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#L269)
• 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#L271
  • 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 things first (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L195)
    • Calculate the total difficulty and compare it to the parent's TD (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L276)
    • Verify the proof of work (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L293)
  • Transition the state (e.g., apply transactions) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L199)
  • Give coin base block gas limit which transactions use as gas pool to buy gas off (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L88)
  • Create a new state transition object which will help us with the transition (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L117)
    • 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#L135)
    • Check the tx nonce: tx.nonce == account.nonce (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L123)
    • Check if we can buy the gas of the coin base (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L139)
    • Use TxGas (500) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L154)
    • Create a contract if address = 0x0 * 32 (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L174)
    • OR run the code if the recipient has any code to execute (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L180)
      • Create VmEnv and use that as the Virtual machine's environment for creating or executing now contracts (https://github.com/ethereum/go-ethereum/blob/docbranch/core/vm_env.go)
      • Create Execution object which takes care of the actual Vm instantiation (https://github.com/ethereum/go-ethereum/blob/docbranch/core/execution.go#L35)
        • Get the recipient and sender (https://github.com/ethereum/go-ethereum/blob/docbranch/core/execution.go#L39)
        • Transfer value (err is set incase of insufficient funds) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/execution.go#L42)
        • Snapshot the state for rollback feature (https://github.com/ethereum/go-ethereum/blob/docbranch/core/execution.go#L51)
        • defer checking for depth and oog errors so that we may rollback to the previous snapshot (https://github.com/ethereum/go-ethereum/blob/docbranch/core/execution.go#L52)
        • Check for precompiled contract (https://github.com/ethereum/go-ethereum/blob/docbranch/core/execution.go#L61) see (https://github.com/ethereum/go-ethereum/blob/docbranch/vm/address.go#L23) for all pre compiled contracts.
        • 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#L39)
          • Create a new closure which holds the code, gas and information about the caller (https://github.com/ethereum/go-ethereum/blob/docbranch/vm/vm_debug.go#L49)
          • 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#L88) uses the jump positions in order to determine whether the JUMP landed on a valid 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) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/state_transition.go#L178)
  • Update the state changes made during the state transition (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L140)
  • Create a new receipt for validity checks at the end of the transaction processing (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L143)
  • Validate the receipts by creating a new bloom filter out of it and compare it against the received block's bloom (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L204)
  • Validate the transaction hash (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L210)
  • Validate the receipt hash (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L216)
  • Accumulate the reward for the miner (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L222)
    • Validate the uncle's parent (must be in chain) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L311)
    • Validate the uncle's block number (not greater than 6) (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L316)
    • Validate the uncle's not includes multiple times (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L320)
    • Reward miner (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L338)
  • Update the state with all changes and validate the merkle root (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L228)
  • Calculate the total difficulty of the block (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L234)
  • Sync the state to the db (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L236)
  • Return the total difficulty if the process was a success (https://github.com/ethereum/go-ethereum/blob/docbranch/core/block_manager.go#L245)
• Write block to the database (https://github.com/ethereum/go-ethereum/blob/docbranch/core/chain_manager.go#L292)
• 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#L293) if greater than:
  • Set new TD (https://github.com/ethereum/go-ethereum/blob/docbranch/core/chain_manager.go#L298)
  • Insert in to the canonical chain by setting it as current block (https://github.com/ethereum/go-ethereum/blob/docbranch/core/chain_manager.go#L292)

fin