Using CardFilter.All causes huge hit in performance

[gregsdennis]

Reported by @techfooninja

I'm primarily using the Board.Cards property, since I'm interested in all cards on the board, regardless of which list they're in. When I run the following code, it executes relatively quickly (5-10 seconds for the 15-20 boards I care about):

this.trello = new TrelloFactory().Me().Result;
foreach (var board in this.trello.Boards)
{
    // board.Cards.Filter(CardFilter.All);  // <-- This causes huge perf hit
    await board.Cards.Refresh();
}

But if I uncomment the filter line, I hit a massive performance hit, possibly even more than 100x (waiting several minutes and it just finished the first board).

Details:

• Used in a .NET Framework 4.6.2 Console Application on a Windows 10 machine (Version 1809, OS Build 17763.379). I see the same behavior on a Windows Server 2016 machine (Version 1607, OS Build 14393.2906)
• The first board I'm trying this on has 8 lists, about 40 visible cards, and 15 archived cards
• Looking at the Fiddler trace, it looks like the API is returning all of the cards relatively quickly (within a second or two of the default query), but it appears that the parsing/processing of the response is what is getting hung up.
• I'm using a paid Manatee.Trello license
• I downloaded the git repo and referenced it in my project instead of using the nuget package. I'm not really familiar with the library code, so I haven't been able to debug fully myself. But it looks like there is a lot of time being spent on line 42 of ReadOnlyActionCollection.cs, which is:

internal ReadOnlyActionCollection(Type type, Func<string> getOwnerId, TrelloAuthorization auth)
    : base(getOwnerId, auth)
{
    _updateRequestType = RequestTypes[type];

    EventAggregator.Subscribe(this);
}

Maybe there is a concurrency performance issue with the lock used in EventAggregator.cs on line 58?:

public static void Subscribe(IHandle subscriber)
{
    if (subscriber == null) throw new ArgumentNullException(nameof(subscriber));

    lock (Handlers)
    {
        if (Handlers.Any(x => x.Matches(subscriber))) return;

        Handlers.Add(new Handler(subscriber));
    }
}

[gregsdennis]

Thanks for the report. I'll check it out.

The event aggregator is actually pulled out of Caliburn.Micro and unchanged (to my recollection). I might be able to remove that lock, but I need to contemplate it first.

[gregsdennis]

Do you need the actions on the cards? Turning off the actions download (via Card.DownloadedFields) might be a workaround for now.

[techfooninja]

No, I don't need actions, and disabling them did return it back to a reasonable performance for my purposes. Thanks for the workaround!

[gregsdennis]

Be aware that comments are actions, too. But if you need them I'd suggest refreshing them separately. Trello's API gets iffy when requesting collections within collections.

[techfooninja]

Thanks for the clarification. For this project, I don't need to access the comments, I just want to make sure they're not being deleted. A brief test shows that comments remain unchanged, which is perfect for my case here.

[gregsdennis]

This might also be related to #306.

@techfooninja, can you update to 3.10.1 and see if you have any improvements? It looks like you're not using consistency processing, so it should be faster for you.