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Tackling gRPC with Kotlin WIRE 3 @oldergod @egorand

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Why gRPC?

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Service definition language Protocol Buffers Cross platform/language HTTP/2 superpowers

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Protocol Buffers

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Schema-based Rich tooling support Lightweight on the wire Strong backwards compatibility guarantees

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Schema

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } }

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } Syntax proto2 proto3 Package Options java_package custom Messages Enums Tags

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } Syntax proto2 proto3 Package Options java_package custom Messages Enums Tags int 1 to 536,870,911 Field rules

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } Package Options java_package custom Messages Enums Tags int 1 to 536,870,911 Field rules required optional repeated

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } java_package custom Messages Enums Tags int 1 to 536,870,911 Field rules required optional repeated Field types double float int32 int64 uint32

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } Enums Tags int 1 to 536,870,911 Field rules required optional repeated Field types double float int32 int64 uint32 uint64 sint32 sint64 fixed32 fixed64 sfixed32 sfixed64 bool string bytes

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } Tags int 1 to 536,870,911 Field rules required optional repeated Field types double float int32 int64 uint32 uint64 sint32 sint64 fixed32 fixed64 sfixed32 sfixed64 bool string bytes

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } Field rules required optional repeated Field types double float int32 int64 uint32 uint64 sint32 sint64 fixed32 fixed64 sfixed32 sfixed64 bool string bytes

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Bytes

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } }

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } val person = Person( id = 23, name = "egor", occupation = PRESIDENT ) val bytes = Person.ADAPTER.encode(person) println(bytes.toByteString().hex()) // 0817120465676f721802

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"proto2"; com.squareup; ava_package = "com.squareup"; Person { ed int32 id = 1; al string name = 2; al Occupation occupation = 3; ccupation { WARE_DEVELOPER = 0; ENT = 1; IDENT = 2; 0817120465676f721802

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08 17 12 04 65 67 6f 72 18 02 "proto2"; com.squareup; ava_package = "com.squareup"; Person { ed int32 id = 1; al string name = 2; al Occupation occupation = 3; ccupation { WARE_DEVELOPER = 0; ENT = 1; IDENT = 2; == 10 bytes

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } 08 17 12 04 65 67 6f 72

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } 08 17 12 Tag: id(1) Field encoding: VARINT(0) 0000 0001 << 3 0000 1000 | 0 0000 1000 == 08

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } 08 17 12 04 65 67 6f 72 18 id = 23

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } 08 17 12 04 Tag: name(2) Field encoding: LENGTH_DELIMITED(2) 0000 0010 << 3 0001 0000 | 2 0000 1010 == 12

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } 17 12 04 65 67 6f 72 18 02 “egor”.length()

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } 17 12 04 65 67 6f 72 18 02 “egor”.length() ‘e’ ‘g’ ‘o’ ‘r’

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } 6f 72 18 02 Tag: occupation(3) Field encoding: VARINT(0) 0000 0011 << 3 0001 1000 | 0 0001 1000 == 18

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syntax = "proto2"; package com.squareup; option java_package = "com.squareup"; message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } 72 18 02 occupation = PRESIDENT

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Backwards compatibility

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message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } v1

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message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } v1 val person = Person( id = 23, name = "egor", occupation = PRESIDENT ) val v1 = Person.ADAPTER .encode(person) .toByteString().hex() // 0817120465676f721802

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v2 message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; required int32 age = 4; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } + // 0817120465676f721802 val personV2 = Person.ADAPTER .decode( “0817120465676f721802" .decodeHex() ) println(personV2) Exception in thread "main" java.lang.IllegalStateException: Required field not set: age

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v2 message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; optional int32 age = 4; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } + // 0817120465676f721802 val personV2 = Person.ADAPTER .decode( “0817120465676f721802" .decodeHex() ) println(personV2) Person{id=23, name=egor, occupation=PRESIDENT}

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v2 message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } - // 0817120465676f721802 val personV2 = Person.ADAPTER .decode( “0817120465676f721802" .decodeHex() ) println(personV2) Person{name=egor, occupation=PRESIDENT}

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v2 message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } - // 0817120465676f721802 val personV2 = Person.ADAPTER .decode( “0817120465676f721802" .decodeHex() ) println(personV2) Person{id=23, occupation=PRESIDENT}

