Add the example for WasmEdge + Kafka / Redpanda + MySQL application to take messages from a queue and save into a database table.

Signed-off-by: Michael Yuan <michael@secondstate.io>

wasmedge-kafka-mysql/.docker/docker-compose.yml

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+services:
+  redpanda:
+    image: docker.redpanda.com/vectorized/redpanda:v22.2.2
+    command:
+      - redpanda start
+      - --smp 1
+      - --overprovisioned
+      - --node-id 0
+      - --kafka-addr PLAINTEXT://0.0.0.0:29092,OUTSIDE://0.0.0.0:9092
+      - --advertise-kafka-addr PLAINTEXT://redpanda:29092,OUTSIDE://redpanda:9092
+      - --pandaproxy-addr 0.0.0.0:8082
+      - --advertise-pandaproxy-addr localhost:8082
+    ports:
+      - 8081:8081
+      - 8082:8082
+      - 9092:9092
+      - 9644:9644
+      - 29092:29092
+    volumes:
+      - ./kafka:/app
+  etl:
+    image: etl-kafka
+    build:
+      context: etl
+      platforms:
+        - wasi/wasm32
+    environment:
+      DATABASE_URL: mysql://root:whalehello@db:3306/mysql
+      KAFKA_URL: kafka://redpanda:9092/order
+      RUST_BACKTRACE: full
+      RUST_LOG: info
+    restart: unless-stopped
+    runtime: io.containerd.wasmedge.v1
+  db:
+    image: mariadb:10.9
+    environment:
+      MYSQL_ROOT_PASSWORD: whalehello

wasmedge-kafka-mysql/README.md

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+# Compose sample application
+
+we demonstrate a microservice written in Rust. It subscribes to a Kafka queue topic on a Redpanda server, and then transforms and saves each message into a MySQL database (mariaDB) table. The microservice is compiled into WebAssembly (Wasm) and runs in the WasmEdge Runtime, which is a secure and lightweight alternative to natively compiled Rust apps in Linux containers.
+
+## Use with Docker Development Environments
+
+You will need a version of Docker Desktop or Docker CLI with Wasm support.
+
+* [Install Docker Desktop + Wasm (Beta)](https://docs.docker.com/desktop/wasm/)
+* [Install Docker CLI + Wasm](https://github.com/chris-crone/wasm-day-na-22/tree/main/server)
+
+## WasmEdge server with Redpanda and MySQL database
+
+Project structure:
+
+```
+.
++-- compose.yml
+|-- etl
+    |-- Dockerfile
+    |-- Cargo.toml
+    +-- src
+        |-- main.rs
+|-- kafka
+    |-- order.json
+|-- db
+    |-- db-password.txt
+```
+
+The [compose.yml](compose.yml) is as follows.
+
+```yaml
+services:
+  redpanda:
+    image: docker.redpanda.com/vectorized/redpanda:v22.2.2
+    command:
+      - redpanda start
+      - --smp 1
+      - --overprovisioned
+      - --node-id 0
+      - --kafka-addr PLAINTEXT://0.0.0.0:29092,OUTSIDE://0.0.0.0:9092
+      - --advertise-kafka-addr PLAINTEXT://redpanda:29092,OUTSIDE://redpanda:9092
+      - --pandaproxy-addr 0.0.0.0:8082
+      - --advertise-pandaproxy-addr localhost:8082
+    ports:
+      - 8081:8081
+      - 8082:8082
+      - 9092:9092
+      - 9644:9644
+      - 29092:29092
+    volumes:
+      - ./kafka:/app
+
+  etl:
+    image: etl-kafka
+    build:
+      context: etl
+      platforms:
+        - wasi/wasm32
+    environment:
+      DATABASE_URL: mysql://root:whalehello@db:3306/mysql
+      KAFKA_URL: kafka://redpanda:9092/order
+      RUST_BACKTRACE: full
+      RUST_LOG: info
+    restart: unless-stopped
+    runtime: io.containerd.wasmedge.v1
+
+  db:
+    image: mariadb:10.9
+    environment:
+      MYSQL_ROOT_PASSWORD: whalehello
+```
+
+The compose file defines an application with three services `redpanda`, `etl` and `db`. The `redpanda` is a Kafka-compatible messaging server that produces messages in a queue topic. The `etl` service, in the WasmEdge container, subscribes to the queue topic and receives incoming messages. Each incoming message is parsed and stored in the `db` MySQL database server.
+
+## Deploy with docker compose
+
+```bash
+$ docker compose up -d
+...
+ ⠿ Network wasmedge-kafka-mysql_default       Created                      0.1s
+ ⠿ Container wasmedge-kafka-mysql-redpanda-1  Created                      0.3s
+ ⠿ Container wasmedge-kafka-mysql-etl-1       Created                      0.3s
+ ⠿ Container wasmedge-kafka-mysql-db-1        Created                      0.3s
+```
+
+## Expected result
+
+```bash
+$ docker compose ps
+NAME                              COMMAND                  SERVICE             STATUS              PORTS
+wasmedge-kafka-mysql-db-1         "docker-entrypoint.s…"   db                  running             3306/tcp
+wasmedge-kafka-mysql-etl-1        "kafka.wasm"             etl                 running
+wasmedge-kafka-mysql-redpanda-1   "/entrypoint.sh 'red…"   redpanda            running             0.0.0.0:8081-8082->8081-8082/tcp, :::8081-8082->8081-8082/tcp, 0.0.0.0:9092->9092/tcp, :::9092->9092/tcp, 0.0.0.0:9644->9644/tcp, :::9644->9644/tcp, 0.0.0.0:29092->29092/tcp, :::29092->29092/tcp
+```
+
+After the application starts, 
+log into the Redpanda container and send a message to the queue topic `order` as follows.
+
+```bash
+$ docker compose exec redpanda /bin/bash
+redpanda@1add2615774b:/$ cd /app
+redpanda@1add2615774b:/app$ cat order.json | rpk topic produce order
+Produced to partition 0 at offset 0 with timestamp 1667922788523.
+```
+
+To see the data in the database container, you can use the following commands.
+
+```bash
+$ docker compose exec db /bin/bash
+root@c97c472db02e:/# mysql -u root -pwhalehello mysql
+mysql> select * from orders;
+... ...
+```
+

