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pmlogger - Man Page

create an archive for performance metrics


pmlogger [-CLNoPruy?] [-c conffile] [-d directory] [-h host] [-H hostname] [-I version] [-K spec] [-l logfile] [-m note] [-n pmnsfile] [-p pid] [-s endsize] [-t interval] [-T endtime] [-U username] [-v volsize] [-V version] [-x fd] archive


pmlogger creates the archives of performance metric values that may be “played back” by other Performance Co-Pilot (see PCPIntro(1)) tools. These logs form the basis of the VCR paradigm and retrospective performance analysis services common to the PCP toolkit.

The mandatory argument archive is the base name for the physical files that constitute an archive. The archive argument may contain strftime(3) meta-characters, which will be substituted prior to creating the archive files. When pmlogger is run as a service (see pmlogger_daily(1)), the standard archive base name template is %Y%m%d.%H.%M.

The -V option specifies the version for the archive that is generated. By default the archive version $PCP_ARCHIVE_VERSION (set to 3 in current PCP releases) is used, and the only values currently supported for version are 2 or 3.

Unless directed to another host by the -h option or when directly using PMDAs via the -o option, pmlogger will contact the Performance Metrics Collector Daemon (PMCD) on the local host and use that as the source of the metric values to be logged.

To support the required flexibility and control over what is logged and when, pmlogger maintains an independent two level logging state for each instance of each performance metric. At the first (mandatory) level, logging is allowed to be on (with an associated interval between samples), or off or maybe. In the latter case, the second (advisory) level logging is allowed to be on (with an associated interval between samples), or off.

The mandatory level allows universal specification that some metrics must be logged, or must not be logged. The default state for all instances of all metrics when pmlogger starts is mandatory maybe and advisory off.

Use pmlc(1) to interrogate and change the logging state once pmlogger is running.

If a metric's state is mandatory (on or off) and a request is made to change it to mandatory maybe, the new state is mandatory maybe and advisory off. If a metric's state is already advisory (on or off) and a request is made to change it to mandatory maybe, the current state is retained.

It is not possible for pmlogger to log specific instances of a metric and all instances of the same metric concurrently. If specific instances are being logged and a request to log all instances is made, then all instances of the metric will be logged according to the new request, superseding any prior logging request for the metric. A request to log all instances of a metric will supersede any previous request to log all instances. A request to log specific instances of a metric when all instances are already being logged is refused. To do this one must turn off logging for all instances of the metric first. In each case, the validity of the request is checked first; for example a request to change a metric's logging state to advisory on when it is currently mandatory off is never permitted (it is necessary to change the state to mandatory maybe first).

Optionally, each system running pmcd(1) may also be configured to run a “primary” pmlogger instance. This pmlogger instance is launched by $PCP_RC_DIR/pmlogger, and is affected by the files $PCP_SYSCONF_DIR/pmlogger/control, $PCP_SYSCONF_DIR/pmlogger/control.d/*, (use chkconfig(8), systemctl(1) or similar platform-specific commands to activate or disable the primary pmlogger instance), $PCP_SYSCONFIG_DIR/pmlogger (environment variable settings for the primary pmlogger) $PCP_SYSCONF_DIR/pmlogger/pmlogger.options (command line options passed to the primary pmlogger) and $PCP_VAR_DIR/config/pmlogger/config.default (the default initial configuration file for the primary pmlogger).

The primary pmlogger instance is identified by the -P option. There may be at most one “primary” pmlogger instance on each system. The primary pmlogger instance (if any) must be running on the same host as the pmcd(1) to which it connects (if any), so the -h and -P options are mutually exclusive.

Logging of some metrics is possible even in the absence of a local pmcd(1), using the "local context" mode of operation. This is activated using the -o option, and causes pmlogger to make use of local DSO PMDAs instead of communicating with pmcd(1). When operating using a local context, the -K option may be used to control the DSO PMDAs that should be made accessible. The spec argument conforms to the syntax described in pmSpecLocalPMDA(3). More than one -K option may be used.

