Documentation
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Overview ¶
Package headnotify implements Lantern's chain-head change distributor.
It's the bridge between a Store's OnHeadChange callback (which fires on every new head) and the per-WebSocket subscriber channels that Filecoin.ChainNotify hands out.
Semantics match Lotus:
- When a subscriber connects, the first message is always {Type:"current", Val: <current head>}.
- For every subsequent canonical head, fan out {Type:"apply", Val: <new tipset>}. On reorg, fan out a sequence of {Type:"revert"} events for the orphaned tipsets followed by {Type:"apply"} events for the new chain.
- Per-subscriber buffer is bounded (default 64 events). When a subscriber's channel is full we drop the oldest events (matching Lotus' slow-subscriber behaviour) and emit a log warning.
Written for Lantern. Not a direct lift of Lotus' notifee plumbing, but the head-change event shape (HeadChange{Type,Val}) is the same wire format Curio expects.
Index ¶
Constants ¶
const DefaultBufferSize = 64
DefaultBufferSize is the per-subscriber bounded buffer depth.
Lotus' default is similar; we pick 64 to absorb ~30s of mainnet epochs without dropping under normal load.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Distributor ¶
type Distributor struct {
// contains filtered or unexported fields
}
Distributor fans out head-change events from a header store to many subscribers (one per active WebSocket ChainNotify session).
func New ¶
func New(store *hstore.Store, bufferSize int) *Distributor
New returns a Distributor backed by the given header store. The distributor does NOT start listening on the store until Start() is called.
func (*Distributor) CurrentHead ¶
func (d *Distributor) CurrentHead() *ltypes.TipSet
CurrentHead returns the most recent head the distributor has observed, or nil if no head has been published yet.
func (*Distributor) PublishCustom ¶
func (d *Distributor) PublishCustom(events []api.HeadChange)
PublishCustom lets the daemon push an arbitrary head-change sequence (e.g. a synthetic "current" reset). Used during startup if the daemon wants to advertise the trusted-root head before the header store has caught up.
func (*Distributor) Start ¶
func (d *Distributor) Start()
Start hooks the distributor into the header store. Idempotent.
func (*Distributor) Subscribe ¶
func (d *Distributor) Subscribe(ctx context.Context) <-chan []api.HeadChange
Subscribe returns a new channel that receives head-change events. The first event is always {Type:"current"} with the current head (or empty if no head is available yet). Cancelling ctx unsubscribes.
The returned channel is closed by the distributor when ctx is done.
func (*Distributor) SubscriberCount ¶
func (d *Distributor) SubscriberCount() int
SubscriberCount returns the number of active subscribers.
Source Files