[ANN] Pedestal 0.7.0

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Pedestal 0.7.0

Pedestal is a set of Clojure libraries that bring the core Clojure principles - Simplicity, Power, and Focus - to server-side development.

This release marks significant improvements to Pedestal, while laying the cornerstones for further improvements.
The primary focus has been upgrading from Jetty 9 to Jetty 11 (and from Servlet API 3.1 to 5); much additional effort
has been invested in improving the developer experience, rewriting support for application observability,
enhancements to performance, deprecation of unused (or unsupported) code, as well as an intense focus on documentation improvements.

Although this release does include unavoidable breaking changes, we hope that for most applications, the upgrade process will
be as simple as changing the version number. Applications that made direct use of Jetty APIs, or servlet APIs (using the javax.servlet namespace),
will require additional scrutiny to upgrade, as will applications that make extensive use of the (now deprecated)
observability functions provided by the io.pedestal/pedestal.log library.

GitHub: GitHub - pedestal/pedestal: The Pedestal Server-side Libraries
Documentation: http://pedestal.io/

BREAKING CHANGES:

  • Library pedestal.jetty has been upgraded from Jetty 9 to Jetty 11
  • Library pedestal.immutant has been removed
  • Library pedestal.tomcat has been removed
  • Library pedestal.aws has been removed
  • Namespace io.pedestal.http.jetty.websockets has been removed, and replaced with io.pedestal.http.websockets
  • Namespace io.pedestal.interceptor.error has been moved to a new library, io.pedestal/pedestal.error
  • Library pedestal.service no longer has a dependency on org.clojure/core.match; the new pedestal.error library has that dependency
  • Interceptors that attach an invalid :response value (not a map, for example) will now cause an exception to be thrown
  • Interceptors may now attach a partial :response map, containing just a :status key

Other changes:

  • When using io.pedestal.http/dev-interceptors, uncaught exceptions are now formatted using org.clj-commons/pretty in the response sent to the client
  • Pedestal is now compatible with Clojure 1.10.1 and above
  • In io.pedestal.interceptor.chain:
    • New macros bind and unbind make it easier for interceptors to manipulate dynamic variables exposed to following interceptors
    • New function on-enter-async is used to register a callback invoked when execution first goes asynchronous
    • New function queue is used to peek at what interceptors remain on the queue
    • New function add-observer to add a callback after each interceptor executes in each stage
  • New function io.pedestal.interceptor.chain.debug/debug-observer to observe and log changes to the context made by interceptors
  • New function io.pedestal.http/enable-debug-interceptor-observer to setup debug-observer
  • New service map keys have been introduced:
    • Support handling of uncaught exceptions
    • May now specify an initial context map
    • May now specify an interceptor responsible for request tracing
  • There is now a clojure.spec specification for the structure of the service map, and for the structure of the different route specifications and the expanded routing table
  • Added a deps-new template, io.pedestal/embedded, for creating a new Pedestal project around embedded Jetty
  • Use of many deprecated functions and macros now cause deprecation warnings to be printed to stderr
  • Metrics and tracing have been reimplemented from the ground up around Open Telemetry (https://opentelemetry.io/)
  • Libraries pedestal.log and pedestal.error contain clj-kondo configuration files to inform clj-kondo about their macros
  • New function io.pedestal.http/respond-with to streamline adding a :response to the interceptor context
  • Easier application configuration: logger, metrics, and tracing configuration can occur inside a pedestal-config.edn file (or pedestal-test-config.edn for tests), as well as via JVM system properties and environment variables
  • Improvements to REPL-based development, including printing the expanded routing table at startup (when in development mode)

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