feat: unix socket support for flagd provider (#42)

Signed-off-by: Florian Bacher <[email protected]>

Author: bacherfl

.github/workflows/linux-ci.yml

@@ -16,7 +16,7 @@ jobs:
 
     strategy:
       matrix:
-        version: [net6.0]
+        version: [net6.0,net7.0]
 
     steps:
     - uses: actions/checkout@v3

.github/workflows/windows-ci.yml

@@ -16,7 +16,7 @@ jobs:
 
     strategy:
       matrix:
-        version: [net462,net6.0]
+        version: [net462,net6.0,net7.0]
 
     steps:
     - uses: actions/checkout@v3

build/Common.prod.props

@@ -6,7 +6,7 @@
   </PropertyGroup>
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;net462</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;net462;net5.0;net6.0;net7.0</TargetFrameworks>
     <RepositoryType>git</RepositoryType>
     <RepositoryUrl>https://github.com/open-feature/dotnet-sdk</RepositoryUrl>
     <Description>OpenFeature is an open standard for feature flag management, created to support a robust feature flag ecosystem using cloud native technologies. OpenFeature will provide a unified API and SDK, and a developer-first, cloud-native implementation, with extensibility for open source and commercial offerings.</Description>

src/OpenFeature.Contrib.Providers.Flagd/FlagdProvider.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Linq;
 using System.Threading.Tasks;
+
 using Google.Protobuf.WellKnownTypes;
 using Grpc.Core;
 using Grpc.Net.Client;
@@ -12,6 +13,7 @@
 using Value = OpenFeature.Model.Value;
 using ProtoValue = Google.Protobuf.WellKnownTypes.Value;
 using System.Net.Http;
+using System.Net.Sockets;
 
 namespace OpenFeature.Contrib.Providers.Flagd
 {
@@ -26,27 +28,38 @@ public sealed class FlagdProvider : FeatureProvider
         /// <summary>
         ///     Constructor of the provider. This constructor uses the value of the following
         ///     environment variables to initialise its client:
-        ///     FLAGD_HOST - The host name of the flagd server (default="localhost")
-        ///     FLAGD_PORT - The port of the flagd server (default="8013")
-        ///     FLAGD_TLS  - Determines whether to use https or not (default="false")
+        ///     FLAGD_HOST         - The host name of the flagd server (default="localhost")
+        ///     FLAGD_PORT         - The port of the flagd server (default="8013")
+        ///     FLAGD_TLS          - Determines whether to use https or not (default="false")
+        ///     FLAGD_SOCKET_PATH - Path to the unix socket (default="")
         /// </summary>
         public FlagdProvider()
         {
             var flagdHost = Environment.GetEnvironmentVariable("FLAGD_HOST") ?? "localhost";
             var flagdPort = Environment.GetEnvironmentVariable("FLAGD_PORT") ?? "8013";
             var flagdUseTLSStr = Environment.GetEnvironmentVariable("FLAGD_TLS") ?? "false";
+            var flagdSocketPath = Environment.GetEnvironmentVariable("FLAGD_SOCKET_PATH") ?? "";
 
 
-            var protocol = "http";
-            var useTLS = bool.Parse(flagdUseTLSStr);
-
-            if (useTLS)
+            Uri uri;
+            if (flagdSocketPath != "")
             {
-                protocol = "https";
+                uri = new Uri("unix://" + flagdSocketPath);
             }
+            else
+            {
+                var protocol = "http";
+                var useTLS = bool.Parse(flagdUseTLSStr);
 
-            var url = new Uri(protocol + "://" + flagdHost + ":" + flagdPort);
-            _client = buildClientForPlatform(url);
+                if (useTLS)
+                {
+                    protocol = "https";
+                }
+
+                uri = new Uri(protocol + "://" + flagdHost + ":" + flagdPort);
+            }
+
+            _client = buildClientForPlatform(uri);
         }
 
         /// <summary>
@@ -373,14 +386,37 @@ private static Value ConvertToPrimitiveValue(ProtoValue value)
 
