nil check and error handling for client status in heartbeat responses

client/client.go

@@ -2024,7 +2024,8 @@ func (c *Client) updateNodeStatus() error {
 	}
 
 	// Check heartbeat response for information about the server-side scheduling
-	// state of this node
+	// state of this node. If there are errors on the server side, this will come
+	// back as an empty string.
 	c.UpdateConfig(func(c *config.Config) {
 		if resp.SchedulingEligibility != "" {
 			c.Node.SchedulingEligibility = resp.SchedulingEligibility

nomad/node_endpoint.go

@@ -301,8 +301,17 @@ func (n *Node) constructNodeServerInfoResponse(nodeID string, snap *state.StateS
 	}
 
 	// Add ClientStatus information to heartbeat response.
-	node, _ := snap.NodeByID(nil, nodeID)
-	reply.SchedulingEligibility = node.SchedulingEligibility
+	if node, err := snap.NodeByID(nil, nodeID); err == nil && node != nil {
+		reply.SchedulingEligibility = node.SchedulingEligibility
+	} else if err != nil {
+		// emit an error to the log and leave the string as empty, which is treated
+		// as a no-op in the client response handler.
+		n.logger.Error("constructNodeServerInfoResponse: error fetching node by id",
+			"node_id", nodeID, "err", err)
+	} else {
+		n.logger.Error("constructNodeServerInfoResponse: node==nil without error",
+			"node_id", nodeID)
+	}
 
 	// TODO(sean@): Use an indexed node count instead
 	//