When launched as a non-primary instance, pmlogger will exit immediately if the configuration file causes no metric logging to be scheduled. The -L option overrides this behavior, and causes a non-primary pmlogger instance to “linger”, presumably pending some future dynamic re-configuration and state change via pmlc(1). pmlogger will also linger without the -L option being used if all the metrics to be logged are logged as once only metrics. When the once only metrics have been logged, a warning message will be generated stating that the event queue is empty and no more events will be scheduled.

By default all diagnostics and errors from pmlogger are written to the file pmlogger.log in the directory where pmlogger is launched. The -l option may be used to override the default behavior. If the log file cannot be created or is not writable, output is written to standard error instead. If the logfile for the -l option is "-" (i.e. -l-) then log messages are written to the standard output stream. This can be particularly useful when running pmlogger manually, rather than as a service daemon.

The -N option directs pmlogger to notify a service manager, typically systemd(1), when it has started and is about to begin writing PCP archives. This option would only normally be used when pmlogger is run as a daemon service under the control of a service manager. For more details, see __pmServerNotifyServiceManagerReady(3) and systemd(1). On platforms that do not use a service manager that supports notifications, the -N option is basically a no-op.

If specified, the -s option instructs pmlogger to terminate after a certain size in records, bytes or time units has been accumulated. If endsize is an integer then endsize records will be written to the archive. If endsize is an integer suffixed by b or bytes then endsize bytes of the archive data will be written out (note, however, that archive record boundaries will not be broken and so this limit may be slightly surpassed). Other viable file size units include: K, Kb, KiB, Kbyte, Kilobyte for kilobytes and M, Mb, MiB, Mbyte, Megabyte for megabytes and G, Gb, GiB, Gbyte, Gigabyte for gigabytes. These units may be optionally suffixed by an s and may be of mixed case. Alternatively endsize may be an integer or a floating point number suffixed using a time unit as described in PCPIntro(1) for the interval argument (to the standard PCP -t command line option).

Some examples of different formats:
-s 100
-s 100bytes
-s 100K
-s 100Mb
-s 10Gbyte
-s 10mins
-s 1.5hours

The default is for pmlogger to run forever.

The -r option causes the size of the physical record(s) for each group of metrics and the expected contribution of the group to the size of the PCP archive for one full day of collection to be reported in the log file. This information is reported the first time each group is successfully written to the archive.

The -U option specifies the user account under which to run pmlogger. The default is the current user account for interactive use. When run as a daemon, the unprivileged "pcp" account is used in current versions of PCP, but in older versions the superuser account ("root") was used by default.

The archive is potentially a multi-volume data set, and the -v option causes pmlogger to start a new volume after a certain size in records, bytes, or time units has been accumulated for the current volume. The format of this size specification is identical to that of the -s option (see above). The default is for pmlogger to create a single volume archive. Additional volume switches can also be forced asynchronously by either using pmlc(1) or sending pmlogger a SIGHUP signal (see below). Note, if a scheduled volume switch is in operation due to the -v option, then its counters will be reset after an asynchronous switch.

Independent of any -v option, each volume of an archive is limited to no more than 2^31 bytes, so pmlogger will automatically create a new volume for the archive before this limit is reached.

Normally pmlogger operates on the distributed Performance Metrics Name Space (PMNS), however if the -n option is specified an alternative local PMNS is loaded from the file pmnsfile.

Under normal circumstances, pmlogger will run forever (except for a -s option or a termination signal). The -T option may be used to limit the execution time using the format of time as prescribed by PCPIntro(1). The time is interpreted within the time zone of the PMCD server, unless the -y option is given, within which case the time zone at this logger host is used.

Some examples of different formats:
-T 10mins
-T '@ 11:30'

From this it can be seen that -T 10mins and -s 10mins perform identical actions.

Alternatively, pmlogger runtime may be limited to the lifetime of another process by using the -p or --PID option to nominate the PID of the process of interest. In this case the pmlogger will exit when the other process no longer exists.

When pmlogger receives a SIGHUP signal, the current volume of the archive is closed, and a new volume is opened. This mechanism (or the alternative mechanism via pmlc(1)) may be used to manage the growth of the archive files - once a log volume is closed, that file may be archived without ill-effect on the continued operation of pmlogger. See also the -v option above.

