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Version: 1.x

🐘 SQLDB Postgres Example

This example is a WebAssembly component that makes use of:

📦 Dependencies​

Before starting, ensure that you have the following installed in addition to the Go toolchain:

  • tinygo 0.33+
  • docker for easily running instances of [postgres]
  • wash for building and running the components and [wasmCloud][wasmcloud] hosts
  • wasm-tools for Go bindings

👟 Quickstart​

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

Since wash supports declarative deployments (powered by Wasmcloud Application Deployment Manager (wadm)), you can get started quickly using the local.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 --allow-file-load true

[!NOTE] > wash up will run as long as the host is running (you can cancel it with Ctrl-C). You can also run it with the -d flag to run it in the background. If you start a host this way, you can stop it with wash down

Deploy the example application with WADM​

console
wash app deploy wadm.yaml

[!WARNING] If you simply want to stop the deployment, run wash app delete <application name>. You can also run wash app delete wadm.yaml if you don't want to look up the application name.

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

console
wash 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 go_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).

Running tests​

You can also run tests using wadge. Because this uses custom interfaces (wasmcloud:postgres), there is a test harness component in the test-harness directory of this example. You can modify this harness (or create another one for other test cases). If you change the harness, you'll need to rm build/test-harness.wasm. When you run wash build again it will build the test harness component. Alternatively, you can run go generate ./... to regenerate the test harness.