txn: add service operations

agent/consul/state/catalog.go

@@ -735,6 +735,36 @@ func (s *Store) EnsureService(idx uint64, node string, svc *structs.NodeService)
 	return nil
 }
 
+// ensureServiceCASTxn updates a service only if the existing index matches the given index.
+// Returns a bool indicating if a write happened and any error.
+func (s *Store) ensureServiceCASTxn(tx *memdb.Txn, idx uint64, node string, svc *structs.NodeService) (bool, error) {
+	// Retrieve the existing entry.
+	existing, err := tx.First("nodes", "id", node)
+	if err != nil {
+		return false, fmt.Errorf("node lookup failed: %s", err)
+	}
+
+	// Check if the we should do the set. A ModifyIndex of 0 means that
+	// we are doing a set-if-not-exists.
+	if svc.ModifyIndex == 0 && existing != nil {
+		return false, nil
+	}
+	if svc.ModifyIndex != 0 && existing == nil {
+		return false, nil
+	}
+	e, ok := existing.(*structs.Node)
+	if ok && svc.ModifyIndex != 0 && svc.ModifyIndex != e.ModifyIndex {
+		return false, nil
+	}
+
+	// Perform the update.
+	if err := s.ensureServiceTxn(tx, idx, node, svc); err != nil {
+		return false, err
+	}
+
+	return true, nil
+}
+
 // ensureServiceTxn is used to upsert a service registration within an
 // existing memdb transaction.
 func (s *Store) ensureServiceTxn(tx *memdb.Txn, idx uint64, node string, svc *structs.NodeService) error {
@@ -1111,15 +1141,26 @@ func (s *Store) NodeService(nodeName string, serviceID string) (uint64, *structs
 	idx := maxIndexTxn(tx, "services")
 
 	// Query the service
-	service, err := tx.First("services", "id", nodeName, serviceID)
+	service, err := s.nodeServiceTxn(tx, nodeName, serviceID)
 	if err != nil {
 		return 0, nil, fmt.Errorf("failed querying service for node %q: %s", nodeName, err)
 	}
 
+	return idx, service, nil
+}
+
+func (s *Store) nodeServiceTxn(tx *memdb.Txn, nodeName, serviceID string) (*structs.NodeService, error) {
+	// Query the service
+	service, err := tx.First("services", "id", nodeName, serviceID)
+	if err != nil {
+		return nil, fmt.Errorf("failed querying service for node %q: %s", nodeName, err)
+	}
+
 	if service != nil {
-		return idx, service.(*structs.ServiceNode).ToNodeService(), nil
+		return service.(*structs.ServiceNode).ToNodeService(), nil
 	}
-	return idx, nil, nil
+
+	return nil, nil
 }
 
 // NodeServices is used to query service registrations by node name or UUID.
@@ -1214,6 +1255,35 @@ func serviceIndexName(name string) string {
 	return fmt.Sprintf("service.%s", name)
 }
 
+// deleteServiceCASTxn is used to try doing a service delete operation with a given
+// raft index. If the CAS index specified is not equal to the last observed index for
+// the given service, then the call is a noop, otherwise a normal delete is invoked.
+func (s *Store) deleteServiceCASTxn(tx *memdb.Txn, idx, cidx uint64, nodeName, serviceID string) (bool, error) {
+	// Look up the service.
+	service, err := tx.First("services", "id", nodeName, serviceID)
+	if err != nil {
+		return false, fmt.Errorf("check lookup failed: %s", err)
+	}
+	if service == nil {
+		return false, nil
+	}
+
+	// If the existing index does not match the provided CAS
+	// index arg, then we shouldn't update anything and can safely
+	// return early here.
+	existing, ok := service.(*structs.ServiceNode)
+	if !ok || existing.ModifyIndex != cidx {
+		return existing == nil, nil
+	}
+
+	// Call the actual deletion if the above passed.
+	if err := s.deleteServiceTxn(tx, idx, nodeName, serviceID); err != nil {
+		return false, err
+	}
+
+	return true, nil
+}
+
 // deleteServiceTxn is the inner method called to remove a service
 // registration within an existing transaction.
 func (s *Store) deleteServiceTxn(tx *memdb.Txn, idx uint64, nodeName, serviceID string) error {

agent/consul/state/txn.go

@@ -175,6 +175,59 @@ func (s *Store) txnNode(tx *memdb.Txn, idx uint64, op *structs.TxnNodeOp) (struc
 	return nil, nil
 }
 
+// txnService handles all Service-related operations.
+func (s *Store) txnService(tx *memdb.Txn, idx uint64, op *structs.TxnServiceOp) (structs.TxnResults, error) {
+	var entry *structs.NodeService
+	var err error
+
+	switch op.Verb {
+	case api.ServiceGet:
+		entry, err = s.nodeServiceTxn(tx, op.Node, op.Service.ID)
+
+	case api.ServiceSet:
+		err = s.ensureServiceTxn(tx, idx, op.Node, &op.Service)
+
+	case api.ServiceCAS:
+		var ok bool
+		ok, err = s.ensureServiceCASTxn(tx, idx, op.Node, &op.Service)
+		if !ok && err == nil {
+			err = fmt.Errorf("failed to set service %q on node %q, index is stale", op.Service.ID, op.Node)
+		}
+
+	case api.ServiceDelete:
+		err = s.deleteServiceTxn(tx, idx, op.Node, op.Service.ID)
+
+	case api.ServiceDeleteCAS:
+		var ok bool
+		ok, err = s.deleteServiceCASTxn(tx, idx, op.Service.ModifyIndex, op.Node, op.Service.ID)
+		if !ok && err == nil {
+			err = fmt.Errorf("failed to delete service %q on node %q, index is stale", op.Service.ID, op.Node)
+		}
+
+	default:
+		err = fmt.Errorf("unknown Service verb %q", op.Verb)
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	// For a GET we keep the value, otherwise we clone and blank out the
+	// value (we have to clone so we don't modify the entry being used by
+	// the state store).
+	if entry != nil {
+		if op.Verb == api.ServiceGet {
+			result := structs.TxnResult{Service: entry}
+			return structs.TxnResults{&result}, nil
+		}
+
+		clone := *entry
+		result := structs.TxnResult{Service: &clone}
+		return structs.TxnResults{&result}, nil
+	}
+
+	return nil, nil
+}
+
 // txnCheck handles all Check-related operations.
 func (s *Store) txnCheck(tx *memdb.Txn, idx uint64, op *structs.TxnCheckOp) (structs.TxnResults, error) {
 	var entry *structs.HealthCheck
@@ -247,6 +300,12 @@ func (s *Store) txnDispatch(tx *memdb.Txn, idx uint64, ops structs.TxnOps) (stru
 			ret, err = s.txnKVS(tx, idx, op.KV)
 		case op.Intention != nil:
 			err = s.txnIntention(tx, idx, op.Intention)
+		case op.Node != nil:
+			ret, err = s.txnNode(tx, idx, op.Node)
+		case op.Service != nil:
+			ret, err = s.txnService(tx, idx, op.Service)
+		case op.Check != nil:
+			ret, err = s.txnCheck(tx, idx, op.Check)
 		default:
 			err = fmt.Errorf("no operation specified")
 		}

agent/structs/txn.go

@@ -34,6 +34,7 @@ type TxnNodeResult *Node
 // a transaction.
 type TxnServiceOp struct {
 	Verb    api.ServiceOp
+	Node    string
 	Service NodeService
 }