When pmlogger receives a SIGUSR2 signal, the current archive is closed, and a new archive is opened. For this to succeed, the original archive argument must include strftime(3) meta characters (e.g. %Y%m%d.%H.%M), otherwise pmlogger will exit because the archive files will already exist and pmlogger will not over-write existing archive files. Note that SIGUSR2 triggers pmlogger to re-exec itself and re-parse all original arguments. This means that any relative time limits placed on it's termination time or sampling limit are reset and begin again. This only affects relative termination times, not absolute times e.g. -T 5s is affected, but -T 5pm is not.

Historically the buffers for the current archive may be flushed to disk using the flush command of pmlc(1), or by using the -u option. The current version of pmlogger and the libpcp routines that underpin pmlogger unconditionally use unbuffered writes and a single fwrite(3) for each logical record written, and so “flushing” does not force any additional data to be written to the file system. The -u option and the pmlc(1) flush command are retained for backwards compatibility.

When launched with the -x option, pmlogger will accept asynchronous control requests on the file descriptor fd. This option is only expected to be used internally by PCP applications that support “live record mode”.

The -m option allows the string note to be appended to the map file for this instance of pmlogger in the $PCP_TMP_DIR/pmlogger directory. This is currently used internally to document the file descriptor (fd) when the -x option is used, or to indicate that this pmlogger instance was started under the control of pmlogger_check(1), (-m pmlogger_check) or was re-exec'd (see execvp(3)) due to a SIGUSR2 signal being received as described above (-m reexec).

The -H option allows the hostname written into the archive label to be overridden. This mirrors the -H option of pmcd(1) , but allows it to be specified on the pmlogger process. Without this option, the value returned from the logged pmcd(1) is used.

The -C option will cause the configuration file to be parsed and pmlogger will then exit without creating an output archive, so when -C is specified, the archive command line argument is not required. Any errors in the configuration file are reported.

The -d or --directory option may be used to specify the directory where the archive should be created. directory may include sh(1) metacharacters, like $(...) or `...` or $var and pmlogger will expand these to produce a final directory path. The resultant path must be absolute, not relative. The -d option is intended primarily for use by pmlogger_check(1) and normal users would not typically need to use the option, as the directory for archive is either implied by archive if it contains directory components else the current directory by default.

Configuration File Syntax

The configuration file may be specified with the -c option. If it is not, configuration specifications are read from standard input.

If conffile does not exist, then a search is made in the directory $PCP_VAR_DIR/config/pmlogger for a file of the same name, and if found that file is used, e.g. if config.mumble does not exist in the current directory and the file $PCP_VAR_DIR/config/pmlogger/config.mumble does exist, then -c config.mumble and -c $PCP_VAR_DIR/config/pmlogger/config.mumble are equivalent.

The syntax for the configuration file is as follows.

  1. Words are separated by white space (space, tab or newline).
  2. The symbol “#” (hash) introduces a comment, and all text up to the next newline is ignored.
  3. Keywords (shown in bold below) must appear literally (i.e. in lower case).
  4. Each specification begins with the optional keyword log, followed by one of the states mandatory on, mandatory off, mandatory maybe, advisory on or advisory off.
  5. For the on states, a logging interval must follow using the syntax “once”, or “default”, or “every N timeunits”, or simply “N timeunits” - N is an unsigned integer, and timeunits is one of the keywords msec, millisecond, sec, second, min, minute, hour or the plural form of one of the above.

    Internal limitations require the interval to be smaller than (approximately) 74 hours. An interval value of zero is a synonym for once. An interval of default means to use the default logging interval of 60 seconds; this default value may be changed to interval with the -t command line option.

    The interval argument follows the syntax described in PCPIntro(1), and in the simplest form may be an unsigned integer (the implied units in this case are seconds).

