Start all, with a controlled concurrency

Fix #536

gns3server/handlers/api/controller/node_handler.py

@@ -17,6 +17,7 @@
 
 from gns3server.web.route import Route
 from gns3server.controller import Controller
+from gns3server.utils.asyncio.pool import Pool
 
 from gns3server.schemas.node import (
     NODE_OBJECT_SCHEMA,
@@ -103,8 +104,10 @@ class NodeHandler:
     def start_all(request, response):
 
         project = Controller.instance().get_project(request.match_info["project_id"])
+        pool = Pool(concurrency=3)
         for node in project.nodes.values():
-            yield from node.start()
+            pool.append(node.start)
+        yield from pool.join()
         response.set_status(204)
 
     @Route.post(
@@ -122,8 +125,10 @@ class NodeHandler:
     def stop_all(request, response):
 
         project = Controller.instance().get_project(request.match_info["project_id"])
+        pool = Pool(concurrency=3)
         for node in project.nodes.values():
-            yield from node.stop()
+            pool.append(node.stop)
+        yield from pool.join()
         response.set_status(204)
 
     @Route.post(
@@ -141,8 +146,10 @@ class NodeHandler:
     def suspend_all(request, response):
 
         project = Controller.instance().get_project(request.match_info["project_id"])
+        pool = Pool(concurrency=3)
         for node in project.nodes.values():
-            yield from node.suspend()
+            pool.append(node.suspend)
+        yield from pool.join()
         response.set_status(204)
 
     @Route.post(
@@ -160,10 +167,13 @@ class NodeHandler:
     def reload_all(request, response):
 
         project = Controller.instance().get_project(request.match_info["project_id"])
+        pool = Pool(concurrency=3)
         for node in project.nodes.values():
-            yield from node.stop()
+            pool.append(node.stop)
+        yield from pool.join()
         for node in project.nodes.values():
-            yield from node.start()
+            pool.append(node.start)
+        yield from pool.join()
         response.set_status(204)
 
     @Route.post(