[Ethereum] How to access contract events through RPC

Until the abigen will generate code to access events through the contract interface you should use Client.SubscribeFilterLogs method. It's pretty self-explained. You have to provide a channel which will be fed by logs. Also, don't forget to listen on Subscription.Err().

Check consensys article: Technical Introduction to Events and Logs in Ethereum for information about handling Logs in Ethereum.

Example:

query := ethereum.FilterQuery{
    FromBlock: nil,
    ToBlock:   nil,
    // Topics [][]common.Hash
    Addresses: []common.Address{myContractAddress}}
var logs = make(chan types.Log, 2)
s, err := client.SubscribeFilterLogs(context.TODO(), query, logs)
// check err
errChan := s.Err()
for {
    select {
    case err := <-errChan:
        logger.Error("Logs subscription error", err)
        break
    case l := <-logs:
        logger.Info("new log", log15.Spew(l))
    }
}

It sounds like the concern is listeners could multiply in a way that might not scale. There's no silver bullet that I'm aware of that would let a single listener filter events like you would need. This third way is a variant of the two options I understand you are considering.

Consider handling transactions the way you want to, and adding logically centralized logging functions. For example, the contract factory. Arrange things so factory-created contracts rely on the centralized logging functions instead of internal event emitters.

If you have:

contract Factory { ...
contract Created {
  event LogSomething(bytes32 Id); 
  ...
  LogSomething(Id);

Re-arrange as

contract Hub {
  event LogSomething(address contract, bytes32 Id);
  ...
  function logSomething(bytes32 Id);
    LogSomething(msg.sender, Id); // msg.sender will be the "spoke" that called Hub function.

contract Created{ 
   ...
   function important(bytes32 id) {
      .. 
      Hub.logSomething(Id);

Factory should probably be called Hub in the case that it's relied upon for more than just minting contracts.

Hope it helps.