Truncate large console logs in libvirt.

Resolves bug 1081436 where they were returning a 5.5gb console log
to the user.

Change-Id: I0d98c83e801f8936d35789b5e8f8283f49483c4e

nova/tests/fake_libvirt_utils.py

@@ -86,7 +86,10 @@ def extract_snapshot(disk_path, source_fmt, snapshot_name, out_path, dest_fmt):
 
 class File(object):
     def __init__(self, path, mode=None):
-        self.fp = StringIO.StringIO(files[path])
+        if path in files:
+            self.fp = StringIO.StringIO(files[path])
+        else:
+            self.fp = StringIO.StringIO(files[os.path.split(path)[-1]])
 
     def __enter__(self):
         return self.fp

nova/tests/test_libvirt.py

@@ -2304,6 +2304,7 @@ class LibvirtConnTestCase(test.TestCase):
                                        CONF.base_dir_name))
 
     def test_get_console_output_file(self):
+        fake_libvirt_utils.files['console.log'] = '01234567890'
 
         with utils.tempdir() as tmpdir:
             self.flags(instances_path=tmpdir)
@@ -2313,11 +2314,7 @@ class LibvirtConnTestCase(test.TestCase):
             instance = db.instance_create(self.context, instance_ref)
 
             console_dir = (os.path.join(tmpdir, instance['name']))
-            os.mkdir(console_dir)
             console_log = '%s/console.log' % (console_dir)
-            f = open(console_log, "w")
-            f.write("foo")
-            f.close()
             fake_dom_xml = """
                 <domain type='kvm'>
                     <devices>
@@ -2340,10 +2337,18 @@ class LibvirtConnTestCase(test.TestCase):
             libvirt_driver.libvirt_utils = fake_libvirt_utils
 
             conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)
-            output = conn.get_console_output(instance)
-            self.assertEquals("foo", output)
+
+            try:
+                prev_max = libvirt_driver.MAX_CONSOLE_BYTES
+                libvirt_driver.MAX_CONSOLE_BYTES = 5
+                output = conn.get_console_output(instance)
+            finally:
+                libvirt_driver.MAX_CONSOLE_BYTES = prev_max
+
+            self.assertEquals('67890', output)
 
     def test_get_console_output_pty(self):
+        fake_libvirt_utils.files['pty'] = '01234567890'
 
         with utils.tempdir() as tmpdir:
             self.flags(instances_path=tmpdir)
@@ -2353,11 +2358,7 @@ class LibvirtConnTestCase(test.TestCase):
             instance = db.instance_create(self.context, instance_ref)
 
             console_dir = (os.path.join(tmpdir, instance['name']))
-            os.mkdir(console_dir)
             pty_file = '%s/fake_pty' % (console_dir)
-            f = open(pty_file, "w")
-            f.write("foo")
-            f.close()
             fake_dom_xml = """
                 <domain type='kvm'>
                     <devices>
@@ -2376,17 +2377,27 @@ class LibvirtConnTestCase(test.TestCase):
                 return FakeVirtDomain(fake_dom_xml)
 
             def _fake_flush(self, fake_pty):
-                with open(fake_pty, 'r') as fp:
-                    return fp.read()
+                return 'foo'
+
+            def _fake_append_to_file(self, data, fpath):
+                return 'pty'
 
             self.create_fake_libvirt_mock()
             libvirt_driver.LibvirtDriver._conn.lookupByName = fake_lookup
             libvirt_driver.LibvirtDriver._flush_libvirt_console = _fake_flush
+            libvirt_driver.LibvirtDriver._append_to_file = _fake_append_to_file
             libvirt_driver.libvirt_utils = fake_libvirt_utils
 
             conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)
-            output = conn.get_console_output(instance)
-            self.assertEquals("foo", output)
+
+            try:
+                prev_max = libvirt_driver.MAX_CONSOLE_BYTES
+                libvirt_driver.MAX_CONSOLE_BYTES = 5
+                output = conn.get_console_output(instance)
+            finally:
+                libvirt_driver.MAX_CONSOLE_BYTES = prev_max
+
+            self.assertEquals('67890', output)
 
     def test_get_host_ip_addr(self):
         conn = libvirt_driver.LibvirtDriver(fake.FakeVirtAPI(), False)

nova/tests/test_virt_drivers.py

@@ -14,8 +14,11 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import __builtin__
 import base64
+import mox
 import netaddr
+import StringIO
 import sys
 import traceback
 
@@ -25,6 +28,7 @@ from nova import exception
 from nova.openstack.common import importutils
 from nova.openstack.common import log as logging
 from nova import test
+from nova.tests import fake_libvirt_utils
 from nova.tests.image import fake as fake_image
 from nova.tests import utils as test_utils
 from nova.virt import fake
@@ -428,6 +432,7 @@ class _VirtDriverTestCase(_FakeDriverBackendTestCase):
 
     @catch_notimplementederror
     def test_get_console_output(self):
+        fake_libvirt_utils.files['dummy.log'] = ''
         instance_ref, network_info = self._get_running_instance()
         console_output = self.connection.get_console_output(instance_ref)
         self.assertTrue(isinstance(console_output, basestring))

nova/utils.py

@@ -1180,3 +1180,24 @@ def mkfs(fs, path, label=None):
         args.extend([label_opt, label])
     args.append(path)
     execute(*args)
+
+
+def last_bytes(file_like_object, num):
+    """Return num bytes from the end of the file, and remaining byte count.
+
+    :param file_like_object: The file to read
+    :param num: The number of bytes to return
+
+    :returns (data, remaining)
+    """
+
+    try:
+        file_like_object.seek(-num, os.SEEK_END)
+    except IOError, e:
+        if e.errno == 22:
+            file_like_object.seek(0, os.SEEK_SET)
+        else:
+            raise
+
+    remaining = file_like_object.tell()
+    return (file_like_object.read(), remaining)