protocol

Documentation

Overview

Package protocol provides the logic to tie together storage and validation for a Chain Protocol blockchain.

This comprises all behavior that's common to every full node, as well as other functions that need to operate on the blockchain state.

Here are a few examples of typical full node types.

Generator

A generator has two basic jobs: collecting transactions from other nodes and putting them into blocks.

To add a transaction to the pending transaction pool, call AddTx for each one.

To add a new block to the blockchain, call GenerateBlock, sign the block (possibly collecting signatures from other parties), and call CommitBlock.

Signer

A signer validates blocks generated by the Generator and signs at most one block at each height.

Participant

A participant node in a network may select outputs for spending and compose transactions.

To publish a new transaction, prepare your transaction (select outputs, and compose and sign the tx) and send the transaction to the network's generator. To wait for confirmation, call WaitForBlock on successive block heights and inspect the blockchain state until you find that the transaction has been either confirmed or rejected. Note that transactions may be malleable if there's no commitment to TXSIGHASH.

To ingest a block, call ValidateBlock and CommitBlock.

Index

• Variables
• func NewInitialBlock(pubkeys []ed25519.PublicKey, nSigs int, timestamp time.Time) (*bc.Block, error)
• type Chain
  • func NewChain(ctx context.Context, initialBlockHash bc.Hash, store Store, pool Pool, ...) (*Chain, error)
  • func (c *Chain) AddTx(ctx context.Context, tx *bc.Tx) error
  • func (c *Chain) CommitBlock(ctx context.Context, block *bc.Block, snapshot *state.Snapshot) error
  • func (c *Chain) GenerateBlock(ctx context.Context, prev *bc.Block, snapshot *state.Snapshot, now time.Time) (b *bc.Block, result *state.Snapshot, err error)
  • func (c *Chain) GetBlock(ctx context.Context, height uint64) (*bc.Block, error)
  • func (c *Chain) Height() uint64
  • func (c *Chain) Recover(ctx context.Context) (*bc.Block, *state.Snapshot, error)
  • func (c *Chain) State() (*bc.Block, *state.Snapshot)
  • func (c *Chain) Store() Store
  • func (c *Chain) ValidateBlock(ctx context.Context, prevState *state.Snapshot, prev, block *bc.Block) (*state.Snapshot, error)
  • func (c *Chain) ValidateBlockForSig(ctx context.Context, block *bc.Block) error
  • func (c *Chain) ValidateTxCached(tx *bc.Tx) error
  • func (c *Chain) WaitForBlock(height uint64) <-chan struct{}
  • func (c *Chain) WaitForBlockSoon(ctx context.Context, height uint64) <-chan error
• type Pool
• type Store

Variables

var ErrBadBlock = errors.New("invalid block")

ErrBadBlock is returned when a block is invalid.

var ErrStaleState = errors.New("stale blockchain state")

ErrStaleState is returned when the Chain does not have a current blockchain state.

var (
	// ErrTheDistantFuture is returned when waiting for a blockheight
	// too far in excess of the tip of the blockchain.
	ErrTheDistantFuture = errors.New("block height too far in future")
)

Functions

func NewInitialBlock

func NewInitialBlock(pubkeys []ed25519.PublicKey, nSigs int, timestamp time.Time) (*bc.Block, error)

Types

type Chain

type Chain struct {
	InitialBlockHash  bc.Hash
	MaxIssuanceWindow time.Duration // only used by generators
	// contains filtered or unexported fields
}

Chain provides a complete, minimal blockchain database. It delegates the underlying storage to other objects, and uses validation logic from package validation to decide what objects can be safely stored.

func NewChain

func NewChain(ctx context.Context, initialBlockHash bc.Hash, store Store, pool Pool, heights <-chan uint64) (*Chain, error)

NewChain returns a new Chain using store as the underlying storage.

func (*Chain) AddTx

func (c *Chain) AddTx(ctx context.Context, tx *bc.Tx) error

AddTx inserts tx into the set of "pending" transactions available to be included in the next block produced by GenerateBlock. It should only be called by the Generator.

It performs context-free validation of the tx, but does not validate against the current state tree.

It is okay to add the same transaction more than once; subsequent attempts will have no effect and return a nil error. It is also okay to add conflicting transactions to the pool. The conflict will be resolved when a block lands.

