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Sawtooth Cookie Jar

Simple cookie jar example of a Sawtooth application.

Introduction

This is a minimal example of a Sawtooth 1.1 application, with a transaction processor and corresponding client. This example demonstrates a simple use case, where a baker bakes or eats cookies saved in a virtual cookie jar.

A baker can:

  1. bake one or more cookies to add to the cookie jar
  2. eat one or more cookies in the cookie jar
  3. count the cookies in the cookie jar

All cookie jar transactions have the same 6 hex digit prefix, which is the first 6 hex characters of the SHA-512 hash of "cookiejar" (that is, "a4d219"). The cookie jar is identified by mycookiejar with a corresponding public/private keypair. The cookie jar count is stored at an 70 hex digit address derived from:

  • a 6-hex character prefix (the "cookiejar" Transaction Family namespace) and
  • the first 64 hex characters of the SHA-512 hash of the "mycookiejar" public key in hex.

Purpose

The material is made for the introduction to Hyperledger Sawtooth workshop on the 31st of October in Sofia, Bulgaria and is based on the original cookiejar example by Dan Anderson.

Components

The cookie jar transaction family contains two parts, both having a version in Python 3 and Go:

  1. The client application has two parts:
  • pyclient/cookiejar_client.py or goclient/client.go containing the client class which interfaces to the Sawtooth validator via the REST API
  • pyclient/cookiejar.py or goclient/actions.go and goclient/main.go as the Cookie Jar CLI app The client container is built with files setup.py and respective Dockerfiles.
  1. The Transaction Processor, pyprocessor/cookiejar_tp.py or goprocessor/main.go and goprocessor/handler.go

Docker Usage

Prerequisites

This example uses docker-compose and Docker containers. If you do not have these installed please follow the instructions here: https://docs.docker.com/install/

NOTE

The preferred OS environment is Ubuntu Linux 16.04.3 LTS x64. Although other Linux distributions which support Docker should work.

Building Docker containers

To build and run the code

sudo docker-compose up --build

The docker-compose.yaml file creates a genesis block, which contain initial Sawtooth settings, generates Sawtooth and client keys, and starts the Validator, Settings TP, Cookie Jar TP, and REST API.

Docker client

In a separate shell from above, launch the client shell container:

sudo docker exec -it cookiejar-client bash

You can locate the correct Docker client container name, if desired, with sudo docker ps .

In the client shell you just started above, run the cookiejar.py application. Here are some sample commands:

cookiejar(.py) bake 100  # Add 100 cookies to the cookie jar
cookiejar(.py) eat 50    # Remove 50 cookies from the cookie jar
cookiejar(.py) count     # Display the number of cookies in the cookie jar

To stop the validator and destroy the containers, type ^c in the docker-compose window, wait for it to stop, then type

sudo docker-compose down

Simple Events Handler

A simple events handler is included. To run, start the validator then type the following on the command line: ./events/events_client.py

A version in Go is also included.

Exercises for the User

  • Add a new function, empty which empties the cookie jar (sets the count to 0) in the client and processor
  • Add the ability to specify the cookie jar owner key (client only). Use Simplewallet as an example
  • Replace simple CSV serialization with CBOR serialization in the client and processor. Use the Sawtooth "inkey" example application as a pattern.
  • Replace simple CSV serialization with Protobuf serialization in the client and processor. Use the Sawtooth "XO" example application as a pattern
  • Translate a transaction processor into another programming language. See Simplewallet and Sawtooth SDK examples
  • Also translate the Python client into another programming language. Note that the client and transaction processor do not need to be written in the same language

License

This example and Hyperledger Sawtooth software are licensed under the Apache License Version 2.0 software license.

Photo of sawtooth cookie cutters
Antique sawtooth cookie cutters.

© Copyright 2018-2019, Intel Corporation and Arjan van Eersel.