JetBrains has released Ktor 3.4, an update to its Kotlin-based framework for asynchronous server-side and client-side application development. The release brings duplex streaming to the OkHttp client engine and introduces a new HttpRequestLifecycle plugin that enables the cancellation of in-flight HTTP requests when the client disconnects.

Ktor 3.4 was announced January 23. Instructions for getting started can be found at ktor.io.

The new HttpRequestLifecycle plugin, which enables cancellation of in-flight HTTP requests when the client disconnects, is useful when there is a need to cancel a long-running or resource-intensive in-flight request. When the client disconnects, the coroutine handling the request is canceled, along with launch or async coroutines started by the client, and structured concurrency cleans all resources. This feature is currently supported only for the Netty and CIO engines.

Ktor 3.4 also introduces a new API for dynamically documenting endpoints that works in tandem with a new compiler plugin. Instead of building a Swagger front end from a static file, the model is built at runtime from details embedded in the routing tree. To generate documentation, developers can enable it through the Ktor Gradle plugin, then it will automatically provide details in code via the new describe API.

Also in Ktor 3.4, the OkHttp client engine now supports duplex streaming, enabling clients to send request body data and receive response data simultaneously, in contrast to regular HTTP calls, where the request body must be fully sent before the response begins. Duplex streaming is available for HTTP/2 connections and can be enabled using the new duplexStreamingEnabled property in OkHttpConfig.

And the Compression plugin now supports Ztsd via a ktor-server-compression-zstd module. Zstd is a fast compression algorithm with high compression ratios, low compression times, and a configurable compression level.