1. New Xrootd Monitoring Stream
Federated Data Workshop
September 13, 2012
Andrew Hanushevsky, SLAC

2. Current Monitoring State
xrootd provides a wide range of data
Periodic summary data (xml based)
Real time detail data (binary based)
Login identification
Filename mapping information
File access information
Seek based I/O
File close summary (bytes r/w only)
Major efforts ongoing to digest data
Atlas: Julia Andreeva, Danila Oleynik, Artem Petrosyan, and Ilija Vukotic
CMS: Matevz Tadel

3. The Monitoring Issue Only detail stream provides sufficient data
Used to derive intermediate information
Real-Time per-file transfers
Though difficult to get it reasonably correct
Sigma’s for I/O block size
Raw data far exceeds derived data size
Desire to send just enough data
Less likely to overwhelm collector
Solution is to create a new “f” stream

4. The New Real-Time “f” Stream
Binary stream for only file-based information
Intermediate detail between summary and detail
Provides accurate Real-Time per-file transfers
Computed Sigma’s for I/O block size
Configured via the xrootd.monitor directive
Option: fstats interval [fn] [io] [ops] [sigma]
fn include filename in open record
io provide per-file I/O statistics each interval
ops include operation counts in close record
Sigma calculate sigma values

5. The “f” Stream Open Record
Inserted into stream when file opened
struct XrdXrootdMonFileHdr // 8 {
char recType; // close | io | open | ops | time
char recFlag; // Record type-specific flags (e.g. open mode, fn present, etc)
short recSize; // Size of this record in bytes
int fileID; // dictid of file for all rectypes except "time“ };
struct XrdXrootdMonFileOpn
XrdXrootdMonFileHdr Hdr; // 8
long long fsz; // 8 file size at time of open
// tfn[]; // n "<tid>\n<lfn>\0" of size(Hdr.RecSize - 16)

6. The “f” Stream I/O Record
One record per open file (each interval)
struct XrdXrootdMonStatIO {
long long read; // Bytes read from file so far using read()
long long readv; // Bytes read from file so far using readv()
long long write; // Bytes written to file so far };
struct XrdXrootdMonFileIO
XrdXrootdMonFileHdr Hdr; // 8
XrdXrootdMonStatIO Bytes; // 24

7. The “f” Stream close Record I
One record per open file (each interval)
Operation count information (only if ops or sigma selected)
struct XrdXrootdMonStatOps {
int read; // Number of read() calls
int readv; // Number of readv() calls
int write; // Number of write() calls
short rsMin; // Smallest readv() segment count
short rsMax; // Largest readv() segment count
long long rsegs; // Number of readv() segments
int rdMin; // Smallest read() request size
int rdMax; // Largest read() request size
int rvMin; // Smallest readv() segment size
int rvMax; // Largest readv() segment size
int wrMin; // Smallest write() request size
int wrMax; // Largest write() request size };

8. The “f” Stream close Record II
One record per closed file
Operation sigma information (only if sigma selected)
struct XrdXrootdMonStatSD {
int read; // Sigma for read size
int readv; // Sigma for readv size
Int rsegs; // Sigma for seg size
int write; // Sigma for write size
wrMax; // Largest write() request size };
struct XrdXrootdMonFileOps
XrdXrootdMonFileHdr Hdr; // 8
XrdXrootdMonStatOps Ops; // 48
XrdXrootdMonStatSD Sigma; // 16