It is an error to call AddTx before the initial block has landed. Use WaitForBlock to guarantee this.

func (*Chain) CommitBlock

func (c *Chain) CommitBlock(ctx context.Context, block *bc.Block, snapshot *state.Snapshot) error

CommitBlock commits the block to the blockchain.

This function:

• saves the block to the store.
• saves the state tree to the store (optionally).
• executes all new-block callbacks.

The block parameter must have already been validated before being committed.

func (*Chain) GenerateBlock

func (c *Chain) GenerateBlock(ctx context.Context, prev *bc.Block, snapshot *state.Snapshot, now time.Time) (b *bc.Block, result *state.Snapshot, err error)

GenerateBlock generates a valid, but unsigned, candidate block from the current pending transaction pool. It returns the new block and a snapshot of what the state snapshot is if the block is applied.

After generating the block, the pending transaction pool will be empty.

func (*Chain) GetBlock

func (c *Chain) GetBlock(ctx context.Context, height uint64) (*bc.Block, error)

GetBlock returns the block at the given height, if there is one, otherwise it returns an error.

func (*Chain) Height

func (c *Chain) Height() uint64

Height returns the current height of the blockchain.

func (*Chain) Recover

func (c *Chain) Recover(ctx context.Context) (*bc.Block, *state.Snapshot, error)

Recover performs crash recovery, restoring the blockchain to a complete state. It returns the latest confirmed block and the corresponding state snapshot.

If the blockchain is empty (missing initial block), this function returns a nil block and an empty snapshot.

func (*Chain) State

func (c *Chain) State() (*bc.Block, *state.Snapshot)

State returns the most recent state available. It will not be current unless the current process is the leader. Callers should examine the returned block header's height if they need to verify the current state.

func (*Chain) Store

func (c *Chain) Store() Store

Store returns the Store used by the blockchain.

func (*Chain) ValidateBlock

func (c *Chain) ValidateBlock(ctx context.Context, prevState *state.Snapshot, prev, block *bc.Block) (*state.Snapshot, error)

ValidateBlock performs validation on an incoming block, in advance of committing the block. ValidateBlock returns the state after the block has been applied.

func (*Chain) ValidateBlockForSig

func (c *Chain) ValidateBlockForSig(ctx context.Context, block *bc.Block) error

ValidateBlockForSig performs validation on an incoming _unsigned_ block in preparation for signing it. By definition it does not execute the sigscript.

func (*Chain) ValidateTxCached

func (c *Chain) ValidateTxCached(tx *bc.Tx) error

ValidateTxCached checks a cache of prevalidated transactions before attempting to perform a context-free validation of the tx.

func (*Chain) WaitForBlock

func (c *Chain) WaitForBlock(height uint64) <-chan struct{}

WaitForBlock returns a channel that waits for the block at the given height.

func (*Chain) WaitForBlockSoon

func (c *Chain) WaitForBlockSoon(ctx context.Context, height uint64) <-chan error

WaitForBlockSoon returns a channel that waits for the block at the given height, but it is an error to wait for a block far in the future. WaitForBlockSoon will timeout if the context times out. To wait unconditionally, the caller should use WaitForBlock.

type Pool

type Pool interface {
	// Insert adds a transaction to the pool.
	// It doesn't check for validity, or whether the transaction
	// conflicts with another.
	// It is required to be idempotent.
	Insert(context.Context, *bc.Tx) error

	// Dump wipes the pending transaction pool and returns all
	// transactions that were in the pool.
	Dump(context.Context) ([]*bc.Tx, error)
}

Pool provides storage for transactions in the pending transaction pool.

type Store

type Store interface {
	Height(context.Context) (uint64, error)
	GetBlock(context.Context, uint64) (*bc.Block, error)
	LatestSnapshot(context.Context) (*state.Snapshot, uint64, error)

	SaveBlock(context.Context, *bc.Block) error
	FinalizeBlock(context.Context, uint64) error
	SaveSnapshot(context.Context, uint64, *state.Snapshot) error
}

Store provides storage for blockchain data: blocks and state tree snapshots.

Note, this is different from a state snapshot. A state snapshot provides access to the state at a given point in time -- outputs and issuance memory. The Chain type uses Store to load state from storage and persist validated data.