         private static Service.ServiceClient buildClientForPlatform(Uri url)
         {
-#if NETSTANDARD2_0
-            return new Service.ServiceClient(GrpcChannel.ForAddress(url));
+            var useUnixSocket = url.ToString().StartsWith("unix://");
+
+            if (!useUnixSocket)
+            {
+#if NET462
+                 return new Service.ServiceClient(GrpcChannel.ForAddress(url, new GrpcChannelOptions
+                {
+                    HttpHandler = new WinHttpHandler()
+                }));
 #else
-            return new Service.ServiceClient(GrpcChannel.ForAddress(url, new GrpcChannelOptions
+                return new Service.ServiceClient(GrpcChannel.ForAddress(url));
+#endif
+            }
+
+#if NET5_0_OR_GREATER
+            var udsEndPoint = new UnixDomainSocketEndPoint(url.ToString().Substring("unix://".Length));
+            var connectionFactory = new UnixDomainSocketConnectionFactory(udsEndPoint);
+            var socketsHttpHandler = new SocketsHttpHandler
+            {
+                ConnectCallback = connectionFactory.ConnectAsync
+            };
+            
+            // point to localhost and let the custom ConnectCallback handle the communication over the unix socket
+            // see https://learn.microsoft.com/en-us/aspnet/core/grpc/interprocess-uds?view=aspnetcore-7.0 for more details
+            return new Service.ServiceClient(GrpcChannel.ForAddress("http://localhost", new GrpcChannelOptions
             {
-                HttpHandler = new WinHttpHandler()
+                HttpHandler = socketsHttpHandler
             }));
 #endif
+            // unix socket support is not available in this dotnet version
+            throw new Exception("unix sockets are not supported in this version.");
         }
     }
 }

src/OpenFeature.Contrib.Providers.Flagd/README.md

@@ -76,21 +76,29 @@ namespace OpenFeatureTestApp
 
 The URI of the flagd server to which the `flagd Provider` connects to can either be passed directly to the constructor, or be configured using the following environment variables:
 
-| Option name           | Environment variable name       | Type    | Default   | Values        |
-| --------------------- | ------------------------------- | ------- | --------- | ------------- |
-| host                  | FLAGD_HOST                      | string  | localhost |               |
-| port                  | FLAGD_PORT                      | number  | 8013      |               |
-| tls                   | FLAGD_TLS                       | boolean | false     |               |
+| Option name      | Environment variable name      | Type    | Default   | Values        |
+|------------------|--------------------------------|---------|-----------| ------------- |
+| host             | FLAGD_HOST                     | string  | localhost |               |
+| port             | FLAGD_PORT                     | number  | 8013      |               |
+| tls              | FLAGD_TLS                      | boolean | false     |               |
+| unix socket path | FLAGD_SOCKET_PATH              | string  |           |               |
 
-So for example, if you would like to pass the URI directly, you can initialise it as follows:
+Note that if `FLAGD_SOCKET_PATH` is set, this value takes precedence, and the other variables (`FLAGD_HOST`, `FLAGD_PORT`, `FLAGD_TLS`) are disregarded.
+
+
+If you rely on the environment variables listed above, you can use the empty constructor which then configures the provider accordingly:
 
 ```csharp
-var flagdProvider = new FlagdProvider(new Uri("http://localhost:8013"));
+var flagdProvider = new FlagdProvider();
 ```
 
-Or, if you rely on the environment variables listed above, you can use the empty costructor:
-
+Alternatively, if you would like to pass the URI directly, you can initialise it as follows:
 
 ```csharp
-var flagdProvider = new FlagdProvider();
+// either communicate with Flagd over HTTP ...
+var flagdProvider = new FlagdProvider(new Uri("http://localhost:8013"));
+
+// ... or use the unix:// prefix if the provider should communicate via a unix socket
+var unixFlagdProvider = new FlagdProvider(new Uri("unix://socket.tmp"));  
 ```
+

src/OpenFeature.Contrib.Providers.Flagd/UnixDomainSocketConnectionFactory.cs

@@ -0,0 +1,49 @@
+using System;
+using System.IO;
+using System.Net;
+using System.Net.Http;
+using System.Net.Sockets;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace OpenFeature.Contrib.Providers.Flagd
+{
+    /// <inheritdoc/>
+    public class UnixDomainSocketConnectionFactory
+    {
+        private readonly EndPoint _endPoint;
+
+        /// <summary>
+        ///     Constructor of the connection factory
+        ///     <param name="endpoint">The path to the unix socket</param>
+        /// </summary>
+        public UnixDomainSocketConnectionFactory(EndPoint endpoint)
+        {
+            _endPoint = endpoint;
+        }
+
+#if NET5_0_OR_GREATER
+        /// <summary>   
+        ///     ConnectAsync is a custom implementation of the ConnectAsync method used by the grpc client
+        /// </summary>
+        /// <param name="_">unused - SocketsHttpConnectionContext</param>
+        /// <param name="cancellationToken">The cancellation token</param>
+        /// <returns>A ValueTask object representing the given</returns>
+        public async ValueTask<Stream> ConnectAsync(SocketsHttpConnectionContext _, CancellationToken cancellationToken = default)
+        {
+            var socket = new Socket(AddressFamily.Unix, SocketType.Stream, ProtocolType.Unspecified);
+
+            try
+            {
+                await socket.ConnectAsync(_endPoint, cancellationToken).ConfigureAwait(false);
+                return new NetworkStream(socket, true);
+            }
+            catch (Exception ex)
+            {
+                socket.Dispose();
+                throw new HttpRequestException($"Error connecting to '{_endPoint}'.", ex);
+            }
+        }
+#endif
+    }
+}