gRPC with Kotlin Coroutines

gRPC is a technology that allows you to call server side logic from any platform using protocol buffers. What are the libraries available that allow you to create and consume gRPC services using coroutines? What are the debugging and monitoring tools we could use for gRPC?

In this talk, I will share with you how to build a gRPC server using the gRPC-Kotlin library. We’ll explore how to use protocol buffers to define different types of rpc calls that are unary and bidirectional. On the client side, we’ll also use this library to consume our gRPC service. gRPC-Kotlin provides an API that uses Flows to make rpc calls. We’ll explore how it works internally. For each rpc call we implement using coroutines, I’ll show you how to unit test it.

In addition to gRPC Kotlin, other libraries for creating and consuming gRPC services are Wire by Square and Kroto-plus. We’ll compare its features and its coroutines API with gRPC-Kotlin. By the end of this talk, you will have a better understanding on how to build and consume gRPC services with Kotlin coroutines.

https://www.youtube.com/watch?v=V3BzDyQVeGw

Transcript

1. Mohit Sarveiya gRPC with Kotlin Coroutines www.twitter.com/heyitsmohit www.codingwithmohit.com
2. gRPC with Kotlin Coroutines • Build gRPC Server • Using Channels & Flow with gRPC • Build gRPC Client in Kotlin
3. Server gRPC
4. Server gRPC service
5. Server(Go) gRPC service Client(Java) Client(Python) Client(Javascript) service service service
6. Server(Go) gRPC service Client(Java) Client(Python) Client(Javascript)
7. Server(Go) gRPC service Client(Java) Client(Python) Client(Javascript) call call call
8. Server(Go) gRPC service Client(Java) Client(Python) Client(Javascript) call call call HTTP 2
9. gRPC-Kotlin kroto-plus Client Server
10. Use Case • Tracks your route.
11. Use Case • Tracks your route. • Get a place from location.
12. Use Case • Tracks your route. • Get a place from location. • List Places around location.
13. Use Case • Tracks your route. • Get a place from location. • List Places around location. • Chat with others at location. Shoreline Golf links 2940 N Shoreline Blvd Mountain View, CA 94043 Start typing
14. Building gRPC Server
15. Building gRPC Server • Configure Server with Kroto-Plus • Create Service with Protocol Buffers • Implement Service • Start Server
16. marcoferrer/kroto-plus Kroto-Plus+ gRPC Kotlin Coroutines Protobuf DSL Scripting for Protoc Build passing Download 0.6.1
17. gRPC Server Modules Server src database api
18. gRPC Server Modules Server src database api Server Startup / Read from RPC
19. gRPC Server Modules Server src database api Reading/Writing from DB
20. gRPC Server Modules Server src database api Define RPC Calls and Messages
21. gRPC Server Modules Server src database api Proto Buff Service proto
22. gRPC Server Modules Server src database api Create Proto Buff File proto places.proto
23. Service syntax = “proto3”; Protocol Buffer Version
24. Service syntax = “proto3”; service Places { } Declare Service
25. RPC Call Types • Unary • Server Streaming • Client Streaming • Bidirectional
26. Unary RPC Call Client Server Location
27. Unary RPC Call Client Server Place
28. Unary RPC Call syntax = “proto3”; service Places { rpc GetPlace(Location) returns (Place) {}; } Unary RPC Call
29. Unary RPC Call syntax = “proto3”; service Places { rpc GetPlace(Location) returns (Place) {}; keyword
30. Unary RPC Call syntax = “proto3”; service Places { rpc GetPlace(Location) returns (Place) {}; } Name of RPC call
31. Unary RPC Call syntax = “proto3”; service Places { rpc GetPlace(Location) returns (Place) {}; } Take a Location
32. Unary RPC Call syntax = “proto3”; service Places { rpc GetPlace(Location) returns (Place) {}; } Returns Place
33. Unary RPC Call syntax = “proto3”; service Places { rpc GetPlace(Location) returns (Place) {}; } Unary RPC Call
34. Unary RPC Call syntax = “proto3”; service Places { rpc GetPlace(Location) returns (Place) {}; How do we define our messages?
