XrdOssStats Directory Reference

Directory dependency graph for XrdOssStats:

Files
	XrdOssStatsConfig.cc
	XrdOssStatsConfig.hh
	XrdOssStatsDirectory.hh
	XrdOssStatsFile.cc
	XrdOssStatsFile.hh
	XrdOssStatsFileSystem.cc
	XrdOssStatsFileSystem.hh

Detailed Description

The plugin in this directory provides Prometheus-style statistics for the OSS layer, allowing a server administrator to track the storage load on the server and slow I/O operations

The statistics plugin can be loaded with the following configuration:

ofs.osslib ++ libXrdOssStats.so

Additionally, the following configurations are available:

fsstats.trace all
fsstats.slowop 1.5s

The options are:

• fsstats.trace: The log level for the plugin; valid settings are all|err|warning|info|debug|none. Default is warning.
• fsstats.slowop: A cutoff where, over this value, operations are labeled as "slow". Slow operations are tracked separately from the overall server operations, allowing administrators to observe periods of overload. A unit is required; valid units include m (minutes), s (seconds), and ms.

Using the Statistics

The statistics plugin is only activated if loaded and the oss type is enabled in the g-stream monitoring. This can be done through this example configuration:

xrootd.mongstream oss throttle use send json dflthdr localhost:1234

Such setting will send a JSON-formatted UDP packet to the socket at localhost:1234.

The statistics recorded (explained in detail below) count the operations performed by the filesystem and their total duration. They are useful in an external monitoring system such as Prometheus that can manage time series data.

For example, the first derivative of the read operation total time represents, on average, how many read operations are active.

Operation times are incremented periodically while the operation is running, avoiding a large "spike" at the end of long-running operations.

The plugin keeps separate statistics for "slow" operations, allowing the administrator to understand frequency and duration of operations while the server is performing poorly. The threshold for "slow" can be set by the administrator; it defaults to 2.0 seconds.

When the server restarts all counters are reset to 0.

Statistics Recorded

When loaded, the OSS plugin provides statistics via the XRootD server g-stream functionality with the following JSON object:

{
    "event:"oss_stats_XX",
    "reads: XX,
    "writes": XX,
    "stats": XX,
    "pgreads": XX,
    "pgwrites": XX,
    "readvs": XX,
    "readv_segs": XX,
    "dirlists": XX,
    "dirlist_ents": XX,
    "truncates": XX,
    "unlinks": XX,
    "chmods": XX,
    "opens": XX,
    "renames": XX,
    "slow_reads": XX,
    "slow_writes": XX,
    "slow_stats": XX,
    "slow_pgreads": XX,
    "slow_pgwrites": XX,
    "slow_readvs": XX,
    "slow_readv_segs": XX,
    "slow_dirlists": XX,
    "slow_dirlist_ents": XX,
    "slow_truncates": XX,
    "slow_unlinks": XX,
    "slow_chmods": XX,
    "slow_opens": XX,
    "slow_renames": XX,
    "open_t": YY,
    "read_t": YY,
    "readv_t": YY,
    "pgread_t": YY,
    "write_t": YY,
    "pgwrite_t": YY,
    "dirlist_t": YY,
    "stat_t": YY,
    "truncate_t": YY,
    "unlink_t": YY,
    "rename_t": YY,
    "chmod_t": YY,
    "slow_open_t": YY,
    "slow_read_t": YY,
    "slow_readv_t": YY,
    "slow_pgread_t": YY,
    "slow_write_t": YY,
    "slow_pgwrite_t": YY,
    "slow_dirlist_t": YY,
    "slow_stat_t": YY,
    "slow_truncate_t": YY,
    "slow_unlink_t": YY,
    "slow_rename_t": YY,
    "slow_chmod_t": YY
}

The keys have the following definition:

• event: The type of g-stream information. oss_stats for the default OSS path; oss_stats_pfc for the statistics from the PFC storage
• read: Count of read operations
• writes: Count of write operations
• stats: Count of "stat" operations
• pgreads: Count of aligned page reads with checksums
• pgwrites: Count of aligned page writes with checksums
• readvs: Count of vector read operations
• readv_segs: Sum of the number of segments in vector reads
• dirlists: Count of the number of times a directory listing has begun
• dirlist_ents: Sum of the number of entries in listed directories
• truncates: Count of truncate operations
• unlinks: Count of unlink (remove) operations
• chmods: Count of "change mode" (chmod) operations
• opens: Count of how many files have been opened
• renames: Count of rename operations
• $FOO_t (where $FOO is a named operation above): Total duration of operations of type $FOO in floating point seconds . For example, if open_t is equal to 20.3, then the sum of all open operation durations is 20.3 seconds.
• slow_$FOO (where $FOO is another counter): Total count or duration of type $FOO for slow operations. A "slow operation" is any operation whose duration is larger than the slow operation threshold (defaults to 2 seconds but can be managed by setting fsstats.slowop). For example, if an open operation takes 2.5 seconds then the values of slow_open_t and open_t would increase by 2.5 while slow_opens and opens would increase by 1. If an open operation takes 1.0 seconds then only the value of open_t would increase by 1.0 and opens would increase by 1.