nomad: document some potential races

nomad/client_endpoint.go

@@ -235,6 +235,8 @@ func (c *Client) createNodeEvals(nodeID string, nodeIndex uint64) ([]string, uin
 	}
 
 	// Commit this evaluation via Raft
+	// XXX: There is a risk of partial failure where the node update succeeds
+	// but that the EvalUpdate does not.
 	_, evalIndex, err := c.srv.raftApply(structs.EvalUpdateRequestType, update)
 	if err != nil {
 		return nil, 0, err

nomad/job_endpoint.go

@@ -67,6 +67,8 @@ func (j *Job) Register(args *structs.JobRegisterRequest, reply *structs.JobRegis
 	}
 
 	// Commit this evaluation via Raft
+	// XXX: There is a risk of partial failure where the JobRegister succeeds
+	// but that the EvalUpdate does not.
 	_, evalIndex, err := j.srv.raftApply(structs.EvalUpdateRequestType, update)
 	if err != nil {
 		j.srv.logger.Printf("[ERR] nomad.job: Eval create failed: %v", err)

nomad/plan_apply.go

@@ -154,6 +154,8 @@ func evaluateNodePlan(snap *state.StateSnapshot, plan *structs.Plan, nodeID stri
 	}
 
 	// If the node does not exist or is not ready for schduling it is not fit
+	// XXX: There is a potential race between when we do this check and when
+	// the Raft commit happens.
 	if node == nil || node.Status != structs.NodeStatusReady {
 		return false, nil
 	}