phamvancam2104/ethereum

Collection of demos for interacting with the Ethereum Blockchain

Ethereum Blockchain Demos

Collection of demos for interacting with the Ethereum Blockchain

Pre-reqs: To access the Ethereum Blockchain, we'll be using geth, the official Go Ethereum CLI client. It is the entry point into the Ethereum network (main-, test- or private net), capable of running as a full node (default) archive node (retaining all historical state) or a light node (retrieving data live).

Starting a ethereum/client-go container:

docker pull ethereum/client-go:v1.8.3

docker run -d --name ethereum-node \
-p 8545:8545 -p 30303:30303 \
ethereum/client-go:v1.8.3 \
--syncmode light \
--rpc --rpcaddr 0.0.0.0

This allows you to view and query events from the blockchain locally via a number of tools/bindings:

• cUrl

  curl -H "Content-Type: application/json" --data '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":83}' -X POST http://localhost:8545
  
  {"jsonrpc":"2.0","id":83,"result":"0x51ed3f"}
  
  

• python web3

  from web3 import Web3, HTTPProvider, IPCProvider
  web3 = Web3(HTTPProvider('http://localhost:8545'))
  
  # Retrieve the last block number available from geth RPC
  currentblock = web3.eth.getBlock('latest').number
  

Demos

• 01_Intro - Basic Introduction to interacting with ethereum chain from a jupyter notebook
• 02_Retrieving Smart Contract Logs - Query and parse transactions to find those which include smart contract events.
• 03_Streaming Events to Kafka - Retrieve Transaction Logs and produce to a kafka topic

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Background

When most people think of "Blockchain", they think about Alice Sending Bob 2 coins, and that transaction being recorded on a public ledger.

On the Ethereum chain however, the public ledger holds both currency transfers AND code (Smart Contract) execution logs.

Not all HelloWorld are the same

In a traditional object oriented language, running a "HelloWorld.exension" should result in the same output whether Alice runs the file or Bob runs the file.

On the ethereum blockchain, when a program is written, it must be "deployed" to the blockchain by a user's wallet. This means that although 2 ".sol" programs may have 100% identical code, they will each by pushed to the blockchain and have a unique "Contract Address", along with some metadata such as the user who deployed the contract.

Here we will use remix.ethereum.org, a free Solidity Web Compiler, to showcase a simple Hello World smart contract deployed by Alice vs Hello World Deployed by Bobbie

• HelloWorld.sol deployed by alice's wallet 0xca35b7d915458ef540ade6068dfe2f44e8fa733c:

  • 

• HelloWorld.sol deployed by Bob's wallet 0x14723a09acff6d2a60dcdf7aa4aff308fddc160c:

• 

Even more interesting, once a "smart contract" is deployed to a "contract address", EACH FUNCTION in the smart contract has a unique "MethodID" and "Topic" which can be used to see when that given function belonging to the smart contract was invoked.