Docker: Custom App Container

In this guide, you'll learn how to package your custom app with a Fluvio client into a Docker image, and how to run a container with docker CLI.

This tutorial assumes you have a fluvio cluster running. If you don't, follow the Quickstart to get set up.

Example custom Fluvio client

To help illustrate the basic development workflow for all services using a Fluvio client, we'll create this sample Rust service.

Run these commands to initialize the project

$ cargo new fluvio-rust-client
$ cd fluvio-rust-client
$ cargo add async-std --features attributes
$ cargo add chrono fluvio

Copy this code into src/main.rs

use async_std::stream::StreamExt;
use chrono::Local;
use fluvio::metadata::topic::TopicSpec;
use fluvio::{Fluvio, RecordKey};

const TOPIC_NAME: &str = "hello-rust";
const PARTITION_NUM: u32 = 0;
const PARTITIONS: u32 = 1;
const REPLICAS: u32 = 1;

/// This is an example of a basic Fluvio workflow in Rust
///
/// 1. Establish a connection to the Fluvio cluster
/// 2. Create a topic to store data in
/// 3. Create a producer and send some bytes
/// 4. Create a consumer, and stream the data back
#[async_std::main]
async fn main() {
    // Connect to Fluvio cluster
    let fluvio = Fluvio::connect().await.unwrap();

    // Create a topic
    let admin = fluvio.admin().await;
    let topic_spec = TopicSpec::new_computed(PARTITIONS, REPLICAS, None);
    let _topic_create = admin
        .create(TOPIC_NAME.to_string(), false, topic_spec)
        .await;

    // Create a record
    let record = format!("Hello World! - Time is {}", Local::now().to_rfc2822());

    // Produce to a topic
    let producer = fluvio::producer(TOPIC_NAME).await.unwrap();
    producer.send(RecordKey::NULL, record).await.unwrap();
    // Fluvio batches outgoing records by default, so flush producer to ensure all records are sent
    producer.flush().await.unwrap();

    // Consume last record from topic
    let consumer = fluvio::consumer(TOPIC_NAME, PARTITION_NUM).await.unwrap();
    let mut stream = consumer.stream(fluvio::Offset::from_end(1)).await.unwrap();
    if let Some(Ok(record)) = stream.next().await {
        let string = String::from_utf8_lossy(record.value());
        println!("{}", string);
    }
}

Example Dockerfile

Save the following Dockerfile. This Dockerfile adds our workflow an starts it with cargo run, which will always build the code before it starts.

FROM rust:1.73.0

# Run as the `fluvio` user instead of root
ENV USER=fluvio
RUN useradd --create-home "$USER"
USER $USER
WORKDIR /home/fluvio

# Copy your Rust project and run it
COPY --chown=$USER:$USER Cargo.toml .
COPY --chown=$USER:$USER src ./src
CMD /usr/local/cargo/bin/cargo run

Running docker image

The fluvio clients search for connection information from a config file located at $HOME/.fluvio/config.

Run with docker run

In this example, we build our docker image with docker build then start a container from the image with docker run. We volume mount our host's config file to the container when we start.

$ docker build -t fluvio-client-example .
$ docker run -v $HOME/.fluvio/config:/home/fluvio/.fluvio/config --init --rm fluvio-client-example

Afer running you'll see the following output:

Running `target/debug/fluvio-rust-client`
Hello World! - Time is Tue, 10 Oct 2023 21:09:05 +0000

The same event has been published to the topic:

$ fluvio consume -Bd hello-rust
Consuming records from 'hello-rust' starting from the beginning of log
Hello World! - Time is Tue, 10 Oct 2023 21:09:05 +0000

Run with docker compose (alternative)

Copy this yaml file and save it as docker-compose.yaml

# docker-compose.yaml
version: "3"
services:
  example:
    build: .
    volumes:
      - $HOME/.fluvio/config:/home/fluvio/.fluvio/config:ro

In this example, we build our docker image with docker compose build then start a container from the image with docker compose up. We volume mount our host's config file to the container when we start.

$ docker compose build
$ docker compose up