wasmedge-kafka-mysql/compose.yml

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+services:
+  redpanda:
+    image: docker.redpanda.com/vectorized/redpanda:v22.2.2
+    command:
+      - redpanda start
+      - --smp 1
+      - --overprovisioned
+      - --node-id 0
+      - --kafka-addr PLAINTEXT://0.0.0.0:29092,OUTSIDE://0.0.0.0:9092
+      - --advertise-kafka-addr PLAINTEXT://redpanda:29092,OUTSIDE://redpanda:9092
+      - --pandaproxy-addr 0.0.0.0:8082
+      - --advertise-pandaproxy-addr localhost:8082
+    ports:
+      - 8081:8081
+      - 8082:8082
+      - 9092:9092
+      - 9644:9644
+      - 29092:29092
+    volumes:
+      - ./kafka:/app
+  etl:
+    image: etl-kafka
+    build:
+      context: etl
+      platforms:
+        - wasi/wasm32
+    environment:
+      DATABASE_URL: mysql://root:whalehello@db:3306/mysql
+      KAFKA_URL: kafka://redpanda:9092/order
+      RUST_BACKTRACE: full
+      RUST_LOG: info
+    restart: unless-stopped
+    runtime: io.containerd.wasmedge.v1
+  db:
+    image: mariadb:10.9
+    environment:
+      MYSQL_ROOT_PASSWORD: whalehello

wasmedge-kafka-mysql/db/db-password.txt

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+whalehello

wasmedge-kafka-mysql/etl/Cargo.toml

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+[package]
+name = "kafka"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0.65"
+mega_etl = {git = "https://github.com/second-state/MEGA.git"}
+tokio_wasi = {version = '1.21', features = ["rt", "macros"]}
+env_logger = "0.9"
+log  = "0.4"
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+http_req_wasi  = "0.10"
+lazy_static = "1.4.0"

