feat: add capnp

Signed-off-by: kjuulh <contact@kjuulh.io>

examples/publish_subscribe/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "sq-example-publish-subscribe"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]
+sq-sdk = { path = "../../crates/sq-sdk" }
+tokio = { version = "1", features = ["full"] }
+clap = { version = "4", features = ["derive"] }

examples/publish_subscribe/src/main.rs

@@ -0,0 +1,92 @@
+use clap::{Parser, Subcommand};
+use sq_sdk::{Consumer, ConsumerConfig, Producer, ProducerConfig, ProducerMessage};
+
+#[derive(Parser)]
+#[command(about = "SQ publish/subscribe example")]
+struct Cli {
+    #[arg(long, default_value = "127.0.0.1:6064")]
+    address: String,
+
+    #[command(subcommand)]
+    command: Commands,
+}
+
+#[derive(Subcommand)]
+enum Commands {
+    /// Publish N messages to a topic.
+    Publish {
+        #[arg(long, default_value = "demo")]
+        topic: String,
+        #[arg(long, default_value_t = 100)]
+        count: u64,
+    },
+    /// Subscribe to a topic and print received messages.
+    Subscribe {
+        #[arg(long, default_value = "demo")]
+        topic: String,
+        #[arg(long, default_value = "example-group")]
+        group: String,
+    },
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let cli = Cli::parse();
+
+    match cli.command {
+        Commands::Publish { topic, count } => {
+            let mut producer = Producer::connect(ProducerConfig {
+                address: cli.address,
+                ..Default::default()
+            })
+            .await?;
+
+            println!("Publishing {count} messages to topic '{topic}'...");
+
+            for i in 0..count {
+                let msg = ProducerMessage::new(&topic, format!("message-{i}"));
+                let result = producer.send(&topic, None, msg.value.as_slice()).await?;
+                if i % 10 == 0 {
+                    println!("  sent {i}/{count} (offset={})", result.offset);
+                }
+            }
+
+            println!("Done. Published {count} messages.");
+        }
+        Commands::Subscribe { topic, group } => {
+            let mut consumer = Consumer::connect(ConsumerConfig {
+                address: cli.address,
+                consumer_group: group.clone(),
+                topic: topic.clone(),
+                auto_commit: true,
+                ..Default::default()
+            })
+            .await?;
+
+            println!("Subscribing to topic '{topic}' with group '{group}'...");
+            println!("Press Ctrl+C to stop.\n");
+
+            let mut total = 0u64;
+            loop {
+                let messages = consumer.poll().await?;
+                if messages.is_empty() {
+                    tokio::time::sleep(tokio::time::Duration::from_millis(100)).await;
+                    continue;
+                }
+
+                for msg in &messages {
+                    let value = String::from_utf8_lossy(&msg.value);
+                    println!(
+                        "[offset={} partition={}] {}",
+                        msg.offset, msg.partition, value
+                    );
+                }
+
+                total += messages.len() as u64;
+                println!("  ({total} messages received so far)");
+            }
+        }
+    }
+
+    Ok(())
+}