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v2 message Person { required int32 id = 1; optional string name = 2; optional string name = 4; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } - + // 0817120465676f721802 val personV2 = Person.ADAPTER .decode( “0817120465676f721802" .decodeHex() ) println(personV2) Person{id=23, occupation=PRESIDENT}

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v2 message Person { required int32 id = 1; optional string name = 2; optional string name = 3; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } - + - // 0817120465676f721802 val personV2 = Person.ADAPTER .decode( “0817120465676f721802" .decodeHex() ) println(personV2) Exception in thread "main" java.net.ProtocolException: Expected LENGTH_DELIMITED but was 0

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v2 message Person { required int32 id = 1; optional string name = 2; optional float name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } - + // 0817120465676f721802 val personV2 = Person.ADAPTER .decode( “0817120465676f721802" .decodeHex() ) println(personV2) Person{id=23, name=4.7418825E30, occupation=PRESIDENT}

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v2 message Person { required int32 id = 1; optional string name = 2; optional string maName = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } } - + // 0817120465676f721802 val personV2 = Person.ADAPTER .decode( “0817120465676f721802" .decodeHex() ) println(personV2) Person{id=23, maName=egor, occupation=PRESIDENT}

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Supported languages Java C# C++ Python Objective-C JavaScript Ruby Go Dart PHP

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Why WIRE ?

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message Person { required int32 id = 1; optional string name = 2; optional Occupation occupation = 3; enum Occupation { SOFTWARE_DEVELOPER = 0; STUDENT = 1; PRESIDENT = 2; } }

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// Generated by the protocol buffer compiler. DO NOT EDIT! // source: com/squareup/person.proto package com.squareup; public final class PersonOuterClass { private PersonOuterClass() {} public static void registerAllExtensions( com.google.protobuf.ExtensionRegistryLite registry) { } public static void registerAllExtensions( com.google.protobuf.ExtensionRegistry registry) { registerAllExtensions( (com.google.protobuf.ExtensionRegistryLite) registry); } public interface PersonOrBuilder extends // @@protoc_insertion_point(interface_extends:com.squareup.Person) com.google.protobuf.MessageOrBuilder { /** * required int32 id = 1; */ boolean hasId(); /** * required int32 id = 1; */

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*/ public static final class Person extends com.google.protobuf.GeneratedMessageV3 implements // @@protoc_insertion_point(message_implements:com.squareup.Person) PersonOrBuilder { private static final long serialVersionUID = 0L; // Use Person.newBuilder() to construct. private Person(com.google.protobuf.GeneratedMessageV3.Builder> builder) { super(builder); } private Person() { name_ = ""; occupation_ = 0; } @java.lang.Override public final com.google.protobuf.UnknownFieldSet getUnknownFields() { return this.unknownFields; } private Person( com.google.protobuf.CodedInputStream input, com.google.protobuf.ExtensionRegistryLite extensionRegistry) throws com.google.protobuf.InvalidProtocolBufferException { this(); if (extensionRegistry == null) { throw new java.lang.NullPointerException(); }

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while (!done) { int tag = input.readTag(); switch (tag) { case 0: done = true; break; case 8: { bitField0_ |= 0x00000001; id_ = input.readInt32(); break; } case 18: { com.google.protobuf.ByteString bs = input.readBytes(); bitField0_ |= 0x00000002; name_ = bs; break; } case 24: { int rawValue = input.readEnum(); @SuppressWarnings("deprecation") com.squareup.PersonOuterClass.Person.Occupation value = com.squareup.PersonOuterClass.Person.Occupation.valueOf(rawValue); if (value == null) { unknownFields.mergeVarintField(3, rawValue); } else { bitField0_ |= 0x00000004; occupation_ = rawValue;

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public Occupation findValueByNumber(int number) { return Occupation.forNumber(number); } }; public final com.google.protobuf.Descriptors.EnumValueDescriptor getValueDescriptor() { return getDescriptor().getValues().get(ordinal()); } public final com.google.protobuf.Descriptors.EnumDescriptor getDescriptorForType() { return getDescriptor(); } public static final com.google.protobuf.Descriptors.EnumDescriptor getDescriptor() { return com.squareup.PersonOuterClass.Person.getDescriptor().getEnumTypes().get(0); } private static final Occupation[] VALUES = values(); public static Occupation valueOf( com.google.protobuf.Descriptors.EnumValueDescriptor desc) { if (desc.getType() != getDescriptor()) { throw new java.lang.IllegalArgumentException( "EnumValueDescriptor is not for this type."); } return VALUES[desc.getIndex()];

