[Question]: Complex Pipeline Keys documentation example not working as expected

[jwagon]

What are you wanting to achieve?

Hi,

I copied the code from from here:

https://www.pollydocs.org/advanced/dependency-injection.html#complex-pipeline-keys

Exactly into my project, but I kept getting "unable to find a resilience pipeline" exceptions.

What code or approach do you have so far?

When I looked through the code, specifically here:

Polly/src/Polly.Core/Registry/ResiliencePipelineRegistry.cs

Line 76 in 0e134b5

if (_pipelines.TryGetValue(key, out pipeline))

public override bool TryGetPipeline(TKey key, [NotNullWhen(true)] out ResiliencePipeline? pipeline)
    {
        EnsureNotDisposed();

        if (_pipelines.TryGetValue(key, out pipeline))
        {
            return true;
        }

        if (_builders.TryGetValue(key, out var configure))
        {
            pipeline = GetOrAddPipeline(key, configure);
            return true;
        }

        pipeline = null;
        return false;
    }

It seems like if there is no pipeline defined with the key specified, like in your example:

 ResiliencePipeline instanceA = pipelineProvider.GetPipeline(new MyPipelineKey(ResiliencePipelines.NetSuite, "instance-A"));

It should go ahead and look in the _builders dictionary and build a new pipeline, with that new key, adding it to _pipelines, correct?

But I think (?) the problem is that in your example, PipelineNameComparer.GetHashCode takes the InstanceName into account:

public sealed class PipelineNameComparer : IEqualityComparer<MyPipelineKey>
{
    public bool Equals(MyPipelineKey x, MyPipelineKey y) => x.PipelineName == y.PipelineName;

    public int GetHashCode(MyPipelineKey obj) => (obj.PipelineName, obj.InstanceName).GetHashCode(); // <--- InstanceName is respected here, but maybe it shouldn't be?
}

I think (?) paying attention to InstanceName breaks your example, because when the key search in _builders (above) happens, it won't find any values.

Further, if I change that GetHashCode function to look like this, things work as I'd expect:

    public int GetHashCode(MyPipelineKey obj) => obj.PipelineName.GetHashCode();

I'm not sure what I might be breaking by making that change though, or if I'm just doing something else wrong somewhere.

Thoughts?

Additional context

No response

[martintmk]

@jwagon

You are correct in your investigation. The PipelineNameComparer should not include InstanceName. Fix is quite straightforward, I can do it over the weekend or you can open the PR yourself.

[jwagon]

@jwagon

You are correct in your investigation. The PipelineNameComparer should not include InstanceName. Fix is quite straightforward, I can do it over the weekend or you can open the PR yourself.

@martintmk

PR opened, lemme know if I missed anything.