pcpintro(3) — Linux manual page

NAME | INTRODUCTION | GENERAL ERRORS | CLIENT-PMCD ERRORS | CLIENT-ARCHIVE ERRORS | TIME CONTROL ERRORS | NAMESPACE ERRORS | PMCD-PMDA ERRORS | PCP ENVIRONMENT | SEE ALSO | COLOPHON

PCPINTRO(3)             Library Functions Manual             PCPINTRO(3)

NAME         top

       PCPIntro - introduction to the Performance Co-Pilot (PCP)
       libraries

INTRODUCTION         top

       Performance Co-Pilot (PCP) is a toolkit designed for monitoring
       and managing system-level performance.

       The PCP libraries support the APIs required to create new
       performance monitoring tools and new agents (or PMDAs) to export
       performance data.  The libpcp library is used in both cases.  The
       libpcp_pmda library is used only for PMDAs.

       Individual library routines are documented in their own manual
       page entries.

       Most routines return an integer value; greater than equal to zero
       for success and less than zero for an error.  The error codes
       have symbolic names defined in <pcp/pmapi.h>.  Other negative
       values are used to encode errors that can be mapped to the
       traditional errno values defined in <errno.h>, with the value
       negated.  To translate all PCP error codes into useful messages
       use either pmerr(1) or pmErrStr(3); the latter may also be used
       to decode the -errno cases.

GENERAL ERRORS         top

       These common errors may occur in various PCP interactions.

       PM_ERR_TIMEOUT
           Timeout waiting for a response from PMCD
           Many interactions between PCP applications involve
           synchronous message passing, and these are subject to timeout
           constraints.  These errors are most frequently encountered
           when using network connections with slow data rates or long
           latencies.

           For client-pmcd timeouts, refer to PCPIntro(1) for
           environment variables that may be used to modify the timeout
           thresholds.  For pmcd-PMDA timeouts refer to the -t and -q
           options of pmcd(1) and the PCP metric pmcd.control.timeout
           that can be dynamically changed with pmstore(1).

       PM_ERR_APPVERSION
           Metric not supported by this version of monitored application
           Some performance metrics are unavailable from specific
           versions of the associated PMDA, or may be unavailable
           because the underlying instrumentation has changed or is not
           installed or is not enabled.  This error is used in results
           from pmFetch(3) to indicate these situations.

       PM_ERR_IPC
           IPC protocol failure
           Generic protocol failure on a pipe or socket connecting two
           PCP applications, eg. client-pmcd, or client-pmtime, or
           PMDA-pmcd or pmlc-pmlogger.

       PM_ERR_TEXT
           Oneline or help text is not available
           Set by a PMDA, and passed back to a PCP client, to indicate
           that the PMDA is unable to supply the requested metric or
           instance domain help text.

       PM_ERR_VALUE
           Missing metric value(s)
           This error is used for a number of conditions in which the
           value of a performance metric is inappropriate for the
           context in which it is being used, eg.

           (a) Bad value for the metric pmcd.timezone when trying to set
               the timezone via pmNewContextZone(3) for a remote or
               archive context.

           (b) Attempting to interpolate values for a metric with non-
               numeric data type from a set of PCP archives.

           (c) A bad result data structure passed to pmStore(3).

       PM_ERR_NAME
           Unknown metric name
           Just what the message says.

       PM_ERR_PMID
           Unknown or illegal metric identifier
           Just what the message says.

       PM_ERR_INDOM
           Unknown or illegal instance domain identifier
           A request nominates an instance domain that is unknown or
           PM_INDOM_NULL.  May occur as a consequence of the instance
           domain identifier passed by a PCP client to pmGetInDom(3),
           pmLookupInDom(3), pmNameInDom(3), pmGetInDomArchive(3),
           pmLookupInDomArchive(3), pmNameInDomArchive(3) or a request
           passed from pmcd(1) to a PMDA.

       PM_ERR_EOF
           IPC channel closed
           End of file on a pipe or socket connecting two PCP
           applications, eg. client-pmcd, or client-pmtime or PMDA-pmcd.

       PM_ERR_NOCONTEXT
           Attempt to use an illegal context
           Typically caused by a PCP client that tries to make calls
           before calling pmNewContext(3) or after calling
           pmDestroyContext(3).

       PM_ERR_PERMISSION
           No permission to perform requested operation
           PCP-specific access controls apply to pmcd(1) and
           pmlogger(1).  Platform-specific permission errors are
           returned as -EPERM.

       PM_ERR_CONV
           Impossible value or scale conversion
           Some value conversion requests are illegal, eg. bad debug
           flag symbolic name for -D/--debug option, or asking
           pmExtractValue(3) to translate non-numeric data types to
           numbers and vice versa.