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*/ public boolean hasOccupation() { return ((bitField0_ & 0x00000004) != 0); } /** * optional .com.squareup.Person.Occupation occupation = 3; */ public com.squareup.PersonOuterClass.Person.Occupation getOccupation() { @SuppressWarnings("deprecation") com.squareup.PersonOuterClass.Person.Occupation result = com.squareup.PersonOuterClass.Person.Occupation.valueOf(occupation_); return result == null ? com.squareup.PersonOuterClass.Person.Occupation.SOFTWARE_DEVELOPER : result; } private byte memoizedIsInitialized = -1; @java.lang.Override public final boolean isInitialized() { byte isInitialized = memoizedIsInitialized; if (isInitialized == 1) return true; if (isInitialized == 0) return false; if (!hasId()) { memoizedIsInitialized = 0; return false; } memoizedIsInitialized = 1;

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} if (!(obj instanceof com.squareup.PersonOuterClass.Person)) { return super.equals(obj); } com.squareup.PersonOuterClass.Person other = (com.squareup.PersonOuterClass.Person) obj if (hasId() != other.hasId()) return false; if (hasId()) { if (getId() != other.getId()) return false; } if (hasName() != other.hasName()) return false; if (hasName()) { if (!getName() .equals(other.getName())) return false; } if (hasOccupation() != other.hasOccupation()) return false; if (hasOccupation()) {

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Not readable for both Egor or Benoit ~95 methods for 3 fields + 3 values enum

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Small number of methods Readable code Immutable Support for chained builder pattern Inherit documentation from .proto files

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WIRE 3

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gRPC support Kotlin code generation Gradle plugin

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gRPC support

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What RPC are you ?

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service RouteGuide {a }b

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service RouteGuide {a // A simple RPC. rpc GetFeature(Point) returns (Feature) {} }b

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service RouteGuide {a // A simple RPC. rpc GetFeature(Point) returns (Feature) {} // A server-to-client streaming RPC. rpc ListFeatures(Rectangle) returns (stream Feature) {} }b

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service RouteGuide {a // A simple RPC. rpc GetFeature(Point) returns (Feature) {} // A server-to-client streaming RPC. rpc ListFeatures(Rectangle) returns (stream Feature) {} // A client-to-server streaming RPC. rpc RecordRoute(stream Point) returns (RouteSummary) {} }b

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service RouteGuide {a // A simple RPC. rpc GetFeature(Point) returns (Feature) {} // A server-to-client streaming RPC. rpc ListFeatures(Rectangle) returns (stream Feature) {} // A client-to-server streaming RPC. rpc RecordRoute(stream Point) returns (RouteSummary) {} // A Bidirectional streaming RPC. rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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service RouteGuide {a // A simple RPC. rpc GetFeature(Point) returns (Feature) {} // A server-to-client streaming RPC. rpc ListFeatures(Rectangle) returns (stream Feature) {} // A client-to-server streaming RPC. rpc RecordRoute(stream Point) returns (RouteSummary) {} // A Bidirectional streaming RPC. rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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Which side are you on ?

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rpcRole = 'client or server?'

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rpcRole = 'client or server?' enum class RpcRole { CLIENT, SERVER; }

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rpcCallStyle = 'suspending or blocking?'

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rpcCallStyle = 'suspending or blocking?' enum class RpcCallStyle { SUSPENDING, BLOCKING; }

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singleMethodServices = true || false

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rpcCallStyle = 'blocking' rpcRole = 'server' singleMethodServices = true rpcCallStyle = 'suspending' rpcRole = 'client' singleMethodServices = false Client ? Server ?

