Remove EventGridClient altogether and use HTTP REST calls for Event Grid

[Jandev]

To make this package as light as possible and remove the dependencies to Azure Event Grid packages it would be great to use the REST API to publish events on Event Grid.

This will take some rework in the overall design, but should be quite doable.

[jayendranarumugam]

Hi @Jandev , I'm planning to implement like this

HttpContent httpContent = new StringContent(JsonConvert.SerializeObject(eventGridEventCollection) , UTF8Encoding.UTF8, "application/json");
httpContent.Headers.Add("aeg-sas-key", topicKey);
await httpClient.PostAsync(topicEndPoint, httpContent, cancellationToken);

Where the httpClient will be initialized and injected at the constructor itself

 public EventGridAsyncCollector(EventGridAttribute attribute)
        {
            this.eventCollection = new List<Event>();
            this.httpClient = new HttpClient();
            this.topicEndPoint = new Uri(attribute.TopicEndpoint).ToString();
            this.topicKey = attribute.TopicKey;
        }

Any comments on this?

[Jandev]

Looks like a great start.
The HttpClient should also be possible to be injected by the client/Function, for inspiration you can check my HTTP Binding or use something like dependency injection by registering a named HTTP Client in the EventGridStartup.

The goal is to get rid of the EventGrid package to slim down this one. I think this means the model of the Event Grid events should also be implemented in this binding.

I'm on my phone now, so can't check the code. Will be able to check it on Monday. But, as I mentioned, these samples of pseudo code look very promising.

Update
From what I'm reading in the docs, we indeed need to have a model which matches the Event Grid model for an event and send this to the REST endpoint.

[jayendranarumugam]

Hi @Jandev , I was referring your Http Binding link and came up with like this

EventGridAttribute model by including the httpclient

public HttpClient HttpClient { get; set; }

EventGridBinding.cs

 public class EventGridBinding : IExtensionConfigProvider
    {
        internal static HttpClient HttpClient;

        public void Initialize(ExtensionConfigContext context)
        {
            var ruleCommand = context.AddBindingRule<EventGridAttribute>();
            ruleCommand.BindToInput(BuildFromAttribute);
            ruleCommand.BindToCollector(attribute => new EventGridAsyncCollector(attribute));
        }

        private HttpClient BuildFromAttribute(EventGridAttribute attribute)
        {
            if (HttpClient == null)
            {
                HttpClient = attribute.HttpClient ?? new HttpClient();
            }

            return HttpClient;
        }
    }

The Problem I'm getting is always the HttpClient is getting null from the client, No breakpoint also hitting inisde the BuildFromAttribute . I'm thinking like I used BindtoInput which means its not able to work under collector . Could you please help here?

[Jandev]

Great effort!

I think it's because the BindToInput is only meant for input-binding. This Event Grid binding is an output binding, so the BuildFromAttribute will indeed never be invoked.

If you check the HttpCommandAsyncCollector in the other repository, you'll see I'm doing the same 3 lines in the AddAsync.

My guess is, the AddAsync needs to change into something like the following:

public Task AddAsync(Event item, CancellationToken cancellationToken = new CancellationToken())
{
	if (HttpBinding.HttpClient == null)
	{
	    HttpBinding.HttpClient = attribute.HttpClient ?? new HttpClient();
	}
    this.eventCollection.Add(item);

    return Task.CompletedTask;
}

Just like in the HttpBinding repository.

If I recall correct events are sent using a POST, so the FlushAsync will have to be changed to do a POST with the body & headers like you proposed earlier.

I'm not able to check & test it at the moment though, so I'm guessing a bit over here.

[jayendranarumugam]

Hi @Jandev , Thanks for all your support ! I've just drafted a #16 . Could you please review that and provide your feedback