[Libguestfs] [PATCH v3] v2v: -o rhv-upload: Use Unix domain socket to access imageio (RHBZ#1588088).

[Richard W.M. Jones]

In the case where virt-v2v runs on the same server as the imageio
daemon that we are talking to, it may be possible to optimize access
using a Unix domain socket.

This is only an optimization.  If it fails or if we're not running on
the same server it will fall back to the usual HTTPS over TCP
connection.

Thanks: Nir Soffer, Daniel Erez.
---
 v2v/rhv-upload-plugin.py | 61 +++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 58 insertions(+), 3 deletions(-)

diff --git a/v2v/rhv-upload-plugin.py b/v2v/rhv-upload-plugin.py
index f215eaecf..354cc524c 100644
--- a/v2v/rhv-upload-plugin.py
+++ b/v2v/rhv-upload-plugin.py
@@ -19,11 +19,12 @@
 import builtins
 import json
 import logging
+import socket
 import ssl
 import sys
 import time
 
-from http.client import HTTPSConnection
+from http.client import HTTPSConnection, HTTPConnection
 from urllib.parse import urlparse
 
 import ovirtsdk4 as sdk
@@ -56,6 +57,28 @@ def debug(s):
         print(s, file=sys.stderr)
         sys.stderr.flush()
 
+def find_host(connection):
+    """Return the current host object or None."""
+    try:
+        with builtin_open("/etc/vdsm/vdsm.id") as f:
+            vdsm_id = f.readline().strip()
+    except Exception as e:
+        return None
+    debug("hw_id = %r" % vdsm_id)
+
+    hosts_service = connection.system_service().hosts_service()
+    hosts = hosts_service.list(
+        search="hw_id=%s" % vdsm_id,
+        case_sensitive=False,
+    )
+    if len(hosts) == 0:
+        return None
+
+    host = hosts[0]
+    debug("host.id = %r" % host.id)
+
+    return types.Host(id = host.id)
+
 def open(readonly):
     # Parse out the username from the output_conn URL.
     parsed = urlparse(params['output_conn'])
@@ -121,9 +144,11 @@ def open(readonly):
     transfers_service = system_service.image_transfers_service()
 
     # Create a new image transfer.
+    host = find_host(connection)
     transfer = transfers_service.add(
         types.ImageTransfer(
             disk = types.Disk(id = disk.id),
+            host = host,
             inactivity_timeout = 3600,
         )
     )
@@ -170,6 +195,7 @@ def open(readonly):
     can_flush = False
     can_trim = False
     can_zero = False
+    unix_socket = None
 
     http.putrequest("OPTIONS", destination_url.path)
     http.putheader("Authorization", transfer.signed_ticket)
@@ -186,6 +212,7 @@ def open(readonly):
         can_flush = "flush" in j['features']
         can_trim = "trim" in j['features']
         can_zero = "zero" in j['features']
+        unix_socket = j.get('unix_socket')
 
     # Old imageio servers returned either 405 Method Not Allowed or
     # 204 No Content (with an empty body).  If we see that we leave
@@ -197,8 +224,17 @@ def open(readonly):
         raise RuntimeError("could not use OPTIONS request: %d: %s" %
                            (r.status, r.reason))
 
-    debug("imageio features: flush=%r trim=%r zero=%r" %
-          (can_flush, can_trim, can_zero))
+    debug("imageio features: flush=%r trim=%r zero=%r unix_socket=%r" %
+          (can_flush, can_trim, can_zero, unix_socket))
+
+    # If we are connected to imageio on the local host and the
+    # transfer features a unix_socket then we can reconnect to that.
+    if host is not None and unix_socket is not None:
+        try:
+            http = UnixHTTPConnection(unix_socket)
+            debug("optimizing connection using unix socket %r" % unix_socket)
+        except:
+            pass
 
     # Save everything we need to make requests in the handle.
     return {
@@ -463,3 +499,22 @@ def close(h):
         raise
 
     connection.close()
+
+# Modify http.client.HTTPConnection to work over a Unix domain socket.
+# Derived from uhttplib written by Erik van Zijst under an MIT license.
+# (https://pypi.org/project/uhttplib/)
+# Ported to Python 3 by Irit Goihman.
+
+class UnsupportedError(Exception):
+    pass
+
+class UnixHTTPConnection(HTTPConnection):
+    def __init__(self, path, timeout=socket._GLOBAL_DEFAULT_TIMEOUT):
+        self.path = path
+        HTTPConnection.__init__(self, "localhost", timeout=timeout)
+
+    def connect(self):
+        self.sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+        if self.timeout is not socket._GLOBAL_DEFAULT_TIMEOUT:
+            self.sock.settimeout(timeout)
+        self.sock.connect(self.path)
-- 
2.16.2