pmlogextract(1)
NAME
pmlogextract - reduce, extract, concatenate and merge Performance Co- Pilot archives
SYNOPSIS
pmlogextract [-dfwz] [-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 will 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.
COMMAND LINE 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.
-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 are 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. 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.
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