pmgetarchivelabel(3) — Linux manual page

PMGETARCHIVELABEL(3)    Library Functions Manual    PMGETARCHIVELABEL(3)

NAME

       pmGetArchiveLabel, pmGetHighResArchiveLabel - fetch the label
       record from a set of performance metrics archives

C SYNOPSIS

       #include <pcp/pmapi.h>

       int pmGetArchiveLabel(pmLogLabel *lp);
       int pmGetHighResArchiveLabel(pmHighResLogLabel *lp);

       cc ... -lpcp

DESCRIPTION

       Within the framework of the Performance Co-Pilot (PCP), archives
       of performance metrics values may be accumulated and saved using
       the program pmlogger(1) and the LOGIMPORT(3) programming
       interface.

       The routines pmGetArchiveLabel and pmGetHighResArchiveLabel may
       be used to fetch the label record from a set of archives that has
       already been opened using pmNewContext(3), or pmDupContext(3),
       and thereby associated with the current Performance Metrics
       Application Programming Interface (PMAPI) context.

       It is recommended that new applications use the high resolution
       API and existing applications transition to this interface over
       time.

       The result returned via the pointer lp is a structure that must
       be pre-allocated by the caller and has one of the following two
       formats (defined in pmapi.h).

         typedef struct {
           int        magic;       /* PM_LOG_MAGIC | archive format version no. */
           pid_t      pid;         /* PID of logger */
           struct timespec start;  /* start of this archive */
           char       hostname[PM_MAX_HOSTNAMELEN];   /* collection host full name */
           char       timezone[PM_MAX_TIMEZONELEN];   /* generic, squashed $TZ */
           char       zoneinfo[PM_MAX_ZONEINFOLEN];   /* local platform $TZ */
         } pmHighResLogLabel;

         typedef struct {
           int        ll_magic;    /* PM_LOG_MAGIC | archive format version no. */
           pid_t      ll_pid;      /* PID of logger */
           struct timeval ll_start;/* start of this archive */
           char       ll_hostname[PM_LOG_MAXHOSTLEN]; /* name of collection host */
           char       ll_tz[40];   /* $TZ at collection host */
         } pmLogLabel;

       Both forms can be used with either version 2 or version 3
       archives.  However, the pmHighResLogLabel structure provides the
       higher resolution start time stored in the newer format, as well
       as the full timezone and extended length host name fields.  For
       detailed information about the archive on-disk format, refer to
       LOGARCHIVE(5).

       For an application using pmGetHighResArchiveLabel, the most
       useful information from the archive label is likely to be in the
       fields start, hostname, timezone, and zoneinfo.

       The zoneinfo field contains the most detailed timezone
       information available, and should be used if present (non-zero
       length string).  It will only not be present in the case of
       version 2 archives - this is a new field added as part of the
       version 3 format.  The timezone field will always be present,
       however it is the 'squashed' timezone value and in certain
       situations is not the most accurate timezone.

       For older applications using pmGetArchiveLabel, the most useful
       information from the archive label is likely to be in the fields
       ll_start, ll_hostname or ll_tz.  Note that the size of the
       ll_hostname field is PM_LOG_MAXHOSTLEN (64 bytes) which is less
       than MAXHOSTNAMELEN (see gethostbyname(3)) on some platforms.
       These semantics are necessary to retain backwards compatibility
       with the PCP archive file format.

       Both pmGetArchiveLabel and pmGetHighResArchiveLabel return zero
       for success.

DIAGNOSTICS

       PM_ERR_NOCONTEXT
              the current PMAPI context is either invalid, or not
              associated with a set of archives

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

SEE ALSO

       pmlogger(1), LOGIMPORT(3), PMAPI(3), pmDupContext(3),
       pmGetConfig(3), pmNewContext(3), LOGARCHIVE(5), pcp.conf(5) and
       pcp.env(5).

COLOPHON

       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 2024-06-14.
       (At that time, the date of the most recent commit that was found
       in the repository was 2024-06-14.)  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              PMGETARCHIVELABEL(3)

Pages that refer to this page: pmgetarchiveend(3), pmgetcontexthostname(3), __pmparsetime(3), pmparsetimewindow(3)

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