       PM_ERR_TRUNC
           Truncation in value conversion
           Some conversion requests to pmExtractValue(3) cannot be
           performed based on the metric types and values involved, in
           this case conversion would result in loss of precision.

       PM_ERR_SIGN
           Negative value in conversion to unsigned
           Some conversion requests to pmExtractValue(3) cannot be
           performed based on the metric types and values involved, in
           this case converting a negative value to an unsigned value.

       PM_ERR_TYPE
           Unknown or illegal metric type
           The metric type is held in the metric descriptor and
           sometimes encoded in the metric values returned from a call
           to pmFetch(3).  Legal values for the metric type are defined
           by the PM_TYPE_* macros in <pcp/pmapi.h>.

       PM_ERR_UNIT
           Illegal pmUnits specification
           Some conversion requests to pmConvScale(3) cannot be
           performed due to illegal or incompatible specifications of
           the source and destination units.

       PM_ERR_PROFILE
           Explicit instance identifier(s) required
           Some PMDAs, especially the proc PMDA, will not return ``all
           instances'' for a pmFetch(3) request due to the cost.  The
           client must explicitly built an instance profile using
           pmAddProfile(3) and/or pmDelProfile(3) before calling
           pmFetch(3).  See also the -F/--fetchall option to pminfo(1).

       PM_ERR_INST
           Unknown or illegal instance identifier
           A request to a PMDA nominates an instance that is unknown.
           May occur as a consequence of the profile established prior
           to a pmFetch(3) call, or an explicit instance name or
           identifier to pmLookupInDom(3) or pmNameInDom(3).

       PM_ERR_MODE
           Illegal mode specification
           Illegal mode argument to pmSetMode(3).

       PM_ERR_PROFILESPEC
           NULL pmInDom with non-NULL instlist
           Bad arguments passed from a PCP client to pmAddProfile(3).

       PM_ERR_TOOSMALL
           Insufficient elements in list
           Parameter passing error by caller specifying a list with less
           than one element to pmFetch(3), pmLookupName(3) or
           pmStore(3).

       PM_ERR_FAULT
           QA fault injected
           For testing, there is a ``fault injection'' version of libpcp
           and this error indicates a misuse of the fault injection
           infrastructure.

       PM_ERR_THREAD
           Operation not supported for multi-threaded applications
           As documented in PMAPI(3) and elsewhere, some libpcp routines
           are intended solely for use from single-threaded
           applications.

       PM_ERR_NOCONTAINER
           Container not found The user supplied container name does not
           match any known container.

       PM_ERR_BADSTORE
           Bad input to pmstore
           The metric value provided for a pmStore(3) operation is in
           the wrong format, or of the wrong type or has the wrong
           number of values.

       PM_ERR_TOOBIG
           Result size exceeded
           Indicates a fatal error in the message (or PDU) passing
           protocol between two PCP applications.  This is an internal
           error, and other than an exotic networking failure, should
           not occur.

       PM_ERR_RESET
           PMCD reset or configuration change
           Not used.

           Refer to pmFetch(3) for an alternative mechanism that may be
           used to notify a PCP client when pmcd(1) has experienced one
           or more configuration changes since the last request from the
           client.  Usually these changes involve a change to the
           namespace exported via pmcd and/or changes to the PMDAs under
           pmcd's control.

       PM_ERR_FAULT
           QA fault injected
           Used only for PCP Quality Assurance (QA) testing.

       PM_ERR_NYI
           Functionality not yet implemented
           Self explanatory and rarely used.

       PM_ERR_GENERIC
           Generic error, already reported above
           Rarely used, this error may be returned when the error
           condition is a consequent of some earlier returned error and
           a more precise characterization is not possible.

       PM_ERR_BADDERIVE
           Derived metric definition failed
           When registering a derived metric, the metric expression is
           either syntactically or semantically incorrect.

       PM_ERR_NOLABELS
           No support for metric label metadata
           Operation requires metric labels, but none are available.

CLIENT-PMCD ERRORS         top

       These errors may occur in the interactions between a PCP client
       and pmcd(1) providing real-time performance data.

       PM_ERR_NOAGENT
              No PMCD agent for domain of request
              A request sent to pmcd(1) requires information from an
              agent or PMDA that does not exist.  Usually this means the
              namespace being used by the client application contains
              metric names from a previously installed PMDA.

       PM_ERR_CONNLIMIT
              PMCD connection limit for this host exceeded
              The client connection limit for pmcd(1) is controlled by
              the optional access controls in $PCP_PMCDCONF_PATH.  By
              default there is no limit imposed by the PCP code, and
              this error would not be seen.

