transport layer and multiple connections (was Re: [PATCH] FTP transport)

[Matthieu Moy]

Daniel Silverstone <dsilvers at digital-scurf.org> writes:

>> (I don't know whether this comes from the transport layer of from
>> ftp.py itself, though)
>
> The transport layer clones several times before it ever does anything,
> which caused the connection to be created several times because it was
> lazy. Now it's lazy but memoized safely.

Actually, I believe this should be fixed in the transport layer
itself. get_transport may be called several times with the same
argument (an example in "push" :

        try:
            br_to = Branch.open(location) # <- calls get_transport(location)
        except NotBranchError:
            # create a branch.
            transport = get_transport(location).clone('..')

)

A relatively simple fix would be to keep a dictionary
(location -> transport), and to reuse the existing one if it exists in
get_location.

The patch below does this, but it seems too obvious to be true. Is
there a reason not to do it this way? Well, at least, a 
"push sftp://host.com/not/yet/created/directory" promps my password
once instead of three times.

=== modified file 'bzrlib/transport/__init__.py'
--- bzrlib/transport/__init__.py
+++ bzrlib/transport/__init__.py
@@ -352,13 +352,21 @@
         raise NotImplementedError
 
 
+transport_pool = {};
+
 def get_transport(base):
     global _protocol_handlers
     if base is None:
         base = '.'
     for proto, klass in _protocol_handlers.iteritems():
         if proto is not None and base.startswith(proto):
-            return klass(base)
+            # check in the pool only if "base" matches a protocol.
+            # (avoids problems with relative paths)
+            if transport_pool.has_key(base):
+                return transport_pool[base]
+            k = klass(base)
+            transport_pool[base] = k
+            return k
     # The default handler is the filesystem handler
     # which has a lookup of None
     return _protocol_handlers[None](base)



-- 
Matthieu