35. Unary RPC Call service Places { message Location { double latitude = 1; double longitude = 2; } } Location message
36. Unary RPC Call service Places { message Location { double latitude = 1; double longitude = 2; } } Keyword
37. Unary RPC Call service Places { message Location { double latitude = 1; double longitude = 2; } } Message name
38. Unary RPC Call service Places { message Location { double latitude = 1; double longitude = 2; } Fields
39. Unary RPC Call service Places { message Location { double latitude = 1; double longitude = 2; } Type
40. Unary RPC Call service Places { message Location { double latitude = 1; double longitude = 2; } Type .proto Type C++ Java Go double double Double *float64 int32 int32 int *int32 Int64 long int/long *int64 https://developers.google.com/protocol-buffers/docs/overview#scalar
41. Unary RPC Call service Places { message Location { double latitude = 1; double longitude = 2; } Field numbers
42. Unary RPC Call syntax = “proto3”; service Places { rpc GetPlace(Location) returns (Place) {}; } How do we define Place message?
43. Unary RPC Call message Place { string name = 1; Location location = 2; } Name & Location
44. Unary RPC Call message Place { string name = 1; Location location = 2; 
 PlaceType placeType = 3; } Enum
45. Unary RPC Call message Place { string name = 1; Location location = 2; 
 PlaceType placeType = 3; enum PlaceType { Landmark = 0; Driving_Range = 1; Golf_Course = 2; Restaurant = 3; Retail = 4; } Enum
46. Unary RPC Call message Place { string name = 1; Location location = 2; PlaceType placeType = 3; enum PlaceType { … } int64 checkins = 4; int64 comments = 5; } Int Scaler Types
47. Unary RPC Call syntax = “proto3”; service Places { rpc GetPlace(Location) returns (Place) {}; } Unary RPC Call
48. Unary RPC Call syntax = “proto3”; service Places { rpc CheckIn(Place) returns () {}; } Check in to place
49. Unary RPC Call syntax = “proto3”; service Places { rpc CheckIn(Place) returns () {}; } How do we return an empty?
50. Unary RPC Call protocolbuffers/protobuf protobuf/src/google/protobuf/empty.proto message Empty { }
51. Unary RPC Call syntax = “proto3”; import "google/protobuf/empty.proto"; service Places { rpc CheckIn(Place) returns () {}; } Import
52. Unary RPC Call syntax = “proto3”; import "google/protobuf/empty.proto"; service Places { rpc CheckIn(Place) returns (google.protobuf.Empty) {}; } Empty
53. Unary RPC Call syntax = “proto3”; import "google/protobuf/empty.proto"; service Places { rpc CheckIn(Place) returns (google.protobuf.Empty) {}; }
54. RPC Call Types • Unary • Server Streaming • Client Streaming • Bidirectional
55. Server Streaming Client Server Location(s)
56. Server Streaming Client Server Stream of Places
57. Server Streaming service Places { rpc ListPlaces(Area) returns (stream Place) {}; } Server Streaming RPC Call
58. Server Streaming service Places { rpc ListPlaces(Area) returns (stream Place) {}; } Cluster of Locations
59. Server Streaming message Area { Location lo = 1; Location hi = 2; } Cluster of Locations
60. Server Streaming service Places { rpc ListPlaces(Area) returns (stream Place) {}; } stream keyword
61. Server Streaming service Places { rpc ListPlaces(Area) returns (stream Place) {}; } Server Streaming RPC Call
62. RPC Call Types • Unary • Server Streaming • Client Streaming • Bidirectional
63. Client Streaming Client Server Location(s)
64. Client Streaming Client Server Trip Summary
65. Client Streaming service Places { rpc RecordTrip(stream Location) returns (TripSummary) {}; }
66. Client Streaming service Places { rpc RecordTrip(stream Location) returns (TripSummary) {}; } Client Stream
67. Client Streaming service Places { rpc RecordTrip(stream Location) returns (TripSummary) {}; } Return single message
68. Client Streaming service Places { rpc RecordTrip(stream Location) returns (TripSummary) {}; }
69. RPC Call Types • Unary • Server Streaming • Client Streaming • Bidirectional
70. Bidirectional RPC Call Client Server Comments
71. Bidirectional RPC Call Client Server Replies
72. Bidirectional RPC Call service Places { rpc Chat(stream Comment) returns (stream Comment) {}; } Bidirectional RPC Call
73. Bidirectional RPC Call service Places { rpc Chat(stream Comment) returns (stream Comment) {}; } stream keyword
74. RPC Call Types • Unary • Server Streaming • Client Streaming • Bidirectional
