feat!: supports multi endpoints

.github/workflows/ci.yml

@@ -70,34 +70,10 @@ jobs:
       - name: Unit Tests
         run: dotnet test tests/GreptimeDB.Ingester.Tests --no-build --configuration Release --verbosity normal
 
-  compatibility-net6-net7:
-    name: Compatibility (net6/net7)
-    runs-on: ubuntu-latest
-
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v6
-        with:
-          submodules: recursive
-
-      - name: Setup .NET
-        uses: actions/setup-dotnet@v5
-        with:
-          dotnet-version: 10.0.x
-
-      - name: Restore
-        run: dotnet restore
-
-      - name: Build net6.0
-        run: dotnet build src/GreptimeDB.Ingester/GreptimeDB.Ingester.csproj --no-restore --configuration Release -f net6.0
-
-      - name: Build net7.0
-        run: dotnet build src/GreptimeDB.Ingester/GreptimeDB.Ingester.csproj --no-restore --configuration Release -f net7.0
-
   integration-tests:
     name: Integration Tests
     runs-on: ubuntu-latest
-    needs: [build, compatibility-net6-net7]
+    needs: [build]
 
     steps:
       - name: Checkout

CHANGELOG.md

@@ -0,0 +1,36 @@
+# Changelog
+
+All notable changes to this project are documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Added
+
+- Multi-endpoint support via `GreptimeClientOptions.Endpoints` (`IList<string>`).
+  Supplying more than one endpoint enables client-side load balancing with
+  automatic failover across endpoints. Single-element lists behave as the
+  previous single-node case. Backed by `Grpc.Net.Client.Balancer`.
+- `GreptimeClientOptions.LoadBalancing` (`LoadBalancingStrategy`) selects the
+  multi-endpoint balancing policy. Supported: `Random` (default — picks a
+  ready endpoint uniformly at random per call, avoiding the herding pattern
+  that round-robin can produce when many short-lived clients start at the
+  same time) and `RoundRobin`.
+
+### Changed
+
+- **BREAKING:** Dropped `net6.0` and `net7.0` target frameworks. Minimum
+  supported runtime is now `net8.0`. Both removed TFMs are past Microsoft's
+  end-of-support, and `Grpc.Net.Client.Balancer` (required for the new
+  multi-endpoint client-side load balancer) is only shipped in the package's
+  `net8.0+` build, not its `netstandard2.1` build.
+  Users on `net6.0` / `net7.0` should pin to the `0.1.x` line, which keeps
+  those TFMs supported.
+
+### Deprecated
+
+- `GreptimeClientOptions.Endpoint` (single-endpoint string). Use
+  `GreptimeClientOptions.Endpoints` instead. The property is retained for
+  backward compatibility and will be removed in a future release.

Directory.Build.props

@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup>
-    <TargetFrameworks>net6.0;net7.0;net8.0;net9.0;net10.0</TargetFrameworks>
+    <TargetFrameworks>net8.0;net9.0;net10.0</TargetFrameworks>
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
     <LangVersion>latest</LangVersion>

Directory.Packages.props

@@ -14,6 +14,7 @@
     <PackageVersion Include="Apache.Arrow.Flight" Version="22.1.0" />
 
     <!-- DI and Configuration -->
+    <PackageVersion Include="Microsoft.Extensions.DependencyInjection" Version="10.0.5" />
     <PackageVersion Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.5" />
     <PackageVersion Include="Microsoft.Extensions.Options" Version="10.0.5" />
     <PackageVersion Include="Microsoft.Extensions.Logging.Abstractions" Version="10.0.5" />

README.md

@@ -5,7 +5,7 @@
 [![NuGet Downloads](https://img.shields.io/nuget/dt/GreptimeDB.Ingester.svg)](https://www.nuget.org/packages/GreptimeDB.Ingester)
 [![NuGet Grpc](https://img.shields.io/nuget/v/GreptimeDB.Ingester.Grpc.svg)](https://www.nuget.org/packages/GreptimeDB.Ingester.Grpc)
 [![License](https://img.shields.io/badge/license-Apache%202.0-blue.svg)](LICENSE)
-![.NET](https://img.shields.io/badge/.NET-6.0%20%7C%207.0%20%7C%208.0%20%7C%209.0%20%7C%2010.0-purple)
+![.NET](https://img.shields.io/badge/.NET-8.0%20%7C%209.0%20%7C%2010.0-purple)
 
 .NET SDK for writing data to [GreptimeDB](https://github.com/GreptimeTeam/greptimedb).
 
