commit	418d52d16de18ba204aa407a7a860e4b18f5f9de	[log] [tgz]
author	Kun Zhang <zhangkun83@users.noreply.github.com>	Wed Mar 22 18:29:31 2017 -0700
committer	GitHub <noreply@github.com>	Wed Mar 22 18:29:31 2017 -0700
tree	f152779fec1da50b77485e10feda516166954eca
parent	3ffa5a9660452e007a636f73fa28f44d9f49eda5 [diff]

 core: unify EquivalentAddressGroup and its immitators. (#2755)

Resolves #2716

- Add attributes to EquivalentAddressGroup
- Deprecate ResolvedServerInfoGroup by EquivalentAddressGroup
- Deprecate ResolvedServerInfo, because attributes for a single address
  with an address group is not found to be useful.
- The changes on the NameResolver and LoadBalancer interfaces are backward-compatible
  in the next release, with which implementors can switch to the new API smoothly.

As a related change, redefine the semantics of DnsNameResolver and
RoundRobinLoadBalancer:

- Before: DnsNameResolver returns all addresses in one address group.
  RoundRobinLoadBalancer ignores the grouping of addresses and
  round-robin on every single addresses.  It doesn't work well with the
  one-server-multiple-address setup, e.g., both IPv4 and IPv6 addresses
  are returned for a single serve, even if they are put in the same
  address group by the NameResolver.

- After: DnsNameResolver returns every address in its own
  EAG. RoundRobinLoadBalancer takes an EAG as a whole, and only
  round-robin on the list of EAGs. The new behavior is a better
  interpretation of the EAGs, and really allows the case where one
  server has more than one addresses (e.g., IPv4 and IPv6).

This change will affect users that use custom LoadBalancer with the
stock DnsNameResolver, and those who use custom NameResolver with the
stock RoundRobinLoadBalancer.

Users who use both the stock DnsNameResolver and RoundRobinLoadBalancer
or PickFirstBalancer will see no behavioral change. Because they will
still round-robin on individual addresses from DNS, or do pick-first on
all addresses from DNS (PickFirstBalancer flattens all addresses).

The result is a simpler API and reduction of boilderplates.

18 files changed

tree: f152779fec1da50b77485e10feda516166954eca

README.md

gRPC-Java - An RPC library and framework

gRPC-Java works with JDK 6. TLS usage typically requires using Java 8, or Play Services Dynamic Security Provider on Android. Please see the Security Readme.

Download

Download the JARs. Or for Maven with non-Android, add to your pom.xml:

<dependency>
  <groupId>io.grpc</groupId>
  <artifactId>grpc-netty</artifactId>
  <version>1.2.0</version>
</dependency>
<dependency>
  <groupId>io.grpc</groupId>
  <artifactId>grpc-protobuf</artifactId>
  <version>1.2.0</version>
</dependency>
<dependency>
  <groupId>io.grpc</groupId>
  <artifactId>grpc-stub</artifactId>
  <version>1.2.0</version>
</dependency>

Or for Gradle with non-Android, add to your dependencies:

compile 'io.grpc:grpc-netty:1.2.0'
compile 'io.grpc:grpc-protobuf:1.2.0'
compile 'io.grpc:grpc-stub:1.2.0'

For Android client, use grpc-okhttp instead of grpc-netty and grpc-protobuf-lite or grpc-protobuf-nano instead of grpc-protobuf:

compile 'io.grpc:grpc-okhttp:1.2.0'
compile 'io.grpc:grpc-protobuf-lite:1.2.0'
compile 'io.grpc:grpc-stub:1.2.0'

Development snapshots are available in Sonatypes's snapshot repository.

For protobuf-based codegen, you can put your proto files in the src/main/proto and src/test/proto directories along with an appropriate plugin.

For protobuf-based codegen integrated with the Maven build system, you can use protobuf-maven-plugin (Eclipse and NetBeans users should also look at os-maven-plugin's IDE documentation):

<build>
  <extensions>
    <extension>
      <groupId>kr.motd.maven</groupId>
      <artifactId>os-maven-plugin</artifactId>
      <version>1.4.1.Final</version>
    </extension>
  </extensions>
  <plugins>
    <plugin>
      <groupId>org.xolstice.maven.plugins</groupId>
      <artifactId>protobuf-maven-plugin</artifactId>
      <version>0.5.0</version>
      <configuration>
        <protocArtifact>com.google.protobuf:protoc:3.0.2:exe:${os.detected.classifier}</protocArtifact>
        <pluginId>grpc-java</pluginId>
        <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.2.0:exe:${os.detected.classifier}</pluginArtifact>
      </configuration>
      <executions>
        <execution>
          <goals>
            <goal>compile</goal>
            <goal>compile-custom</goal>
          </goals>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>

For protobuf-based codegen integrated with the Gradle build system, you can use protobuf-gradle-plugin:

apply plugin: 'java'
apply plugin: 'com.google.protobuf'

buildscript {
  repositories {
    mavenCentral()
  }
  dependencies {
    // ASSUMES GRADLE 2.12 OR HIGHER. Use plugin version 0.7.5 with earlier
    // gradle versions
    classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.0'
  }
}

protobuf {
  protoc {
    artifact = "com.google.protobuf:protoc:3.0.2"
  }
  plugins {
    grpc {
      artifact = 'io.grpc:protoc-gen-grpc-java:1.2.0'
    }
  }
  generateProtoTasks {
    all()*.plugins {
      grpc {}
    }
  }
}

How to Build

If you are making changes to gRPC-Java, see the compiling instructions.

Navigating Around the Source

Here's a quick readers' guide to the code to help folks get started. At a high level there are three distinct layers to the library: Stub, Channel & Transport.

Stub

The Stub layer is what is exposed to most developers and provides type-safe bindings to whatever datamodel/IDL/interface you are adapting. gRPC comes with a plugin to the protocol-buffers compiler that generates Stub interfaces out of .proto files, but bindings to other datamodel/IDL should be trivial to add and are welcome.

Key Interfaces

Stream Observer

Channel

The Channel layer is an abstraction over Transport handling that is suitable for interception/decoration and exposes more behavior to the application than the Stub layer. It is intended to be easy for application frameworks to use this layer to address cross-cutting concerns such as logging, monitoring, auth etc. Flow-control is also exposed at this layer to allow more sophisticated applications to interact with it directly.

Common

Client

Server

Transport

The Transport layer does the heavy lifting of putting and taking bytes off the wire. The interfaces to it are abstract just enough to allow plugging in of different implementations. Transports are modeled as Stream factories. The variation in interface between a server Stream and a client Stream exists to codify their differing semantics for cancellation and error reporting.

Note the transport layer API is considered internal to gRPC and has weaker API guarantees than the core API under package io.grpc.

gRPC comes with three Transport implementations:

The Netty-based transport is the main transport implementation based on Netty. It is for both the client and the server.
The OkHttp-based transport is a lightweight transport based on OkHttp. It is mainly for use on Android and is for client only.
The inProcess transport is for when a server is in the same process as the client. It is useful for testing.

Common

Client

Server

Examples

The examples and the Android example are standalone projects that showcase the usage of gRPC.