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import sys
from gluster import *
# Negative-lookup-caching example. If a file wasn't there the last time we
# looked, it's probably still not there. This translator keeps track of
# those failed lookups for us, and returns ENOENT without needing to pass the
# call any further for repeated requests.
# If we were doing this for real, we'd need separate caches for each xlator
# instance. The easiest way to do this would be to have xlator.__init__
# "register" each instance in a module-global dict, with the key as the C
# translator address and the value as the xlator object itself. For testing
# and teaching, it's sufficient just to have one cache. The keys are parent
# GFIDs, and the entries are lists of names within that parent that we know
# don't exist.
cache = {}
# TBD: we need a better way of handling per-request data (frame->local in C).
dl.get_id.restype = c_long
dl.get_id.argtypes = [ POINTER(call_frame_t) ]
def uuid2str (orig):
return "%08x%08x%08x%08x" % (orig[0], orig[1], orig[2], orig[3])
class xlator (Translator):
def __init__ (self, c_this):
self.requests = {}
Translator.__init__(self,c_this)
def lookup_fop (self, frame, this, loc, xdata):
pargfid = uuid2str(loc.contents.pargfid)
print "lookup FOP: %s:%s" % (pargfid, loc.contents.name)
# Check the cache.
if cache.has_key(pargfid):
if loc.contents.name in cache[pargfid]:
print "short-circuiting for %s:%s" % (
pargfid, loc.contents.name)
dl.unwind_lookup(frame,0,this,-1,2,None,None,
None,None)
return 0
key = dl.get_id(frame)
self.requests[key] = (pargfid, loc.contents.name[:])
# TBD: get real child xl from init, pass it here
dl.wind_lookup(frame,POINTER(xlator_t)(),loc,xdata)
return 0
def lookup_cbk (self, frame, cookie, this, op_ret, op_errno, inode, buf,
xdata, postparent):
print "lookup CBK: %d (%d)" % (op_ret, op_errno)
key = dl.get_id(frame)
pargfid, name = self.requests[key]
# Update the cache.
if op_ret == 0:
print "found %s, removing from cache" % name
if cache.has_key(pargfid):
cache[pargfid].discard(name)
elif op_errno == 2: # ENOENT
print "failed to find %s, adding to cache" % name
if cache.has_key(pargfid):
cache[pargfid].add(name)
else:
cache[pargfid] = set([name])
del self.requests[key]
dl.unwind_lookup(frame,cookie,this,op_ret,op_errno,
inode,buf,xdata,postparent)
return 0
def create_fop (self, frame, this, loc, flags, mode, umask, fd, xdata):
pargfid = uuid2str(loc.contents.pargfid)
print "create FOP: %s:%s" % (pargfid, loc.contents.name)
key = dl.get_id(frame)
self.requests[key] = (pargfid, loc.contents.name[:])
# TBD: get real child xl from init, pass it here
dl.wind_create(frame,POINTER(xlator_t)(),loc,flags,mode,umask,
fd,xdata)
return 0
def create_cbk (self, frame, cookie, this, op_ret, op_errno, fd, inode,
buf, preparent, postparent, xdata):
print "create CBK: %d (%d)" % (op_ret, op_errno)
key = dl.get_id(frame)
pargfid, name = self.requests[key]
# Update the cache.
if op_ret == 0:
print "created %s, removing from cache" % name
if cache.has_key(pargfid):
cache[pargfid].discard(name)
del self.requests[key]
dl.unwind_create(frame,cookie,this,op_ret,op_errno,fd,inode,buf,
preparent,postparent,xdata)
return 0
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