Iggy Java Examples

This directory contains comprehensive sample applications that showcase various usage patterns of the Iggy java client SDK, from basic operations to advanced multi-tenant scenarios.

Java 17 and Gradle 9.2.1 are recommended for running the examples.

Running Examples

Iggy requires valid credentials to authenticate client requests. The examples assume that the server is using the default root credentials, which can be enabled in one of two ways:

1. Start the server with default credentials:

   cargo run --bin iggy-server -- --with-default-root-credentials
   

2. Set the appropriate environment variables before starting the server with cargo run --bin iggy-server:

   macOS/Linux:

   export IGGY_ROOT_USERNAME=iggy
   export IGGY_ROOT_PASSWORD=iggy
   

   Windows(Powershell):

   $env:IGGY_ROOT_USERNAME = "iggy"
   $env:IGGY_ROOT_PASSWORD = "iggy"
   

Note
This setup is intended only for development and testing, not production use.

By default, all server data is stored in the local_data directory (this can be changed via system.path in config.toml).

Root credentials are applied only on the very first startup, when no data directory exists yet. Once the server has created and populated the data directory, the existing stored credentials will always be used, and supplying the --with-default-root-credentials flag or setting the environment variables will no longer override them.

If the server has already been started once and your example returns Error: InvalidCredentials, then this means the stored credentials differ from the defaults.

You can reset the credentials in one of two ways:

1. Delete the existing data directory, then start the server again with the default-credential flag or environment variables.

2. Use the --fresh flag to force a reset:

   cargo run --bin iggy-server -- --with-default-root-credentials --fresh
   

   This will ignore any existing data directory and re-initialize it with the default credentials.

For server configuration options and help:

cargo run --bin iggy-server -- --help

You can also customize the server using environment variables:

## Example: Enable HTTP transport and set custom address
IGGY_HTTP_ENABLED=true IGGY_TCP_ADDRESS=0.0.0.0:8090 cargo run --bin iggy-server

Basic Examples

Getting Started

A good introduction for newcomers to Iggy:

./gradlew runGettingStartedProducer
./gradlew runGettingStartedConsumer

Message Headers

Shows metadata management using custom headers:

./gradlew runMessageHeadersProducer
./gradlew runMessageHeadersConsumer

Demonstrates using header keys and values for message metadata instead of payload-based typing, with header-based message routing.

Message Envelopes

JSON envelope pattern for polymorphic message handling:

./gradlew runMessageEnvelopeProducer
./gradlew runMessageEnvelopeConsumer

Uses MessagesGenerator to create OrderCreated, OrderConfirmed, and OrderRejected messages wrapped in JSON envelopes for type identification.

Advanced Examples

Multi-Tenant Architecture

Complex example demonstrating enterprise-level isolation:

./gradlew runMultiTenantProducer
./gradlew runMultiTenantConsumer

Features multiple tenant setup, user creation with stream-specific permissions, concurrent producers/consumers across tenants, and security isolation.

High-Volume Data Generation

Testing and benchmarking support:

./gradlew runSinkDataProducer

Produces high-throughput data (1000+ messages per batch) with realistic user records.

Stream Builder Examples

Stream Builder

Building streams with advanced configuration:

./gradlew runStreamBasic

Shows how to use the stream builder API to create and configure streams with custom settings.

Async Client Examples

Async Producer

High-throughput async production with pipelining:

./gradlew runAsyncProducer

Shows:

• CompletableFuture chaining patterns
• Pipelining multiple sends without blocking
• Performance comparison with blocking client

Async Consumer

Non-blocking async consumption with advanced patterns:

./gradlew runAsyncConsumer

Shows:

• Backpressure management (don't poll faster than you can process)
• Error recovery with exponential backoff
• Thread pool separation (Netty I/O threads vs. processing threads)
• Offset-based polling with CompletableFuture

CRITICAL ASYNC PATTERN - Thread Pool Management:

The async client uses Netty's event loop threads for I/O operations. NEVER block these threads with:

• .join() or .get() inside thenApply/thenAccept
• Thread.sleep()
• Blocking database calls
• Long-running computations

If your message processing involves blocking operations, offload to a separate thread pool using thenApplyAsync(fn, executor).

Blocking vs. Async - When to Use Each

The Iggy Java SDK provides two client types: blocking (synchronous) and async (non-blocking). Choose based on your use case:

Use Blocking Client When

• Writing scripts, CLI tools, or simple applications
• Sequential code is easier to reason about
• Integration tests

Use Async Client When

• Need high throughput
• Application is already async/reactive (Spring WebFlux, Vert.x)
• Want to pipeline multiple requests over a single connection
• Building services that handle many concurrent streams

Key Async Patterns

CompletableFuture Chaining

client.connect()
    .thenCompose(v -> client.login())
    .thenCompose(identity -> client.streams().createStream("my-stream"))
    .thenAccept(stream -> System.out.println("Created: " + stream.name()))
    .exceptionally(ex -> {
        System.err.println("Error: " + ex.getMessage());
        return null;
    });

Pipelining for Throughput

List<CompletableFuture<Void>> sends = new ArrayList<>();
for (int i = 0; i < 10; i++) {
    sends.add(client.messages().sendMessages(...));
}
CompletableFuture.allOf(sends.toArray(new CompletableFuture[0])).join();

Thread Pool Offloading

// WRONG - blocks Netty event loop
client.messages().pollMessages(...)
    .thenAccept(polled -> {
        saveToDatabase(polled);  // blocking I/O!
    });

// CORRECT - offloads to processing pool
var processingPool = Executors.newFixedThreadPool(8);
client.messages().pollMessages(...)
    .thenAcceptAsync(polled -> {
        saveToDatabase(polled);  // runs on processingPool
    }, processingPool);