WebAssembly Jobs and CronJobs in Kubernetes

# Install canary of the command trigger plugin
spin plugins install --yes \
  --url https://github.com/fermyon/spin-trigger-command/releases/download/canary/trigger-command.json

# Install or Upgrade the command-rust template
spin templates install --upgrade \
 --git https://github.com/fermyon/spin-trigger-command

Copying remote template source
Installing template command-rust...
Installed 1 template(s)

+-------------------------------------------+
| Name           Description                |
+===========================================+
| command-rust   Command handler using Rust |
+-------------------------------------------+

# Create a new Spin App using the command-rust template
spin new -t command-rust -a hello-command-trigger

cd hello-command-trigger

# Build the Spin App
spin build

Building component hello-command-trigger with `cargo component build --target wasm32-wasi --release`
# ... snip ...
Finished building all Spin components

# Run the Spin App
spin up
Logging component stdio to ".spin/logs/"
Hello, Fermyon!

# ./src/migrations/spin.toml
spin_manifest_version = 2

[application]
name = "migrations"
version = "0.1.0"
authors = ["Fermyon Engineering <engineering@fermyon.com>"]
description = ""

[variables]
db_host = { default = "localhost" }
db_connection_string = { default = "postgres://timmy:secret@localhost/todo" }

[[trigger.command]]
component = "migrations"

[component.migrations]
source = "target/wasm32-wasi/release/migrations.wasm"
allowed_outbound_hosts = ["postgres://{{ db_host }}"]

[component.migrations.variables]
connection_string = "{{ db_connection_string }}"

[component.migrations.build]
command = "cargo component build --target wasm32-wasi --release"
watch = ["src/**/*.rs", "Cargo.toml"]

// ./src/stats-generator/src/main.rs
use anyhow::{Context, Result};
use spin_sdk::{
    pg::{Connection, Decode, ParameterValue},
    variables,
};

const SQL_INSERT_STATS: &str = "INSERT INTO Stats (open, done) VALUES ($1, $2)";
const SQL_GET_TASK_STATS: &str = "SELECT done FROM Tasks";

pub struct Stats {
    pub open: i64,
    pub done: i64,
}

fn get_connection() -> Result<Connection> {
    let connection_string = variables::get("connection_string")?;
    Connection::open(&connection_string)
        .with_context(|| "Error establishing connection to PostgreSQL database")
}

fn main() -> Result<()> {
    println!("Generating stats");
    let connection = get_connection()?;
    let row_set = connection.query(SQL_GET_TASK_STATS, &[])?;
    let stats = row_set
        .rows
        .iter()
        .fold(Stats { open: 0, done: 0 }, |mut acc, stat| {
            if bool::decode(&stat[0]).unwrap() {
                acc.done += 1;
            } else {
                acc.open += 1;
            }
            acc
        });
    let parameters = [
        ParameterValue::Int64(stats.open),
        ParameterValue::Int64(stats.done),
    ];
    connection
        .execute(SQL_INSERT_STATS, &parameters)
        .with_context(|| "Error while writing stats")?;
	println!("Done.");
  Ok(())
}

# ./kubernetes/migrations.yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: todo-migrations
spec:
  ttlSecondsAfterFinished: 600
  template:
    spec:
      runtimeClassName: wasmtime-spin-v2
      containers:
        - name: migrations
          image: ttl.sh/spin-todo-migrations:24h
          command:
            - /
          env:
            - name: "SPIN_VARIABLE_DB_HOST"
              value: "todo-db"
            - name: "SPIN_VARIABLE_DB_CONNECTION_STRING"
              valueFrom:
                secretKeyRef:
                  name: db-config
                  key: connectionstring
      restartPolicy: Never

# ./kubernetes/stats-generator.yaml
apiVersion: batch/v1
kind: CronJob
metadata:
  name: stats-generator
spec:
  schedule: "*/2 * * * *"
  jobTemplate:
    spec:
      template:
        spec:
          runtimeClassName: wasmtime-spin-v2
          containers:
            - name: cron
              image: ttl.sh/spin-todo-cron:24h
              command:
                - /
              env:
                - name: "SPIN_VARIABLE_DB_HOST"
                  value: "todo-db"
                - name: "SPIN_VARIABLE_DB_CONNECTION_STRING"
                  valueFrom:
                    secretKeyRef:
                      name: db-config
                      key: connectionstring
          restartPolicy: OnFailure

# Deploy the PostgreSQL database
kubectl apply -f kubernetes/db.yaml

# Wait for the database pod to become ready
kubectl wait --for=condition=Ready pod -l app=postgres

# Deploy the Migrations Job
kubectl apply -f kubernetes/migrations.yaml

# Deploy the HTTP API
kubectl apply -f kubernetes/api.yaml

# Deploy the CronJob
kubectl apply -f kubernetes/stats-generator.yaml

# Setup port-forwarding from localhost to the todo-api service
kubectl port-forward svc/todo-api 8080:80

Forwarding from 127.0.0.1:8080 -> 80
Forwarding from [::1]:8080 -> 80

# Send GET request to /tasks
curl localhost:8080/tasks
[
  {
    "id": "ba6f77a2-73a7-4948-891a-73532b941cbf",
    "content": "Arrange books on the shelf",
    "done": false
  },
  // ...
]

# Send GET request to /stats
curl localhost:8080/stats
[
  {
    "date": "2024-11-04 10:22:00",
    "open_tasks": 12,
    "done_tasks": 13
  }
]

curl localhost:8080/stats
[
  {
    "date": "2024-11-04 10:24:00",
    "open_tasks": 12,
    "done_tasks": 13
  },
  {
    "date": "2024-11-04 10:22:00",
    "open_tasks": 12,
    "done_tasks": 13
  }
]