huskies: merge 1144 story Gateway trampoline-restart: detached helper survives the gateway's own death

server/src/gateway/mod.rs

@@ -4,6 +4,9 @@
 //! Business logic lives in `service::gateway`, HTTP handlers in `http::gateway`.
 //! This file contains only the `run` entrypoint and `build_gateway_route` wiring.
 
+/// Gateway rebuild — builds the new binary and launches the detached trampoline.
+pub mod rebuild;
+
 use crate::http::gateway::*;
 use crate::rebuild::ShutdownReason;
 use crate::service::gateway::{self, GatewayState};

server/src/gateway/rebuild.rs

@@ -0,0 +1,115 @@
+//! Gateway rebuild — builds the new huskies binary and hands off to the trampoline.
+//!
+//! The trampoline is spawned as a detached process (new Unix session) so that it
+//! survives the gateway's own death.  On success the gateway continues running
+//! until the trampoline kills it; the new gateway then posts "gateway X.Y.Z ready".
+
+use std::path::Path;
+
+/// Build the huskies binary and launch the detached trampoline to swap the gateway.
+///
+/// Returns `Err(message)` (shown to the user in chat) if the build or trampoline
+/// launch fails.  On success returns `Ok(())` — the trampoline is now running
+/// in a detached process and will kill this gateway and replace it with the new
+/// binary within 10 s.
+pub async fn rebuild_gateway(config_dir: &Path, gateway_port: u16) -> Result<(), String> {
+    let manifest_dir = std::path::Path::new(env!("CARGO_MANIFEST_DIR"));
+    let workspace_root = manifest_dir
+        .parent()
+        .ok_or("cannot determine workspace root from CARGO_MANIFEST_DIR")?;
+
+    crate::slog!(
+        "[gateway-rebuild] Building from workspace root: {}",
+        workspace_root.display()
+    );
+
+    // Rebuild the frontend bundle so rust-embed picks up the latest assets.
+    let frontend_dir = workspace_root.join("frontend");
+    if frontend_dir.join("package.json").exists() {
+        crate::slog!("[gateway-rebuild] Building frontend");
+        let fe_output = tokio::task::spawn_blocking({
+            let dir = frontend_dir.clone();
+            move || {
+                std::process::Command::new("npm")
+                    .args(["run", "build"])
+                    .current_dir(&dir)
+                    .output()
+            }
+        })
+        .await
+        .map_err(|e| format!("frontend build task panicked: {e}"))?
+        .map_err(|e| format!("failed to run npm run build: {e}"))?;
+
+        if !fe_output.status.success() {
+            let stderr = String::from_utf8_lossy(&fe_output.stderr);
+            return Err(format!("Frontend build failed:\n{stderr}"));
+        }
+        crate::slog!("[gateway-rebuild] Frontend build succeeded");
+    }
+
+    // Build the server binary matching the current profile.
+    let build_args: Vec<&str> = if cfg!(debug_assertions) {
+        vec!["build", "-p", "huskies"]
+    } else {
+        vec!["build", "--release", "-p", "huskies"]
+    };
+    crate::slog!("[gateway-rebuild] cargo {}", build_args.join(" "));
+
+    let output = tokio::task::spawn_blocking({
+        let root = workspace_root.to_path_buf();
+        move || {
+            std::process::Command::new("cargo")
+                .args(&build_args)
+                .current_dir(&root)
+                .output()
+        }
+    })
+    .await
+    .map_err(|e| format!("build task panicked: {e}"))?
+    .map_err(|e| format!("failed to run cargo build: {e}"))?;
+
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        crate::slog!("[gateway-rebuild] Build failed");
+        return Err(format!("Build failed:\n{stderr}"));
+    }
+
+    crate::slog!("[gateway-rebuild] Build succeeded — launching trampoline");
+
+    // Paths for the new and old binaries.
+    let new_binary = if cfg!(debug_assertions) {
+        workspace_root.join("target/debug/huskies")
+    } else {
+        workspace_root.join("target/release/huskies")
+    };
+
+    let old_binary =
+        std::env::current_exe().map_err(|e| format!("cannot locate current binary: {e}"))?;
+
+    let huskies_dir = config_dir.join(".huskies");
+    std::fs::create_dir_all(&huskies_dir)
+        .map_err(|e| format!("cannot create .huskies dir: {e}"))?;
+    let backup_binary = huskies_dir.join("huskies_backup");
+
+    // Current gateway args (skip argv[0]).
+    let gateway_args: Vec<String> = std::env::args().skip(1).collect();
+
+    let job = crate::trampoline::TrampolineJob {
+        gateway_pid: std::process::id(),
+        new_binary_path: new_binary,
+        old_binary_path: old_binary,
+        backup_binary_path: backup_binary,
+        gateway_args,
+        health_url: format!("http://127.0.0.1:{gateway_port}/api/gateway"),
+    };
+
+    let job_path = huskies_dir.join("trampoline.json");
+    crate::trampoline::write_job_atomic(&job, &job_path)?;
+
+    let exe = std::env::current_exe()
+        .map_err(|e| format!("cannot locate current binary for trampoline: {e}"))?;
+    crate::trampoline::spawn_detached_trampoline(&exe, &job_path)?;
+
+    crate::slog!("[gateway-rebuild] Trampoline launched — gateway will be replaced shortly");
+    Ok(())
+}