使用Spring避免数据库轮询的最佳方法

Question

I have web service for reading and updating data and using spring, spring JDBC for DB access. My controller can be accessed by many channels like desktop, mobile etc. If data is updated using desktop, then same should reflect in mobile immediately. Current approach is calling service continuously to get updated data. I feel that it is worst approach and causing DB performance issue as well.

Is there a possible way such that GET service is called only when there is DB update by other channel instead of continuous polling ? What is best approach for this and how to implement it ?

Answer 1

Continuously calling the service seems like a really bad idea. I think you need a database trigger that fires when rows are inserted/updated/deleted. It could POST something to a Web Service or put something on a Message Queue.

Good luck.

Answer 2

I can think of an architectural answer to the problem. Use a messaging solution between the spring controller and the database. Infact you will need two queues

• EventSink queue - Publish all data change requests originating from any of the channels to this queue.The subscriber will be the service managing the database update aka dbservice .

• EventBroadcast queue - Publish the changed data post db update to this queue. Ideally the dbservice should handle this publish within the same transaction as db update. All channels can subscribe to this queue to receive the update.

  The merits to consider this approach would involve

• Pros - this approach involves no database services so both performance and de-coupling from database changes.

• Cons - Increased complexity

Answer 3

Continuously polling is not as bad as you might imagine. Pushing messages to clients without them making a request requires web-sockets or of the like to achieve this. If it is not a large repose from the server, and is not too often, as in many millions and millions of requests then I would leave it for now.

If however this is a large amount of bandwidth we are talking about it then you wouldn't want to be polling. You would probably want to look at a subscriber type pattern whereby clients would subscribe to be notified when a specific event occurs. When this event occurs the server would then send a message to the clients.

Detecting this event shouldn't require polling a database. The modification to the database should trigger the event. You might do this with point-cuts in Spring if you are into that sort of thing.