Slightly safer multi node (#15538)

update

Co-authored-by: Luca Antiga <[email protected]>

Author: tchaton

src/lightning_app/components/multi_node.py

@@ -58,27 +58,30 @@ def run(
         self._cloud_compute = cloud_compute
         self._work_args = work_args
         self._work_kwargs = work_kwargs
-        self.has_initialized = False
+        self.has_started = False
 
     def run(self) -> None:
-        # 1. Create & start the works
-        if not self.has_initialized:
-            for node_rank in range(self.nodes):
-                self.ws.append(
-                    self._work_cls(
-                        *self._work_args,
-                        cloud_compute=self._cloud_compute,
-                        **self._work_kwargs,
-                        parallel=True,
+        if not self.has_started:
+
+            # 1. Create & start the works
+            if not self.ws:
+                for node_rank in range(self.nodes):
+                    self.ws.append(
+                        self._work_cls(
+                            *self._work_args,
+                            cloud_compute=self._cloud_compute,
+                            **self._work_kwargs,
+                            parallel=True,
+                        )
                     )
-                )
-                # Starting node `node_rank`` ...
-                self.ws[-1].start()
-            self.has_initialized = True
+                    # Starting node `node_rank`` ...
+                    self.ws[-1].start()
+
+            # 2. Wait for all machines to be started !
+            if not all(w.status.stage == WorkStageStatus.STARTED for w in self.ws):
+                return
 
-        # 2. Wait for all machines to be started !
-        if all(w.status.stage == WorkStageStatus.STARTED for w in self.ws):
-            return
+            self.has_started = True
 
         # Loop over all node machines
         for node_rank in range(self.nodes):