PCPINTRO(3) Library Functions Manual PCPINTRO(3)
PCPIntro - introduction to the Performance Co-Pilot (PCP) libraries
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.
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 One-line 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.
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.
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.
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.
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.
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.
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.
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).
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 firstname.lastname@example.org. This page was obtained from the project's upstream Git repository ⟨https://github.com/performancecopilot/pcp.git⟩ 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 email@example.com 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)