@@ -19,6 +19,13 @@
 dotnet add package GreptimeDB.Ingester
 ```
 
+> **.NET 6.0 / 7.0 users:** the latest version requires .NET 8.0 or newer.
+> Stay on the `0.1.x` line for net6.0 / net7.0 support:
+>
+> ```bash
+> dotnet add package GreptimeDB.Ingester --version 0.1.*
+> ```
+
 ## Quick Start
 
 ```csharp
@@ -29,7 +36,7 @@ using GreptimeDB.Ingester.Types;
 // Create client
 var client = new GreptimeClient(new GreptimeClientOptions
 {
-    Endpoint = "http://localhost:4001",
+    Endpoints = new List<string> { "http://localhost:4001" },
     Database = "public"
 });
 
@@ -54,7 +61,7 @@ await client.DisposeAsync();
 ```csharp
 var client = new GreptimeClient(new GreptimeClientOptions
 {
-    Endpoint = "http://localhost:4001",
+    Endpoints = new List<string> { "http://localhost:4001" },
     Database = "public",
     ConnectTimeout = TimeSpan.FromSeconds(5),
     WriteTimeout = TimeSpan.FromSeconds(30)
@@ -66,7 +73,7 @@ With basic auth:
 ```csharp
 var client = new GreptimeClient(new GreptimeClientOptions
 {
-    Endpoint = "http://localhost:4001",
+    Endpoints = new List<string> { "http://localhost:4001" },
     Database = "public",
     Authentication = new AuthenticationOptions
     {
@@ -76,11 +83,53 @@ var client = new GreptimeClient(new GreptimeClientOptions
 });
 ```
 
+## Multiple Endpoints
+
+Pass more than one endpoint to enable client-side load balancing and failover
+across a GreptimeDB cluster:
+
+```csharp
+var client = new GreptimeClient(new GreptimeClientOptions
+{
+    Endpoints = new List<string>
+    {
+        "http://node-a:4001",
+        "http://node-b:4001",
+        "http://node-c:4001",
+    },
+    Database = "public",
+});
+```
+
+A single-element list takes the direct-channel fast path (no balancer); two
+or more endpoints route through `Grpc.Net.Client.Balancer` with the configured
+strategy. All endpoints must share the same scheme (all `http` or all `https`)
+and must be plain `host:port` URIs without a path/query/fragment.
+
+### Load-balancing strategy
+
+`LoadBalancing` selects the policy used in the multi-endpoint case:
+
+```csharp
+new GreptimeClientOptions
+{
+    Endpoints = new List<string> { "http://node-a:4001", "http://node-b:4001" },
+    LoadBalancing = LoadBalancingStrategy.Random,     // default
+    // LoadBalancing = LoadBalancingStrategy.RoundRobin,
+};
+```
+
+- `Random` (default) — pick a ready endpoint uniformly at random per call.
+  Avoids the herding pattern that round-robin can produce when many
+  short-lived clients start simultaneously.
+- `RoundRobin` — cycle through ready endpoints in order.
+
 ## Features
 
 - **Unary Write** - Simple single-request writes via gRPC
 - **Streaming Write** - High-throughput streaming via gRPC for multiple tables
 - **Bulk Write** - Maximum throughput via Apache Arrow Flight
+- Multi-endpoint client-side load balancing (random / round-robin) with failover
 - Type coercion between .NET and GreptimeDB types
 - Health check
 - DI integration
@@ -176,7 +225,7 @@ catch (GreptimeDB.Ingester.Exceptions.GreptimeException ex)
 ```csharp
 services.AddGreptimeClient(options =>
 {
-    options.Endpoint = "http://localhost:4001";
+    options.Endpoints = new List<string> { "http://localhost:4001" };
     options.Database = "public";
 });
 ```

examples/benchmark.cs

@@ -25,7 +25,7 @@
 // --- Health check ---
 var client = new GreptimeClient(new GreptimeClientOptions
 {
-    Endpoint = endpoint,
+    Endpoints = new List<string> { endpoint },
     Database = database,
