Wire 3 : Tackling gRPC with Kotlin

Video: https://youtu.be/xo_zVPAXbBg

Co-Presented by @egorand and @oldergod.
Protocol Buffers (or Protobuf) is an efficient schema-based data serialization protocol, and gRPC is a high-performance, HTTP/2-based RPC framework. The two work together flawlessly to help you build world class distributed systems.

At Square, client and server engineers collaborate on Protobuf schemas to define APIs. We also built Wire - a library which processes schemas and generates Java code that applications can use to send and receive data. Last year we started working on Wire 3, which is rewritten in Kotlin, generates Kotlin code, and adds a number of exciting features:

- Protobuf messages as data classes
- Multiplatform runtime module
- Coroutines-based gRPC APIs
- Gradle plugin

In this session, we’ll take a deep dive into these features, and talk about how we leveraged Kotlin to create better APIs. We’ll show you how to get the best out of Protobuf and gRPC for your server and client applications using Wire.

Transcript

1. Tackling gRPC with Kotlin
   WIRE 3
   @oldergod @egorand
   

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2. View Slide

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4. Why gRPC?
   

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

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6. Protocol Buffers
   

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

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8. Schema
   

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9. 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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10. 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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11. 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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12. 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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13. 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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14. 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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15. 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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16. 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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17. Bytes
    

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18. 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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19. 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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20. "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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21. 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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22. 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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23. 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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24. 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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25. 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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26. 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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27. 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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28. 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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29. 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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30. Backwards compatibility
    

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31. 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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32. 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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33. 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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34. 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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35. 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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36. 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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37. 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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38. 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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39. 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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40. 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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41. Supported languages
    Java C# C++ Python
    Objective-C JavaScript
    Ruby
    Go
    Dart PHP
    

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42. Why WIRE ?
    

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43. 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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44. View Slide

45. // 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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46. */
    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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47. 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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48. 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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49. */
    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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50. }
    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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51. View Slide

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

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53. View Slide

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

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55. WIRE 3
    

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56. gRPC support
    Kotlin code generation
    Gradle plugin
    

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57. gRPC support
    

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58. What RPC are you ?
    

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59. service RouteGuide {a
    }b
    

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

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61. 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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62. 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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63. 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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64. 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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65. Which side are you on ?
    

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66. rpcRole = 'client or server?'
    

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

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68. rpcCallStyle = 'suspending or blocking?'
    

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

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70. singleMethodServices = true || false
    

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

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72. gRPC codegen
    

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73. 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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74. 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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75. 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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76. 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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77. 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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78. 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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79. 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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80. 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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81. 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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82. 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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83. 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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84. 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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85. 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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86. 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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87. 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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88. 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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89. 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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90. 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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91. 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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92. 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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93. 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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94. 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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95. Kotlin coroutine or not Kotlin coroutine ?
    

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96. Kotlin Codegen
    

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97. 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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98. Data classes, but not quite!
    

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99. 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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100. 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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101. && 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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102. }
     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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103. Data classes, but not quite!
     Builder deprecated, use copy()
     

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104. 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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105. 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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106. Data classes, but not quite!
     Builder deprecated, use copy()
     Nullability: required vs optional
     

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

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109. 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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110. 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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111. 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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112. Bonus: multiplatform runtime!*
     * - coming soon
     

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

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115. Gradle Plugin
     

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116. 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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117. 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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118. 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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119. 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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120. WIRE 3
     Real World Business Use Case Demo
     

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

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122. What's next ?
     

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

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124. WIRE III
     

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125. 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
     

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