fix(multiplayer): recover recorded allocations

server/store/allocation_match_adapter.go

@@ -20,6 +20,10 @@ func (s AllocatingMatchClaims) ClaimAllocatingMatch(ctx context.Context, now tim
 	return item.Request, found, err
 }
 
+func (s AllocatingMatchClaims) FindProviderAllocation(ctx context.Context, request domain.AllocationRequest) (domain.Allocation, bool, error) {
+	return FindProviderAllocation(ctx, s.DB, request)
+}
+
 func (s AllocatingMatchClaims) BindAllocatedMatch(ctx context.Context, allocation domain.Allocation) error {
 	return BindAllocatedMatch(ctx, s.DB, allocation)
 }

server/store/allocation_match_sql.go

@@ -1,6 +1,7 @@
 package store
 
 import (
+	"bytes"
 	"context"
 	"database/sql"
 	"fmt"
@@ -47,6 +48,30 @@ const ReleaseAllocatedMatchClaimSQL = `UPDATE matches
 SET allocation_id = NULL, allocation_claimed_at = NULL
 WHERE match_id = $1 AND state = 'ALLOCATING' AND allocation_id = $2 AND server_id IS NULL`
 
+// FindProviderAllocation verifies whether a recovered lease has already
+// crossed the durable provider boundary. A worker can then bind it without
+// issuing a second external allocation request after a crash.
+func FindProviderAllocation(ctx context.Context, db *sql.DB, request domain.AllocationRequest) (domain.Allocation, bool, error) {
+	if db == nil || request.AllocationID == "" || request.MatchID == "" || request.Region == "" || request.Build == "" || request.Protocol <= 0 || (request.Transport != "enet" && request.Transport != "steam_sdr") {
+		return domain.Allocation{}, false, fmt.Errorf("invalid provider allocation lookup")
+	}
+	var allocation domain.Allocation
+	var digest []byte
+	err := db.QueryRowContext(ctx, SelectAllocationSQL, request.AllocationID).Scan(&allocation.AllocationID, &allocation.MatchID, &allocation.ServerID, &allocation.Region, &allocation.Build, &allocation.Protocol, &allocation.Transport, &allocation.AllocatedAt, &digest)
+	if err == sql.ErrNoRows {
+		return domain.Allocation{}, false, nil
+	}
+	if err != nil {
+		return domain.Allocation{}, false, err
+	}
+	want := allocationRequestDigest(request)
+	if !bytes.Equal(digest, want[:]) || allocation.MatchID != request.MatchID || allocation.Region != request.Region || allocation.Build != request.Build || allocation.Protocol != request.Protocol || allocation.Transport != request.Transport {
+		return domain.Allocation{}, false, domain.ErrConflict
+	}
+	allocation.State = domain.ServerAllocated
+	return allocation, true, nil
+}
+
 // ClaimAllocatingMatch returns one durable provider work item. The fixed
 // allocation ID is retained across a lease recovery, allowing every later
 // reconciliation step to reject a different server for the same match.