graphql-engine/v3/README.md

# Hasura GraphQL Engine V3

[![Docs](https://img.shields.io/badge/docs-v3.x-brightgreen.svg?style=flat)](https://hasura.io/docs/3.0/index/)

Hasura V3 is the API execution engine, based over the Open Data Domain Specification (OpenDD spec) and Native Data Connector Specifications (NDC spec), which powers the Hasura Data Delivery Network (DDN). The engine expects to run against an OpenDDS metadata file and exposes a GraphQL endpoint according to the specified metadata. The engine needs a data connector to run alongside, for the execution of data source specific queries.

## Data connectors

Hasura V3 engine does not execute queries directly - instead it sends IR (Abstracted, intermediate query) to NDC agents (aka data connectors). To run queries on a database, we'll need to run the data connector that supports the database.

Available Data connectors are listed at the [Connector Hub](https://hasura.io/connectors)

For local development, we use the reference agent implementation that is a part of the [NDC spec](https://github.com/hasura/ndc-spec).

To start the reference agent only, you can do:
```sh
docker compose up reference_agent
```
and point the host name `reference_agent` to localhost in your `/etc/hosts` file.

## Run V3 engine (with reference agent)

### Using `cargo`
Hasura V3 engine is written in rust, hence `cargo` is required to build and run V3 engine locally.

To start the v3 engine locally, we need a `metadata.json` file and an auth config file.

Following are steps to run V3 engine with a reference agent (read only, in memory, relational database with sample tables), and an sample metadata file, exposing a fixed GraphQL schema. This can be used to understand the build setup and the new V3 engine concepts.

   ```sh
   RUST_LOG=DEBUG cargo run --release --bin engine -- \
     --metadata-path open-dds/examples/reference.json \
    --authn-config-path auth_config.json
   ```

A dev webhook implementation is provided in `hasura-authn-webhook/dev-auth-webhook`,
that exposes the `POST /validate-request` which accepts converts the headers present
in the incoming request to a object containing session variables, note that only headers
that start with `x-hasura-` will be returned in the response.

The dev webhook can be run using the following command:

```sh
docker compose up auth_hook
```
and point the host name `auth_hook` to localhost in your `/etc/hosts` file.

Open <http://localhost:3000> for GraphiQL.

Use `--port` option to start v3-engine on a different port.
```sh
RUST_LOG=DEBUG cargo run --release --bin engine -- \
     --port 8000 --metadata-path open-dds/examples/reference.json
```
Now, open <http://localhost:8000> for GraphiQL.

### With docker
You can also start Hasura V3 engine, reference_agent, dev Authentication webhook and jaegar for
tracing (accessible at localhost:4002) using docker (without the need of using `cargo`)

```sh
METADATA_PATH=open-dds/examples/reference.json AUTHN_CONFIG_PATH=auth_config.json docker compose up
``` 

## Run V3 engine (with Postgres)
[NDC Postgres](https://github.com/hasura/ndc-postgres) is the official connector by Hasura for Postgres Database. For running V3 engine for GraphQL API on Postgres, you need to run NDC Postgres Connector and have a `metadata.json` file that is authored specifically for your Postgres database and models (tables, views, functions).

The recommended way to author `metadata.json` for Postgres, is via Hasura DDN.

Follow the [Hasura DDN Guide](https://hasura.io/docs/3.0/getting-started/overview/) to create a Hasura DDN project, connect your cloud or local Postgres Database (Hasura DDN provides a secure tunnel mechanism to connect your local database easily), and model your GraphQL API. You can then download the authored metadata.json and use the following steps to run GraphQL API on your local Hasura V3 engine.

### Steps to run metadata with V3 engine locally

1. Download metadata from DDN project, using Hasura V3 CLI
    ```sh
    hasura3 build create --dry-run > ddn-metadata.json
    ```

2. Following steps are to generate Postgres metadata object and run the Postgres Connector. These steps refer to the [NDC Postgres](https://github.com/hasura/ndc-postgres) repository:

    1. Start the Postgres connector in configuration mode (Config server). A config server provides additional endpoints for database instrospection and provide the schema of the database. Output of the config server will form the Postgres Metadata object.
   