wasmedge-kafka-mysql/etl/Dockerfile

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+FROM --platform=$BUILDPLATFORM rust:1.64 AS buildbase
+RUN <<EOT bash
+    set -ex
+    apt-get update
+    apt-get install -y \
+        git \
+        clang
+    rustup target add wasm32-wasi
+EOT
+# This line installs WasmEdge including the AOT compiler
+RUN curl -sSf https://raw.githubusercontent.com/WasmEdge/WasmEdge/master/utils/install.sh | bash
+
+FROM buildbase AS build
+COPY Cargo.toml .
+COPY src ./src 
+# Build the Wasm binary
+RUN --mount=type=cache,target=/usr/local/cargo/git/db \
+    --mount=type=cache,target=/usr/local/cargo/registry/cache \
+    --mount=type=cache,target=/usr/local/cargo/registry/index \
+    cargo build --target wasm32-wasi --release
+# This line builds the AOT Wasm binary
+RUN /root/.wasmedge/bin/wasmedgec target/wasm32-wasi/release/kafka.wasm kafka.wasm
+
+FROM scratch
+ENTRYPOINT [ "kafka.wasm" ]
+COPY --link --from=build /kafka.wasm /kafka.wasm

wasmedge-kafka-mysql/etl/src/main.rs

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+use mega_etl::{async_trait, Pipe, Transformer, TransformerError, TransformerResult};
+
+use serde::{Deserialize, Serialize};
+#[derive(Serialize, Deserialize, Debug)]
+struct Order {
+    order_id: i32,
+    product_id: i32,
+    quantity: i32,
+    amount: f32,
+    shipping: f32,
+    tax: f32,
+    shipping_address: String,
+}
+
+#[async_trait]
+impl Transformer for Order {
+    async fn transform(inbound_data: &Vec<u8>) -> TransformerResult<Vec<String>> {
+        let s = std::str::from_utf8(&inbound_data)
+            .map_err(|e| TransformerError::Custom(e.to_string()))?;
+        let order: Order = serde_json::from_str(String::from(s).as_str())
+            .map_err(|e| TransformerError::Custom(e.to_string()))?;
+        log::info!("{:?}", &order);
+        let mut ret = vec![];
+        let sql_string = format!(
+            r"INSERT INTO orders VALUES ({:?}, {:?}, {:?}, {:?}, {:?}, {:?}, {:?}, CURRENT_TIMESTAMP);",
+            order.order_id,
+            order.product_id,
+            order.quantity,
+            order.amount,
+            order.shipping,
+            order.tax,
+            order.shipping_address,
+        );
+        dbg!(sql_string.clone());
+        ret.push(sql_string);
+        Ok(ret)
+    }
+
+    async fn init() -> TransformerResult<String> {
+        Ok(String::from(
+            r"CREATE TABLE IF NOT EXISTS orders (order_id INT, product_id INT, quantity INT, amount FLOAT, shipping FLOAT, tax FLOAT, shipping_address VARCHAR(50), date_registered TIMESTAMP DEFAULT CURRENT_TIMESTAMP);",
+        ))
+    }
+}
+
+#[tokio::main(flavor = "current_thread")]
+async fn main() -> anyhow::Result<()> {
+    env_logger::init();
+
+    // can use builder later
+    let database_uri = std::env::var("DATABASE_URL")?;
+    let kafka_uri = std::env::var("KAFKA_URL")?;
+    let mut pipe = Pipe::new(database_uri, kafka_uri).await;
+
+    // This is async because this calls the async transform() function in Order
+    pipe.start::<Order>().await?;
+    Ok(())
+}

wasmedge-kafka-mysql/kafka/order.json

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+{"order_id": 1,"product_id": 12,"quantity": 2,"amount": 56.0,"shipping": 15.0,"tax": 2.0,"shipping_address": "Mataderos 2312"}