Make sanity checks for nfsboot deployments run earlier

Move some code to the '.check' extension to verify that the deployment
can happen *before* spending 5 minutes unpacking and configuring the
rootfs.

This is not a perfect solution yet because when multiple systems are
being deployed in a cluster, we do not check all systems and then
deploy them all. Instead, we check one, then deploy it, then check the
second, etc.

2 files changed, 70 insertions, 55 deletions

diff --git a/morphlib/exts/nfsboot.check b/morphlib/exts/nfsboot.check
index 092a1df7..e240dd72 100755
--- a/morphlib/exts/nfsboot.check
+++ b/morphlib/exts/nfsboot.check
@@ -17,18 +17,84 @@
 '''Preparatory checks for Morph 'nfsboot' write extension'''
 
 import cliapp
+import os
 
 import morphlib.writeexts
 
 
 class NFSBootCheckExtension(morphlib.writeexts.WriteExtension):
+
+    _nfsboot_root = '/srv/nfsboot'
+
     def process_args(self, args):
         if len(args) != 1:
             raise cliapp.AppException('Wrong number of command line args')
 
+        location = args[0]
+
         upgrade = self.get_environment_boolean('UPGRADE')
         if upgrade:
             raise cliapp.AppException(
                 'Upgrading is not currently supported for NFS deployments.')
 
+        hostname = os.environ.get('HOSTNAME', None)
+        if hostname is None:
+            raise cliapp.AppException('You must specify a HOSTNAME.')
+        if hostname == 'baserock':
+            raise cliapp.AppException('It is forbidden to nfsboot a system '
+                                      'with hostname "%s"' % hostname)
+
+        self.test_good_server(location)
+
+        version_label = os.getenv('VERSION_LABEL', 'factory')
+        versioned_root = os.path.join(self._nfsboot_root, hostname, 'systems',
+                                      version_label)
+        if self.version_exists(versioned_root, location):
+            raise cliapp.AppException(
+                'Root file system for host %s (version %s) already exists on '
+                'the NFS server %s. Deployment aborted.' % (hostname,
+                version_label, location))
+
+    def test_good_server(self, server):
+        # Can be ssh'ed into
+        try:
+            cliapp.ssh_runcmd('root@%s' % server, ['true'])
+        except cliapp.AppException:
+            raise cliapp.AppException('You are unable to ssh into server %s'
+                                      % server)
+
+        # Is an NFS server
+        try:
+            cliapp.ssh_runcmd(
+                'root@%s' % server, ['test', '-e', '/etc/exports'])
+        except cliapp.AppException:
+            raise cliapp.AppException('server %s is not an nfs server'
+                                      % server)
+        try:
+            cliapp.ssh_runcmd(
+                'root@%s' % server, ['systemctl', 'is-enabled',
+                                     'nfs-server.service'])
+
+        except cliapp.AppException:
+            raise cliapp.AppException('server %s does not control its '
+                                      'nfs server by systemd' % server)
+
+        # TFTP server exports /srv/nfsboot/tftp
+        try:
+            cliapp.ssh_runcmd(
+                'root@%s' % server, ['test' , '-d', '/srv/nfsboot/tftp'])
+        except cliapp.AppException:
+            raise cliapp.AppException('server %s does not export '
+                                      '/srv/nfsboot/tftp' % server)
+
+    def version_exists(self, versioned_root, location):
+        try:
+            cliapp.ssh_runcmd('root@%s' % location,
+                ['test', '-d', versioned_root])
+        except cliapp.AppException:
+            return False
+
+        return True
+
+
 NFSBootCheckExtension().run()
diff --git a/morphlib/exts/nfsboot.write b/morphlib/exts/nfsboot.write
index 34a72972..3bb66821 100755
--- a/morphlib/exts/nfsboot.write
+++ b/morphlib/exts/nfsboot.write
@@ -1,5 +1,5 @@
 #!/usr/bin/python
-# Copyright (C) 2013  Codethink Limited
+# Copyright (C) 2013-2014  Codethink Limited
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -60,38 +60,18 @@ class NFSBootWriteExtension(morphlib.writeexts.WriteExtension):
             raise cliapp.AppException('Wrong number of command line args')
 
         temp_root, location = args
-        hostname = self.get_hostname(temp_root)
-        if hostname == 'baserock':
-            raise cliapp.AppException('It is forbidden to nfsboot a system '
-                                      'with hostname "baserock"')
 
-        self.test_good_server(location)
         version_label = os.getenv('VERSION_LABEL', 'factory')
+        hostname = os.environ.get('HOSTNAME')
+
         versioned_root = os.path.join(self._nfsboot_root, hostname, 'systems',
                                       version_label)
-        if self.version_exists(versioned_root, location):
-            raise cliapp.AppException('Version %s already exists on'
-                                      ' this device. Deployment aborted'
-                                      % version_label)
+
         self.copy_rootfs(temp_root, location, versioned_root, hostname)
         self.copy_kernel(temp_root, location, versioned_root, version_label,
                          hostname)
         self.configure_nfs(location, hostname)
 
-    def version_exists(self, versioned_root, location):
-        try:
-            cliapp.ssh_runcmd('root@%s' % location,
-                ['test', '-d', versioned_root])
-        except cliapp.AppException:
-            return False
-
-        return True
-
-    def get_hostname(self, temp_root):
-        hostnamepath = os.path.join(temp_root, 'etc', 'hostname')
-        with open(hostnamepath) as f:
-            return f.readline().strip()
-
     def create_local_state(self, location, hostname):
         statedir = os.path.join(self._nfsboot_root, hostname, 'state')
         subdirs = [os.path.join(statedir, 'home'),
@@ -209,37 +189,6 @@ mv "$temp" "$target"
                 'root@%s' % location, ['systemctl', 'restart',
                                        'nfs-server.service'])
 
-    def test_good_server(self, server):
-        # Can be ssh'ed into
-        try:
-            cliapp.ssh_runcmd('root@%s' % server, ['true'])
-        except cliapp.AppException:
-            raise cliapp.AppException('You are unable to ssh into server %s'
-                                      % server)
-
-        # Is an NFS server
-        try:
-            cliapp.ssh_runcmd(
-                'root@%s' % server, ['test', '-e', '/etc/exports'])
-        except cliapp.AppException:
-            raise cliapp.AppException('server %s is not an nfs server'
-                                      % server)
-        try:
-            cliapp.ssh_runcmd(
-                'root@%s' % server, ['systemctl', 'is-enabled',
-                                     'nfs-server.service'])
-
-        except cliapp.AppException:
-            raise cliapp.AppException('server %s does not control its '
-                                      'nfs server by systemd' % server)
-
-        # TFTP server exports /srv/nfsboot/tftp
-        try:
-            cliapp.ssh_runcmd(
-                'root@%s' % server, ['test' , '-d', '/srv/nfsboot/tftp'])
-        except cliapp.AppException:
-            raise cliapp.AppException('server %s does not export '
-                                      '/srv/nfsboot/tftp' % server)
 
 NFSBootWriteExtension().run()