Release notes v8.0.0

After many months of work, eleven alphas, six betas and two release candidates, we are pleased to announce the GA release of the Elasticsearch .NET Client v8.0.0.

The overall themes of this release have been based around redesigning the client for the future, standardizing serialization, performance improvements, codebase simplification, and code-generation.

The following release notes explain the current state of the client, missing features, breaking changes and our rationale for some of the design choices we have introduced.

Mature code becomes increasingly hard to maintain over time, and our ability to make timely releases has diminished as code complexity has increased. Major releases allow us to simplify and better align our language clients with each other in terms of design. Here, it is crucial to find the right balance between uniformity across programming languages and the idiomatic concerns of each language. For .NET, we will typically compare and contrast with Java and Go to make sure that our approach is equivalent for each of these. We also take heavy inspiration from Microsoft framework design guidelines and the conventions of the wider .NET community.

We have shipped the new code-generated client as a new NuGet package with a new root namespace, Elastic.Clients.Elasticsearch. The new v8 client is built upon the foundations of the v7 NEST client, but there are changes. By shipping as a new package, the expectation is that migration can be managed with a phased approach.

While this is a new package, we have aligned the major version (v8.x.x) with the supported Elasticsearch server version to clearly indicate the client/server compatibility. The v8 client is designed to work with version 8 of Elasticsearch.

The v7 NEST client continues to be supported but will not gain new features or support for new Elasticsearch endpoints. It should be considered deprecated in favour of the new client.

For the initial 8.0.0 release we have limited the features we are shipping. Over the course of the 8.x releases, we will reintroduce features. Therefore, if something is missing, it may not be permanently omitted. We will endeavour to communicate our plans as and when they become available.

If a feature you depend on is missing (and not explicitly documented below as a feature that we do not plan to reintroduce), please open an issue or comment on a relevant existing issue to highlight your need to us. This will help us prioritise our roadmap.

Given the size of the Elasticsearch API surface today, it is no longer practical to maintain thousands of types (requests, responses, queries, aggregations, etc.) by hand. To ensure consistent, accurate and timely alignment between language clients and Elasticsearch, the 8.x clients, and many of the associated types are now automatically code-generated from a shared specification. This is a common solution to maintaining alignment between client and server among SDKs and libraries, such as those for Azure, AWS and the Google Cloud Platform.

Code-generation from a specification has inevitably led to some differences between the existing v7 NEST types and those available in the new v7 Elasticsearch .NET Client. For the 8.0.0 release, we generate strictly from the specification, special casing a few areas to improve usability or to align with language idioms.

The base type hierarchy for concepts such as Properties, Aggregations and Queries is no longer present in generated code, as these arbitrary groupings do not align with concrete concepts of the public server API. These considerations do not preclude adding syntactic sugar and usability enhancements to types in future releases on a case-by-case basis.

The .NET client includes a transport layer responsible for abstracting HTTP concepts and to provide functionality such as our request pipeline. This supports round-robin load-balancing of requests to nodes, pinging failed nodes and sniffing the cluster for node roles.

In v7, this layer shipped as Elasticsearch.Net and was considered our low-level client which could be used to send and receive raw JSON bytes between the client and server.

As part of the work for 8.0.0, we have moved the transport layer out into a new dedicated package and repository, named Elastic.Transport. This supports reuse across future clients and allows consumers with extremely high-performance requirements to build upon this foundation.

The v7 NEST high-level client used an internalized and modified version of Utf8Json for request and response serialization. This was introduced for its performance improvements over Json.NET, the more common JSON framework at the time.

While Utf8Json provides good value, we have identified minor bugs and performance issues that have required maintenance over time. Some of these are hard to change without more significant effort. This library is no longer maintained, and any such changes cannot easily be contributed back to the original project.

With .NET Core 3.0, Microsoft shipped new System.Text.Json APIs that are included in-the-box with current versions of .NET. We have adopted System.Text.Json for all serialization. Consumers can still define and register their own Serializer implementation for their document types should they prefer to use a different serialization library.

By adopting System.Text.Json, we now depend on a well-maintained and supported library from Microsoft. System.Text.Json is designed from the ground up to support the latest performance optimizations in .NET and, as a result, provides both fast and low-allocation serialization.

Testing code is an important part of software development. We recommend that consumers prefer introducing an abstraction for their use of the Elasticsearch .NET Client as the prefered way to decouple consuming code from client types and support unit testing.

In order to support user testing scenarios, we have unsealed the ElasticsearchClient type and made its methods virtual. This supports mocking the type directly for unit testing. This is an improvement over the original IElasticClient interface from NEST (v7) which only supported mocking of top-level client methods.

We have also introduced a TestableResponseFactory in Elastic.Transport to make it easier to create response instances with specific status codes and validity that can be used during unit testing.

