Notes & Java / Golang / C++ code for Google Protocol Buffers
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.
What things you need to install:
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;
}
Copy 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
Piotr Wera - Initial work - pwera
This project is licensed under the MIT License - see the LICENSE.md file for details