eth/catalyst, miner: build the execution payload async (#24866)

* eth/catalyst: build the execution payload async

* miner: added comment, added test case

* eth/catalyst: miner: move async block production to miner

* eth/catalyst, miner: support generate seal block async

* miner: rework GetSealingBlockAsync to use a passed channel

* miner: apply rjl's diff

* eth/catalyst: nitpicks

Co-authored-by: Gary Rong <garyrong0905@gmail.com>

eth/catalyst/queue.go

@@ -18,6 +18,7 @@ package catalyst
 
 import (
 	"sync"
+	"time"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/beacon"
@@ -34,11 +35,52 @@ const maxTrackedPayloads = 10
 // latest one; but have a slight wiggle room for non-ideal conditions.
 const maxTrackedHeaders = 10
 
+// payload wraps the miner's block production channel, allowing the mined block
+// to be retrieved later upon the GetPayload engine API call.
+type payload struct {
+	lock   sync.Mutex
+	done   bool
+	empty  *types.Block
+	block  *types.Block
+	result chan *types.Block
+}
+
+// resolve extracts the generated full block from the given channel if possible
+// or fallback to empty block as an alternative.
+func (req *payload) resolve() *beacon.ExecutableDataV1 {
+	// this function can be called concurrently, prevent any
+	// concurrency issue in the first place.
+	req.lock.Lock()
+	defer req.lock.Unlock()
+
+	// Try to resolve the full block first if it's not obtained
+	// yet. The returned block can be nil if the generation fails.
+
+	if !req.done {
+		timeout := time.NewTimer(500 * time.Millisecond)
+		defer timeout.Stop()
+
+		select {
+		case req.block = <-req.result:
+			req.done = true
+		case <-timeout.C:
+			// TODO(rjl49345642, Marius), should we keep this
+			// 100ms timeout allowance? Why not just use the
+			// default and then fallback to empty directly?
+		}
+	}
+
+	if req.block != nil {
+		return beacon.BlockToExecutableData(req.block)
+	}
+	return beacon.BlockToExecutableData(req.empty)
+}
+
 // payloadQueueItem represents an id->payload tuple to store until it's retrieved
 // or evicted.
 type payloadQueueItem struct {
-	id      beacon.PayloadID
-	payload *beacon.ExecutableDataV1
+	id   beacon.PayloadID
+	data *payload
 }
 
 // payloadQueue tracks the latest handful of constructed payloads to be retrieved
@@ -57,14 +99,14 @@ func newPayloadQueue() *payloadQueue {
 }
 
 // put inserts a new payload into the queue at the given id.
-func (q *payloadQueue) put(id beacon.PayloadID, data *beacon.ExecutableDataV1) {
+func (q *payloadQueue) put(id beacon.PayloadID, data *payload) {
 	q.lock.Lock()
 	defer q.lock.Unlock()
 
 	copy(q.payloads[1:], q.payloads)
 	q.payloads[0] = &payloadQueueItem{
-		id:      id,
-		payload: data,
+		id:   id,
+		data: data,
 	}
 }
 
@@ -78,7 +120,7 @@ func (q *payloadQueue) get(id beacon.PayloadID) *beacon.ExecutableDataV1 {
 			return nil // no more items
 		}
 		if item.id == id {
-			return item.payload
+			return item.data.resolve()
 		}
 	}
 	return nil