Temporal is a durable execution system that transparently makes your code durable, fault-tolerant, and simple.

This project provides an unofficial Haskell SDK along with supporting packages for authoring workflows and activities.

Warning

This project is still under heavy development. It is in production use at Mercury, but we currently make no stability guarantees for external users of the project.

For documentation and samples, see:

• General Temporal docs

Packages

This monorepo contains the following packages:

Subfolder	Package	Description
./	temporal-sdk	The developer-facing core package. Use this to author and execute Temporal Workflows and Activities.
core/	temporal-sdk-core	Core FFI bindings that interface with the rust core library.
codec-encryption/	temporal-codec-encryption	A simple implementation of at-rest encryption for payloads.
codec-server	temporal-sdk-codec-server	A WAI middleware to transform payloads for use with the Temporal Web UI.
optimal-codec/	temporal-sdk-optimal-codec	Given a set of preferred codecs for Activity and Workflow inputs and outputs, choose the optimal codec for each value.
protos/	temporal-api-protos	Raw protocol buffer modules for exotic use cases.

Development Environment

This project uses Nix to manage the development environment and dependencies. Nix ensures a reproducible and consistent build environment across different systems.

Note

Stack support is for convenience, but not guaranteed by CI to compile consistently.

It is recommended to set up direnv and nix-direnv to automatically load the Nix environment when you enter the project directory. After installing direnv, run the following command in the project root to bootstrap the development environment.

direnv allow

Useful Development Commands

nix develop --impure enters the development shell for the Haskell program if you aren't using direnv. This shell includes the necessary tools and dependencies for development, such as GHC, Cabal, and the Rust toolchain.

Inside the development shell, you can use cabal commands as usual. Cabal is the official build tool for this project.

• nix build .\#{packageName}-{ghcVersion} builds the given package for a given GHC version.
• nix build .\#temporal-bridge builds the Rust library (temporal-bridge) that provides bindings to the Temporal Core library.
• devenv up starts a local Temporal server for development and testing purposes.

The flake.nix file defines different shells for each supported GHC version (ghc96, ghc98). You can enter the shell for a specific GHC version with the following command:

nix develop .\#{ghcVersion} --impure

Replace {ghcVersion} with the desired GHC version (e.g., ghc96, ghc98).

Note

The first time you run nix develop or nix build, Nix will download and build all the necessary dependencies, which may take some time. Subsequent runs will be faster as Nix will reuse the cached dependencies.