Block processing

This is a brief description on how block processing works (e.g., block 20 => block 21 => etc)

Block processing starts in the ChainManager (https://github.com/ethereum/go-ethereum/blob/docbranch/core/chain_manager.go)

• Block(s) are inserted using InsertChain(...) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/chain_manager.go#L324)
• Each block is then processed by the Processor which in our case is always the BlockManager https://github.com/ethereum/go-ethereum/blob/docbranch/core/chain_manager.go#L326
  • Block validation and processing all happens with the BlockManager https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go
  • Checked if the block already's in storage (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L171)
  • Check if we have the parent (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L175)
  • Validate the easy, less intensive tasks first (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L189)
    • Calculate the difficulty and compare it to the parent's difficulty (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L272)
    • Verify the proof of work (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L290)
  • Transition the state (e.g., apply transactions) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L193)
  • Set the gas limit. Transactions will use the gasPool to "buy" gas from the coinbase (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L87)
  • Attempt to transition the state using the current message (transaction) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L116)
    • All transactional state changes happen within the StateTransition object and start at the TransitionState method (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L150)
    • Check the tx nonce: tx.nonce == account.nonce (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L138)
    • Check if we can buy the gas of the coin base (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L110)
    • Use TxGas (500) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L169)
    • Create a contract if len(address) == 0 (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L189)
      • Run init code (see Create VmEnv) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L190)
      • Charge additional gas for creation bytes (i.e., len(ret) * createByteGas) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L193)
      • Set the return data as contract code (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L196)
    • Or run the code if the recipient has any code to execute (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L200)
      • Use the VmEnv and call either Create or Call (depending on the address). The VmEnv will instantiate a new Execution handler which will take care of starting the virtual machine. The VmEnv will be used to throughout the entire process. The virtual machine itself has access to the VmEnv and will this object to call in to other contracts or create new accounts. (https://github.com/ethereum/go-ethereum/blob/docbranch/core/vm_env.go#L46)
      • Execute given code (https://github.com/ethereum/go-ethereum/blob/docbranch/core/execution.go#L34)
      • Make sure we haven't reached max depth (https://github.com/ethereum/go-ethereum/blob/docbranch/core/execution.go#L38)
        • Transfer value (err is set incase of insufficient funds) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/execution.go#L46)
        • Snapshot the state for rollback feature (value transfers happen regardless of errors) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/execution.go#L55)
        • Execute code given (https://github.com/ethereum/go-ethereum/blob/docbranch/core/execution.go#L69)
          • Enter VM run loop (https://github.com/ethereum/go-ethereum/blob/docbranch/vm/vm_debug.go#L40)
          • Create a new Context which holds the code, gas and information about the caller (https://github.com/ethereum/go-ethereum/blob/docbranch/vm/vm_debug.go#L50)
          • Check for precompiled contract (https://github.com/ethereum/go-ethereum/blob/docbranch/vm/vm_debug.go#L68) see (https://github.com/ethereum/go-ethereum/blob/docbranch/vm/address.go#L23) for all pre compiled contracts and run it if there's a contract at that address (https://github.com/ethereum/go-ethereum/blob/docbranch/vm/vm_debug.go#L935)
          • Analyse valid jump positions (https://github.com/ethereum/go-ethereum/blob/docbranch/vm/vm_debug.go#L75). It's worth noting that jump (https://github.com/ethereum/go-ethereum/blob/docbranch/vm/vm_debug.go#L83) uses the jump positions in order to determine whether the JUMP(I) landed on a valid position. Valid positions for jump are: any JUMPDEST (0x5c) which is not part of a PUSH instruction (e.g. PUSH 0x5c would be an invalid jump position).
          • .... Run code .... (evaluation of code is a different topic)
          • Eventually the execution will end, be it a success or a failure (stack err, OOG, depth level, etc) and return a value and whether it was successful.
  • Evaluate outcome and set the code accordingly (if action was create)
  • Update the state changes made during the state transition (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L138)
  • Create a new receipt. Receipts are checked for validity at the end of the transaction processing (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L141).
  • Validate the block's bloom by concatenating the receipts log and run it through the bloom filter (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L200 & https://github.com/ethereum/go-ethereum/blob/docbranch/core/types/bloom9.go#L11)
  • Validate the transaction hash (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L206)
  • Validate the receipt hash (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L212)
  • Accumulate the reward for the miner (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L219)
    • Validate the uncle's parent (must be in chain) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L312)
    • Validate the uncle's block number (not greater than 6) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L317)
    • Validate the uncle's not includes multiple times (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L321)
    • Reward miner (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L339)
  • Update the state with all changes and validate the merkle root (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L223)
  • Calculate the total difficulty of the block (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L231)
  • Sync the state to the db (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L233)
  • Return the total difficulty if the process was a success (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L242)
• Write block to the database (https://github.com/ethereum/go-ethereum/blob/docbranch/core/chain_manager.go#L242)
• Compare the total difficulty of the process block to our current known TD (https://github.com/ethereum/go-ethereum/blob/docbranch/core/chain_manager.go#L244) if greater than:
  • Set new TD (https://github.com/ethereum/go-ethereum/blob/docbranch/core/chain_manager.go#L288)
  • Insert in to the canonical chain by setting it as current block (https://github.com/ethereum/go-ethereum/blob/docbranch/core/chain_manager.go#L211)

fin