Home/ Questions/Q 9255709
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-18T11:46:19+00:00

I am trying to implement a 2-player turn-based game with a GAE backend. The

  • 0

I am trying to implement a 2-player turn-based game with a GAE backend. The first thing this game requires is a very simple match making system that operates like this:

  1. User A asks the backend for a match. The back ends tells him to come back later
  2. User B asks the backend for a match. He will be matched with A.
  3. User C asks the backend for a match. The back ends tells him to come back later
  4. User D asks the backend for a match. He will be matched with C.
  5. and so on…

(edit: my assumption is that if I can figure this one out, most other operation i a turn based game can use the same implementation)

This can be done quite easily in Apple Gamecenter and Xbox Live, however I would rather implement this on an open and platform independent backend like GAE. After some research, I have found the following options for a GAE implementation:

  • use memcache. However, there is no guarantee that the memcache is synchronized across different instances. I did some tests and could actually see match request disappearing due to memcache mis-synchronization.
  • Harden memcache with Sharding Counters. This does not always solve the multiple instance problem and mayabe results in high memcache quota usage.
  • Use memcache with Compare and Set. Does not solve the multiple instance problem when used as a mutex.
  • task queues. I have no idea how to use these but someone mentioned as a possible solution. However, I am afraid that queues will eat me GAE quota very quickly.
  • push queues. Same as above.
  • transaction. Same as above. Also probably very expensive.
  • channels. Same as above. Also probably very expensive.

Given that the match making is a very basic operation in online games, I cannot be the first one encountering this. Hence my questions:

  • Do you know of any safe mechanism for match making?
  • If multiple solutions exist, which is the cheapest (in terms of GAE quota usage) solution?
Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    You could accomplish this using a cron tasks in a scheme like this:

    define MatchRequest:
    requestor = db.StringProperty()
    opponent = db.StringProperty(default = '')

    User A asks for a match, a MatchRequest entity is created with A as the requestor and the opponent blank.
    User A polls to see when the opponent field has been filled.
    User B asks for a match, a MatchRequest entity is created with B as as the requestor.
    User B pools to see when the opponent field has been filled.

    A cron job that runs every 20 seconds? or so runs:

    1. Grab all MatchRequest where opponent == ”
    2. Make all appropriate matches
    3. Put all the MatchRequests as a transaction

    Now when A and B poll next they will see that they they have an opponent.

    According to the GAE docs on crons free apps can have up to 20 free cron tasks. The computation required for these crons for a small amount of users should be small.

    This would be a safe way but I’m not sure if it is the cheapest way. It’s also pretty easy to implement.

    • 0