       PM_ERR_AGAIN
              Try again. Information not currently available
              Used to notify a PCP client that the PMDA responsible for
              delivering the information is temporarily unavailable.
              See also PM_ERR_PMDANOTREADY.

       PM_ERR_NOPROFILE
              Missing profile - protocol botch
              Internal error in the communication between a client
              application and pmcd(1) - should not occur.

       PM_ERR_NEEDCLIENTCERT
              PMCD requires a client certificate Authentication failure.

       PM_ERR_PMDAFENCED
              PMDA is currently fenced and unable to respond to requests
              A privileged user has decided to isolate a PMDA from
              pmcd(1) using a pmStore(1) operation on the
              pmcd.agent.fenced metric, which means all fetch-level
              requests to that PMDA are being blocked.

CLIENT-ARCHIVE ERRORS         top

       These errors may occur in the interactions between a PCP client
       and the library routines that provide historical performance data
       from PCP archives created by pmlogger(1).

       PM_ERR_LOGFILE
              Missing archive file
              Each PCP archive consists of multiple physical files as
              described in pmlogger(1).  This error occurs when one of
              the physical files is missing or cannot be opened for
              reading.

       PM_ERR_EOL
              End of PCP archive log
              An attempt is made to read past the end file of the last
              volume of a set of PCP archives, or past the end of the
              time window (as specified with a -T/--finish option) for a
              set of PCP archives.

       PM_ERR_NOTHOST
              Operation requires context with host source of metrics
              Calls to pmStore(3) require a host context and are not
              supported for PCP archives.

              For archives created with versions of PCP prior to 4.0,
              the pmLookupText(3) and pmLookupInDomText(3) calls will
              return this code for archive PMAPI contexts (help and one-
              line text was not previously recorded in archive logs).

       PM_ERR_LOGREC
              Corrupted record in a PCP archive log
              PCP archives can become corrupted for a variety of
              reasons, but the most common is premature termination of
              pmlogger(1) without flushing its output buffers.

       PM_ERR_LABEL
              Illegal label record at start of a PCP archive log file
              Each physical file in a PCP archive should begin with a
              common label record.  This is a special case of
              PM_ERR_LOGREC errors.

       PM_ERR_NODATA
              Empty archive log file
              An empty physical file can never be part of a valid PCP
              archive (at least the label record should be present).
              This is a special case of PM_ERR_LOGREC errors.

       PM_ERR_NOTARCHIVE
              Operation requires context with archive source of metrics
              A call to one of the archive variant routines, i.e.
              pmFetchArchive(3), pmGetInDomArchive(3),
              pmLookupInDomArchive(3) or pmNameInDomArchive(3), when the
              current context is not associated with a set of PCP
              archives.

       PM_ERR_PMID_LOG
              Metric not defined in the PCP archive log
              A PCP client has requested information about a metric, and
              there is no corresponding information in the set of PCP
              archives.  This should not happen for well-behaved PCP
              clients.

       PM_ERR_INDOM_LOG
              Instance domain identifier not defined in the PCP archive
              log
              A PCP client has requested information about an instance
              domain for one or more performance metrics, and there is
              no corresponding information in the set of PCP archives.
              If the client is using metric descriptors from the set of
              archives to identify the instance domain, this is less
              likely to happen.

              Because instance domains may vary over time, clients may
              need to use the variant routines pmGetInDomArchive(3) or
              pmLookupInDomArchive(3) or pmNameInDomArchive(3) to
              manipulate the union of the instances in an instance
              domain over the life of an archive.

       PM_ERR_INST_LOG
              Instance identifier not defined in the PCP archive log
              A PCP client has requested information about a specific
              instance of a performance metric, and there is no
              corresponding information in the set of PCP archives.  If
              the client is using instance names from the instance
              domain in the set of archives (rather than hard-coded
              instance names) and instance identifiers from the results
              returned by pmFetch(3) or pmFetchArchive(3) this is less
              likely to happen.

              Because instance domains may vary over time, clients may
              need to use the variant routines pmLookupInDomArchive(3)
              or pmNameInDomArchive(3) to manipulate the union of the
              instances in an instance domain over the life of an
              archive.

       PM_ERR_LOGOVERLAP
              Archives overlap in time
              When using a context associated with a set of archives,
              the archives in the set may not overlap in time.

       PM_ERR_LOGHOST
              Archives differ by host
              When using a context associated with a set of archives,
              the archives in the set must all have been generated on
              the same host.

