PMLOGREDUCE(1)PMLOGREDUCE(1)NAMEpmlogreduce - temporal reduction of Performance Co-Pilot archives
SYNOPSIS
$PCP_BINADM_DIR/pmlogreduce [-z] [-A align] [-S starttime] [-s samples]
[-T endtime] [-t interval] [-v volsamples] [-Z timezone] input output
DESCRIPTIONpmlogreduce reads one Performance Co-Pilot (PCP) archive identified by
input (this must be a PCP archive created by pmlogger(1), pmlogex‐
tract(1) or pmlogreduce(1)), and creates a temporally reduced PCP ar‐
chive in output. The data reduction involves statistical and temporal
reduction of samples with an output sampling interval defined by the -t
option in the output archive (independent of the sampling intervals in
the input archive), and is further controlled by other command line
arguments.
For some metrics, temporal data reduction is not going to be helpful,
so for metrics with types PM_TYPE_AGGREGATE or PM_TYPE_EVENT, a warning
is issued if these metrics are found in input and they will be skipped
and not appear in the output archive.
COMMAND LINE OPTIONS
The command line options for pmlogreduce are as follows:
-A align
Specify a ``natural'' alignment of the output sample times;
refer to PCPIntro(1).
-S starttime
Define the start of a time window to restrict the samples
retrieved from the input archive; refer to PCPIntro(1).
-s samples
The argument samples defines the number of samples to be written
to output. If samples is 0 or -s is not specified, pmlogreduce
will sample until the end of the PCP archive, or the end of the
time window as specified by -T, whichever comes first. The -s
option will override the -T option if it occurs sooner.
-T endtime
Define the termination of a time window to restrict the samples
retrieved from the input archive; refer to PCPIntro(1).
-v volsamples
The output archive is potentially a multi-volume data set, and
the -v option causes pmlogreduce to start a new volume after
volsamples log records have been written to the output archive.
Independent of any -v option, each volume of an archive is lim‐
ited to no more than 2^31 bytes, so pmlogreduce will automati‐
cally create a new volume for the archive before this limit is
reached.
-t interval
Consecutive samples in the output archive will appear with a
time delta defined by interval; refer to PCPIntro(1). Note the
default value is 600 (seconds, i.e. 10 minutes).
-Z timezone
Use timezone when displaying the date and time, or interpreting
the -S and -T options. Timezone is in the format of the envi‐
ronment variable TZ as described in environ(5).
-z Use the local timezone of the host from the input archive when
displaying the date and time, or interpreting the -S and -T
options. The default is to initially use the timezone of the
local host.
DATA REDUCTION
The statistical and temporal reduction follows the following rules:
1. Consecutive records from input are read without interpolation, and
at most one output record is written for each interval, summarizing
the performance data over that period.
2. If the semantics of a metric indicates it is instantaneous or dis‐
crete then output value is computed as the arithmetic mean of the
observations (if any) over each interval.
3. If the semantics of a metric indicates it is a counter then the
following transformations are applied:
a) Metrics with 32-bit precision are promoted to 64-bit precision.
b) Any counter wrap (overflow) is noted, and appropriate adjust‐
ment made in the value of the metric over each interval. This
will be correct in the case of a single counter wrap, but will
silently underestimate in the case where more than one counter
wrap occurs between consecutive observations in the input ar‐
chive, and silently overestimate in the case where a counter is
reset occurs between consecutive observations in the input ar‐
chive; unfortunately these situations cannot be detected, but
are believed to be rare events for the sort of production moni‐
toring environments where pmlogreduce is most likely to be
deployed.
4. Any changes in instance domains, and indeed all metadata, is pre‐
served.
5. Any ``mark'' records in the input archive (as created by pmlogex‐
tract(1)) will be preserved in the output archive, so periods where
no data is available are maintained, and data interpolation will
not occur across these periods when the output archive is subse‐
quently processed with PCP applications.
FILES
For each of the input and output archives, several physical files are
used.
archive.meta
metadata (metric descriptions, instance domains, etc.) for
the archive log
archive.0 initial volume of metrics values (subsequent volumes have
suffixes 1, 2, ...) - for input these files may have been
previously compressed with bzip2(1) or gzip(1) and thus may
have an additional .bz2 or .gz suffix.
archive.index
temporal index to support rapid random access to the other
files in the archive log.
PCP ENVIRONMENT
Environment variables with the prefix PCP_ are used to parameterize the
file and directory names used by PCP. On each installation, the file
/etc/pcp.conf contains the local values for these variables. The
$PCP_CONF variable may be used to specify an alternative configuration
file, as described in pcp.conf(4).
SEE ALSOPCPIntro(1), pmdumplog(1), pmlc(1), pmlogextract(1), pmlogger(1),
pcp.conf(4) and pcp.env(4).
DIAGNOSTICS
All error conditions detected by pmlogreduce are reported on stderr
with textual (if sometimes terse) explanation.
Should the input archive be corrupted (this can happen if the pmlogger
instance writing the archive suddenly dies), then pmlogreduce will
detect and report the position of the corruption in the file, and any
subsequent information from the input archive will not be processed.
If any error is detected, pmlogreduce will exit with a non-zero status.
CAVEATS
The preamble metrics (pmcd.pmlogger.archive, pmcd.pmlogger.host, and
pmcd.pmlogger.port), which are automatically recorded by pmlogger at
the start of the archive, may not be present in the archive output by
pmlogreduce. These metrics are only relevant while the archive is
being created, and have no significance once recording has finished.
Performance Co-Pilot SGI PMLOGREDUCE(1)
