt "fmt" ADO NOT EDIT` ͬͯॻ͍͓ͯ͘ͱ ͍ΖΜͳπʔϧͰແࢹͯ͠΋Β͑·͢ // Code generated by protoc-gen-go. DO NOT EDIT. // source: content.proto package api_pb import ( context "context" ίʔυੜ੒

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©2019 Wantedly, Inc. Boilerplate ੜ੒ FH TUSJOHFSΊΜͲ͍͘͞εχϖοτͷੜ੒ HSBQJΞϓϦέʔγϣϯίʔυͷTDBGGPMEJOH ʮϢʔβ͕ฤू͢ΔίʔυʯʮϢʔβ͕৮Βͳ͍΄͏͕ྑ͍ίʔυʯΛ  ͦΕͧΕผϑΝΠϧʹు͍͓ͯ͘ͷ͕ྑ͍ʢཧ༝͸͖ͬ͞ͱҰॹʣ ʮϢʔβ͕ฤू͢Δίʔυʯ͸࠷খݶʹཹΊΔ // NewBookServiceServer creates a new BookServiceServer instance func NewBookServiceServer() BookServiceServer { return &bookServiceServerImpl{} } type bookServiceServerImpl struct { } func (s *bookServiceServerImpl) ListBooks(ctx context.Context, r // TODO: Not yet implemented. return nil, status.Error(codes.Unimplemented, "TODO: You shoul } func (s *bookServiceServerImpl) GetBook(ctx context.Context, req // TODO: Not yet implemented. return nil, status.Error(codes.Unimplemented, "TODO: You shoul } func (s *bookServiceServerImpl) CreateBook(ctx context.Context, // TODO: Not yet implemented. return nil, status.Error(codes.Unimplemented, "TODO: You shoul } func (s *bookServiceServerImpl) UpdateBook(ctx context.Context, // TODO: Not yet implemented. return nil, status.Error(codes.Unimplemented, "TODO: You shoul } func (s *bookServiceServerImpl) DeleteBook(ctx context.Context, // TODO: Not yet implemented. return nil, status.Error(codes.Unimplemented, "TODO: You shoul } ίʔυੜ੒

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©2019 Wantedly, Inc. ͍͍ײ͡ʹ΍Δࣾ಺ϥΠϒϥϦ 8): αʔόΛຊ൪؀ڥͰಈ͔͢ʹ͸ɺ"1.ͱBDDFTTMPHͱFSSPSSFQPSUͱʜ  ΍Δ͜ͱ͕͍ͬͺ͍͋Δ Θ͢Εͦ͏ 8)"5 ؀ڥม਺ΛೖΕΔ͚ͩͰ͍͍ײ͡ʹશͯಈ͘Α͏ʹ͍ͨ͠ func run() error { defer servicex.Close() ctx := context.Background() s := grapiserver.New( grpcx.WithDefault(), grapiserver.WithServers( NewContentServiceServer(), ), ) return s.Serve() } উखʹ͍Ζ͍Ζ΍Δ

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©2019 Wantedly, Inc. ͍͍ײ͡ʹ΍Δࣾ಺ϥΠϒϥϦ ؀ڥม਺ಡΈग़͠dॾʑͷॳظԽΛATFSWJDFYAͱ͍͏ύοέʔδͷ  AJOJU AͰશ෦উखʹ΍Δ AJOJU AͳͷͰJNQPSU͑͞͞Ε͍ͯΕ͹Α͍ ˠAEFGFSTFSWJDFY$MPTF AΛॻ͔ͤΔ͚ͩͰΑ͍ ʢCMBOLJNQPSU͡Όͳ͍ͷ͸खͰॻ͘ͷΊΜͲ͍͔͘͞Βʣ func run() error { defer servicex.Close() ctx := context.Background() s := grapiserver.New( grpcx.WithDefault(), grapiserver.WithServers( NewContentServiceServer(), ), ) return s.Serve() } func init() { loadEnv() initErrorReporter() initLogger() // ... } উखʹ͍Ζ͍Ζ΍Δ

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©2019 Wantedly, Inc. $PNQPVOEGVODPQUJPO 1SPEVDUJPOSFBEZͳαʔόʹඞਢͷػೳ͕શͯ༗ޮʹͳΔΑ͏ͳ  ΧελϜGVODUJPOBMPQUJPOΛͭ͘Δ 'VODUJPOBMPQUJPO͸͍͍͕ͩͨ  AGVOD $POpH A͔AGVOD $POpH $POpHAͳͷͰɺ߹੒Ͱ͖Δ func WithDefault() grapiserver.Option { opts := []grapiserver.Option{ grapiserver.WithGrpcServerUnaryInterceptors( grpc_ctxtags.UnaryServerInterceptor(ctxtagsOptio ClientMetadataUnaryServerInterceptor(), AccessLoggingUnaryServerInterceptor(), grpc_zap.UnaryServerInterceptor(zap.L(), ...), ErrorsUnaryServerInterceptor(), RecoveryUnaryServerInterceptor(), AuthUnaryServerInterceptor(), ), // ... } return func(c *grapiserver.Config) { for _, f := range opts { f(c) } } } func run() error { defer servicex.Close() ctx := context.Background() s := grapiserver.New( grpcx.WithDefault(), grapiserver.WithServers( উखʹ͍Ζ͍Ζ΍Δ

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©2019 Wantedly, Inc. ͜Μͳʹউखͳ͜ͱͯ͠ྑ͍ͷ͔ʁ ϏδωεϩδοΫʹؔΘΔΑ͏ͳίʔυͩͱμϝ ڞ༗ίʔυ͸ଟ͚Ε͹ଟ͍΄ͲΑ͘ͳ͍ͬͯʮϚΠΫϩαʔϏεΞʔΩςΫνϟʯʹॻ͍ͯͨ  ͱ͸͍͑ɺ͜ͷࣾ಺ϥΠϒϥϦ͕ղܾ͢Δͷ͸ϏδωεϩδοΫͱ͸શવผͷϨΠϠͰ͋Γɺ  ΧελϚΠζཉٻ΋ߴ͘ͳ͍ՕॴͳͷͰΪϦΪϦηʔϑʢʁʣ ͱ͸͍͑։ൃऀͷखݩͷ؀ڥͰมͳಈ͖Λ͠ͳ͍Α͏ɺࡉ৺ͷ஫ҙΛ෷͍࣮ͭͭ૷ উखʹ͍Ζ͍Ζ΍Δ

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lڷʹೖͬͯ͸ڷʹै͑z ͪΌΜͱ(Pͷ׳शʹԊͬͨ"1*ʹ͠Α͏ ֦ுੑΛอͭ ೉͍͜͠ͱΛ΍Ζ͏ͱͨ͠ͱ͖ʹࠔΒͳ͍Α͏ʹ͠Α͏ ࠷ѱίΞʹͳͬͯΔύοέʔδʹ΋৮ΕΒΕΔΑ͏ʹ͠Α͏ ίʔυੜ੒Λ͏·͘࢖͏͜ͱΛݕ౼͠Α͏ ࢖͍͗͢ɾ࢖͍ॴʹ͸ཁ஫ҙʂ Ϣʔβ͕ݶΒΕΔɺดͨ͡ίϯςΩετɺϏδωεϩδοΫ͕བྷ·ͳ͍ͳΒɺ  উखʹ৭ʑ΍Δύοέʔδ΋͋Γ͔΋ʂʁ