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gRPC codegen

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Client Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b wire { kotlin { rpcCallStyle = 'suspending' rpcRole = 'client' singleMethodServices = false } }

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interface RouteGuideClient : Service { } Client Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideClient : Service { suspend fun GetFeature(request: Point): Feature } Client Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideClient : Service { suspend fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle): ReceiveChannel } Client Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideClient : Service { suspend fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle): ReceiveChannel fun RecordRoute(): Pair, Deferred> } Client Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideClient : Service { suspend fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle): ReceiveChannel fun RecordRoute(): Pair, Deferred> fun RouteChat(): Pair, ReceiveChannel> } Client Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideClient : Service { suspend fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle): ReceiveChannel fun RecordRoute(): Pair, Deferred> fun RouteChat(): Pair, ReceiveChannel> } Client Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideClient : Service { suspend fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle): ReceiveChannel fun RecordRoute(): Pair, Deferred> fun RouteChat(): Pair, ReceiveChannel> } Client Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b val grpcClient = GrpcClient.Builder() .client(okHttpClient) .baseUrl("https://10.0.2.2:8443") .build() val whiteboardClient = grpcClient.create(WhiteboardClient::class)

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interface RouteGuideClient : Service { suspend fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle): ReceiveChannel fun RecordRoute(): Pair, Deferred> fun RouteChat(): Pair, ReceiveChannel> } Client Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideClient : Service { suspend fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle): ReceiveChannel fun RecordRoute(): Pair, Deferred> fun RouteChat(): Pair, ReceiveChannel> } Client Side dependencies { implementation 'com.squareup.wire:wire-grpc-client:3.0.0-rc01' }

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Server Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b wire { kotlin { rpcCallStyle = 'blocking' rpcRole = 'server' singleMethodServices = true } }

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interface RouteGuideBlockingServer : Service { } Server Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideBlockingServer : Service { fun GetFeature(request: Point): Feature } Server Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideBlockingServer : Service { fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle, response: MessageSink) } Server Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideBlockingServer : Service { fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle, response: MessageSink) } Server Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b interface MessageSink { fun write(message: T) fun close() }

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interface RouteGuideBlockingServer : Service { fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle, response: MessageSink) } Server Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideBlockingServer : Service { fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle, response: MessageSink) fun RecordRoute(request: MessageSource): RouteSummary } Server Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideBlockingServer : Service { fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle, response: MessageSink) fun RecordRoute(request: MessageSource): RouteSummary } Server Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b interface MessageSource { fun read(): T? fun close() }

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interface RouteGuideBlockingServer : Service { fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle, response: MessageSink) fun RecordRoute(request: MessageSource): RouteSummary } Server Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideBlockingServer : Service { fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle, response: MessageSink) fun RecordRoute(request: MessageSource): RouteSummary fun RouteChat(request: MessageSource, response: MessageSink) } Server Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideBlockingServer : Service { fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle, response: MessageSink) fun RecordRoute(request: MessageSource): RouteSummary fun RouteChat(request: MessageSource, response: MessageSink) } Server Side service RouteGuide {a rpc GetFeature(Point) returns (Feature) {} rpc ListFeatures(Rectangle) returns (stream Feature) {} rpc RecordRoute(stream Point) returns (RouteSummary) {} rpc RouteChat(stream RouteNote) returns (stream RouteNote) {} }b

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interface RouteGuideBlockingServer : Service { fun GetFeature(request: Point): Feature fun ListFeatures(request: Rectangle, response: MessageSink) fun RecordRoute(request: MessageSource): RouteSummary fun RouteChat(request: MessageSource, response: MessageSink) } Server Side dependencies { api 'com.squareup.wire:wire-runtime:3.0.0-rc01' }

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Kotlin coroutine or not Kotlin coroutine ?

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Kotlin Codegen

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class Person( @field:WireField( tag = 1, adapter = "com.squareup.wire.ProtoAdapter#INT32", label = WireField.Label.REQUIRED ) val id: Int, @field:WireField( tag = 2, adapter = "com.squareup.wire.ProtoAdapter#STRING" ) val name: String? = null, @field:WireField( tag = 3, adapter = "com.squareup.Person${'$'}Occupation#ADAPTER" ) val occupation: Occupation? = null, unknownFields: ByteString = ByteString.EMPTY ) : Message(ADAPTER, unknownFields) { override fun equals(other: Any?): Boolean { if (other === this) return true if (other !is Person) return false return unknownFields == other.unknownFields && id == other.id

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Data classes, but not quite!