    2. Run the following command in the [ndc-postgres](https://github.com/hasura/ndc-postgres) repository:
 
        ```bash
        just run-config
        ```

    3. Generate the postgres configuration using the `new-configuration.sh` script by running the following
    command (in another terminal) in the [ndc-postgres](https://github.com/hasura/ndc-postgres) repository:

        ```bash
        ./scripts/new-configuration.sh localhost:9100 '<postgres database url>' > pg-config.json
        ```
    4. Now shutdown the postgres config server and start the Postgres Connector using the `pg-config.json` generated in the above
    step, by running the following command:
      
        Please specify different `PORT` for different data connectors:

        ```bash
        PORT=8100 \
        RUST_LOG=INFO \
            cargo run --bin ndc-postgres --release -- serve --configuration pg-config.json > /tmp/ndc-postgres.log
        ```
    5. Fetch the schema for the data connector object by running the following command:
        ```bash
        curl -X GET http://localhost:8100/schema | jq . > pg-schema.json
        ```
    6. Finally, generate the `DataConnector` object:
        ```bash
        jq --null-input --arg name 'default' --arg port '8100' --slurpfile schema pg-schema.json '{"kind":"DataConnector","version":"v2","definition":{"name":"\($name)","url":{"singleUrl":{"value":"http://localhost:\($port)"}},"schema":$schema[0]}}' > pg-metadata.json
        ```

3. Now you have the NDC Postgres connector running, and have obtained the Postgres metadata (`pg-metadata.json`) which is required for the V3 engine.

4. In `ddn-metadata.json` (from step 1.), replace the `HasuraHubDataConnector` objects with `DataConnector` objects generated inside the `pg-metadata.json` file.
   
5. Remove the object for `kind: AuthConfig` from `ddn-metadata.json`, move it to a separate file `auth_config.json`, and remove the `kind` field from it.
   
6. Remove the object for `kind: CompatibilityConfig` from `ddn-metadata.json`. If desired, a `flags` field can be added to the OSS metadata to enable the flags corresponding to that compatibility date in the DDN metadata.

7. Finally, start the v3-engine using the modified metadata using the following command (using the modified `ddn-metadata.json` and `auth_config.json` from Step 5):
    ```bash
    RUST_LOG=DEBUG cargo run --release --bin engine -- \
     --metadata-path ddn-metadata.json auth_config.json
    ```
    You should have the v3-engine up and running at http://localhost:3000

**Note**: We understand that these steps are not very straightforward, and we intend to continuously improve the developer experience of running OSS V3 Engine.

## Running tests

To run the test suite, you need to docker login to `ghcr.io` first:

```bash
docker login -u <username> -p <token> ghcr.io
```

where `username` is your github username, and `token` is your github PAT. The PAT needs to have the `read:packages` scope and `Hasura SSO` configured. See [this](https://docs.github.com/en/packages/working-with-a-github-packages-registry/working-with-the-container-registry#authenticating-with-a-personal-access-token-classic) for more details.


Next run the postgres NDC locally using `docker compose up postgres_connector` and point the host name `postgres_connector` to localhost in your `/etc/hosts` file.

Next run the custom NDC locally using `docker compose up custom_connector` and point the host name `custom_connector` to localhost in your `/etc/hosts` file OR you can run `cargo run --bin agent` and then do `cargo test`.

### Testing/Development with the chinook database

The `engine/tests/chinook` contains static files required to run v3-engine run with the chinook database as a data connector.

To get this running, you can run the following command:

```bash
METADATA_PATH=engine/tests/schema.json AUTHN_CONFIG_PATH=auth_config.json docker compose up postgres_connector engine
```

If you are running the v3-engine locally through cargo, then you'll need to update the value of the
`singleUrl` present in the `engine/tests/chinook/chinook_engine_metadata.json**
from http://postgres_connector:8100 to http://localhost:8100 .

### Running tests with a single command

Alternatively, the tests can be run in the same Docker image as CI:

```sh
just test
```

### Updating goldenfiles

There are some tests where we compare the output of the test against an expected golden file. If you make some changes which expectedly change the goldenfile, you can regenerate them like this:

Locally (with postgres_connector pointing to localhost)

```sh
  REGENERATE_GOLDENFILES=1 cargo test
```

Docker:

```sh
  just update-golden-files
```

### Running coverage report

We can check for coverage of unit tests by running:

```sh
just coverage
```

You can also give a filter expression (which is passed to `grep -E`) to give coverage only for matched files:

```sh
just coverage "open-dds|engine"
```

## Run benchmarks

The benchmarks operate against the reference agent using the same test cases as the test suite, and need a similar setup.

To run benchmarks for the lexer, parser and validation:

```bash
cargo bench -p lang-graphql "lexer"
cargo bench -p lang-graphql "parser"
cargo bench -p lang-graphql "validation/.*"
```

Alternatively, the benchmarks can be run in the same Docker image as CI:

```sh
just ci-bench
```