PMCONNECTLOGGER(3)

NAME
__pmConnectLogger - connect to a performance metrics logger control port

C SYNOPSIS
#include "pmapi.h"
#include "libpcp.h"

int __pmConnectLogger(const char *hostname, int pid);

cc ... -lpcp

CAVEAT
This documentation is intended for internal Performance Co-Pilot (PCP) developer use.

These interfaces are not part of the PCP APIs that are guaranteed to remain fixed across releases, and they may not work, or may provide different semantics at some point in the future.

DESCRIPTION
Each instance of the Performance Co-Pilot (PCP) archive logger program pmlogger(1) supports a control port on which __pmControlLog(3) requests are received, and responses sent. Optionally, the pmlogger(1) instance may be designated the ``primary'' logger.

__pmConnectLogger may be used to establish a control port connection to the pmlogger(1) instance identified by process id pid on the host hostname.

One special case is supported; for the reserved pid value of PM_LOG_CONTROL_PORT the requested connection is to the control port for the ``primary'' logger, whatever its process id might be.

On success, __pmConnectLogger returns a non-negative integer, that is a file descriptor that may be used in subsequent communication with the pmlogger(1) instance, e.g. for __pmControlLog(3).

As the control port to pmlogger(1) is not mulitplexed, applications using __pmConnectLogger should use close(2) to terminate the connection to pmlogger(1) as soon as they have finished communicating.

If the application connects, and the pmlogger(1) instance subsequently terminates, e.g. because the associated pmcd(1) instance is terminated, the application will have to explicitly re-establish connection to a re-started pmlogger(1) instance by calling __pmConnectLogger again.

DIAGNOSTICS

PM_ERR_PERMISSION
    no permission to connect to the specified pmlogger(1) instance

-ECONNREFUSED
    the designated pmlogger(1) instance does not exist

-EEADDRINUSE
    the requested control port is already in use

SEE ALSO
pmcd(1), pmlc(1), pmlogger(1), PMAPI(3) and __pmControlLog(3).