DataCore.Adapter.Http.Proxy

DataCore.Adapter.Http.Proxy

Proxy adapter that connects to a remote adapter via HTTP.

Installation

Add a NuGet package reference to IntelligentPlant.AppStoreConnect.Adapter.Http.Proxy.

Creating a Proxy Instance

var options = new HttpAdapterProxyOptions() {
    Id = "some-id",
    Name = "some-name",
    RemoteId = "{SOME_ADAPTER_ID}"
};

var httpClient = new HttpClient() {
    BaseAddress = "https://my-site.com/"
};
var adapterHttpClient = new AdapterHttpClient(httpClient);

var proxy = new HttpAdapterProxy(adapterHttpClient, Options.Create(options), NullLoggerFactory.Instance);
await proxy.StartAsync(cancellationToken);

Using the Proxy

You can use the proxy as you would any other IAdapter instance:

var readRaw = proxy.Features.Get<IReadRawTagValues>();

var now = DateTime.UtcNow;

await foreach (var item in readRaw.ReadRawTagValues(context, new ReadRawTagValuesRequest() {
    Tags = new[] { "Sensor_001", "Sensor_002" },
    UtcStartTime = now.Subtract(TimeSpan.FromDays(7)),
    UtcEndTime = now,
    SampleCount = 0, // i.e. all raw values inside the time range
    BoundaryType = RawDataBoundaryType.Inside
}, cancellationToken)) {
    DoSomethingWithValue(item);
}

Implementing Per-Call Authentication

Per-call authentication can be applied by configuring the proxy's underlying HttpClient to use a DelegatingHandler that will set appropriate headers on outgoing HTTP requests. The static CreateRequestTransformHandler method on the AdapterHttpClient class can be used to create an appropriate handler:

public void ConfigureServices(IServiceCollection services) {

    services.AddHttpClient("AdapterProxy", options => {
        options.BaseAddress = new Uri("https://my-site.com/");
    })
    .AddHttpMessageHandler(AdapterHttpClient.CreateRequestTransformHandler(async (request, principal, cancellationToken) => {
        if (principal == null) {
            return;
        }

        string accessToken;

        // Add your logic to get the access token for the principal...

        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
    }));

}

You can then use this client when creating the AdapterHttpClient that is passed to the proxy:

async Task<IAdapter> CreateProxy(IHttpClientFactory factory) {
    var options = new HttpAdapterProxyOptions() {
        Id = "some-id",
        Name = "some-name",
        RemoteId = "{SOME_ADAPTER_ID}"
    };

    var httpClient = factory.CreateClient("AdapterProxy");
    var adapterHttpClient = new AdapterHttpClient(httpClient);

    var proxy = new HttpAdapterProxy(httpClient, Options.Create(options), NullLoggerFactory.Instance);
    await proxy.StartAsync(cancellationToken);

    return proxy;
}

The ClaimsPrincipal that is passed to the callback delegate is passed through from the IAdapterCallContext that is specified when an adapter feature method is called.

Enabling SignalR Functionality

By default, the HTTP proxy cannot enable any features that use long-running subscriptions (such as snapshot tag value and event message subscriptions). However, if the remote host has the adapter SignalR API enabled, the HTTP proxy can enable these features via SignalR connections.

SignalR functionality is enabled by configuring the SignalROptions property on the HttpAdapterProxyOptions class:

var options = new HttpAdapterProxyOptions() {
    Id = "some-id",
    Name = "some-name",
    RemoteId = "{SOME_ADAPTER_ID}",
    SignalROptions = new SignalROptions {
        TimeToLive = TimeSpan.FromSeconds(30),
        ConnectionFactory = (Uri url, IAdapterCallContext context) => new HubConnectionBuilder()
            .WithDataCoreAdapterConnection(url)
            .WithAutomaticReconnect()
            .Build()
    }
};

The proxy creates a separate connection for each calling identity. By default, a connection is uniquely identified using the ClaimTypes.NameIdentifier claim for the calling user, falling back to the ClaimTypes.Name claim. You can assign a delegate to the SignalROptions.ConnectionIdentityFactory property to customise the identity for a given caller.

The SignalROptions.TimeToLive property defines the time that a connection will remain open for when there are no active subscriptions for the connection.

If HttpAdapterProxyOptions.SignalROptions is null, SignalR capabilities are disabled. If the HttpAdapterProxyOptions.CompatibilityVersion property is set to Version_3_0 or higher, the proxy will make an HTTP API call to the remote host to confirm if the SignalR API is available before enabling features that require SignalR. For lower compatibility versions, specifying a non-null HttpAdapterProxyOptions.SignalROptions value will assume that the SignalR API is available.