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gerrit-public.fairphone.software / platform / external / grpc-grpc / 75d5c0f024438944425cf1bd3163b07c6f6e55b5
commit75d5c0f024438944425cf1bd3163b07c6f6e55b5[log] [tgz]
authorAlistair Veitch <aveitch@google.com>Tue Feb 02 09:43:02 2016 -0800
committerAlistair Veitch <aveitch@google.com>Tue Feb 02 09:43:02 2016 -0800
tree8130c65c6e654bc42187342cb3d8004379422dfa
parent7c43f4909242b62881389c7d4cfc9541c70151b6 [diff]
post merge
421 files changed
tree: 8130c65c6e654bc42187342cb3d8004379422dfa
  1. doc/
  2. etc/
  3. examples/
  4. include/
  5. src/
  6. templates/
  7. test/
  8. third_party/
  9. tools/
  10. vsprojects/
  11. .clang-format
  12. .editorconfig
  13. .gitignore
  14. .gitmodules
  15. .istanbul.yml
  16. .rspec
  17. .travis.yml
  18. binding.gyp
  19. BUILD
  20. build.yaml
  21. composer.json
  22. CONTRIBUTING.md
  23. Gemfile
  24. grpc.bzl
  25. grpc.gemspec
  26. gRPC.podspec
  27. INSTALL
  28. LICENSE
  29. Makefile
  30. MANIFEST.md
  31. package.json
  32. PATENTS
  33. PYTHON-MANIFEST.in
  34. Rakefile
  35. README.md
  36. requirements.txt
  37. setup.cfg
  38. setup.py
  39. tox.ini
README.md

Build Status

gRPC - An RPC library and framework

Copyright 2015-2016 Google Inc.

#Documentation

You can find more detailed documentation and examples in the doc and examples directories respectively.

#Installation

See grpc/INSTALL for installation instructions for various platforms.

#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 are in different states of development. We are seeking contributions for all of these libraries.

LanguageSourceStatus
Shared C [core library][src/core] (src/core)Beta - the surface API is stable
C++[src/cpp] (src/cpp)Beta - the surface API is stable
Ruby[src/ruby] (src/ruby)Beta - the surface API is stable
NodeJS[src/node] (src/node)Beta - the surface API is stable
Python[src/python] (src/python)Beta - the surface API is stable
PHP[src/php] (src/php)Beta - the surface API is stable
C#[src/csharp] (src/csharp)Beta - the surface API is stable
Objective-C[src/objective-c] (src/objective-c)Beta - the surface API is stable

See 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 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 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. 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.