| commit | 9f56b8cea2fc82f19b2ae8133f3b109dfb4a26c1 | [log] [tgz] |
|---|---|---|
| author | ZHANG Dapeng <zdapeng@google.com> | Fri Jul 17 13:33:44 2020 -0700 |
| committer | GitHub <noreply@github.com> | Fri Jul 17 13:33:44 2020 -0700 |
| tree | c6cef0ca74d11aa816bc73a9088f0f194a4193b1 | |
| parent | 8ab2c751500160ea37779025d345eb79577e6e14 [diff] |
api: change ConfigSelector.Result to use callback instead of interceptor We found that the interceptor approach for `ConfigSelector` would be adding a layer of indirection for no gain: The API Result selectConfig(LoadBalancer.PickSubchannelArgs args) consumes headers among other inputs, because route matching might need to match the headers; and the API produces ClientInterceptor among other outputs. But the headers is not available until clientCall.start(listner, headers), whereas the interceptor need be applied to the call before clientCall.start(). So the input is not available until the output is applied. That means we will need to delay calling the downstream newCall() (which will either be RealChannel or the interceptor) until start() is called. So we want to change to the other approach similar to what c-core is taking: Have `Result(Object config, CallOptions, Runnable committedCallback)`, where CallOption is the selector modified CallOption, and committedCallback is used to monitor the call lifecycle.
gRPC-Java works with JDK 7. gRPC-Java clients are supported on Android API levels 14 and up (Ice Cream Sandwich and later). Deploying gRPC servers on an Android device is not supported.
TLS usage typically requires using Java 8, or Play Services Dynamic Security Provider on Android. Please see the Security Readme.
For a guided tour, take a look at the quick start guide or the more explanatory gRPC basics.
The examples and the Android example are standalone projects that showcase the usage of gRPC.
Download the JARs. Or for Maven with non-Android, add to your pom.xml:
<dependency> <groupId>io.grpc</groupId> <artifactId>grpc-netty-shaded</artifactId> <version>1.30.2</version> </dependency> <dependency> <groupId>io.grpc</groupId> <artifactId>grpc-protobuf</artifactId> <version>1.30.2</version> </dependency> <dependency> <groupId>io.grpc</groupId> <artifactId>grpc-stub</artifactId> <version>1.30.2</version> </dependency> <dependency> <!-- necessary for Java 9+ --> <groupId>org.apache.tomcat</groupId> <artifactId>annotations-api</artifactId> <version>6.0.53</version> <scope>provided</scope> </dependency>
Or for Gradle with non-Android, add to your dependencies:
implementation 'io.grpc:grpc-netty-shaded:1.30.2' implementation 'io.grpc:grpc-protobuf:1.30.2' implementation 'io.grpc:grpc-stub:1.30.2' compileOnly 'org.apache.tomcat:annotations-api:6.0.53' // necessary for Java 9+
For Android client, use grpc-okhttp instead of grpc-netty-shaded and grpc-protobuf-lite instead of grpc-protobuf:
implementation 'io.grpc:grpc-okhttp:1.30.2' implementation 'io.grpc:grpc-protobuf-lite:1.30.2' implementation 'io.grpc:grpc-stub:1.30.2' compileOnly 'org.apache.tomcat:annotations-api:6.0.53' // necessary for Java 9+
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>1.6.2</version> </extension> </extensions> <plugins> <plugin> <groupId>org.xolstice.maven.plugins</groupId> <artifactId>protobuf-maven-plugin</artifactId> <version>0.6.1</version> <configuration> <protocArtifact>com.google.protobuf:protoc:3.12.0:exe:${os.detected.classifier}</protocArtifact> <pluginId>grpc-java</pluginId> <pluginArtifact>io.grpc:protoc-gen-grpc-java:1.30.2:exe:${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:
plugins { id 'com.google.protobuf' version '0.8.8' } protobuf { protoc { artifact = "com.google.protobuf:protoc:3.12.0" } plugins { grpc { artifact = 'io.grpc:protoc-gen-grpc-java:1.30.2' } } generateProtoTasks { all()*.plugins { grpc {} } } }
The prebuilt protoc-gen-grpc-java binary uses glibc on Linux. If you are compiling on Alpine Linux, you may want to use the Alpine grpc-java package which uses musl instead.
APIs annotated with @Internal are for internal use by the gRPC library and should not be used by gRPC users. APIs annotated with @ExperimentalApi are subject to change in future releases, and library code that other projects may depend on should not use these APIs.
We recommend using the grpc-java-api-checker (an Error Prone plugin) to check for usages of @ExperimentalApi and @Internal in any library code that depends on gRPC. It may also be used to check for @Internal usage or unintended @ExperimentalApi consumption in non-library code.
If you are making changes to gRPC-Java, see the compiling instructions.
At a high level there are three distinct layers to the library: Stub, Channel, and Transport.
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 are easy and encouraged.
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.
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. 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: