Ubuntu Manpage: pmlogreduce - temporal reduction of Performance Co-Pilot archives

NAME

       pmlogreduce - temporal reduction of Performance Co-Pilot archives

SYNOPSIS

       $PCP_BINADM_DIR/pmlogreduce  [-z?]   [-A  align] [-s samples] [-S starttime] [-t interval]
       [-T endtime] [-v volsamples] [-Z timezone] input output

DESCRIPTION

       pmlogreduce reads one set of Performance Co-Pilot (PCP) archives identified by  input  and
       creates  a  temporally  reduced PCP archive in output.  input is a comma-separated list of
       names, each of which may be the base name of  an  archive  or  the  name  of  a  directory
       containing  one  or  more  archives.  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 archives), 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.

OPTIONS

The available command line options are:

-A align, --align=align
Specify a ``natural'' alignment of the output sample times; refer to PCPIntro(1).

-s samples, --samples=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 set
of PCP archives, 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.

-S starttime, --start=starttime
Define the start of a time window to restrict the samples retrieved from the input
archives; refer to PCPIntro(1).

-t interval, --interval=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).

-T endtime, --finish=endtime
Define the termination of a time window to restrict the samples retrieved from the
input archives; 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 limited to no more than
2^31 bytes, so pmlogreduce will automatically create a new volume for the archive
before this limit is reached.

-z, --hostzone
Use the local timezone of the host from the input archives 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.

-Z timezone, --timezone=timezone
Use timezone when displaying the date and time, or interpreting the -S and -T
options. Timezone is in the format of the environment variable TZ as described in
environ(7).

-?, --help
Display usage message and exit.

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 discrete 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 adjustment 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 archives, and
silently overestimate in the case where a counter reset occurs between consecutive
observations in the input archives; unfortunately these situations cannot be
detected, but are believed to be rare events for the sort of production monitoring
environments where pmlogreduce is most likely to be deployed.

4. Any changes in instance domains, and indeed all metadata, is preserved.

5. Any ``mark'' records in the input archives (as created by pmlogextract(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
subsequently processed with PCP applications.

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.

DIAGNOSTICS

       All  error  conditions  detected  by  pmlogreduce  are reported on stderr with textual (if
       sometimes terse) explanation.

       Should the input archives 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 archives will not be
       processed.

       If any error is detected, pmlogreduce will exit with a non-zero status.

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(5).