pmlogextract(1) — Linux manual page


PMLOGEXTRACT(1)          General Commands Manual         PMLOGEXTRACT(1)

NAME         top

       pmlogextract - reduce, extract, concatenate and merge Performance
       Co-Pilot archives

SYNOPSIS         top

       pmlogextract [-dfmwxz?]  [-c configfile] [-S starttime] [-s
       samples] [-T endtime] [-v volsamples] [-Z timezone] input [...]

DESCRIPTION         top

       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         top

       The available command line options are:

       -c config, --config=config
            Extract only the metrics specified in config from the input
            PCP archive log(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 log is not removed.

       -f, --first
            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

       -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 samples
            retrieved or specify a ``natural'' alignment of the output
            sample times; refer to PCPIntro(1).  See also the -w option.

       -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,
            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, --finish=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

       -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.

       -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 log(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 log.  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.  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
            logs.  The default is to initially use the timezone of the
            local host.

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


       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

       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.


       This is an example of a valid configfile:

               # config file for pmlogextract

               kernel.percpu.cpu.sys ["cpu0","cpu1"]

MARK RECORDS         top

       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.


       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.

CAVEATS         top

       The preamble metrics (pmcd.pmlogger.archive,,
       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         top

       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 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

FILES         top

       For each of the input and output archive logs, several physical
       files are used.

            metadata (metric descriptions, instance domains, etc.) for
            the archive log

            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.

            temporal index to support rapid random access to the other
            files in the archive log.


       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

       For environment variables affecting PCP tools, see

SEE ALSO         top

       PCPIntro(1), pmdumplog(1), pmlc(1), pmlogger(1), pmlogreduce(1),
       pmlogrewrite(1), pcp.conf(5), pcp.env(5) and PMNS(5).

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.
       Information about the project can be found at 
       ⟨⟩.  If you have a bug report for this manual
       page, send it to  This page was obtained from the
       project's upstream Git repository
       ⟨⟩ on 2021-08-27.
       (At that time, the date of the most recent commit that was found
       in the repository was 2021-08-27.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

Performance Co-Pilot               PCP                   PMLOGEXTRACT(1)

Pages that refer to this page: ganglia2pcp(1)pcpintro(1)pmdumplog(1)pmlogcheck(1)pmlogger_check(1)pmlogger_merge(1)pmloglabel(1)pmlogpaste(1)pmlogreduce(1)pmlogrewrite(1)pmlogsummary(1)pmrep(1)sar2pcp(1)pmfetch(3)pmfetcharchive(3)LOGARCHIVE(5)