Merge "Add more error handling to glance xenapi plugin"

plugins/xenserver/xenapi/etc/xapi.d/plugins/glance

@@ -26,6 +26,7 @@ try:
     import json
 except ImportError:
     import simplejson as json
+import md5
 import os
 import os.path
 import pickle
@@ -46,6 +47,10 @@ CHUNK_SIZE = 8192
 KERNEL_DIR = '/boot/guest'
 
 
+class RetryException(Exception):
+    pass
+
+
 def _copy_kernel_vdi(dest, copy_args):
     vdi_uuid = copy_args['vdi_uuid']
     vdi_size = copy_args['vdi_size']
@@ -68,10 +73,60 @@ def _copy_kernel_vdi(dest, copy_args):
     return filename
 
 
-def _download_tarball(sr_path, staging_path, image_id, glance_host,
+def _download_tarball(request, staging_path):
-                      glance_port, auth_token, num_retries):
+    """Make one attempt to download and extract the image tarball"""
+    try:
+        response = urllib2.urlopen(request)
+    except urllib2.HTTPError, error:
+        raise RetryException(error)
+    except urllib2.URLError, error:
+        raise RetryException(error)
+
+    tar_cmd = "tar -zx --directory=%(staging_path)s" % locals()
+    tar_proc = _make_subprocess(tar_cmd, stderr=True, stdin=True)
+
+    checksum = md5.new()
+    etag = response.info().getheader('etag', None)
+    if etag is None:
+        etag = response.info().getheader('x-image-meta-checksum', None)
+
+    url = request.get_full_url()
+    logging.info("Reading image data from %s" % url)
+
+    length_read = 0
+    while True:
+        chunk = response.read(CHUNK_SIZE)
+        if chunk == '':
+            break
+        length_read += len(chunk)
+        checksum.update(chunk)
+        tar_proc.stdin.write(chunk)
+
+    logging.info("Read %(length_read)s bytes from %(url)s" % locals())
+
+    try:
+        _finish_subprocess(tar_proc, tar_cmd)
+    except Exception, error:
+        raise RetryException(error)
+
+    checksum = checksum.hexdigest()
+    if etag is None:
+        msg = "No ETag found for comparison to checksum %(checksum)s"
+        logging.info(msg % locals())
+    elif checksum != etag:
+        msg = 'ETag %(etag)s does not match computed md5sum %(checksum)s'
+        raise RetryException(msg % locals())
+    else:
+        msg = "Verified image checksum %(checksum)s"
+        logging.info(msg % locals())
+
+    return
+
+
+def _download_tarball_with_retry(sr_path, image_id, glance_host,
+                                 glance_port, auth_token, num_retries):
     """Download the tarball image from Glance and extract it into the staging
-    area.
+    area. Retry if there is any failure.
     """
     # Build request headers
     headers = {}
@@ -80,50 +135,27 @@ def _download_tarball(sr_path, staging_path, image_id, glance_host,
 
     url = "http://%(glance_host)s:%(glance_port)d/v1/images/"\
           "%(image_id)s" % locals()
-
+    logging.info("Downloading %s" % url)
-    logging.debug("Downloading tarball from %(url)s" % locals())
 
     request = urllib2.Request(url, headers=headers)
-    response = None
+    sleep_time = 0.5
 
     for try_num in xrange(1, num_retries + 2):
         try:
-            response = urllib2.urlopen(request)
+            staging_path = _make_staging_area(sr_path)
-            break
+            _download_tarball(request, staging_path)
+            return staging_path
+        except RetryException, error:
+            msg = "Downloading %(url)s attempt %(try_num)d error: %(error)s"
+            logging.error(msg % locals())
 
-        except urllib2.HTTPError, error:
+        _cleanup_staging_area(staging_path)
-            if error.code == 404:
+        time.sleep(sleep_time)
-                msg = "Image '%s' not found in Glance" % image_id
+        sleep_time = min(2 * sleep_time, 15)
-                logging.error(msg)
-                raise Exception(msg)
 
-            elif try_num == (num_retries + 1):
+    msg = "Unable to retrieve %(url)s after %(try_num)d attempt(s)." % locals()
-                msg = "Unable to retrieve image after %d attempts." % try_num
+    logging.error(msg)
-                logging.error(msg)
+    raise Exception(msg)
-                raise Exception(msg)
-
-        except urllib2.URLError, error:
-            pass
-
-        logging.error("Download attempt %d error: %s" % (try_num, error))
-        time.sleep(1)
-
-    if response is None:
-        msg = "Unable to retrieve image: %(error)s" % locals()
-        logging.error(msg)
-        raise Exception(msg)
-
-    tar_cmd = "tar -zx --directory=%(staging_path)s" % locals()
-    tar_proc = _make_subprocess(tar_cmd, stderr=True, stdin=True)
-
-    logging.info("Reading image data from %s" % url)
-
-    chunk = response.read(CHUNK_SIZE)
-    while chunk:
-        tar_proc.stdin.write(chunk)
-        chunk = response.read(CHUNK_SIZE)
-
-    _finish_subprocess(tar_proc, tar_cmd)
 
 
 def _import_vhds(sr_path, staging_path, uuid_stack):
@@ -397,7 +429,8 @@ def _cleanup_staging_area(staging_path):
     it's safe to remove the staging-area because the SR will keep the link
     count > 0 (so the VHDs in the SR will not be deleted).
     """
-    shutil.rmtree(staging_path)
+    if os.path.exists(staging_path):
+        shutil.rmtree(staging_path)
 
 
 def _make_subprocess(cmdline, stdout=False, stderr=False, stdin=False):
@@ -436,15 +469,17 @@ def download_vhd(session, args):
     auth_token = params["auth_token"]
     num_retries = params["num_retries"]
 
-    staging_path = _make_staging_area(sr_path)
+    staging_path = None
     try:
-        _download_tarball(sr_path, staging_path, image_id, glance_host,
+        staging_path = _download_tarball_with_retry(sr_path, image_id,
-                          glance_port, auth_token, num_retries)
+                                                    glance_host, glance_port,
+                                                    auth_token, num_retries)
         # Right now, it's easier to return a single string via XenAPI,
         # so we'll json encode the list of VHDs.
         return json.dumps(_import_vhds(sr_path, staging_path, uuid_stack))
     finally:
-        _cleanup_staging_area(staging_path)
+        if staging_path is not None:
+            _cleanup_staging_area(staging_path)
 
 
 def upload_vhd(session, args):