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class Person( @field:WireField( tag = 1, adapter = "com.squareup.wire.ProtoAdapter#INT32", label = WireField.Label.REQUIRED ) val id: Int, @field:WireField( tag = 2, adapter = "com.squareup.wire.ProtoAdapter#STRING" ) val name: String? = null, @field:WireField( tag = 3, adapter = "com.squareup.Person${'$'}Occupation#ADAPTER" ) val occupation: Occupation? = null, unknownFields: ByteString = ByteString.EMPTY ) : Message(ADAPTER, unknownFields) { override fun equals(other: Any?): Boolean { if (other === this) return true if (other !is Person) return false return unknownFields == other.unknownFields && id == other.id

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val occupation: Occupation? = null, unknownFields: ByteString = ByteString.EMPTY ) : Message(ADAPTER, unknownFields) { override fun equals(other: Any?): Boolean { if (other === this) return true if (other !is Person) return false return unknownFields == other.unknownFields && id == other.id && name == other.name && occupation == other.occupation } override fun hashCode(): Int { var result = super.hashCode if (result == 0) { result = id.hashCode() result = result * 37 + name.hashCode() result = result * 37 + occupation.hashCode() super.hashCode = result } return result } override fun toString(): String { val result = mutableListOf() result += """id=$id""" if (name != null) result += """name=$name"""

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&& name == other.name && occupation == other.occupation } override fun hashCode(): Int { var result = super.hashCode if (result == 0) { result = id.hashCode() result = result * 37 + name.hashCode() result = result * 37 + occupation.hashCode() super.hashCode = result } return result } override fun toString(): String { val result = mutableListOf() result += """id=$id""" if (name != null) result += """name=$name""" if (occupation != null) result += """occupation=$occupation""" return result.joinToString(prefix = "Person{", separator = ", ", postfix = "}") } @Deprecated( message = "Shouldn't be used in Kotlin", level = DeprecationLevel.HIDDEN ) override fun newBuilder(): Nothing { throw AssertionError()

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} return result } override fun toString(): String { val result = mutableListOf() result += """id=$id""" if (name != null) result += """name=$name""" if (occupation != null) result += """occupation=$occupation""" return result.joinToString(prefix = "Person{", separator = ", ", postfix = "}") } @Deprecated( message = "Shouldn't be used in Kotlin", level = DeprecationLevel.HIDDEN ) override fun newBuilder(): Nothing { throw AssertionError() } fun copy( id: Int = this.id, name: String? = this.name, occupation: Occupation? = this.occupation, unknownFields: ByteString = this.unknownFields ): Person = Person(id, name, occupation, unknownFields) companion object { @JvmField

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Data classes, but not quite! Builder deprecated, use copy()

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class Person( @field:WireField( tag = 1, adapter = "com.squareup.wire.ProtoAdapter#INT32", label = WireField.Label.REQUIRED ) val id: Int, @field:WireField( tag = 2, adapter = "com.squareup.wire.ProtoAdapter#STRING" ) val name: String? = null, @field:WireField( tag = 3, adapter = "com.squareup.Person${'$'}Occupation#ADAPTER" ) val occupation: Occupation? = null, unknownFields: ByteString = ByteString.EMPTY ) : Message(ADAPTER, unknownFields) { override fun equals(other: Any?): Boolean { if (other === this) return true if (other !is Person) return false return unknownFields == other.unknownFields && id == other.id

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if (occupation != null) result += """occupation=$occupation""" return result.joinToString(prefix = "Person{", separator = ", ", postfix = "}") } @Deprecated( message = "Shouldn't be used in Kotlin", level = DeprecationLevel.HIDDEN ) override fun newBuilder(): Nothing { throw AssertionError() } fun copy( id: Int = this.id, name: String? = this.name, occupation: Occupation? = this.occupation, unknownFields: ByteString = this.unknownFields ): Person = Person(id, name, occupation, unknownFields) companion object { @JvmField val ADAPTER: ProtoAdapter = object : ProtoAdapter( FieldEncoding.LENGTH_DELIMITED, Person::class ) { override fun encodedSize(value: Person): Int = ProtoAdapter.INT32.encodedSizeWithTag(1, value.id) + ProtoAdapter.STRING.encodedSizeWithTag(2, value.name) + Occupation.ADAPTER.encodedSizeWithTag(3, value.occupation) +

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Data classes, but not quite! Builder deprecated, use copy() Nullability: required vs optional

