NAME¶

pmGetArchiveLabel - fetch the label record from a set of performance metrics archive logs

C SYNOPSIS¶

#include <pcp/pmapi.h>

int pmGetArchiveLabel(pmLogLabel *lp);

cc ... -lpcp

DESCRIPTION¶

Within the framework of the Performance Co-Pilot (PCP), archive logs of performance metrics values may be accumulated and saved using the program pmlogger(1).

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

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

/*


 * Label Record at the start of every log file


 */
typedef struct {


  int        ll_magic;    /* PM_LOG_MAGIC | log format version no. */


  pid_t      ll_pid;      /* PID of logger */


  struct timeval ll_start;/* start of this log */


  char       ll_hostname[PM_LOG_MAXHOSTLEN]; /* name of collection host */


  char       ll_tz[40];   /* $TZ at collection host */
} pmLogLabel;

For an application, 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.

pmGetArchiveLabel returns zero for success.

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), PMAPI(3), pmDupContext(3), pmGetConfig(3), pmNewContext(3), pcp.conf(5) and pcp.env(5).

DIAGNOSTICS¶

PM_ERR_NOCONTEXT

the current PMAPI context is either invalid, or not associated with a set of archive logs