Temporal Core SDK

Core SDK that can be used as a base for other Temporal SDKs. It is currently used as the base of:

Documentation

Core SDK documentation can be generated with cargo doc, output will be placed in the target/doc directory.

Architecture doc provides some high-level information about how Core SDK works and how language layers interact with it.

For the reasoning behind the Core SDK, see blog post:

Why Rust powers Temporal’s new Core SDK.

Development

You will need the protoc protobuf compiler installed to build Core.

This repo is composed of multiple crates:

temporal-sdk-core-protos ./sdk-core-protos - Holds the generated proto code and extensions
temporal-client ./client - Defines client(s) for interacting with the Temporal gRPC service
temporal-sdk-core-api ./core-api - Defines the API surface exposed by Core
temporal-sdk-core ./core - The Core implementation
temporal-sdk ./sdk - A (currently prototype) Rust SDK built on top of Core. Used for testing.
rustfsm ./fsm - Implements a procedural macro used by core for defining state machines (contains subcrates). It is temporal agnostic.

Visualized (dev dependencies are in blue):

All the following commands are enforced for each pull request:

Building and testing

You can build and test the project using cargo: cargo build cargo test

Run integ tests with cargo integ-test. By default it will start an ephemeral server. You can also use an already-running server by passing -s external.

Run load tests with cargo test --test heavy_tests.

Formatting

To format all code run: cargo fmt --all

Linting

We are using clippy for linting. You can run it using: cargo clippy --all -- -D warnings

Debugging

The crate uses tracing to help with debugging. To enable it for a test, insert the below snippet at the start of the test. By default, tracing data is output to stdout in a (reasonably) pretty manner.

crate::telemetry::test_telem_console();

The passed in options to initialization can be customized to export to an OTel collector, etc.

To run integ tests with OTel collection on, you can use integ-with-otel.sh. You will want to make sure you are running the collector via docker, which can be done like so:

docker-compose -f docker/docker-compose.yaml -f docker/docker-compose-telem.yaml up

If you are working on a language SDK, you are expected to initialize tracing early in your main equivalent.

Proto files

This repo uses a subtree for upstream protobuf files. The path sdk-core-protos/protos/api_upstream is a subtree. To update it, use:

git pull --squash --rebase=false -s subtree ssh://git@github.com/temporalio/api.git master --allow-unrelated-histories

Do not question why this git command is the way it is. It is not our place to interpret git's ways. This same approach can be taken for updating sdk-core-protos/protos/api_cloud_upstream from the api-cloud repo.

The java testserver protos are also pulled from the sdk-java repo, but since we only need a subdirectory of that repo, we just copy the files with read-tree:

# add sdk-java as a remote if you have not already
git remote add -f -t master --no-tags testsrv-protos git@github.com:temporalio/sdk-java.git
# delete existing protos
git rm -rf sdk-core-protos/protos/testsrv_upstream
# pull from upstream & commit
git read-tree --prefix sdk-core-protos/protos/testsrv_upstream -u testsrv-protos/master:temporal-test-server/src/main/proto
git commit

Fetching Histories

Tests which would like to replay stored histories rely on that history being made available in binary format. You can fetch histories in that format like so (from a local docker server):

cargo run --bin histfetch {workflow_id} [{run_id}]

You can change the TEMPORAL_SERVICE_ADDRESS env var to fetch from a different address.

Style Guidelines

Error handling

Any error which is returned from a public interface should be well-typed, and we use thiserror for that purpose.

Errors returned from things only used in testing are free to use anyhow for less verbosity.

The Rust "SDK"

This repo contains a prototype Rust sdk in the sdk/ directory. This SDK should be considered pre-alpha in terms of its API surface. Since it's still using Core underneath, it is generally functional. We do not currently have any firm plans to productionize this SDK. If you want to write workflows and activities in Rust, feel free to use it - but be aware that the API may change at any time without warning and we do not provide any support guarantees.

temporalio/sdk-core