api_server: add kill switch capability

Added shutdown event-fd acting as a kill switch.
Used to signal the api server thread that it needs to shut down.

Signed-off-by: Egor Lazarchuk <[email protected]>
Co-authored-by: acatangiu <[email protected]>

src/api_server/Cargo.toml

@@ -16,7 +16,7 @@ serde_json = "1.0.78"
 thiserror = "1.0.32"
 
 logger = { path = "../logger" }
-micro_http = { git = "https://github.com/firecracker-microvm/micro-http", rev = "4b18a04" }
+micro_http = { git = "https://github.com/firecracker-microvm/micro-http" }
 mmds = { path = "../mmds" }
 seccompiler = { path = "../seccompiler" }
 utils = { path = "../utils" }

src/api_server/src/lib.rs

@@ -97,6 +97,11 @@ impl ApiServer {
         loop {
             let request_vec = match server.requests() {
                 Ok(vec) => vec,
+                Err(ServerError::ShutdownEvent) => {
+                    server.flush_outgoing_writes();
+                    debug!("shutdown request received, API server thread ending.");
+                    return;
+                }
                 Err(err) => {
                     // print request error, but keep server running
                     error!("API Server error on retrieving incoming request: {}", err);

src/dumbo/Cargo.toml

@@ -13,7 +13,7 @@ bitflags = "1.3.2"
 derive_more = { version = "0.99.17", default-features = false, features = ["from"] }
 
 logger = { path = "../logger" }
-micro_http = { git = "https://github.com/firecracker-microvm/micro-http", rev = "4b18a04" }
+micro_http = { git = "https://github.com/firecracker-microvm/micro-http" }
 utils = { path = "../utils" }
 
 [dev-dependencies]

src/firecracker/src/api_server_adapter.rs

@@ -147,6 +147,8 @@ pub(crate) fn run_with_api(
     // It is used in the config/pre-boot loop which is a simple blocking loop
     // which only consumes API events.
     let api_event_fd = EventFd::new(libc::EFD_SEMAPHORE).expect("Cannot create API Eventfd.");
+    // FD used to signal API thread to stop/shutdown.
+    let api_kill_switch = EventFd::new(libc::EFD_NONBLOCK).expect("Cannot create API kill switch.");
 
     // Channels for both directions between Vmm and Api threads.
     let (to_vmm, from_api) = channel();
@@ -159,7 +161,7 @@ pub(crate) fn run_with_api(
         .remove("api")
         .expect("Missing seccomp filter for API thread.");
 
-    let server = match HttpServer::new(&bind_path) {
+    let mut server = match HttpServer::new(&bind_path) {
         Ok(s) => s,
         Err(ServerError::IOError(inner)) if inner.kind() == std::io::ErrorKind::AddrInUse => {
             let sock_path = bind_path.display().to_string();
@@ -170,6 +172,14 @@ pub(crate) fn run_with_api(
         }
     };
 
+    let api_kill_switch_clone = api_kill_switch
+        .try_clone()
+        .expect("Failed to clone API kill switch");
+
+    server
+        .add_kill_switch(api_kill_switch_clone)
+        .expect("Cannot add HTTP server kill switch");
+
     // Start the separate API thread.
     let api_thread = thread::Builder::new()
         .name("fc_api".to_owned())

src/mmds/Cargo.toml

@@ -21,6 +21,6 @@ versionize_derive = "0.1.5"
 
 dumbo = { path = "../dumbo" }
 logger = { path = "../logger" }
-micro_http = { git = "https://github.com/firecracker-microvm/micro-http", rev = "4b18a04" }
+micro_http = { git = "https://github.com/firecracker-microvm/micro-http" }
 snapshot = { path = "../snapshot" }
-utils = { path = "../utils" }
+utils = { path = "../utils" }