75. RPC Call Types service Places { rpc GetPlace(Location) returns (Place) {}; rpc ListPlaces(Area) returns (stream Place) {}; rpc CheckIn(Place) returns (google.protobuf.Empty) {}; rpc Chat(stream Comment) returns (stream Comment) {}; }
76. Building gRPC Server • Configure Server with Kroto-Plus • Create Service with Protocol Buffers • Implement Service • Start Server
77. Generate Service Proto buffer file Protoc & Kroto-plus Message Builders Coroutine Service
78. Creating Messages message Location { double latitude = 1; double longitude = 2; } class Location { static class Builder { Builder setLatitude(double value) Builder setLongitude(double value) Location build() } }
79. Creating Messages message Location { double latitude = 1; double longitude = 2; } Location.newBuilder() .setLatitude(40.9888341) .setLongitude(-73.8502007) .build()
80. Kotlin-friendly api src / krotoPlusConfig.yml protoBuilders: - unwrapBuilders: true Create inline functions
81. Creating Messages message Location { double latitude = 1; double longitude = 2; } inline fun Location( block: Location.Builder.() "-> Unit ): Location = Location.newBuilder() .apply(block) .build()
82. Creating Messages message Location { double latitude = 1; double longitude = 2; } Location { longitude = 40.9888341 latitude = -73.8502007 }
83. Kotlin-friendly api src / krotoPlusConfig.yml protoBuilders: - unwrapBuilders: true - useDslMarkers: true
84. Creating Messages @DslMarker @Target(AnnotationTarget.CLASS) @Retention(AnnotationRetention.BINARY) annotation class PlacesProtoDslMarker @PlacesProtoDslMarker interface PlacesProtoDslBuilder
85. Generate Coroutines Proto buffer file Protoc & Kroto-plus Message Builders Coroutine Service
86. gRPC with Coroutines api src / krotoPlusConfig.yml grpcCoroutines: [{}] protoBuilders: - unwrapBuilders: true - useDslMarkers: true Generate Coroutines
87. Generate Coroutines abstract class PlacesImplBase }
88. Unary RPC Call abstract class PlacesImplBase rpc GetPlace(Location) returns (Place) {}; }
89. Unary RPC Call abstract class PlacesImplBase rpc GetPlace(Location) returns (Place) {}; suspend fun getPlace(request: Location): Place }
90. Unary RPC Call Client Server Request
91. Unary RPC Call Client Server Scope (Dispatcher) Request Suspending
92. Unary RPC Call Client Server Scope (Dispatcher) Request Suspending
93. Unary RPC Call Client Server Scope (Dispatcher) Response Suspending
94. Unary RPC Call fun serverCallUnary(…) { with(newRpcScope(initialContext)) { launch(start = CoroutineStart.ATOMIC) { handleRequest() } } }
95. Server Streaming abstract class PlacesImplBase rpc ListPlaces(Area) returns (stream Place) {}; }
96. Server Streaming abstract class PlacesImplBase rpc ListPlaces(Area) returns (stream Place) {}; suspend fun listPlaces( request: Area, responseChannel: SendChannel<Place> )
97. Server Streaming abstract class PlacesImplBase rpc ListPlaces(Area) returns (stream Place) {}; suspend fun listPlaces( request: Area, responseChannel: SendChannel<Place> )
98. Server Streaming abstract class PlacesImplBase rpc ListPlaces(Area) returns (stream Place) {}; suspend fun listPlaces( request: Area, responseChannel: SendChannel<Place> )
99. Channel Coroutine interface Channel<E> : SendChannel<E>, ReceiveChannel<E> interface SendChannel<in E> { suspend fun send(element: E) }
100. Server Streaming abstract class PlacesImplBase rpc ListPlaces(Area) returns (stream Place) {}; suspend fun listPlaces( request: Area, responseChannel: SendChannel<Place> )
101. Bidirectional abstract class PlacesImplBase rpc Chat(stream Comment) returns (stream Comment) {};
102. Bidirectional abstract class PlacesImplBase rpc Chat(stream Comment) returns (stream Comment) {}; suspend fun chat( requestChannel: ReceiveChannel<Comment>, responseChannel: SendChannel<Comment> )
103. Bidirectional abstract class PlacesImplBase rpc Chat(stream Comment) returns (stream Comment) {}; suspend fun chat( requestChannel: ReceiveChannel<Comment>, responseChannel: SendChannel<Comment> )
104. Channel Coroutine interface Channel<E> : SendChannel<E>, ReceiveChannel<E> interface ReceiveChannel<out E> { suspend fun receive(): E }
105. Bidirectional abstract class PlacesImplBase rpc Chat(stream Comment) returns (stream Comment) {}; suspend fun chat( requestChannel: ReceiveChannel<Comment>, responseChannel: SendChannel<Comment> )
