Thanks Michael,
Interesting idea piping to itself. I'll keep it in mind when I revisit this
part of the code.
Regards,
On Tuesday, October 7, 2014 3:45:05 PM UTC-7, Michael Frank wrote:
>
> Can i suggest an alternative? Why not use actors to model this
> computation?
>
> For example, you could have a class ProcessAssetsActor. The class has a
> Map<Long,Future> called assetFutures, and a List<Asset> called assets
> containing the received assets. In the preStart() method, you create a
> future to get the asset ids and pipeTo(self). in your receive loop, you
> wait for the initial list of asset ids. once that is received, you create
> a future (again using pipeTo(self)) to get the asset for each assetId, and
> put each assetId and future in assetFutures. as each Asset is received in
> the receive loop, remove the reference from assetFutures and add the Asset
> to assets. when assetFutures is empty, you are done computing. passing
> the result back to the client can be done a few ways; you could for example
> have the ProcessAssetsActor send the result to the parent automatically, or
> you could have the parent actor send a query message to the
> ProcessAssetsActor (using ask() or tell()) and wait for a response message.
>
> This probably seems like a lot of extra work, but i like this pattern for
> a couple reasons:
>
> 1) by using actors you have access to much better error handling.
> 2) as your business requirements change, it is easier to modify your
> business logic in an actor than in a chain of futures.
>
> -Michael
>
> On 10/07/14 13:51, Joe Wong wrote:
>
> Hi,
>
> I have the following events that I'm trying to put into a non blocking
> way. The events are as follows
>
> 1. database call to get list of asset ids.
> 2. create a list of futures to get assets (getting assets can take a while
> and are independent of one another)
> 3. process all the assets and return a Result.
>
> What I have is the following
>
> public Future<Result> buildFuture(){
> //Blocking DB call
> Collection<Long> assetIds = assetDao.getAssetIds();
>
> Collection<Future<Asset>> assetFutures = new
> ArrayList<>(assetIds.size());
>
> for (Long assetId : assetIds) {
> assetFutures.add(createFutureAsset(assetId, executionContext));
> }
>
> Future<Collection<Asset>> futureAssets =
> sequence((Iterable)assetFutures, executionContext);
>
> //once we have all Assets process them and return result
> Future<Result> futureResult = futureAssets.map(
> new Mapper<Collection<Asset>, Result>() {
>
> @Override
> public Result apply(Collection<Asset> assets) {
> //do something with the assets
> return new Result("done");
> }
> },
> executionContext
> );
>
> return futureResult;
> }
>
> What I'm trying to get my head around is how to wrap all 3 events into
> one Future<Result>. Any ideas? Thanks in advance
>
> Regards
>
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