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class Person( @field:WireField( tag = 1, adapter = "com.squareup.wire.ProtoAdapter#INT32", label = WireField.Label.REQUIRED ) val id: Int, @field:WireField( tag = 2, adapter = "com.squareup.wire.ProtoAdapter#STRING" ) val name: String? = null, @field:WireField( tag = 3, adapter = "com.squareup.Person${'$'}Occupation#ADAPTER" ) val occupation: Occupation? = null, unknownFields: ByteString = ByteString.EMPTY ) : Message(ADAPTER, unknownFields) { override fun equals(other: Any?): Boolean { if (other === this) return true if (other !is Person) return false return unknownFields == other.unknownFields && id == other.id

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Data classes, but not quite! Builder deprecated, use copy() Nullability: required vs optional Interoperability with Java

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class Person( @field:WireField( tag = 1, adapter = "com.squareup.wire.ProtoAdapter#INT32", label = WireField.Label.REQUIRED ) @JvmField val id: Int, @field:WireField( tag = 2, adapter = "com.squareup.wire.ProtoAdapter#STRING" ) @JvmField val name: String? = null, @field:WireField( tag = 3, adapter = "com.squareup.Person${'$'}Occupation#ADAPTER" ) @JvmField val occupation: Occupation? = null, unknownFields: ByteString = ByteString.EMPTY ) : Message(ADAPTER, unknownFields) { override fun equals(other: Any?): Boolean {

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if (occupation != null) result += """occupation=$occupation""" return result.joinToString(prefix = "Person{", separator = ", ", postfix = "}") } override fun newBuilder(): Builder { val builder = Builder() builder.id = id builder.name = name builder.occupation = occupation builder.addUnknownFields(unknownFields) return builder } fun copy( id: Int = this.id, name: String? = this.name, occupation: Occupation? = this.occupation, unknownFields: ByteString = this.unknownFields ): Person = Person(id, name, occupation, unknownFields) class Builder : Message.Builder() { @JvmField var id: Int? = null @JvmField var name: String? = null @JvmField

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occupation: Occupation? = this.occupation, unknownFields: ByteString = this.unknownFields ): Person = Person(id, name, occupation, unknownFields) class Builder : Message.Builder() { @JvmField var id: Int? = null @JvmField var name: String? = null @JvmField var occupation: Occupation? = null fun id(id: Int): Builder { this.id = id return this } fun name(name: String?): Builder { this.name = name return this } fun occupation(occupation: Occupation?): Builder { this.occupation = occupation return this }

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Bonus: multiplatform runtime!* * - coming soon

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// wire-runtime apply plugin: 'org.jetbrains.kotlin.multiplatform' kotlin { jvm { withJava() } js() iosX64() iosArm64() linuxX64() macosX64() }

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Gradle Plugin

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tasks.register("generateProtos", JavaExec) { classpath = configurations.wire main = 'com.squareup.wire.WireCompiler' args = [ "--proto_path=$rootDir/protos/src/main/proto", '--kotlin_out=src/main/java', '--includes=com.squareup.wire.whiteboard.Whiteboard', ] } Wire < 3.0

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apply plugin: 'com.squareup.wire' wire { sourcePath { srcDir "$rootDir/protos/src/main/proto" } kotlin { out "src/main/java" includes = ['com.squareup.wire.whiteboard.Whiteboard'] } } WIRE 3

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wire { java { includes = ['com.example.pizza.*'] excludes = ['com.example.sales.*'] exclusive = false out "${buildDir}/custom" android = true androidAnnotations = true compact = true } }

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wire { kotlin { includes = ['com.example.pizza.*'] excludes = ['com.example.sales.*'] exclusive = false out "${buildDir}/custom" android = true javaInterop = true rpcCallStyle = 'blocking' rpcRole = 'server' singleMethodServices = true } }

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WIRE 3 Real World Business Use Case Demo

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Demo Video: https://youtu.be/hGs5wSS7CqA Source Code: https://github.com/square/wire/tree/master/wire-grpc-sample

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What's next ?

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Improve multiplatform support Stabilize gRPC APIs gRPC for Java? Gradle plugin polishing for Android

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WIRE III

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References • gRPC official website: https://grpc.io • Protocol Buffers documentations: https://developers.google.com/protocol-buffers/ • Wire documentations: https://square.github.io/wire/ • Wire source code repository: https://github.com/square/wire/ • Misk microservice container: https://github.com/cashapp/misk