Google Protocol Buffers

Notes & Java / Golang / C++ code for Google Protocol Buffers

Getting Started

These instructions will get you a copy of the project up and running on your local machine for development and testing purposes. See deployment for notes on how to deploy the project on a live system.

Prerequisites

What things you need to install:

• Docker

Give examples

The story

An Evolution of data JSON JavaScript Object Notation. JSON format can be shared across the network. --> put json sample <--

Advantages:

• Data can take any form (arrays, nested elements)
• Easy to read

Disadvantages:

• Data has no schema enforcing
• JSON Obejcts can be quite big in size because of repeated keys Protocol Buffers

syntax = "proto3"

message MyMessage {
    int32 id =1;
    string name = 2;
    bool is_validated = 3;
}

PB is defined by .proto text file. Advantages:

• Explit types.
• Less CPU usage when data compressed.
• Schema is needed to generate code and read the data.
• Documentation can be embedded in the schema.
• 3-10x smaller, 20-100x faster then XML.

Disadvantages:

• Can't open the serialized data with a text editor.

Some big projects like 'etcd' use PB for transporting data.

• Mid 2016 Google release 3rd iteration of PB- proto3.
• In PB field names are not important, smallest tag is 1, largest 2^29, 336,870,911.
• If we try use any greather then 2^29 compiler throws an error:
• Field numbers cannot be greater than 536870911.
• Tags from 19000 - 19999 are google reserved
• Tags numbered from 1 - 15 use 1 byte in space, use them for frequently populated fields
• Tags numbeder from 16 - 2047 use 2 bytes in space.
• Forward and backward compatible change
• Don't change the numeric tags for any existing fields
• With new fields, an old code will just ignore them
• use reserved [tag_number] when removing field Sample: reserved 2, 15 to 19; reserved "aaa", "xyz";
• The alternative is that instead of removing a field, you rename it to OBSOLETE_field_name
• Do not remove any reserved tags
• [oneof] To use Type variant, type oneof; cannot be repeated
• [map] Maps can be used to map scalars to values of any type; map<string, Result> results = 2;
• Map fields cannot be repeated
• There's no ordering for map (it's key value store)
• Protocol buffers can define Services on top of Messages
• A service is a set of endpoints you application can be accessible from
• The advantage of Services & RPC (remote procedure call) is that you can call Servcie API from any client seamlessly

Authors

• Piotr Wera - Initial work - pwera

License

This project is licensed under the MIT License - see the LICENSE.md file for details