  6. Following the state and possible interval specifications comes a “{”, followed by a list of one or more metric specifications and a closing “}”. The list is white space (or comma) separated. If there is only one metric specification in the list, the braces are optional.
  7. A metric specification consists of a metric name optionally followed by a set of instance names. The metric name follows the standard PCP naming conventions, see PMNS(5), and if the metric name is a non-leaf node in the PMNS (see PMNS(5)), then pmlogger will recursively descend the PMNS and apply the logging specification to all descendent metric names that are leaf nodes in the PMNS. The set of instance names is a “[”, followed by a list of one or more space (or comma) separated names, numbers or strings, and a closing “]”. Elements in the list that are numbers are assumed to be internal instance identifiers, other elements are assumed to be external instance identifiers - see pmGetInDom(3) for more information.

    If no instances are given, then the logging specification is applied to all instances of the associated metric.

  8. There may be an arbitrary number of logging specifications.
  9. As of PCP version 4.0 and later, any metric name specification that does not resolve to a leaf node in the PMNS is added to an internal list of possible dynamic subtree roots. PMDAs can dynamically create new metrics below a dynamic root node in their PMNS, and send a notification to clients that the PMNS has changed, see pmdaExtSetFlags(3) and in particular the METRIC CHANGES section for API details. This mechanism is currently supported by pmdaopenmetrics(1) and pmdammv(1). When a fetch issued by pmlogger returns with the PMDA_EXT_NAMES_CHANGE flag set, pmlogger will traverse the internal list of possible dynamic subtree nodes and dynamically discover any new metrics. In effect, as of PCP version 4.0 and later, pmlogger can be configured to dynamically log new metrics that appear in the future, after the configuration file is initially parsed.
  10. Following all of the logging specifications, there may be an optional access control section, introduced by the literal token [access]. Thereafter come access control rules that allow or disallow operations from particular hosts or groups of hosts.

    The operations may be used to interrogate or control a running pmlogger using pmlc(1) and fall into the following classes:


    interrogate the status of pmlogger and the metrics it is logging


    Change advisory logging.


    Change mandatory logging.


    All of the above.

    Access control rules are of the form “allow hostlist : operationslist ;” and “disallow hostlist : operationslist ;”.

    The hostlist follows the syntax and semantics for the access control mechanisms used by PMCD and are fully documented in pmcd(1). An operationslist is a comma separated list of the operations advisory, mandatory, enquire and all.

    A missing [access] section allows all access and is equivalent to allow * : all;.

The configuration (either from standard input or conffile) is initially scanned by pmcpp(1) with the options -rs and -I $PCP_VAR_DIR/config/pmlogger. This extends the configuration file syntax with include file processing (%include), a common location to search for include files ($PCP_VAR_DIR/config/pmlogger), macro definitions (%define), macro expansion (%name and %{name}) and conditional inclusion of lines (%ifdef name ... %else ... %endif and %ifndef name ... %else ... %endif).


The available command line options are:

-c conffile, --config=conffile

Specify the conffile file to use.

-C,  --check

Parse configuration and exit.

-h host, --host=host

Fetch performance metrics from pmcd(1) on host, rather than from the default localhost.

-H hostname, --labelhost=hostname

Specify the hostname to use instead of the one returned by pmcd(1).

-I version, --pmlc-ipc-version=version

Normally, pmlogger and pmlc(1) will autonegotiate a mutually acceptable version for their private IPC channel. Use -I to force pmlogger to offer (at most) version as the version to be used. This option may be required if pmlogger needs to be managed by an older version of pmlc(1) that fails to autonegotiate correctly.

-K spec, --spec-local=spec

When fetching metrics from a local context (see -o), the -K option may be used to control the DSO PMDAs that should be made accessible. The spec argument conforms to the syntax described in pmSpecLocalPMDA(3). More than one -K option may be used.

-l logfile, --log=logfile

Write all diagnostics to logfile instead of the default pmlogger.log.

-L,  --linger

Run even if not the primary logger instance and nothing to log.

-m note, --note=note

Append note to the port map file for this instance.

-n pmnsfile, --namespace=pmnsfile

Load an alternative Performance Metrics Name Space (PMNS(5)) from the file pmnsfile.

-N,  --notify

Notify service manager such as systemd(1) as needed.

-o,  --local-PMDA

Use a local context to collect metrics from DSO PMDAs on the local host without PMCD. See also -K.


Log specified metrics for the lifetime of the pid PID.

-P,  --primary

Run as primary logger instance. See above for more detailed description of this.

