NAME
PCPIntro - introduction to the Performance Co-Pilot (PCP) libraries
INTRODUCTION
Performance Co-Pilot (PCP) is an SGI product 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
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_LICENSE
Current PCP license does not permit this operation
Some pmcd(1) services require a valid PCP Collector license, and
some PCP client applications require a valid PCP Monitor license.
The open source version of pmcd(1) does not require any licenses at
all.
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 PCP archive.
(c) A bad result data structure passed to pmStore(3).
PM_ERR_FILE
Cannot locate a file
Generic error when a named file is expected to already exist.
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 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_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
option to pminfo(1).
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_OBJSTYLE
Caller does not match object style of running kernel
In some cases, a PCP application must be build with the same object
code style as the booted kernel because direct access to kernel
data structures may be required. These cases are a client using
PM_CONTEXT_LOCAL, or pmcd(1), or a DSO-style PMDA to be used by
pmcd.
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_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_NOASCII
ASCII format not supported for this PDU
The ASCII mode PDU support is intended for use only between pmcd
and a PMDA. Consequently not all of the possible PDU types include
encode and decode support for ASCII PDUs.
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.
CLIENT-PMCD ERRORS
These errors may occur in the interactions between a PCP client and
pmcd(1) providing real-time performance data.
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_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_PMCDLICENSE
PMCD is not licensed to accept client connections
If pmcd(1) is running without a valid PCP Collector License,
then it will only accept connections from ‘‘authorized’’ PCP
clients like pminfo(1) or pmlogger(1). This error occurs when
an unauthorized PCP client attempts to connect to an unlicensed
pmcd(1).
PM_ERR_NOPROFILE
Missing profile - protocol botch
Internal error in the communication between a client application
and pmcd(1) - should not occur.
CLIENT-ARCHIVE ERRORS
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_EOL
End of PCP archive log
An attempt is made to read past the end file of the last volume
of a PCP archive, or past the end of the time window (as
specified with a -T option) for a PCP archive.
PM_ERR_NOTHOST
Operation requires context with host source of metrics
Operations involving help text (ie. pmLookupText(3) and
pmLookupInDomText(3)) or calls to pmStore(3) require a host
context and are not supported for PCP archives.
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 PCP archive.
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 PCP archive. 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 PCP archive. If the client is
using metric descriptors from the archive 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 PCP archive. If the client is using instance
names from the instance domain in the archive (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.
TIME CONTROL ERRORS
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.
PM_ERR_WANTACK
Cannot send due to pending acknowledgements
Some client of pmtime(1) is not acknowledging messages from
pmtime, and this is causing other clients to be blocked.
NAMESPACE ERRORS
These errors may occur in the processing of PCP namespace operations.
A PCP namespace, see pmns(4), 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 loaded. As of PCP 2.0
this error is mostly confined to pmnscomp(1) and client
applications that use an uncompiled namespace file with a -n
option.
PM_ERR_NOPMNS
PMNS not accessible
Only occurs when an ASCII namespace is loaded. As of PCP 2.0
this error is mostly confined to pmnscomp(1) and client
applications that use an uncompiled namespace file with a -n
option.
PMCD-PMDA ERRORS
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
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(4). Values for these variables may be
obtained programatically using the pmGetConfig(3) function.
SEE ALSO
pmerr(1), PMAPI(3), pmErrStr(3), pmGetConfig(3), pcp.conf(4) and
pcp.env(4).