I'm guessing that if I replace stat with fstat in XrdOss, I then need
to invoke a streaming option in the root client, so the root client
pulls in the entire root data file into the client before it tries to
interpret and unpack the data stream.
Dan
On Oct 23, 2006, at 1:21 PM, Daniel Engh wrote:
> Hi Andrew,
>
> By making simple changes in XrdOss, I am able to begin streaming a
> root file from my IBP depot into a root session via xrootd. I've
> only swap'd the XrdOssApi.cc open(), read(), and fstat() operations
> with my xio_open(), xio_read(), and xio_fstat(). However, I am
> now stuck on stat operations which are confusing the size of my
> data cache with the size of my index file describing this data cache.
>
> Heres what I do: I have an index file "*.xnode" (like an inode).
> In this case called mydatafile.root.xnd
> xio_open(*.xnode) opens the xnode index file and finds the remote
> data file.
> xio_fstat(*.xnode) reports the size of the remote data file, not
> the xnode index file itself
> xio_stat(*.xnode) reports the size of the xnode index file itself,
> not the remote data file.
> xio_read(*.xnode) streams in the remote data file, not the xnode
> index file.
>
> however xrootd uses both fstat() and stat() redundantly or
> interchangeable and assumes they are the same. (?? I think, I don't
> know) is this correct? I don't understand how or why xrootd needs
> to use both fstat and stat to retrieve the same information -- why
> isn't the initial fstat operation sufficient? what more does a
> subsequent stat operation provide? why aren't subsequent checks
> also fstat?
>
>
> Here's my error message. The interactive root session reports:
>
> root [1] myfile = TFile::Open("root://vpac09//tmp/
> mydatafile.root.xnd");
> Error in <TXNetFile::Init>: file root://vpac09//tmp/
> mydatafile.root.xnd is truncated at 163670 bytes: should be
> 287599163, trying to recover
> Warning in <TXNetFile::Init>: no keys recovered, file has been made
> a Zombie
> Error in <TXNetFile::CreateXClient>: open attempt failed on root://
> vpac09//tmp/mydatafile.root.xnd
>
> my index file /tmp/mydatafile.root.xnd is indeed 163670 bytes.
> The size of the remote rootfile striped on the ibp depots is indeed
> 287599163 bytes.
> xrootd is interpreting these to be the same.
>
> in this example, xrootd calls
> open()
> isCompressed()
> Fstat() ------ initial fstat correctly gets the size of the remote
> data
> statbuff->st_size = 287599163
> getMmap()
> read() 2x
> stat() ------- this gets the size of the *.xnode index file, not
> the size of the remote data stream.
> statbuff->st_size = 163670
> read() 2x
> close() ----- closing much too early!
>
>
> Any general hints on modifying the stat usage would be helpful. It
> looks like I need to keep digging deeper. I can't simply replace
> the stat operations
> with fstat, that produces an error. I need to figure out how these
> numbers are later interpreted and change that.
>
> thanks,
> Dan
>
>
