Implement cluster topology CLI command

cli/src/commands/cluster/mod.rs

@@ -1,22 +1,27 @@
-mod status;
-
-use anyhow::Result;
-use clap::{Args as ClapArgs, Subcommand};
-
-#[derive(ClapArgs)]
-pub struct Args {
-    #[command(subcommand)]
-    pub sub: ClusterCmd,
-}
-
-#[derive(Subcommand)]
-pub enum ClusterCmd {
-    /// Print the live state of every node listed in --config.
-    Status(status::StatusArgs),
-}
-
-pub async fn run(args: Args) -> Result<()> {
-    match args.sub {
-        ClusterCmd::Status(a) => status::run(a).await,
-    }
-}
+mod status;
+mod topology;
+
+use anyhow::Result;
+use clap::{Args as ClapArgs, Subcommand};
+
+#[derive(ClapArgs)]
+pub struct Args {
+    #[command(subcommand)]
+    pub sub: ClusterCmd,
+}
+
+#[derive(Subcommand)]
+pub enum ClusterCmd {
+    /// Print the live state of every node listed in --config.
+    Status(status::StatusArgs),
+
+    /// Print cluster topology.
+    Topology(topology::TopologyArgs),
+}
+
+pub async fn run(args: Args) -> Result<()> {
+    match args.sub {
+        ClusterCmd::Status(a) => status::run(a).await,
+        ClusterCmd::Topology(a) => topology::run(a).await,
+    }
+}

cli/src/commands/cluster/topology.rs

@@ -0,0 +1,36 @@
+use anyhow::{Context, Result};
+use clap::Args as ClapArgs;
+use std::path::PathBuf;
+
+use crate::config;
+
+#[derive(ClapArgs)]
+pub struct TopologyArgs {
+    /// Path to the cluster TOML config file.
+    #[arg(long)]
+    pub config: PathBuf,
+}
+
+pub async fn run(args: TopologyArgs) -> Result<()> {
+    let cfg =
+        config::load(&args.config).with_context(|| format!("load {}", args.config.display()))?;
+
+    println!("OpenLake Cluster Topology");
+    println!("=========================");
+
+    if cfg.nodes.is_empty() {
+        println!(
+            "no openlake cluster detected: {} declares zero nodes",
+            args.config.display()
+        );
+        return Ok(());
+    }
+
+    for node in &cfg.nodes {
+        println!("[node {:>3}] {}", node.id, node.rpc_addr);
+    }
+
+    println!();
+    println!("cluster contains {} node(s)", cfg.nodes.len());
+    Ok(())
+}