mirror of https://github.com/grpc/grpc.git
The C based gRPC (C++, Python, Ruby, Objective-C, PHP, C#)
https://grpc.io/
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
109 lines
5.6 KiB
109 lines
5.6 KiB
[](https://grpc-testing.appspot.com/job/gRPC_master) |
|
|
|
[gRPC - An RPC library and framework](http://github.com/grpc/grpc) |
|
=================================== |
|
|
|
[](https://gitter.im/grpc/grpc?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) |
|
|
|
Copyright 2015 Google Inc. |
|
|
|
# Documentation |
|
|
|
You can find more detailed documentation and examples in the [doc](doc) and [examples](examples) directories respectively. |
|
|
|
# Installation & Testing |
|
|
|
See [INSTALL](INSTALL.md) for installation instructions for various platforms. |
|
|
|
See [tools/run_tests](tools/run_tests) for more guidance on how to run various test suites (e.g. unit tests, interop tests, benchmarks) |
|
|
|
See [Performance dashboard](http://performance-dot-grpc-testing.appspot.com/explore?dashboard=5636470266134528) for the performance numbers for the latest released version. |
|
|
|
# Repository Structure & Status |
|
|
|
This repository contains source code for gRPC libraries for multiple languages written on top of shared C core library [src/core](src/core). |
|
|
|
Libraries in different languages may be in different states of development. We are seeking contributions for all of these libraries. |
|
|
|
| Language | Source | |
|
|-------------------------|-------------------------------------| |
|
| Shared C [core library] | [src/core](src/core) | |
|
| C++ | [src/cpp](src/cpp) | |
|
| Ruby | [src/ruby](src/ruby) | |
|
| Python | [src/python](src/python) | |
|
| PHP | [src/php](src/php) | |
|
| C# | [src/csharp](src/csharp) | |
|
| Objective-C | [src/objective-c](src/objective-c) | |
|
|
|
Java source code is in the [grpc-java](http://github.com/grpc/grpc-java) |
|
repository. Go source code is in the |
|
[grpc-go](http://github.com/grpc/grpc-go) repository. NodeJS source code is in the |
|
[grpc-node](https://github.com/grpc/grpc-node) repository. |
|
|
|
See [MANIFEST.md](MANIFEST.md) for a listing of top-level items in the |
|
repository. |
|
|
|
# Overview |
|
|
|
|
|
Remote Procedure Calls (RPCs) provide a useful abstraction for building |
|
distributed applications and services. The libraries in this repository |
|
provide a concrete implementation of the gRPC protocol, layered over HTTP/2. |
|
These libraries enable communication between clients and servers using any |
|
combination of the supported languages. |
|
|
|
|
|
## Interface |
|
|
|
|
|
Developers using gRPC typically start with the description of an RPC service |
|
(a collection of methods), and generate client and server side interfaces |
|
which they use on the client-side and implement on the server side. |
|
|
|
By default, gRPC uses [Protocol Buffers](https://github.com/google/protobuf) as the |
|
Interface Definition Language (IDL) for describing both the service interface |
|
and the structure of the payload messages. It is possible to use other |
|
alternatives if desired. |
|
|
|
### Surface API |
|
Starting from an interface definition in a .proto file, gRPC provides |
|
Protocol Compiler plugins that generate Client- and Server-side APIs. |
|
gRPC users typically call into these APIs on the Client side and implement |
|
the corresponding API on the server side. |
|
|
|
#### Synchronous vs. asynchronous |
|
Synchronous RPC calls, that block until a response arrives from the server, are |
|
the closest approximation to the abstraction of a procedure call that RPC |
|
aspires to. |
|
|
|
On the other hand, networks are inherently asynchronous and in many scenarios, |
|
it is desirable to have the ability to start RPCs without blocking the current |
|
thread. |
|
|
|
The gRPC programming surface in most languages comes in both synchronous and |
|
asynchronous flavors. |
|
|
|
|
|
## Streaming |
|
|
|
gRPC supports streaming semantics, where either the client or the server (or both) |
|
send a stream of messages on a single RPC call. The most general case is |
|
Bidirectional Streaming where a single gRPC call establishes a stream where both |
|
the client and the server can send a stream of messages to each other. The streamed |
|
messages are delivered in the order they were sent. |
|
|
|
|
|
# Protocol |
|
|
|
The [gRPC protocol](doc/PROTOCOL-HTTP2.md) specifies the abstract requirements for communication between |
|
clients and servers. A concrete embedding over HTTP/2 completes the picture by |
|
fleshing out the details of each of the required operations. |
|
|
|
## Abstract gRPC protocol |
|
A gRPC RPC comprises of a bidirectional stream of messages, initiated by the client. In the client-to-server direction, this stream begins with a mandatory `Call Header`, followed by optional `Initial-Metadata`, followed by zero or more `Payload Messages`. The server-to-client direction contains an optional `Initial-Metadata`, followed by zero or more `Payload Messages` terminated with a mandatory `Status` and optional `Status-Metadata` (a.k.a.,`Trailing-Metadata`). |
|
|
|
## Implementation over HTTP/2 |
|
The abstract protocol defined above is implemented over [HTTP/2](https://http2.github.io/). gRPC bidirectional streams are mapped to HTTP/2 streams. The contents of `Call Header` and `Initial Metadata` are sent as HTTP/2 headers and subject to HPACK compression. `Payload Messages` are serialized into a byte stream of length prefixed gRPC frames which are then fragmented into HTTP/2 frames at the sender and reassembled at the receiver. `Status` and `Trailing-Metadata` are sent as HTTP/2 trailing headers (a.k.a., trailers). |
|
|
|
## Flow Control |
|
gRPC inherits the flow control mechanisms in HTTP/2 and uses them to enable fine-grained control of the amount of memory used for buffering in-flight messages.
|
|
|