-r,  --report

Report record sizes and archive growth rate.

-s endsize, --size=endsize

Terminate after archive size exceeds endsize.

-t interval, --interval=interval

Specify the logging interval. The default value is 60 seconds. Please refer to the Environment and Files sections below regarding the PMLOGGER_INTERVAL environment variable and its impact on the default logging interval.

-T endtime, --finish=endtime

Specify the endtime when to end logging.


Use unbuffered output. This is the default (so this option does nothing).

-U username, --username=username

When in daemon mode, run as user username.

-v volsize, --volsize=volsize

Switch volumes after reaching archive volume size volsize.

-V version, --version=version

Specify archive version. The default and the only accepted value is 2.

-x fd

Allow asynchronous control requests on the file descriptor fd.


Use local timezone instead of the timezone from the pmcd(1) host.

-?,  --help

Display usage message and exit.


For each PCP utility, there is a sample pmlogger configuration file that could be used to create an archive suitable for replaying with that tool (i.e. includes all of the performance metrics used by the tool). For a tool named foo this configuration file is located in $PCP_VAR_DIR/config/pmlogger/config.foo.

The following is a simple default configuration file for a primary pmlogger instance, and demonstrates most of the capabilities of the configuration specification language.

log mandatory on once { hinv.ncpu hinv.ndisk }
log mandatory on every 10 minutes {
    network.interface.in.packets [ "et0" ]
    network.interface.out.packets [ "et0" ]
    nfs.server.reqs [ "lookup" "getattr" "read" "write" ]

log advisory on every 30 minutes {

%include "macros.default"

%ifdef %disk_detail
log mandatory on %disk_detail_freq {

disallow * : all except enquire;
allow localhost : mandatory, advisory;

Hostname Changes

The hostname of the PMCD that is providing metrics to pmlogger is used in several ways.

PMCD's hostname (or the argument from the -H option) is included in the archive label and may be used to ensure that subsequent operations on multiple archives, e.g. pmlogextract(1), are only applied to archives from the same host.

For pmlogger instances using a local PMCD that are launched and managed by pmlogger_check(1) and pmlogger_daily(1), (or the systemd(1) or cron(8) services that use these scripts), the local hostname may also be used to construct the name of a directory where all the archives for the one host are stored, e.g. $PCP_ARCHIVE_DIR/<hostname>.

And PMCD's hostname is also stored in the archive via the pmcd.pmlogger.hostname metric that is used as part of the checks to ensure that there is continuity of performance data after the nightly archive rotation by pmlogger_daily(1).

The hostname of the PMCD host may change during boot time when the system transitions from a temporary hostname to a persistent hostname, or by explicit administrative action anytime after the system has been booted. When this happens, pmlogger may need to take special action, specifically if the pmlogger instance was launched from pmlogger_check(1) or pmlogger_daily(1), then pmlogger must exit.  Under normal circumstances systemd(1) or cron(8) will launch a new pmlogger shortly thereafter, and this new pmlogger instance will be operating in the context of the new hostname for the host where PMCD is running.


The archives are sufficiently precious that pmlogger will not truncate an existing physical file. A message of the form
...: "foo.index" already exists, not over-written
...: File exists indicates this situation has arisen. You must explicitly remove the files and launch pmlogger again.

There may be at most one primary pmlogger instance per monitored host; attempting to bend this rule produces the error:
pmlogger: there is already a primary pmlogger running

Various other messages relating to the creation and/or deletion of files in $PCP_TMP_DIR/pmlogger suggest a permission problem on this directory, or some feral files have appeared therein.



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


initial volume of metrics values (subsequent volumes have suffixes 1, 2, ...)


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


pmlogger maintains the files in this directory as the map between the process id of the pmlogger instance and the IPC port that may be used to control each pmlogger instance (as used by pmlc(1))


default configuration file for the primary logger instance launched from $PCP_RC_DIR/pmlogger


assorted configuration files suitable for creating logs that may be subsequently replayed with the PCP visualization and monitoring tools


Default directory for PCP archive files for performance metric values collected from the host <hostname>.


additional environment variables that will be set when the primary pmlogger instance executes. Only settings of the form "PMLOGGER_VARIABLE=value" will be honoured.


