Specify IAgentRuntime implementation used by a given agent

[virtuallifenl]

What would you like to be added?

I would like to be able to specify the IAgentRuntime implementation used by a given agent.

Proposal(s):

I would like to be able to assign a specific IAgentRuntime derived class per Agent.

For me, it's really not up to me to propose an interface or implementation. I'd be happy to use anything you come up with!

Maybe adding .WithAgentRuntime() to AgentCardBuilder would do the trick, but maybe you don't want to add the Agent Runtime details to the Agent Card.

Alternative(s):

Some alternative interfaces off the top of my head:

Or MapAgentRuntime(Uri, IAgentRuntime)
Or UseAgentRuntime(Func<Uri, IServiceProvider, IAgentRuntime>)
Or UseAgentRuntime(Func<A2AWellKnownAgentCard, IServiceProvider, IAgentRuntime>)

Additional info:

This is the code I'm using now:

var builder = WebApplication.CreateBuilder();

builder.Services.Configure<JsonOptions>(options => {
    options.JsonSerializerOptions.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingDefault;
});
builder.Services.AddDistributedMemoryCache();
builder.Services.AddTransient<IAgentRuntime, AgentRuntime>();
builder.Services.AddA2AWellKnownAgent((provider, builder) => {
    builder
        .WithName("agent1")
        .WithDescription("desc")
        .WithVersion("1")
        .WithProvider(provider => provider
            .WithOrganization("virtuallife")
            .WithUrl(new("https://github.com/virtuallife")))
        .WithUrl(new("/a2a/agent1", UriKind.Relative));

});
builder.Services.AddA2AWellKnownAgent((provider, builder) => {
    builder
        .WithName("agent2")
        .WithDescription("desc")
        .WithVersion("1")
        .WithProvider(provider => provider
            .WithOrganization("virtuallife")
            .WithUrl(new("https://github.com/virtuallife")))
        .WithUrl(new("/a2a/agent2", UriKind.Relative));

});
builder.Services.AddA2AProtocolServer(builder => {
    builder
        .UseAgentRuntime(provider => provider.GetRequiredService<IAgentRuntime>())
        .UseDistributedCacheTaskRepository();
});

var app = builder.Build();
app.MapA2AWellKnownAgentEndpoint();
app.MapA2AHttpEndpoint("/a2a/agent1");
app.MapA2AHttpEndpoint("/a2a/agent2");`

So the client sees both agents on the card. One with endpoint /a2a/agent1 and one with endpoint /a2a/agent2.
The client chooses which agent to talk to by using the correct endpoint.

No matter what endpoint the client uses, the request ends up in an instance of the singular AgentRuntime class set here:
.UseAgentRuntime(provider => provider.GetRequiredService<IAgentRuntime>())"

And once there, the TaskRecord does not contain any information for the AgentRuntime to distinguish between agent1 and agent2.

Therefore, I would like to be able to assign a specific IAgentRuntime derived class per Agent.

Community Notes

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[brandonh-msft]

In my opinion this is an anti-pattern for a few reasons:

1. Single Responsibility Principle: Having an endpoint serve up multiple cards is not (registry behavior) but having an endpoint implement multiple agents is, at least to me.
2. Scale: One of those agents could take a while to complete its work, and then a request comes in for the other agent while the first one is busy, CPU is getting used, etc. Now the scale controller has to scale out just for agent 2 because agent 1 is consuming resources, while agent 2 may only take a second or two to complete. Effectively, you're combining the resources required for both agents under the same umbrella (host machine) which I would advise against.
3. Deployment: If you want to change the behavior of agent 2, you're now having to deploy and restart agent 1 alongside it.

So, my opinion is that it's correct that IAgentRuntime be used for a single agent and not support multiple agent runtimes in the same process.
I haven't explored an example yet, but my gut tells me there's probably a workaround here anyway by using KeyedSingleton services while injecting the IServiceProvider (instead of IAgentRuntime) to pull out the right instance based on the agent you're in. But I don't think A2A.Net should enable this behavior "natively".

[virtuallifenl]

Good point on single responsibility. I agree that a single IAgentRuntime derived class should represent a single agent.

But since we can offer multiple cards within a single ASP.Net host, I do also suggest we can also host multiple agent runtime implementations in one ASP.Net host. Which does not mean one host machine - the same code can be deployed on multiple machines for scalability ofcourse.

In my opinion, this way your concerns are met:

1. Every implementation of IAgentRuntime still has one responsibility.
2. It is still easily scalable because the API can run in a scalable environment (like kubernetes) with a load balancer in front of it, routing to multiple instances on multiple host machines but using the same code base.
3. It's easier to deploy multiple agents at once while it's still also easy to update just one agent.

And it leaves more choice to the user of the library. If the user does want to have one agent per host in a seperate code project - still possible. If the user wants multiple agents in one code base like I do - also possible.

If the library owner does not wish to implement this, I would kindly request an enhanced example that uses the proposed KeyedSingleton to allow this behaviour. The only way I know how to implement it is a lot of work-around code to make something work that should be easy.

Unfortunately, I'm not as good a programmer as the two of you are, so coming up with a PR is out of my league I'm afraid.

[elementhrobbie]

It would be good and useful to have a class MyFirstAgentImplementation implementing IAgentRuntime and a MySecondAgentImplementation implementing IAgentRuntime and add those (with wellknown agents json) to the Web Application Builder.

[cdavernas]

@brandonh-msft WDYT? I think @virtuallifenl made a good point and, even though I tend to agree with you, I guess this decision should ultimately be up to the end user, don't you agree?

[brandonh-msft]

@brandonh-msft WDYT? I think @virtuallifenl made a good point and, even though I tend to agree with you, I guess this decision should ultimately be up to the end user, don't you agree?

It's up to what you want to maintain :)
Effectively you'd have to implement usage of KeyedSingleton for the IAgentRuntime objects you register.