Hot Chocolate (software)

Hot Chocolate (software)
Name	Hot Chocolate
Developer	ChilliCream
Released	2016
Programming language	C#
Operating system	Cross-platform
Platform	.NET
License	MIT License

Hot Chocolate (software) is an open-source GraphQL server implementation for the .NET platform developed by ChilliCream. It provides tools to create GraphQL APIs that integrate with frameworks and services such as ASP.NET Core, Entity Framework Core, Azure, and Docker. Hot Chocolate emphasizes schema-first and code-first development models to support applications built with Visual Studio, JetBrains Rider, and GitHub Actions.

Overview

Hot Chocolate is designed to enable GraphQL service development within ecosystems that include Microsoft, .NET Foundation, and Azure. It targets developers using C#, F#, and tools from JetBrains and Microsoft, aligning with patterns from ASP.NET Core middleware, Entity Framework Core data access, and SignalR for subscriptions. The project integrates with cloud providers such as Amazon Web Services, Microsoft Azure, and Google Cloud Platform through SDKs and DevOps pipelines using GitHub, GitLab, and Azure DevOps. Hot Chocolate interoperates with client libraries like Apollo, Relay, and Urql, and it supports IDEs such as Visual Studio, Visual Studio Code, and Rider.

Architecture and Design

Hot Chocolate's architecture follows modular principles influenced by patterns from ASP.NET Core, OWIN, and middleware pipelines originating in IIS and Kestrel. The design separates schema parsing, execution, and transport layers to interoperate with HTTP/2, WebSocket protocols used by Socket.IO, and gRPC. Core components include a schema registry inspired by GraphQL specification work, a type system that mirrors patterns from System.Text.Json and Newtonsoft.Json, and an execution engine optimized for asynchronous I/O using Task Parallel Library concepts from .NET. Hot Chocolate integrates with dependency injection containers used in ASP.NET Core and inversion of control patterns found in Autofac and Microsoft.Extensions.DependencyInjection. For observability it supports exporters compatible with OpenTelemetry, Application Insights, and Prometheus.

Features and Functionality

Hot Chocolate implements features that align with the GraphQL specification maintained by the GraphQL Foundation and projects like graphql-js and graphql-java. Feature highlights include schema stitching similar to Federation approaches from Apollo, persisted queries comparable to Relay modern persisted query work, and dataloader patterns inspired by Facebook's Dataloader. It supports query batching, field-level middleware similar to policies in ASP.NET Core, schema directives analogous to those in graphql-tools, and real-time capabilities via WebSocket subscriptions using concepts from SignalR and MQTT. Hot Chocolate provides integration with ORMs such as Entity Framework Core and Dapper, authentication and authorization compatible with IdentityServer and OAuth providers like Azure Active Directory, Okta, and Auth0. It offers tooling for schema stitching, federation support reflecting Apollo Federation, and code generation that integrates with Roslyn analyzers, NUnit, xUnit, and MSTest for testing.

Development and Release History

Hot Chocolate originated at ChilliCream and was publicly released in 2016 amid growing adoption of GraphQL started by Facebook, GitHub, and Twitter. The project evolved across releases to incorporate federation support after Apollo's federation announcement, added schema-first tooling influenced by GraphQL Foundation initiatives, and extended platform support for .NET Core and .NET 5/6/7 in step with Microsoft releases. Major milestones included integration with Entity Framework Core updates, support for ASP.NET Core middleware conventions, improvements to performance inspired by benchmarking work from TechEmpower, and adoption of GitHub Actions and Azure Pipelines for CI/CD. The repository has seen contributions from individual developers, corporate teams, and community maintainers collaborating via GitHub, Gitter, and Discord channels.

Adoption and Use Cases

Organizations adopting Hot Chocolate include companies building APIs for e-commerce platforms, fintech services, and media streaming applications that rely on AWS, Azure, or private datacenters. Use cases encompass building storefront backends that integrate with Shopify APIs, headless CMS architectures like Contentful and Strapi, and mobile backends for iOS and Android clients using Apollo Client and Relay Modern. Enterprises leverage Hot Chocolate for microservices patterns with Kubernetes and Helm charts, API gateways such as Kong and Ambassador, and for orchestration alongside service meshes like Istio. Developers employ the server in event-driven systems that use Kafka, RabbitMQ, and Azure Service Bus for messaging.

Performance and Benchmarks

Performance work on Hot Chocolate references benchmarking approaches used by TechEmpower, comparisons with implementations such as Apollo Server, graphql-js, Sangria, and graphql-java, and measurement frameworks like BenchmarkDotNet. Optimizations focus on reducing allocation, improving GraphQL query planning, and enhancing resolver concurrency using ValueTask and Span strategies from .NET. Benchmarks report improvements in throughput and latency when running on Kestrel with HTTP/2, using pooled object allocators similar to System.Buffers, and leveraging caching strategies aligned with Redis and Memcached. Observability in performance tuning integrates with Prometheus exporters, Grafana dashboards, and distributed tracing via Jaeger and Zipkin.

Licensing and Community Contribution

Hot Chocolate is distributed under the MIT License and is hosted on GitHub where contributions follow conventions established by the .NET Foundation and popular open-source projects like ASP.NET Core and Entity Framework Core. The community contributes through pull requests, issue triage, and RFC-style proposals resembling processes used by Rust and Python communities. Corporate sponsorship, community maintainers, and ecosystem partners provide governance models influenced by foundations such as the Linux Foundation and the GraphQL Foundation. Documentation and learning resources are produced by authors, conference presenters at events like Microsoft Ignite, NDC, and GraphQL Summit, and community tutorials on platforms including Pluralsight and YouTube.

Category:.NET software