How to Optimize REST API calls

问题:

I am in process of building Mash up mobile application. I need to call my API Provider and integrate with Facebook , twitter etc. During this process, I have to make multiple REST API calls one after other to same domain(with different path and query parameters ofcourse). Also the API calls has to be sequential as in result of one is required to call the next. What are the ways I can optimize these http calls to avoid the round trip. Suggestions for java and js is welcome

回答1:

The requirements stated are broad. Since you are using the public third party API, that somewhat limits the scope of possible optimizations. There is absolutely nothing that you can do to speed up the APIs as they do not belong to you.

In general I suggest following guidelines which will help you come up with better application.

1. Thumb rule is make as few API calls as possible.
2. Making fewer network calls (resulting from API calls) will imply that the device radio (which is used to communicate with the server over the air) will be less frequently used and hence less power required.
3. Now, making fewer number of calls may not be an option always. So study the public API documentation carefully and make sure you know the all the details of the APIs you need.
4. For example, there could be an API which gives details of an entity upon passing its identifier. If you need the details of 5 such entities then there should be an API which takes a bunch of IDs and returns all the details at once. This way you save multiple calls.
5. Caching is very effective way of reducing the number of API call. So look for any data received from server which can be cached for certain duration.
6. Note that caching would need more memory and hence make sure you are aware of its implication and accordingly decide the amount of data that needs to cached.
7. Apart from memory, the data can be cached on the disc as well, which will help reduce the memory usage. Not sure if you are using Android, please refer to this related post.

On the side note, you can refer to following links which offer general guidelines for developing a mobile App.

1. Make your application blazing fast.
2. Optimizing a Mobile App for Mobile network.

Please note that these are general guidelines. Some may not apply to your particular use case.

回答2:

If you need the results of the first API call in order to make the next API call, then there is nothing you can do client-side to avoid a sequential round-trip for each one. There would either need to be an existing API call that can be used to combine multiple calls into one or you would need to add such an API call to the server or you would need to use a proxy server that does that on your behalf.

If you don't need the results of the first API call in order to make the next API call, but you just want to process the results in sequential order, then you can make all the API calls at once and structure your response code to process them in order (saving any results that arrive out of order for later processing).

回答3:

Programming level - use code optimization/threading/parallel programming.

API level - use pagination/filters/ranges to generate fine-grained data that is tailored to the need of the client.

Cache - Have heard somewhere that the "fastest HTTP call is the one that you don't make" that is, use caching(Memcache/Redis), most of the requests are read operations, wise use of cache control headers are also useful. That spares the database from serving repeated read requests which are expensive. (Not sure if Etags can be of any use ?)

Request/Response - Use JSON serializer and gZip compress techniques for the data transmitted over the web.

Geography - Account for the distance between end users and origin servers, we can use CDNs for storing the static contents of the response, so that it can be served real fast.

(Have heard about asynchronous methods/reactive programming which improves the performance of APIs, but not so sure)

回答4:

REST is unified and therefore, filters and round trips are necessary to accomplish a certain functionality. When it comes to optimization and imitating multiple clients request into ONE, you will slowly start facing challenges of a unified paradigm since it client can be a lot more specific than the contract can do in ONE UNIFIED call. While REST can be heavily optimized to drop the number of API calls to two or even one call, sometimes, your client request will require complex filtering that will require a feedback from the server prior to applying additional filtering logic.

If your requirements that you absolutely have to have ONE API call to handle specific client request from the server instead of the client while all filters is not applicable, then RPC will be your way to go, which will take care of specific business logic in a restful manner from the server to other micro-services (SOA.)

The real question is why you would have the server to handle such request if you want to keep your REST API unified and consistent and have the clients implement their own unique logic. The REST API server should provide the client with hyperlinks/hypermedia to guide the client of best way to reduce the number of API calls whether by filtering or any other entity/resource.

回答5:

If you could use jQuery, I suggest you have a look my plugin jQuery Chain which could help make async call sequential.