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).