Potential memory leak

I am using CandyGraph to render a large number of plots per view (50-100) with multiples views. I noticed that every time I switch the view back and forth, the memory footprint of my page goes up and up.

After using the memory profiler of Chrome, I found out that 72% of the memory was retained by coordinateScopeCache. It turns out that CandyGraph is caching a Regl DrawCommand for every unique coordinate system in getCoordinateScope:

  private getCoordinateScope(coords: CoordinateSystem) {
    let scope = this.coordinateScopeCache.get(coords);
    if (!scope) {
      scope = coords.scope(this.regl);
      this.coordinateScopeCache.set(coords, scope);
    }
    return scope;
  }

https://github.com/wwwtyro/candygraph/blob/master/src/candygraph.ts#L182-L189

Unless I miss something it looks like this cache is never cleared nor is it clearable by a candygraph user. (Something similar seems to be going on for getCompositeScope().)

This seems to be bad for two reasons:

1. Over time, memory must build up because there’s no way to clear the cache.
2. It’s hard not to slow down the memory build up because coords are created every time a plot is created.

I would propose a function similar to clearPositionBuffers that grants access to the internal coordinateScopeCache and compositeScopeCache. This would allow the user to periodically clear both caches entirely or clear caches upon destruction of a plot (e.g., when I navigate to a new view, I know that I will never re-use the previous coordinate instance again, so I can remove it from the cache)

Actually, why not simply making coordinateScopeCache and compositeScopeCache public? There’s no harm in clearing the cache or is there?

Update: I guess similarly, the commandCache is dangerous as it’s not clearable.

[flekschas]

I agree! Exposing the internals is not a good idea. I actually started working on a solution on Friday and seems to work. I’ll post more details after the weekend but my idea was to automatically remove cached objects/functions when they are disposed because it seems like there would never be a case where one would run a draw command on disposed resources.

[shamrin]

@wwwtyro Thank you! Indeed, I forgot to check the parent class of Scissor.

Good idea on keeping the y-axis!