From 0adce9db94793fc25603334268ce771e174fa673 Mon Sep 17 00:00:00 2001 From: Abhishek Kumar Date: Wed, 21 Jan 2015 11:32:18 -0800 Subject: Update README.md Added more details in the Interface and Protocol sections. --- README.md | 53 +++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 47 insertions(+), 6 deletions(-) (limited to 'README.md') diff --git a/README.md b/README.md index 05414d8e21..1e5b61af95 100644 --- a/README.md +++ b/README.md @@ -3,13 +3,12 @@ gRPC - An RPC library and framework Copyright 2015 Google Inc. -Installation ------------- +#Installation See grpc/INSTALL for installation instructions for various platforms. -Overview --------- +#Overview + Remote Procedure Calls (RPCs) provide a useful abstraction for building distributed applications and services. The libraries in this repository @@ -17,15 +16,57 @@ 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. -Protocol --------- +By default, gRPC uses [Protocol Buffers](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. Async +Synchronous RPC calls, that block till 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 +async 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'). + -- cgit v1.2.3