Add remove-node subcommand

closes #160

* Add `remove-node` to remove a specific node from the cluster.
* Add `Cluster.get_node_by_name()` method to return a node based on the node
  name.
* Add optional `stop` option to `Cluster.remove_node()`, to also stop the node
  when `stop=True`.

elasticluster/cluster.py

@@ -346,20 +346,32 @@ def add_nodes(self, kind, num, image_id, image_user, flavor,
             self.add_node(kind, image_id, image_user, flavor,
                           security_group, image_userdata=image_userdata, **extra)
 
-    def remove_node(self, node):
-        """Removes a node from the cluster, but does not stop it. Use this
-        method with caution.
+    def remove_node(self, node, stop=False):
+        """Removes a node from the cluster.
+
+        By default, it doesn't also stop the node, just remove from
+        the known hosts of this cluster.
 
         :param node: node to remove
         :type node: :py:class:`Node`
+
+        :param stop: Stop the node
+        :type stop: bool
+
         """
         if node.kind not in self.nodes:
-            log.error("Unable to remove node %s: invalid node type `%s`.",
+            raise NodeNotFound("Unable to remove node %s: invalid node type `%s`.",
                       node.name, node.kind)
         else:
-            index = self.nodes[node.kind].index(node)
-            if self.nodes[node.kind][index]:
-                del self.nodes[node.kind][index]
+            try:
+                index = self.nodes[node.kind].index(node)
+                if self.nodes[node.kind][index]:
+                    del self.nodes[node.kind][index]
+                if stop:
+                    node.stop()
+                self.repository.save_or_update(self)
+            except ValueError:
+                raise NodeNotFound("Node %s not found in cluster" % node.name)
 
     @staticmethod
     def _start_node(node):
@@ -539,8 +551,7 @@ def timeout_handler(signum, frame):
             for node in pending_nodes:
                 log.error("Stopping node `%s`, since we could not connect to"
                           " it within the timeout." % node.name)
-                node.stop()
-                self.remove_node(node)
+                self.remove_node(node, stop=True)
 
         signal.alarm(0)
 
@@ -637,6 +648,18 @@ def get_all_nodes(self):
         else:
             return []
 
+    def get_node_by_name(self, nodename):
+        """Return the node corresponding with name `nodename`
+
+        :params nodename: Name of the node
+        :type nodename: str
+        """
+        nodes = dict((n.name, n) for n in self.get_all_nodes())
+        try:
+            return nodes[nodename]
+        except KeyError:
+            raise NodeNotFound("Node %s not found" % nodename)
+
     def stop(self, force=False):
         """Destroys all instances of this cluster and calls delete on the
         repository.

elasticluster/main.py

@@ -44,6 +44,7 @@
 from elasticluster.subcommands import SshFrontend
 from elasticluster.subcommands import SftpFrontend
 from elasticluster.subcommands import GC3PieConfig
+from elasticluster.subcommands import RemoveNode
 from elasticluster.conf import Configurator
 from elasticluster.exceptions import ConfigurationError
 from elasticluster.migration_tools import MigrationCommand
@@ -71,6 +72,7 @@ def setup(self):
                     SftpFrontend(self.params),
                     GC3PieConfig(self.params),
                     MigrationCommand(self.params),
+                    RemoveNode(self.params),
                     ]
 
         # global parameters

elasticluster/subcommands.py

@@ -391,6 +391,69 @@ def execute(self):
         print(cluster_summary(cluster))
 
 
+class RemoveNode(AbstractCommand):
+    """
+    Remove a specific node from the cluster
+    """
+    def setup(self, subparsers):
+        parser = subparsers.add_parser(
+            "remove-node", help="Remove a specific node from the cluster",
+            description=self.__doc__)
+        parser.set_defaults(func=self)
+        parser.add_argument('cluster',
+                            help='Cluster from which the node must be removed')
+        parser.add_argument('node', help='Name of node to be removed')
+        parser.add_argument('-v', '--verbose', action='count', default=0,
+                            help="Increase verbosity.")
+        parser.add_argument('--no-setup', action="store_true", default=False,
+                            help="Do not re-configure the cluster after "
+                            "removing the node.")
+        parser.add_argument('--yes', action="store_true", default=False,
+                            help="Assume `yes` to all queries and "
+                                 "do not prompt.")
+    def execute(self):
+        configurator = Configurator.fromConfig(
+            self.params.config, storage_path=self.params.storage,
+            include_config_dirs=True)
+
+        # Get current cluster configuration
+        cluster_name = self.params.cluster
+
+        try:
+            cluster = configurator.load_cluster(cluster_name)
+            cluster.update()
+        except (ClusterNotFound, ConfigurationError), ex:
+            log.error("Error loading cluster %s: %s\n" %
+                      (cluster_name, ex))
+            return
+
+        # Find the node to remove.
+        try:
+            node = cluster.get_node_by_name(self.params.node)
+        except NodeNotFound:
+            log.error("Node %s not found in cluster %s" % (
+                self.params.node, self.params.cluster))
+            sys.exit(1)
+
+        # Run
+        if not self.params.yes:
+            # Ask for confirmation.
+            yesno = raw_input(
+                "Do you really want to remove node %s? [yN] " % node.name)
+            if yesno.lower() not in ['yes', 'y']:
+                print("Aborting as per user request.")
+                sys.exit(0)
+
+        cluster.remove_node(node, stop=True)
+        print("Node %s removed" % node.name)
+
+        if self.params.no_setup:
+            print("NOT reconfiguring the cluster as requested.")
+        else:
+            print("Reconfiguring the cluster.")
+            cluster.setup()
+
+
 class ListClusters(AbstractCommand):
     """
     Print a list of all clusters that have been started.