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NAME | C SYNOPSIS | DESCRIPTION | DIAGNOSTICS | CAVEAT | SEE ALSO | COLOPHON |
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PMDACONNECT(3) Library Functions Manual PMDACONNECT(3)
pmdaConnect - establish a connection between a daemon PMDA and PMCD
#include <pcp/pmapi.h>
#include <pcp/pmda.h>
void pmdaConnect(pmdaInterface *dispatch);
cc ... -lpcp_pmda -lpcp
pmdaConnect initializes an IPC channel between a PMDA(3) and the
pmcd(1) process on the local host. The type of the connection is
dependent on the e_io field of the pmdaExt structure:
pmdaPipe Use stdin/stdout to communicate; assumes this is a
pipe created by pmcd before the PMDA(3) was launched.
pmdaInet Assume pmcd(1) will establish a connection to an IPv4
internet domain socket set up by the PMDA(3). The
name or number of the port must be specified in the
e_sockname or e_port fields of the pmdaExt structure,
respectively.
pmdaIPv6 Assume pmcd(1) will establish a connection to an IPv6
internet domain socket set up by the PMDA(3). The
name or number of the port must be specified in the
e_sockname or e_port fields of the pmdaExt structure,
respectively.
pmdaUnix Assume pmcd(1) will establish a connection to a unix
domain socket set up by the PMDA(3). The port number
must be specified in the e_port field of the pmdaExt
structure.
pmdaUnknown The initial value of e_io which defaults to using
stdin/stdout.
The relevant pmdaExt fields are initialized by pmdaDaemon(3) and set
by pmdaGetOpt(3) or pmdaGetOptions(3) so most PMDAs should not need
to access or modify them.
Traditionally most PMDAs have called pmdaConnect after calls to
pmdaDaemon(3), pmdaGetOptions(3) (or pmdaGetOpt(3)) and pmdaInit(3).
If the PMDA requires significant processing at startup to identify
the available metrics and/or instance domains before pmdaInit(3) can
be called, then it risks timing out during the handshake protocol
that starts as soon as pmcd(1) launches the PMDA and does not
conclude until pmdaConnect is called. In this case, it is advisable
to move the pmdaConnect call, so that it comes after the call to
pmdaGetOptions(3) (or pmdaGetOpt(3)) and before the call to
pmdaInit(3).
pmdaConnect will log the type of connection made to pmcd(1) if the
PMAPI(3) debugging option libpmda has been set in the global
debugging specification, as described in pmSetDebug(3).
If an error occurs that is unrecoverable, dispatch->status is set to
a value less than 0, otherwise it is zero or positive.
The PMDA must be using PMDA_INTERFACE_2 or later, as specified in the
call to pmdaDaemon(3).
pmcd(1), pipe(2), socket(2), PMAPI(3), PMDA(3), pmdaDaemon(3),
pmdaGetOpt(3), pmdaGetOptions(3) and pmdaInit(3).
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
2018-02-02. (At that time, the date of the most recent commit that
was found in the repository was 2018-02-02.) 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 PMDACONNECT(3)
Pages that refer to this page: pmda(3)
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