[Libguestfs] [PATCH 1/2] v2v: -o rhv-upload: Always fetch server options when opening the connection.

[Richard W.M. Jones]

Previously we lazily requested the server options in the can_*
callbacks.  The can_* callbacks are always called by nbdkit straight
after open, so this just adds complexity for no benefit.  This change
simply makes the code always fetch the server options during the open
callback.

This is — functionally at least — mostly just refactoring.  However I
also added a useful debug message so we can see what features the
imageio server is offering.
---
 v2v/rhv-upload-plugin.py | 77 +++++++++++++++++++++++-------------------------
 1 file changed, 37 insertions(+), 40 deletions(-)

diff --git a/v2v/rhv-upload-plugin.py b/v2v/rhv-upload-plugin.py
index 7c5084efd..419008517 100644
--- a/v2v/rhv-upload-plugin.py
+++ b/v2v/rhv-upload-plugin.py
@@ -165,63 +165,60 @@ def open(readonly):
         context = context
     )
 
+    # The first request is to fetch the features of the server.
+    needs_auth = not params['rhv_direct']
+    can_flush = False
+    can_trim = False
+    can_zero = False
+
+    http.putrequest("OPTIONS", destination_url.path)
+    http.putheader("Authorization", transfer.signed_ticket)
+    http.endheaders()
+
+    r = http.getresponse()
+    if r.status == 200:
+        # New imageio never needs authentication.
+        needs_auth = False
+
+        j = json.loads(r.read())
+        can_flush = "flush" in j['features']
+        can_trim = "trim" in j['features']
+        can_zero = "zero" in j['features']
+
+    # Old imageio servers returned either 405 Method Not Allowed or
+    # 204 No Content (with an empty body).  If we see that we leave
+    # all the features as False and they will be emulated.
+    elif r.status == 405 or r.status == 204:
+        pass
+
+    else:
+        raise RuntimeError("could not use OPTIONS request: %d: %s" %
+                           (r.status, r.reason))
+
+    debug("imageio features: flush=%r trim=%r zero=%r unix_socket=%r" %
+          (can_flush, can_trim, can_zero, unix_socket))
+
     # Save everything we need to make requests in the handle.
     return {
-        'can_flush': False,
-        'can_trim': False,
-        'can_zero': False,
+        'can_flush': can_flush,
+        'can_trim': can_trim,
+        'can_zero': can_zero,
         'connection': connection,
         'disk': disk,
         'disk_service': disk_service,
         'failed': False,
-        'got_options': False,
         'highestwrite': 0,
         'http': http,
-        'needs_auth': not params['rhv_direct'],
+        'needs_auth': needs_auth,
         'path': destination_url.path,
         'transfer': transfer,
         'transfer_service': transfer_service,
     }
 
-# Can we issue zero, trim or flush requests?
-def get_options(h):
-    if h['got_options']:
-        return
-    h['got_options'] = True
-
-    http = h['http']
-    transfer = h['transfer']
-
-    http.putrequest("OPTIONS", h['path'])
-    http.putheader("Authorization", transfer.signed_ticket)
-    http.endheaders()
-
-    r = http.getresponse()
-    if r.status == 200:
-        # New imageio never needs authentication.
-        h['needs_auth'] = False
-
-        j = json.loads(r.read())
-        h['can_zero'] = "zero" in j['features']
-        h['can_trim'] = "trim" in j['features']
-        h['can_flush'] = "flush" in j['features']
-
-    # Old imageio servers returned either 405 Method Not Allowed or
-    # 204 No Content (with an empty body).  If we see that we leave
-    # all the features as False and they will be emulated.
-    elif r.status == 405 or r.status == 204:
-        pass
-
-    else:
-        raise RuntimeError("could not use OPTIONS request: %d: %s" %
-                           (r.status, r.reason))
-
 def can_trim(h):
-    get_options(h)
     return h['can_trim']
 
 def can_flush(h):
-    get_options(h)
     return h['can_flush']
 
 def get_size(h):
-- 
2.16.2