106. Streaming Client Server Scope (Dispatcher) Request Send Channel Receive Channel
107. Streaming Client Server Scope (Dispatcher) Request Send Channel Receive Channel
108. Streaming Client Server Scope (Dispatcher) Response Send Channel Receive Channel
109. Generate Service abstract class PlacesImplBase { open suspend fun getPlace(…): Place open suspend fun listPlaces(…) open suspend fun chat(…) open suspend fun recordTrip(…) }
110. Implement Service class PlacesService(): PlacesImplBase() { } Inherit base Implementation
111. Implement Service class PlacesService(): PlacesImplBase() { override val initialContext: CoroutineContext get() = Dispatchers.IO } Specify Dispatcher
112. Implement Service class PlacesService(dispatcher): PlacesImplBase() { override val initialContext: CoroutineContext get() = Dispatchers.IO }
113. Implement Service class PlacesService(dispatcher): PlacesImplBase() { override val initialContext: CoroutineContext get() = dispatcher } Specify Dispatcher
114. Implement Service class PlacesService(dispatcher): PlacesImplBase() { override suspend fun getPlace(request: Location): Place { } }
115. Implement Service class PlacesService(dispatcher): PlacesImplBase() { override suspend fun getPlace(request: Location): Place { val placeFromDB = getPlacesFromDb() .first { it.location "== request } } } Get Place from DB
116. Implement Service class PlacesService(dispatcher): PlacesImplBase() { override suspend fun getPlace(request: Location): Place { val placeFromDB = getPlacesFromDb() .first { it.location "== request } return Place { name = placeFromDb.name !!... } } Map it to Proto Message
117. Implement Service abstract class PlacesImplBase rpc ListPlaces(Area) returns (stream Place) {}; suspend fun listPlaces( request: Area, responseChannel: SendChannel<Place> )
118. Implement Service abstract class PlacesImplBase suspend fun listPlaces( area: Area, responseChannel: SendChannel<Place> ) { val places = getPlaces(area) places.forEach { responseChannel.send(it) } } } Send to Channel
119. Implement Service abstract class PlacesImplBase suspend fun listPlaces( area: Area, responseChannel: SendChannel<Place> ) { val places = getPlaces(area) places.forEach { responseChannel.send(it) } } } How does channel close?
120. Close Channel kroto-plus kroto-plus/ServerCalls.kt rpcScope.launch { block(responseChannel) responseChannel.close() } Closes Channel
121. Errors abstract class PlacesImplBase suspend fun listPlaces( area: Area, responseChannel: SendChannel<Place> ) { val places = getPlaces(area) places.forEach { responseChannel.send(it) } } } Exception occurs?
122. Errors kroto-plus kroto-plus/ServerCalls.kt rpcScope.launch { try { block(responseChannel) responseChannel.close() } finally { cancelScope() } Clean up on error
123. Implement Service class PlacesService(dispatcher): PlacesImplBase { suspend fun getPlace(…): Place suspend fun listPlaces(…) suspend fun chat(…) suspend fun recordTrip(…) }
124. Building gRPC Server • Configure Server with Kroto-Plus • Create Service with Protocol Buffers • Implement Service • Start Server
125. grpc-java grpc-java/ServerBuilder.java class ServerBuilder { forPort(port) addService(service) interceptor(interceptor)
126. Configure gRPC Server val server: Server = ServerBuilder .forPort(port) .addService(PlacesService()) .build()
127. Configure gRPC Server val server: Server = ServerBuilder .forPort(port) .addService(PlacesService()) .build()
128. Start gRPC Server fun start() { server.start() Runtime.getRuntime().addShutdownHook( Thread { server.shutdown() } ) }
129. Start gRPC Server fun main() { val port = 50051 val server = configureServer(port) server.start() server.blockUntilShutdown() }
130. Building gRPC Server • Configure Server with Kroto-Plus • Create Service with Protocol Buffers • Implement Service • Start Server
131. Resources • gRPC Java https:!//github.com/grpc/grpc-java • Kroto-plus https:!//github.com/marcoferrer/kroto-plus • Protocol Buffers https:!//developers.google.com/protocol-buffers/docs/overview • Micronaut https:!//micronaut.io/
132. Building gRPC Client
133. grpc/grpc-kotlin gRPC-Kotlin/JVM - An RPC library and framework grpc-kotlin-stub v0.1.4 protoc-gen-grpc-kotlinstub v0.1.4 grpc-kotlin-stub-lite v0.1.4 A Kotlin/JVM implementation of gRPC: A high performance, open source, general RPC framework that puts mobile and HTTP/2 first. Bazel Build passing Gradle Build passing