       PM_ERR_LOGCHANGETYPE
              The type of a metric differs among archives
              When using a context associated with a set of archives,
              the type of each metric must be same in all of the
              archives.

       PM_ERR_LOGCHANGESEM
              The semantics of a metric differs among archives
              When using a context associated with a set of archives,
              the semantics of each metric must be same in all of the
              archives.

       PM_ERR_LOGCHANGEINDOM
              The instance domain of a metric differs among archives
              When using a context associated with a set of archives,
              the instance domain of each metric must be same in all of
              the archives.

       PM_ERR_LOGCHANGEUNITS
              The units of a metric differs among archives
              When using a context associated with a set of archives,
              the units of each metric must be same in all of the
              archives.

TIME CONTROL ERRORS         top

       These errors may occur in the interactions between a GUI PCP
       client and the time control services provided by pmtime(1).

       PM_ERR_ISCONN
              Already Connected
              A PCP client application called pmTimeConnect(3) when
              already connected to a pmtime(1) instance.

       PM_ERR_NOTCONN
              Not Connected
              A PCP client application called one of the time control
              routines pmTime*(3) when not currently connected to any
              pmtime(1) instance.

       PM_ERR_NEEDPORT
              A non-null port name is required
              If a shared pmtime(1) instance is being created the port
              argument to pmTimeConnect(3) must not be invalid.

NAMESPACE ERRORS         top

       These errors may occur in the processing of PCP namespace
       operations.  A PCP namespace, see PMNS(5), provides the external
       names and the internal identifiers for the available performance
       metrics.

       PM_ERR_NONLEAF
              Metric name is not a leaf in PMNS
              The metric name passed to pmLookupName(3) names a non-
              terminal path in the namespace, i.e. a group of metrics
              rather than a single metric.

       PM_ERR_DUPPMNS
              Attempt to reload the PMNS
              When using an explicit local namespace, it is illegal to
              call either of pmLoadNameSpace(3) or
              pmLoadASCIINameSpace(3) more than once.

       PM_ERR_PMNS
              Problems parsing PMNS definitions
              Only occurs when an ASCII namespace is explicitly loaded.

       PM_ERR_NOPMNS
              PMNS not accessible
              Only occurs when an ASCII namespace is explicitly loaded.

PMCD-PMDA ERRORS         top

       These error codes are used in the interactions between pmcd(1)
       and the PMDAs that provide the performance data.

       PM_ERR_PMDANOTREADY
              PMDA is not yet ready to respond to requests
              Some PMDAs have long initialization or reset times, and
              will respond to pmcd(1) with this error if they are busy
              at the moment.  This error translates to PM_ERR_AGAIN for
              the PCP client who made the request to pmcd which caused
              the initial request to the PMDA.  At some later time the
              PMDA will inform pmcd (see PM_ERR_PMDAREADY) that it is
              now ready to process requests, and client requests will
              begin to succeed.

       PM_ERR_PMDAREADY
              PMDA is now responsive to requests
              Used by PMDAs to asynchronously inform pmcd(1) that they
              are now willing to resume processing requests.  See also
              PM_ERR_PMDANOTREADY.

PCP ENVIRONMENT         top

       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).  Values for these variables may be obtained
       programmatically using the pmGetConfig(3) function.

SEE ALSO         top

       PCPIntro(1), pmcd(1), pmerr(1), pminfo(1), pmtime(1), pmstore(1),
       pmlogger(1), PMAPI(3), pmAddProfile(3), pmDelProfile(3),
       pmConvScale(3), pmNewContext(3), pmDestroyContext(3),
       pmErrStr(3), pmExtractValue(3), pmFetch(3), pmFetchArchive(3),
       pmGetConfig(3), pmGetInDom(3), pmGetInDomArchive(3),
       pmLoadNameSpace(3), pmLookupInDom(3), pmLookupInDomText(3),
       pmLookupName(3), pmLookupText(3), pmNameInDom(3),
       pmNameInDomArchive(3), pmSetMode(3), pmStore(3),
       pmTimeConnect(3), 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 
       ⟨http://www.pcp.io/⟩.  If you have a bug report for this manual
       page, send it to pcp@groups.io.  This page was obtained from the
       project's upstream Git repository
       ⟨https://github.com/performancecopilot/pcp.git⟩ on 2020-12-18.
       (At that time, the date of the most recent commit that was found
       in the repository was 2020-12-18.)  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
       man-pages@man7.org

Performance Co-Pilot               PCP                       PCPINTRO(3)

Pages that refer to this page: pmapi(3)pmierrstr(3)pmwebapi(3)pcp.conf(5)pcp.env(5)pmns(5)