Implement Message Pool

[dutterbutter]

The Message Pool is a subsystem in the Filecoin blockchain system. The message pool acts as the interface between Filecoin nodes and a peer-to-peer network used for off-chain message transmission. It is used by nodes to maintain a set of messages to transmit to the Filecoin VM (for “on-chain” execution).

Spec reference:

• Message Pool

Existing implementations for reference:

• Lotus Message Pool
• Go-Filecoin Message Pool

Needs access to the following subsystems:

• StateTree
• Messages mined into blocks
• MessagePubSub
• SignedMessages

Although the spec is very incomplete you can expect the following data structures/methods:

• struct MessagePool and constructor
• add_new_message
• find_messages //returns set of messages in mempool
• profitable_msgs // returns messages most profitable to mine for the miner
• MessageQuery struct and constructor

From Lotus implementation:

Pool struct

type MessagePool struct {
	lk sync.Mutex

	closer  chan struct{}
	repubTk *time.Ticker

	localAddrs map[address.Address]struct{}

	pending map[address.Address]*msgSet

	curTsLk sync.Mutex // DO NOT LOCK INSIDE lk
	curTs   *types.TipSet

	api Provider

	minGasPrice types.BigInt

	maxTxPoolSize int

	blsSigCache *lru.TwoQueueCache

	changes *lps.PubSub

	localMsgs datastore.Datastore
}

add_new_message:

type msgSet struct {
	msgs      map[uint64]*types.SignedMessage
	nextNonce uint64
}

func newMsgSet() *msgSet {
	return &msgSet{
		msgs: make(map[uint64]*types.SignedMessage),
	}
}

func (ms *msgSet) add(m *types.SignedMessage) error {
	if len(ms.msgs) == 0 || m.Message.Nonce >= ms.nextNonce {
		ms.nextNonce = m.Message.Nonce + 1
	}
	if _, has := ms.msgs[m.Message.Nonce]; has {
		if m.Cid() != ms.msgs[m.Message.Nonce].Cid() {
			log.Error("Add with duplicate nonce")
			return xerrors.Errorf("message to %s with nonce %d already in mpool")
		}
	}
	ms.msgs[m.Message.Nonce] = m

	return nil
}