Provided by: pcp_6.0.3-1_amd64 
NAME
pmlogextract - reduce, extract, concatenate and merge Performance Co-Pilot archives
SYNOPSIS
pmlogextract [-dfmwxz?] [-c configfile] [-S starttime] [-s samples] [-T endtime] [-V
version] [-v volsamples] [-Z timezone] input [...] output
DESCRIPTION
pmlogextract reads one or more Performance Co-Pilot (PCP) archives identified by input and
creates a merged and/or reduced PCP archive in output. Each input argument is either a
name or a comma-separated list of names, and each name is the name of one file from an
archive or 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 archives, while the
nature of data reduction is controlled by the command line arguments. The input arguments
must be archives 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 PCP
archive (with possible conversion to a newer version of the archive format, see -V below),
into the output PCP archive. When two or more PCP archives are specified as input, the
archives are merged (or concatenated) and written to output.
In the output archive a <mark> record may be inserted at a time just past the end of each
of the input archive to indicate a possible temporal discontinuity between the end of one
input archive and the start of the next input archive. 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 records from the input archive(s).
OPTIONS
The available command line options are:
-c config, --config=config
Extract only the metrics specified in config from the input PCP archive(s). The
config syntax accepted by pmlogextract is explained in more detail in the
CONFIGURATION FILE SYNTAX section.
-d, --desperate
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 is not
removed.
-f, --first
For most common uses, all of the input archives 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 archives to be used as the timezone for the output archive.
The default is to use the timezone from the last input archive. The -f option forces
the timezone from the first input archive to be used.
-m, --mark
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, --start=starttime
Define the start of a time window to restrict the records processed; refer to
PCPIntro(1). See also the -w option.
-s samples, --samples=samples
The argument samples defines the number of samples (or records) to be written to
output. If samples is 0 or -s is not specified, pmlogextract will continue until the
end of all the input archives or until 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, --finish=endtime
Define the end of a time window to restrict the records processed; refer to
PCPIntro(1). See also the -w option.
-V version, --outputversion=version
Each PCP archive has a version for the physical record format, currently 2 or 3. By
default, the output archive is created with a version equal to the maximum of the
version of the input archives. The -V option may be used to explicitly force the
version for output, provided version is no smaller than the archive version that
would have been chosen by the default rule.
For example, specifying -V 3 may be used to produce a version 3 output archive from
input archives that could be a mixture of version 2 and/or version 3.
-v volsamples
The output archive 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.
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. For
example, the options -w -S @11:00 -T @15:00 specify that pmlogextract should include
archive records only for the periods from 11am to 3pm on each day. When -w is used,
the output archive will contain <mark> records to indicate the temporal discontinuity
between the end of one time window and the start of the next.
-x It is expected that the metadata (name, PMID, type, semantics and units) for each
metric will be consistent across all of the input PCP archive(s) in which that metric
appears. In rare cases, e.g. in development, in QA and when a PMDA is upgraded, this
may not be the case and pmlogextract will report the issue and abort without creating
the output archive. This is done so the problem can be fixed with pmlogrewrite(1)
before retrying the merge. In unattended or QA environments it may be preferable to
force the merge and omit the metrics with the mismatched metadata. The -x option
does this.
-Z timezone, --timezone=timezone
Use timezone when displaying the date and time in diagnostics. Timezone is in the
format of the environment variable TZ as described in environ(7). The default is to
initially use the timezone of the local host.
-z, --hostzone
Use the local timezone of the host from the input archive(s) when displaying the date
and time in diagnostics. The default is to initially use the timezone of the local
host.
-?, --help
Display usage message and exit.
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 specification 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
or
metric [ instance ... ]
where metric may be a leaf or a non-leaf name of a metric 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 are specified as a list space (or comma) separated of instance
identifiers, with the list enclosed by square brackets. Each instance identifier may be a
number or a string (enclosed in single or double quotes). instance identifiers that are
numbers are assumed to be internal instance identifiers, else the string values are
assumed to be external 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 contributes performance data to the output archive, then
<mark> records may be inserted to indicate a possible temporal 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 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 reboot, 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 that starts at 00:10 and ends at 09:15 on the same day, and another input
archive 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 created by pmlogextract would contain:
00:10.000 first record from first input archive
...
09:15.000 last record from first input archive
09:15.001 <mark> record
09:20.000 first record from second input archive
...
01:10.000 last record from second input archive
The time period where the performance data is missing starts just after 09:15 and ends
just before 09:20. When the output archive 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 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 is specified, pmlogextract performs a number of checks to
ensure the metadata is consistent for metrics appearing in more than one of the input
archives. 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 metadata before using pmlogextract.
Refer to the -x and -d command line options above for alternatives to the default handling
of errors during metadata checks.
CAVEATS
The prologue 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.
DIAGNOSTICS
All error conditions detected by pmlogextract are reported on stderr with textual (if
sometimes terse) explanation.
If one of the input archives contains no archive records then an ``empty archive'' warning
is issued and that archive is skipped.
Should one of the input archive(s) be corrupted (this can happen if the pmlogger instance
writing the archive suddenly dies), then pmlogextract will detect and report the position
of the corruption in the file, and any subsequent information from that archive will not
be processed.
If any error is detected, pmlogextract will exit with a non-zero status.
FILES
For each of the input and output archive, several physical files are used.
archive.meta
metadata (metric descriptions, instance domains, etc.) for the archive
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.
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).
For environment variables affecting PCP tools, see pmGetOptions(3).
SEE ALSO
PCPIntro(1), pmdumplog(1), pmlc(1), pmlogger(1), pmlogreduce(1), pmlogrewrite(1),
pcp.conf(5), pcp.env(5) and PMNS(5).