134. Server Service Proto File
135. Client Server Service Proto File Service Proto File
136. Client Server Service Proto File Service Proto File Client Stub
137. Generated Client class CoroutineStub { }
138. Generated Client class CoroutineStub { } rpc GetPlace(Location) returns (Place) {};
139. Generated Client class CoroutineStub { } rpc GetPlace(Location) returns (Place) {}; suspend fun getPlace(request: Location): Place
140. Generated Client class CoroutineStub { } rpc ListPlaces(Area) returns (stream Place) {}; fun listPlaces(request: Area): Flow<Place> Stream is map to Flow
141. Generated Client class CoroutineStub { } rpc Chat(stream Comment) returns (stream Comment) {}; fun chat(requests: Flow<Comment>): Flow<Comment> Stream is map to Flow
142. Generated Client class CoroutineStub { } suspend fun getPlace(request: Location): Place fun recordTrip(requests: Flow<Location>): TripSummary fun listPlaces(request: Area): Flow<Place> fun chat(requests: Flow<Comment>): Flow<Comment>
143. Using Client val managedChannel = ManagedChannelBuilder .forAddress(host, port) .useTransportSecurity() .build() Specify host and port
144. Using Client val managedChannel = ManagedChannelBuilder .forAddress(host, port) .useTransportSecurity() .build() for https
145. Using Client val managedChannel = ManagedChannelBuilder .forAddress(host, port) .intercept(object : ClientInterceptor { fun interceptCall(method, callOptions, channel) { }) .build() Intercept RPC Calls
146. Using Client val managedChannel = ManagedChannelBuilder .forAddress(host, port) .useTransportSecurity() .build()
147. Using Client val managedChannel = ManagedChannelBuilder .forAddress(host, port) .useTransportSecurity() .build() val client = CoroutineStub(managedChannel)
148. Using Client class GrpcViewModel(val client: CoroutineStub): ViewModel() { }
149. Using Client class GrpcViewModel(val client: CoroutineStub): ViewModel() { fun getPlace(location: Location) { viewModelScope.launch { val place = client.getPlace(location) } } }
150. Using Client class GrpcViewModel(val client: CoroutineStub): ViewModel() { fun listPlaces(area: Area) { viewModelScope.launch { val places: Flow<Place> = client.listPlaces(area) places.collect { } } } }
151. Using Client class GrpcViewModel(val client: CoroutineStub): ViewModel() { fun chat(comments: ReceiveChannel<Comment>) { viewModelScope.launch { client.chat(comments.consumeAsFlow()).collect { } } } } Stream of comments
152. Using Client class GrpcViewModel(val client: CoroutineStub): ViewModel() { fun chat(comments: ReceiveChannel<Comment>) { viewModelScope.launch { client.chat(comments.consumeAsFlow()) .collect { } } } } Convert Channel to Flow
153. Using Client class GrpcViewModel(val client: CoroutineStub): ViewModel() { fun chat(comments: ReceiveChannel<Comment>) { viewModelScope.launch { client.chat(comments.consumeAsFlow()) .collect { } } } } Collect from Flow
154. Using Client class GrpcViewModel(val client: CoroutineStub): ViewModel() { fun getPlace(location: Location) fun listPlaces(area: Area) fun chat(chat: ReceiveChannel<Comment>) }
155. View Model gRPC Client Stub
156. gRPC Client Stub How does it use coroutines?
157. Consumer Coroutine
158. gRPC-java client Start Consumer Coroutine
159. gRPC-java client Request Consumer Coroutine Producer Coroutine Response
160. gRPC-java client Request Consumer Coroutine Producer Coroutine Response Channel (size = 1)
161. gRPC-java client Request Consumer Coroutine Producer Coroutine Response Channel (size = 1)
162. gRPC-java client Request Consumer Coroutine Producer Coroutine Response Channel (size = 1) Flow<Response>
163. View Model gRPC Client Stub
164. Resources • gRPC Kotlin https:!//github.com/grpc/grpc-kotlin • Wire https:!//github.com/square/wire
165. gRPC-Kotlin kroto-plus Client Server
166. https:"//codingwithmohit.com/
167. Resources • Unit Testing Delays, Errors & Retries with Kotlin Flows https:!//codingwithmohit.com/coroutines/unit-testing-delays- errors-retries-with-kotlin-flows/ • Kotlin Assert Flow Delight https:!//codingwithmohit.com/coroutines/kotlin-assert-flow-delight/ • Channels & Flows in Practice https:!//speakerdeck.com/heyitsmohit/channels-and-flows-in-practice
168. Thank You! www.twitter.com/heyitsmohit www.codingwithmohit.com