Update the if-condition of return type to ensure it will fail if rest (…

…#1416)

server is not running successfully.

Signed-off-by: ChenYing Kuo <[email protected]>

DEFAULT_CONFIG.json5

@@ -505,7 +505,7 @@
   //      http_port: 8000,
   //      /// The number of worker thread in TOKIO runtime (default: 2)
   //      /// The configuration only takes effect if running as a dynamic plugin, which can not reuse the current runtime.
-  //      work_thread_num: 0,
+  //      work_thread_num: 2,
   //      /// The number of blocking thread in TOKIO runtime (default: 50)
   //      /// The configuration only takes effect if running as a dynamic plugin, which can not reuse the current runtime.
   //      max_block_thread_num: 50,

plugins/zenoh-plugin-rest/src/lib.rs

@@ -290,7 +290,9 @@ impl Plugin for RestPlugin {
             timeout(Duration::from_millis(1), TOKIO_RUNTIME.spawn(task)).await
         });
 
-        if let Ok(Err(e)) = task {
+        // The spawn task (TOKIO_RUNTIME.spawn(task)) should not return immediately. The server should block inside.
+        // If it returns immediately (for example, address already in use), we can get the error inside Ok
+        if let Ok(Ok(Err(e))) = task {
             bail!("REST server failed within 1ms: {e}")
         }
         Ok(Box::new(RunningPlugin(conf)))