These changes are in addition to our existing support for testing with an InMemoryConnection, virtualized clusters and with our Elastic.Elasticsearch.Managed library for integration testing against real Elasticsearch instances. We will introduce more documentation on testing methodologies in the near future.

The 8.0.0 release focuses on core endpoints, more specifically for common CRUD scenarios. We intend to reduce the feature gap in subsequent versions. We anticipate that this initial release will best suit new applications and may not yet be migration-ready for all existing consumers. We recommend reviewing this documentation carefully to learn about the missing features and reduced API surface details before migrating from the v7 NEST client.

The choice to code-generate a new evolution of the Elasticsearch .NET Client introduces some significant breaking changes. We consciously took the opportunity to refactor and reconsider historic design choices as part of this major release, intending to limit future breaking changes.

The v8 client is shipped as a new NuGet package which can be installed alongside v7 NEST. We anticipate that some consumers may prefer a phased migration with both packages side-by-side for a short period of time to manage complex migrations. In addition, NEST 7.17.x can continue to be used in compatibility mode with Elasticsearch 8.x servers until the v8 Elasticsearch .NET Client features align with application requirements.

We will continue to prioritize the feature roadmap and code-generation work based on feedback from consumers who may rely on features that are initially unavailable.

We have strived to keep the core foundation reasonably similar, but types emitted through code-generation are subject to change between NEST (v7) and the new Elastic.Clients.Elasticsearch (v8) package.

We have renamed the package and top-level namespace for the v8 client to Elastic.Clients.Elasticsearch. All types belong to this namespace. When necessary, to avoid potential conflicts, types are generated into suitable sub-namespaces based on the Elasticsearch specification. Additional using directives may be required to access such types when using the Elasticsearch .NET Client.

Transport layer concepts have moved to the new Elastic.Transport NuGet package and related types are defined under its namespace. Some configuration and low-level transport functionality may require a using directive for the Elastic.Transport namespace.

Type names may have changed from previous versions. We are not listing these explicitly due to the potentially vast number of subtle differences. Type names will now more closely align to those used in the JSON and as documented in the Elasticsearch documentation.

Types may include renamed properties based on the Elasticsearch specification, which differ from the original NEST property names. The types used for properties may also have changed due to code-generation. If you identify missing or incorrectly-typed properties, please open an issue to alert us.

Opinions on "sealing by default" within the .NET ecosystem tend to be quite polarized. Microsoft seal all internal types for potential performance gains and we see a benefit in starting with that approach for the Elasticsearch .NET Client, even for our public API surface.

While it prevents inheritance and, therefore, may inhibit a few consumer scenarios, sealing by default is intended to avoid the unexpected or invalid extension of types that could inadvertently be broken in the future. That said, sealing is not necessarily a final choice for all types; but it is clearly easier for a future release to unseal a previously-sealed class than vice versa. We can therefore choose to unseal as valid scenarios arise, should we determine that doing so is the best solution for those scenarios, such as with mockability of the ElasticsearchClient. This goes back to our clean-slate concept for this new client.

As part of the clean-slate redesign of the new client, we have opted to remove certain features from the v8.0 client. These are listed below:

In previous versions of the NEST client, attributes could be used to configure the mapping behaviour and inference for user types. We have removed support for these attributes and recommend that mapping be completed via the fluent API when configuring client instances. System.Text.Json attributes may be used to rename and ignore properties during source serialization.

The CAT APIs of Elasticsearch are intended for human-readable usage and will no longer be supported via the v8 Elasticsearch .NET Client.

We have removed several interfaces that previously shipped as part of NEST. This is a design decision to simplify the library and avoid interfaces where only a single implementation of that interface is expected to exist, such as IElasticClient in NEST. We have also switched to prefer abstract base classes over interfaces across the library, as this allows us to add enhancements more easily without introducing breaking changes for derived types.

While not an exhaustive list, the following are some of the main features which have not been re-implemented for this initial 8.0.0 GA release. These remain on our roadmap and will be reviewed and prioritized for inclusion in future releases.

In this first release of the code-generated .NET client, we have specifically focused on supporting commonly used endpoints. We have also skipped specific queries and aggregations which need further work to generate code correctly. Before migrating, please refer to the lists below for the endpoints, queries and aggregations currently generated and available in the 8.0.0 GA release to ensure that the features you are using are currently supported.

The following are Elasticsearch endpoints currently generated and available in the 8.0.0 Elasticsearch .NET Client.

The following are query types currently generated and available in the 8.0.0 Elasticsearch .NET Client.

The following are aggregation types currently generated and available in the 8.0.0 Elasticsearch .NET Client.

Please give the new Elastic.Clients.Elasticsearch client a try in your .NET applications. If you run into any problems, please open an issue to raise those with us. Please let us know how you get on and if you have any questions, reach out on the Discuss forums.