(or $PCP_ARCHIVE_DIR/<hostname>/pmlogger.log when started automatically by either $PCP_RC_DIR/pmlogger or one of the pmlogger(1) monitoring scripts such as pmlogger_check(1))
all messages and diagnostics are directed here


Normally pmlogger creates a socket to receive control messages from pmlc(1) on the first available TCP/IP port numbered 4330 or higher. The environment variable PMLOGGER_PORT may be used to specify an alternative starting port number.

If set to the value 1, the PMLOGGER_LOCAL environment variable will cause pmlogger to run in a localhost-only mode of operation, where it binds only to the loopback interface.

The PMLOGGER_REQUEST_TIMEOUT variable may be set by applications such as pmlc(1) to specify a timeout in seconds for connection requests to the pmlogger control port. If not set, connections may block indefinitely. This variable would not normally be set by pmlogger itself.

The PMLOGGER_MAXPENDING variable can be set to indicate the maximum length to which the queue of pending pmlc connections may grow.

The default sampling interval used by pmlogger can be set using the PMLOGGER_INTERVAL variable (if not set, 60 seconds will be used). Both the command line and directives in the configuration file will override this value. It is an integer in units of seconds.

On platforms using systemd(1), and when the -N option is given, the NOTIFY_SOCKET environment variable would normally be set by the service manager prior to launching pmlogger.

Two additional environment variables are used as part of the hand-off from one pmlogger instance to the next during a re-exec operation, namely __PMLOGGER_REEXEC and __PMLOGGER_TZ. The details of how these are used is an internal implementation detail, but end-users should avoid using variables of these names in their shell's environment.

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), pmcd(1), pmlogdump(1), pmlc(1), pmlogger_check(1), pmlogger_daily(1), systemctl(1), systemd(1), execvp(3), PMAPI(3), __pmServerNotifyServiceManagerReady(3), pmSpecLocalPMDA(3), strftime(3), pcp.conf(5), pcp.env(5), pmlogger(5), PMNS(5), chkconfig(8) and cron(8).

Referenced By

ganglia2pcp(1), iostat2pcp(1), LOGARCHIVE(5), LOGIMPORT(3), mrtg2pcp(1), pcp(1), pcp-atop(1), pcp-atopsar(1), PCPCompat(1), pcp-dstat(1), pcp-geolocate(1), PCPIntro(1), PCPIntro(3), pcp-ss(1), pcp-tapestat(1), pcp-vmstat(1), pmAF(3), PMAPI(3), pmcd(1), pmchart(1), pmcheck(1), __pmCleanMapDir(3), __pmConnectLogger(3), __pmControlLog(3), pmcpp(1), pmdanvidia(1), pmdaopenmetrics(1), pmdasockets(1), pmdatrace(1), pmDestroyContext(3), pmdiff(1), pmDiscoverSetup(3), pmdumptext(1), pmDupContext(3), pmfind(1), pmfind_check(1), pmGetArchiveEnd(3), pmGetArchiveLabel(3), pmie(1), pmie_check(1), pmiostat(1), pmlc(1), pmlogcheck(1), pmlogconf(1), pmlogctl(1), pmlogdump(1), pmlogextract(1), pmlogger_check(1), pmlogger.control(5), pmlogger_daily(1), pmlogger_daily_report(1), pmlogger_merge(1), pmlogger_rewrite(1), pmloglabel(1), pmlogmv(1), pmlogreduce(1), pmlogrewrite(1), pmlogsize(1), pmlogsummary(1), pmNewContext(3), pmproxy(1), pmRecord(3), pmsearch(1), pmSearchInfo(3), pmSearchSetup(3), pmSearchTextInDom(3), pmSearchTextQuery(3), pmSearchTextSuggest(3), pmseries(1), pmSeriesDescs(3), pmSeriesQuery(3), pmSeriesSetup(3), pmsnap(1), pmTrimNameSpace(3), pmUseContext(3), pmval(1), PMWEBAPI(3), pmWhichContext(3), sar2pcp(1).

PCP Performance Co-Pilot