Hello Patrick
If you write a file into xrootd, the redirector will first check if the
file already exists. As xrootd does not have a "data catalog" it will ask
the data servers if they have the file. Data servers only return a
positive respond that they have the file. Therefore the redirector waits for 5
seconds (which is configurable) and if none of the data server responded
it assumes that the file does not exist and then redirects the client.
That's why you see the 5 secs wait.
Cheers,
Wilko
On Sat, 8 Dec 2007, Patrick McGuigan wrote:
> I have a basic system working with one client, seven dataservers, and a
> redirector. The client can store correctly but I am observing a consistent
> five second delay when the client is storing data.
>
> I ran xrdcp with -d 3 and the output contains :
>
> 071207 23:03:40 001 Xrd: DoLogin: No prev session info for 10.1.2.255:1094
> 071207 23:03:40 001 Xrd: Open: Access to server granted.
> 071207 23:03:40 001 Xrd: Open: Opening the remote file /xrd/test24/100mb
> 071207 23:03:40 001 Xrd: Open: File open in progress.
> 071207 23:03:40 18805 Xrd: XrdClientMessage::ReadRaw: Reading header (8
> bytes).
> 071207 23:03:40 18805 Xrd: ReadRaw: Reading from 10.1.2.255:1094
> 071207 23:03:40 18805 Xrd: SendGenCommand: Sending command Open
> 071207 23:03:40 18805 Xrd: WriteRaw: Writing 24 bytes to physical connection
> 071207 23:03:40 18805 Xrd: WriteRaw: Writing to substreamid 0
> 071207 23:03:40 18805 Xrd: WriteRaw: Writing 17 bytes to physical connection
> 071207 23:03:40 18805 Xrd: WriteRaw: Writing to substreamid 0
> 071207 23:03:40 18805 Xrd: ReadPartialAnswer: Reading a XrdClientMessage from
> the server [10.1.2.255:1094]...
> 071207 23:03:40 18805 Xrd: XrdClientMessage::ReadRaw: sid: 1, IsAttn: 0,
> substreamid: 0
> 071207 23:03:40 18805 Xrd: XrdClientMessage::ReadRaw: Reading data (4 bytes)
> from substream 0
> 071207 23:03:40 18805 Xrd: ReadRaw: Reading from 10.1.2.255:1094
> 071207 23:03:40 18805 Xrd: BuildMessage: posting id 1
> 071207 23:03:40 18805 Xrd: XrdClientMessage::ReadRaw: Reading header (8
> bytes).
> 071207 23:03:40 18805 Xrd: ReadRaw: Reading from 10.1.2.255:1094
> 071207 23:03:40 18805 Xrd: ReadPartialAnswer: Server [10.1.2.255:1094]
> answered [kXR_wait] (4005)
> 071207 23:03:40 18805 Xrd: CheckErrorStatus: Server [10.1.2.255:1094]
> requested 5 seconds of wait
> 071207 23:03:42 18805 Xrd: DumpPhyConn: Phyconn entry,
> [log in to unmask]:1094', LogCnt=1 Valid
> 071207 23:03:44 18805 Xrd: DumpPhyConn: Phyconn entry,
> [log in to unmask]:1094', LogCnt=1 Valid
> 071207 23:03:45 18805 Xrd: SendGenCommand: Sending command Open
>
>
>
> It appears that the client received a 5 second delay from the redirector. I
> don't seen any useful information in the olbd log of the redirector and the
> xrootd log only indicates that the client was asked to wait:
>
> 071207 22:54:24 15092 odc_send2Man: root.18805:16@compute-0-0 asked to wait 5
> by xrdb path=/xrd/test24/100mb
>
>
> How do I determine why the redirector is sending xXR_wait?
>
> Is the result of my configuration defaulting to round robin scheduling?
>
>
> Thanks,
>
> Patrick
>
>
>
>
>
>
>
