What is the benefit / usage of a AppEngine remote procedure call

I'm trying to grasp the concept of the rpc on appengine. W开发者_如何学编程hen or Why would i need to use one and what are the benefits?

Do they help with staying within your quota? Are they more efficient?

When you use the datastore, memcache, URL Fetch, or many of the other services, you are implicitly creating and using an RPC.

Some methods take an optional RPC argument. You can create an RPC with custom settings, such as a deadline, to give you more control over the call. An example of when setting a deadline on datastore operations can be useful is deferring a write to the task queue on a timeout type failure. Setting a lower deadline will ensure you have enough time to try again or insert a task.

rpc on AppEngine is useful when you want to do a URL fetch and you want to do other things while you're waiting for the response to be completed.

Let's say your URL fetch will take 1 second to complete and you have 'other' processing to do for 1 second which you can do while your waiting. You can launch an rpc call, do the 'other' processing, and when the rpc fetch is finished you can continue the request. The request will take a total of 1 second (plus overhead) with rpc as opposed to the conventional approach which would take 2 seconds.