Blockchain is a topic that's talked about in every industry throughout the globe. It's decentralized and secure nature makes it a great use case for future innovation and development. In order to leverage any blockchain architecture, the end user needs to be able to verify data in a decentralised fashion and not rely on centralized entities such as Google to supply the information that sits on the blockchain. Webinar Recording here: https://www.youtube.com/watch?v=Jb-EgQG3F2k&t=0s&list=PLWbHc_FXPo2jN8cLhwLg7frCx6fJ-GPwM&index=2

1. BlockScout
an open source EVM
blockchain explorer
Andrew Cravenho
BlockScout PM, POA Network

2. Live at BlockScout.com
Contribute at https://github.com/poanetwork/blockscout

3. POA Network
POA Network. 2018
|> Independent Network with a unique state
|> Ethereum Sidechain
|> 2nd Layer Scalability Solution
|> Production Bridges released in April 2018 connecting POA
to Ethereum Network

4. POA Network. 2018

5. What is BlockScout
POA Network. 2018
|> Open Source EVM Block Explorer
|> Tool for analyzing blockchains
|> Read and Write (WIP) Smart Contract functions

6. Why we built it
POA Network. 2018
|> Etherscan is not available to sidechains/forks
|> Source code is not public
|> Decentralized solution to view the blockchain
|> Off-chain data is not available to the public

7. Networks Supported
POA Network. 2018
|> Ethereum Mainnet
|> Kovan Testnet
|> Ropsten Testnet
|> Rinkeby Testnet
|> Ethereum Classic
|> POA Core
|> POA Sokol Testnet
|> xDai Chain
|> More coming soon...

8. Clients Supported
POA Network. 2018
|> Parity
|> Geth
|> Ganache

9. Features of BlockScout
POA Network. 2018
|> Blocks
|> Transactions
|> Receipts
|> Internal Transactions
|> Logs
|> Uncles
|> Block Reorganizations
|> ERC-20 token support
|> ERC-721 token support
|> Contract Verification
|> Query Contract
|> Real-time UI
|> API
|> GraphQL

10. Development Stack
POA Network. 2018
|> Phoenix Framework
|> Elixir - functional and scalable
|> Erlang
|> Postgres

11. Monitoring
POA Network. 2018
|> Wobserver
|> Prometheus
|> Grafana

12. Umbrella Applications
POA Network. 2018
1. block_scount_web - front end UI/UX
2. ethereum_jsonrpc - Ethereum JSON RPC client
3. explorer - import processes to Postgres or ETS
4. Indexer - Fetches data from the blockchain

13. POA Network. 2018
Realtime Indexer
Looks for new blocks being added
to the blockchain. Fetches and
imports the data.
Catch-up Indexer
Works from the tip of the chain and works
backwards.

14. Realtime Indexer
POA Network. 2018
apps/indexer/lib/indexer/block/realtime/fetcher.ex
@impl GenServer
def handle_info(
{subscription, {:ok, %{"number" => quantity}}},
%__MODULE__{
block_fetcher: %Block.Fetcher{} = block_fetcher,
subscription: %Subscription{} = subscription,
previous_number: previous_number
} = state
)
when is_binary(quantity) do
number = quantity_to_integer(quantity)
start_fetch_and_import(number, block_fetcher, previous_number)

15. Catchup Indexer
POA Network. 2018
apps/indexer/lib/indexer/block/catchup/fetcher.ex
# realtime indexer gets the current latest block
first = latest_block_number - 1
last = 0
missing_ranges = Chain.missing_block_number_ranges(first..last)
range_count = Enum.count(missing_ranges)
missing_block_count =
missing_ranges
|> Stream.map(&Enum.count/1)
|> Enum.sum()
Logger.debug(fn ->
"#{missing_block_count} missed blocks in #{range_count} ranges between #{first} and #{last}"
end)

16. Indexer Processes
POA Network. 2018
Realtime Indexer Catch-up Indexer
Transaction Receipts Synchronous Synchronous
Logs Synchronous Synchronous
Token Transfers Synchronous Synchronous
Coin Balances Synchronous Synchronous
Token Balances Synchronous Asynchronous
Token meta data Synchronous Asynchronous
Internal Transactions Synchronous Asynchronous

17. Ethereum JSON RPC Client
POA Network. 2018
|> Receives requests from the indexer
|> Sends Requests to the blockchain
|> Receives data back
|> Maps and prepares the data for import
|> Final data is sent to the Explorer App for Import

18. Ethereum Client Processes
POA Network. 2018
|> eth_getBlockByNumber - returns information related to a block
|> eth_getTransactionReceipt - returns the receipt of a transaction by transaction hash
|> extract token transfers - fetch the token balances by the contract address
|> logs/events
|> eth_getBalance - returns the balance of given address at a given block number
Client Specific Calls
|> Parity - trace_replayTransaction - fetches internal transactions for Parity
|> Geth - debug_traceTransaction - fetches internal transactions for Geth

19. Explorer Umbrella App
POA Network. 2018
|> Handles all the calls to/from Postgres
|> Handles all outgoing API calls (coin prices)
|> Manages accounts (admin/users)
|> Handles ETS tables (Erlang Term Storage)

20. Block Scout Web Umbrella App
POA Network. 2018
|> Frontend
|> Real-time Events
|> GraphQL
|> RPC API
|> Contract Verification and Interaction

21. Reactive Updates
POA Network. 2018
|> Live

22. Smart Contracts
POA Network. 2018
|> Live

23. Transaction Details
POA Network. 2018
|> Live

24. Future Roadmap
POA Network. 2018

25. User Experience Improvements
POA Network. 2018
|> Query Optimization for faster load times (PR)
|> Infinite Scroll (WIP PR)
|> Faster Indexing Times

26. Indexer
POA Network. 2018
|> Define a set of blocks to index
|> Geth Internal Transactions (WIP)
|> Faster Indexing Times- improved infrastructure

27. Customizable Configuration Panel
POA Network. 2018
|> Admin panel (completed)
|> Define CSS colors
|> Logo
|> Social Links
|> Max Memory Consumed
|> Adjust Indexer Backoff Settings
|> RPC Endpoints

28. Data Export
POA Network. 2018
|> Download Transactions via CSV
|> Download Tokens via CSV
|> Download Balance History via CSV

29. Other Roadmap Items
POA Network. 2018
|> GraphQL
|> ERC721 Data Attribute Support
|> Decode Transaction Input by the Contract ABI
|> Decode Logs by the Contract ABI