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Version: 1.x

🐘 SQLDB Postgres Example

This folder contains a WebAssembly component that makes use of:

📦 Dependencies​

  • docker for easily running instances of [postgres]
  • cargo (part of the Rust toolchain) for building this project
  • [wash][wash] for building and running the components and wasmCloud hosts

👟 Quickstart​

As with all other examples, you can get started quickly by using the [Wasmcloud SHell (wash)][wash].

Since wash supports declarative deployments (powered by Wasmcloud Application Deployment Manager (wadm)), you can get started quickly using the wadm.yaml manifest in this folder:

Start a local Postgres cluster​

Before we can connect to a Postgres database cluster, we'll need to have one running. You can run one quickly with docker:

console
docker run \
    --rm \
    -e POSTGRES_PASSWORD=postgres \
    --name pg -p 5432:5432\
    postgres:16.2-alpine

Build this component​

console
wash build

This will create a folder called build which contains sqldb_postgres_query_s.wasm.

[!NOTE] If you're using a local build of the provider (using file://... in wadm.yaml) this is a good time to ensure you've built the [provider archive par.gz][par] for your provider.

Start a wasmCloud host​

console
wash up

[!NOTE] wash up will run as long as the host is running (you can cancel it with Ctrl-C)

Set up configuration for the provider​

Since configuration for Database clusters is usually sensitive information, we must pre-establish configuration for the provider using the [named configuration feature of wasmCloud][named-config].

Named configuration setup​

Set up a named configuration for components that link to the sqldb-postgres provider which is used from wadm.yaml:

console
wash config put default-postgres \
    POSTGRES_HOST=localhost \
    POSTGRES_PORT=5432 \
    POSTGRES_USERNAME=postgres \
    POSTGRES_PASSWORD=postgres \
    POSTGRES_DATABASE=postgres \
    POSTGRES_TLS_REQUIRED=false

Deploy the example application with WADM​

console
wash app deploy --replace wadm.yaml

[!WARNING] If you simply want to stop the deployment, run wash app delete <application name>.

In this case, wash app delete rust-sqldb-postgres should work.

To ensure that the application is deployed you can use wadm app list:

console
wadm app list

If you want to see everything running in the lattice at once:

console
wash get inventory

Invoke the demo component​

Once the component & provider are deployed, you can invoke the example component with wash call:

console
wash call rust_sqldb_postgres_query-querier wasmcloud:examples/invoke.call

Note that the name of the component is prefixed with the WADM application, and the interface on it we call is defined in wit/provider.wit (the call function of the invoke interface).

⌨️ Code guide​

With wasmCloud, you write only the important bits of your business logic, so the code for this component is short, with the important bits highlighted below:

rust
impl Guest for QueryRunner {
    fn call() -> String {
        if let Err(e) = query(CREATE_TABLE_QUERY, &[]) {
            return format!("ERROR - failed to create table: {e}");
        };

        match query(
            INSERT_QUERY,
            &[PgValue::Text(format!("inserted example row!"))],
        ) {
            Ok(rows) => format!("SUCCESS: inserted new row:\n{rows:#?}"),
            Err(e) => format!("ERROR: failed to insert row: {e}"),
        }
    }
}