     WriteTimeout = TimeSpan.FromSeconds(120)
 });

examples/quick-test.cs

@@ -9,7 +9,7 @@
 // --- Write via gRPC ---
 var client = new GreptimeClient(new GreptimeClientOptions
 {
-    Endpoint = "http://localhost:4001",
+    Endpoints = new List<string> { "http://localhost:4001" },
     Database = "public"
 });
 

src/GreptimeDB.Ingester/Arrow/RecordBatchBuilder.cs

@@ -357,14 +357,7 @@ private static Time64Array BuildTime64Array(Table.Table table, int columnIndex,
 
     private void ThrowIfDisposed()
     {
-#if NET7_0_OR_GREATER
         ObjectDisposedException.ThrowIf(_disposed, this);
-#else
-        if (_disposed)
-        {
-            throw new ObjectDisposedException(nameof(RecordBatchBuilder));
-        }
-#endif
     }
 
     public void Dispose()

src/GreptimeDB.Ingester/Client/BulkWriter.cs

@@ -264,14 +264,7 @@ private async Task RunRecvLoopAsync(IAsyncStreamReader<FlightPutResult> response
 
     private void ThrowIfDisposed()
     {
-#if NET7_0_OR_GREATER
         ObjectDisposedException.ThrowIf(_disposed == 1, this);
-#else
-        if (_disposed == 1)
-        {
-            throw new ObjectDisposedException(nameof(BulkWriter));
-        }
-#endif
     }
 
     private void ThrowIfCompleted()

src/GreptimeDB.Ingester/Client/GreptimeClient.cs

@@ -4,6 +4,9 @@
 using GreptimeDB.Ingester.Internal;
 using Grpc.Core;
 using Grpc.Net.Client;
+using Grpc.Net.Client.Balancer;
+using Grpc.Net.Client.Configuration;
+using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Logging.Abstractions;
 
@@ -18,6 +21,7 @@ public sealed partial class GreptimeClient : IAsyncDisposable, IDisposable
     private readonly ILoggerFactory _loggerFactory;
     private readonly ILogger _logger;
     private readonly GrpcChannel _channel;
+    private readonly ServiceProvider? _channelServices;
     private readonly GreptimeDatabase.GreptimeDatabaseClient _client;
     private readonly HealthCheck.HealthCheckClient _healthClient;
     private readonly Lazy<FlightClient> _flightClient;
@@ -35,14 +39,13 @@ public GreptimeClient(GreptimeClientOptions options, ILoggerFactory? loggerFacto
         _loggerFactory = loggerFactory ?? NullLoggerFactory.Instance;
         _logger = _loggerFactory.CreateLogger<GreptimeClient>();
 
-        var channelOptions = new GrpcChannelOptions();
-
-        _channel = GrpcChannel.ForAddress(options.Endpoint, channelOptions);
+        var endpoints = options.ResolveEndpoints();
+        (_channel, _channelServices) = BuildChannel(endpoints, options.LoadBalancing);
         _client = new GreptimeDatabase.GreptimeDatabaseClient(_channel);
         _healthClient = new HealthCheck.HealthCheckClient(_channel);
         _flightClient = new Lazy<FlightClient>(() => new FlightClient(_channel));
 
-        LogClientCreated(_logger, options.Endpoint);
+        LogClientCreated(_logger, endpoints.Count, endpoints[0]);
     }
 
     /// <summary>
@@ -265,6 +268,11 @@ public async Task CloseAsync()
         _disposed = true;
         await DisposeFlightClientAsync().ConfigureAwait(false);
         await _channel.ShutdownAsync().ConfigureAwait(false);
+        _channel.Dispose();
+        if (_channelServices is not null)
+        {
+            await _channelServices.DisposeAsync().ConfigureAwait(false);
+        }
         LogClientClosed(_logger);
     }
 
@@ -285,6 +293,7 @@ public void Dispose()
         _disposed = true;
         DisposeFlightClient();
         _channel.Dispose();
+        _channelServices?.Dispose();
         LogClientDisposed(_logger);
