Provided by: pcp_4.0.1-1_amd64 
NAME
pmlogextract - reduce, extract, concatenate and merge Performance Co-Pilot archives
SYNOPSIS
pmlogextract [-dfmwz] [-c configfile] [-S starttime] [-s samples] [-T endtime] [-v
volsamples] [-Z timezone] input [...] output
DESCRIPTION
pmlogextract reads one or more Performance Co-Pilot (PCP) archive logs identified by input
and creates a temporally merged and/or reduced PCP archive log 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 nature of merging is controlled
by the number of input archive logs, while the nature of data reduction is controlled by
the command line arguments. The input(s) must be sets of PCP archive logs created by
pmlogger(1) with performance data collected from the same host, but usually over different
time periods and possibly (although not usually) with different performance metrics being
logged.
If only one input is specified, then the default behavior simply copies the input set of
PCP archive logs, into the output PCP archive log. When two or more sets of PCP archive
logs are specified as input, the sets of logs are merged (or concatenated) and written to
output.
In the output archive log a <mark> record may be inserted at a time just past the end of
each of the input archive logs to indicate a possible temporal discontinuity between the
end of one input archive log and the start of the next input archive log. See the MARK
RECORDS section below for more information. There is no <mark> record after the end of
the last (in temporal order) of the input archive logs.
OPTIONS
The command line options for pmlogextract are as follows:
-c configfile
Extract only the metrics specified in configfile from the input PCP archive log(s).
The configfile syntax accepted by pmlogextract is explained in more detail in the
Configuration File Syntax section.
-d Desperate mode. Normally if a fatal error occurs, all trace of the partially
written PCP archive output is removed. With the -d option, the output archive log
is not removed.
-f For most common uses, all of the input archive logs will have been collected in the
same timezone. But if this is not the case, then pmlogextract must choose one of
the timezones from the input archive logs to be used as the timezone for the output
archive log. The default is to use the timezone from the last input archive log.
The -f option forces the timezone from the first input archive log to be used.
-m As described in the MARK RECORDS section below, sometimes it is possible to safely
omit <mark> records from the output archive. If the -m option is specified, then
the epilogue and prologue test is skipped and a <mark> record will always be
inserted at the end of each input archive (except the last). This is the original
behaviour for pmlogextract.
-S starttime
Define the start of a time window to restrict the samples retrieved or specify a
``natural'' alignment of the output sample times; refer to PCPIntro(1). See also
the -w option.
-s samples
The argument samples defines the number of samples to be written to output. If
samples is 0 or -s is not specified, pmlogextract will sample until the end of the
PCP archive log, 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 or
specify a ``natural'' alignment of the output sample times; refer to PCPIntro(1).
See also the -w option.
-v volsamples
The output archive log is potentially a multi-volume data set, and the -v option
causes pmlogextract to start a new volume after volsamples log records have been
written to the archive log.
Independent of any -v option, each volume of an archive is limited to no more than
2^31 bytes, so pmlogextract will automatically create a new volume for the archive
before this limit is reached.
-w Where -S and -T specify a time window within the same day, the -w flag will cause
the data within the time window to be extracted, for every day in the archive log.
For example, the options -w -S @11:00 -T @15:00 specify that pmlogextract should
include archive log records only for the periods from 11am to 3pm on each day.
When -w is used, the output archive log will contain <mark> records to indicate the
temporal discontinuity between the end of one time window and the start of the
next.
-Z timezone
Use timezone when displaying the date and time. Timezone is in the format of the
environment variable TZ as described in environ(7).
-z Use the local timezone of the host from the input archive logs. The default is to
initially use the timezone of the local host.
CONFIGURATION FILE SYNTAX
The configfile contains metrics of interest - only those metrics (or instances) mentioned
explicitly or implicitly in the configuration file will be included in the output archive.
Each specifications must begin on a new line, and may span multiple lines in the
configuration file. Instances may also be specified, but they are optional. The format
for each specification is
metric [[instance[,instance...]]]
where metric may be a leaf or a non-leaf name in the Performance Metrics Name Space (PMNS,
see pmns(5)). If a metric refers to a non-leaf node in the PMNS, pmlogextract will
recursively descend the PMNS and include all metrics corresponding to descendent leaf
nodes.
