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Compose sample application

This sample demonstrates a WebAssembly (Wasm) 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 (MariaDB) database table. The microservice is compiled into 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.

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 is as follows.

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 service is a Kafka-compatible messaging server that produces messages in a queue topic. The etl service, in the WasmEdge container that subscribes to the queue topic and receives incoming messages. Each incoming message is parsed and stored in the db MySQL (MariaDB) database server.

Deploy with docker compose

$ 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

$ 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.

$ 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.

$ docker compose exec db /bin/bash
root@c97c472db02e:/# mysql -u root -pwhalehello mysql
mysql> select * from orders;
... ...

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