流星服务器端更新/插入与客户端更新/插入

Question

I have a question about the advantages vs disadvantages of an update/insert of a collection on the client vs server. For example say I have the method which takes a current player, sets him/her no longer as the current player and then creates a new current player.

  Meteor.methods({
       currentPlayer : function () {
              var id = Player.findOne({current:true})._id;
              Player.update(id, {$set:{current:false}});
              Player.insert({current:true});
  ...

What would be the advantages to doing this on the server vs doing the exact same thing on the client side:

  'click #add' : function () {
         var id = Player.findOne({current:true})._id;
         Player.update(id, {$set:{current:false}});
         Player.insert({current:true});
   ...

Maybe there aren't any inherently important differences or advantages to either technique. However if there is I would like to be aware of them. Thanks for your input!

Answer 1

The main difference is latency compensation.

Under the hood, Player.update/insert/remove , uses a Meteor.call anyway. The difference is that it simulates the result of a successful operation on the browser before it has happened.

So say your server is somewhere on the other side of the world where it has a 2-3 second latency. If you update your player using Player.insert/update it would reflect instantly as if it was inserted and updated. This can be make the UI feel responsive.

Using a Meteor.methods waits for the server to send an updated record, meaning when you update something it would take the 2-3 seconds to reflect on your UI.

Using the method's you can be sure that the data has been inserted on the server at the cost of UI responsiveness. (You could also use the Player.insert & Player.update callbacks for this too.

With Meteor.methods you can also simulate this same latency compensation effect by doing the same Meteor.method on the client side with the code that you would like to run to simulate latency compensation.

There's a bit more details on the specifics on how to do this at the docs: http://docs.meteor.com/#meteor_methods

Answer 2

I think Akshat has some great points. Basically there isn't a lot of difference in terms of latency compensation if you define the method on both the client and the server. In my opinion, there are a couple of reasons to use a method:

• The operation can only be completed on the server or it results in some side effect that only makes sense on the server (eg sending an email).

• You are doing an update and the permissions for doing the update are complex. For example maybe only the leader of a game can update certain properties of the players. Cases like that are extremely hard to express in allow/deny rules, but are easy to write using methods.

Personally, I prefer using methods in large projects because I find it's easier to reason about state mutations when all of the changes are forced to funnel through a small set of functions.

On the other hand, if you are working on a smaller project that doesn't have a lot of complex update rules, doing direct collection mutations may be a bit faster to write.