Instances are optional, and may be specified as a list of one or more space (or comma)
separated names, numbers or strings (enclosed in single or double quotes). Elements in
the list that are numbers are assumed to be internal instance identifiers - see
pmGetInDom(3) for more information. If no instances are given, then all instances of the
associated metric(s) will be extracted.
Any additional white space is ignored and comments may be added with a `#' prefix.
CONFIGURATION FILE EXAMPLE
This is an example of a valid configfile:
#
# config file for pmlogextract
#
kernel.all.cpu
kernel.percpu.cpu.sys ["cpu0","cpu1"]
disk.dev ["dks0d1"]
MARK RECORDS
When more than one input archive log contributes performance data to the output archive
log, then <mark> records may be inserted to indicate a possible discontinuity in the
performance data.
A <mark> record contains a timestamp and no performance data and is used to indicate that
there is a time period in the PCP archive log where we do not know the values of any
performance metrics, because there was no pmlogger(1) collecting performance data during
this period. Since these periods are often associated with the restart of a service or
pmcd(1) or a system, there may be considerable doubt as to the continuity of performance
data across this time period.
Most current archives are created with a prologue record at the beginning and an epilogue
record at the end. These records identify the state of pmcd(1) at the time, and may be
used by pmlogextract to determine that there is no discontinuity between the end of one
archive and the next output record, and as a consequence the <mark> record can safely be
omitted from the output archive.
The rationale behind <mark> records may be demonstrated with an example. Consider one
input archive log that starts at 00:10 and ends at 09:15 on the same day, and another
input archive log that starts at 09:20 on the same day and ends at 00:10 the following
morning. This would be a very common case for archives managed and rotated by
pmlogger_check(1) and pmlogger_daily(1).
The output archive log created by pmlogextract would contain:
00:10.000 first record from first input archive log
...
09:15.000 last record from first input archive log
09:15.001 <mark> record
09:20.000 first record from second input archive log
...
01:10.000 last record from second input archive log
The time period where the performance data is missing starts just after 09:15 and ends
just before 09:20. When the output archive log is processed with any of the PCP reporting
tools, the <mark> record is used to indicate a period of missing data. For example using
the output archive above, imagine one was reporting the average I/O rate at 30 minute
intervals aligned on the hour and half-hour. The I/O count metric is a counter, so the
average I/O rate requires two valid values from consecutive sample times. There would be
values for all the intervals ending at 09:00, then no values at 09:30 because of the
<mark> record, then no values at 10:00 because the ``prior'' value at 09:30 is not
available, then the rate would be reported again at 10:30 and continue every 30 minutes
until the last reported value at 01:00.
The presence of <mark> records in a PCP archive log can be established using pmdumplog(1)
where a timestamp and the annotation <mark> is used to indicate a <mark> record.
METADATA CHECKS
When more than one input archive set is specified, pmlogextract performs a number of
checks to ensure the metadata is consistent for metrics appearing in more than one of the
input archive sets. These checks include:
* metric data type is the same
* metric semantics are the same
* metric units are the same
* metric is either always singular or always has the same instance domain
* metrics with the same name have the same PMID
* metrics with the same PMID have the same name
If any of these checks fail, pmlogextract reports the details and aborts without creating
the output archive.
To address these semantic issues, use pmlogrewrite(1) to translate the input archives into
equivalent archives with consistent metdadata before using pmlogextract.
FILES
For each of the input and output archive logs, 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).
SEE ALSO
PCPIntro(1), pmdumplog(1), pmlc(1), pmlogger(1), pmlogreduce(1), pmlogrewrite(1),
pcp.conf(5) and pcp.env(5).
DIAGNOSTICS
All error conditions detected by pmlogextract are reported on stderr with textual (if
sometimes terse) explanation.
Should one of the input archive logs be corrupted (this can happen if the pmlogger
instance writing the log suddenly dies), then pmlogextract will detect and report the
position of the corruption in the file, and any subsequent information from that archive
log will not be processed.
If any error is detected, pmlogextract 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 pmlogextract. These metrics are only relevant while the
archive is being created, and have no significance once recording has finished.