     }
 
@@ -349,6 +358,59 @@ private CallOptions CreateCallOptions(CancellationToken cancellationToken)
             cancellationToken: cancellationToken);
     }
 
+    private static (GrpcChannel Channel, ServiceProvider? Services) BuildChannel(
+        IReadOnlyList<string> endpoints,
+        LoadBalancingStrategy strategy)
+    {
+        // Single endpoint: skip the balancer entirely. This preserves the original
+        // direct-channel behavior, including default TLS authority/SNI handling for
+        // https endpoints (the balancer path uses a synthetic channel authority,
+        // which can break certificate hostname validation).
+        if (endpoints.Count == 1)
+        {
+            return (GrpcChannel.ForAddress(endpoints[0]), null);
+        }
+
+        var addresses = new List<BalancerAddress>(endpoints.Count);
+        string? scheme = null;
+        foreach (var endpoint in endpoints)
+        {
+            var uri = new Uri(endpoint, UriKind.Absolute);
+            scheme ??= uri.Scheme;
+            addresses.Add(new BalancerAddress(uri.DnsSafeHost, uri.Port));
+        }
+
+        var services = new ServiceCollection();
+        services.AddSingleton<ResolverFactory>(new StaticResolverFactory(addresses));
+        if (strategy == LoadBalancingStrategy.Random)
+        {
+            services.AddSingleton<LoadBalancerFactory>(RandomBalancerFactory.Instance);
+        }
+        var serviceProvider = services.BuildServiceProvider();
+
+        LoadBalancingConfig lbConfig = strategy switch
+        {
+            LoadBalancingStrategy.Random => new RandomConfig(),
+            LoadBalancingStrategy.RoundRobin => new RoundRobinConfig(),
+            _ => throw new ArgumentOutOfRangeException(nameof(strategy), strategy, "Unsupported load-balancing strategy."),
+        };
+
+        var channelOptions = new GrpcChannelOptions
+        {
+            ServiceProvider = serviceProvider,
+            ServiceConfig = new ServiceConfig
+            {
+                LoadBalancingConfigs = { lbConfig }
+            },
+            Credentials = scheme == Uri.UriSchemeHttps
+                ? ChannelCredentials.SecureSsl
+                : ChannelCredentials.Insecure
+        };
+
+        var channel = GrpcChannel.ForAddress("static:///greptime", channelOptions);
+        return (channel, serviceProvider);
+    }
+
     private static void CheckResponse(GreptimeResponse response)
     {
         var header = response.Header;
@@ -361,20 +423,13 @@ private static void CheckResponse(GreptimeResponse response)
 
     private void ThrowIfDisposed()
     {
-#if NET7_0_OR_GREATER
         ObjectDisposedException.ThrowIf(_disposed, this);
-#else
-        if (_disposed)
-        {
-            throw new ObjectDisposedException(nameof(GreptimeClient));
-        }
-#endif
     }
 
     #region Logging
 
-    [LoggerMessage(Level = LogLevel.Debug, Message = "GreptimeClient created for endpoint {Endpoint}")]
-    private static partial void LogClientCreated(ILogger logger, string endpoint);
+    [LoggerMessage(Level = LogLevel.Debug, Message = "GreptimeClient created with {EndpointCount} endpoint(s); first: {FirstEndpoint}")]
+    private static partial void LogClientCreated(ILogger logger, int endpointCount, string firstEndpoint);
 
     [LoggerMessage(Level = LogLevel.Debug, Message = "Writing {TableCount} tables with {RowCount} total rows")]
     private static partial void LogWriteStarted(ILogger logger, int tableCount, int rowCount);