nova.conf configurable gzip compression level

Currently only used by XenAPI.

Sets GZIP environment variable before spawning tar -cz to force the
compression level. Defaults to none, which means the GZIP environment
variable is not set and the default (usually -6) is used.

Implements: blueprint image-compression-mode

Change-Id: I02e136b7215a4f2cefc259f40bde9c1b205737ed

2 files changed, 10 insertions, 3 deletions

diff --git a/plugins/xenserver/xenapi/etc/xapi.d/plugins/glance b/plugins/xenserver/xenapi/etc/xapi.d/plugins/glance
index dad9acb4a4..d5984c65d8 100755
--- a/plugins/xenserver/xenapi/etc/xapi.d/plugins/glance
+++ b/plugins/xenserver/xenapi/etc/xapi.d/plugins/glance
@@ -181,8 +181,11 @@ def _upload_tarball(staging_path, image_id, glance_host, glance_port,
             except Exception, error:
                 raise RetryableError(error)
 
+        compression_level = properties.get('xenapi_image_compression_level')
+
         utils.create_tarball(
-                None, staging_path, callback=send_chunked_transfer_encoded)
+                None, staging_path, callback=send_chunked_transfer_encoded,
+                compression_level=compression_level)
 
         try:
             conn.send("0\r\n\r\n")  # Chunked-Transfer terminator
diff --git a/plugins/xenserver/xenapi/etc/xapi.d/plugins/utils.py b/plugins/xenserver/xenapi/etc/xapi.d/plugins/utils.py
index 8404fd961b..e3945236ac 100644
--- a/plugins/xenserver/xenapi/etc/xapi.d/plugins/utils.py
+++ b/plugins/xenserver/xenapi/etc/xapi.d/plugins/utils.py
@@ -355,16 +355,20 @@ def prepare_staging_area(sr_path, staging_path, vdi_uuids, seq_num=0):
         seq_num += 1
 
 
-def create_tarball(fileobj, path, callback=None):
+def create_tarball(fileobj, path, callback=None, compression_level=None):
     """Create a tarball from a given path.
 
     :param fileobj: a file-like object holding the tarball byte-stream.
                     If None, then only the callback will be used.
     :param path: path to create tarball from
     :param callback: optional callback to call on each chunk written
+    :param compression_level: compression level, e.g., 9 for gzip -9.
     """
     tar_cmd = ["tar", "-zc", "--directory=%s" % path, "."]
-    tar_proc = make_subprocess(tar_cmd, stdout=True, stderr=True)
+    env = os.environ.copy()
+    if compression_level and 1 <= compression_level <= 9:
+        env["GZIP"] = "-%d" % compression_level
+    tar_proc = make_subprocess(tar_cmd, stdout=True, stderr=True, env=env)
 
     while True:
         chunk = tar_proc.stdout.read(CHUNK_SIZE)