pmdaattribute(3) [centos man page]

PMDAATTRIBUTE(3)					     Library Functions Manual						  PMDAATTRIBUTE(3)

NAME

       pmdaAttribute - informs a PMDA about client connection attributes

C SYNOPSIS

       #include <pcp/pmapi.h>
       #include <pcp/impl.h>
       #include <pcp/pmda.h>

       int pmdaAttribute(int context, int key, char *value, int length, pmdaExt *pmda);

       cc ... -lpcp_pmda -lpcp

DESCRIPTION

       As  part  of  the Performance Metrics Domain Agent (PMDA) API (see PMDA(3)), pmdaAttribute is the generic callback for responding to client
       connection attributes.  These attributes include client credential information, such as user ID and group ID.

       A PMDA that supports connection attributes will provide a private pmdaAttribute callback by  assignment	to  version.six.attribute  of  the
       pmdaInterface structure, and implement custom logic for any of the attribute key-value pairs of interest to it.

       All  attributes are associated with a specific client context, and these can be uniquely identified using the ctx first argument.  The PMDA
       should track client connections, and disconnections using the pmdaSetEndContextCallBack(3) interface, as a result.   The  pmdaGetContext(3)
       interface may be particularly helpful also.

       All  attributes	are  passed  as key-value pairs and the value is always passed as a null-terminated string of given length.  This includes
       numeric attributes like the user ID.

       The most commonly used attributes would be PCP_ATTR_USERID and  PCP_ATTR_GROUPID  but  others  may  also  be  optionally  passed  (such	as
       PCP_ATTR_USERNAME)  if  they  are  available.   Some  attributes  will  be  consumed  by  pmcd  and  never through passed to PMDAs, such as
       PCP_ATTR_PASSWORD.  A complete list of all possible attributes can be found in the headers listed above, all are prefixed by PCP_ATTR.

DIAGNOSTICS

       pmdaAttribute should return either zero on success, or a negative return code to indicate an error in handling the attribute.  This  return
       code  cannot  be  used  to indicate a client should be disallowed access - such functionality must be performed by the agent in response to
       callbacks for the client in question (using PM_ERR_PERMISSION for those specific callbacks, for that  specific  client.	 In  other  words,
       errors  will  be  be passed to PMCD but there is no guarantee made that the error will be return to the client and result in termination of
       the client, for example.

CAVEAT

       The PMDA must be using PMDA_PROTOCOL_6 or later, as specified in the call to pmdaDSO(3) or pmdaDaemon(3).

SEE ALSO

       PMAPI(3), PMDA(3), pmdaDaemon(3), pmdaDSO(3), pmdaMain(3) and pmdaGetContext(3).

Performance Co-Pilot							PCP							  PMDAATTRIBUTE(3)

Check Out this Related Man Page

PMDAEVENTCLIENT(3)					     Library Functions Manual						PMDAEVENTCLIENT(3)

NAME

       pmdaEventNewClient, pmdaEventEndClient, pmdaEventClients - client context tracking interfaces for event queues

C SYNOPSIS

       #include <pcp/pmapi.h>
       #include <pcp/impl.h>
       #include <pcp/pmda.h>

       int pmdaEventNewClient(int context);
       int pmdaEventEndClient(int context);
       int pmdaEventClients(pmAtomValue *avp);

       cc ... -lpcp_pmda -lpcp

DESCRIPTION

       A Performance Metrics Domain Agent (PMDA) that exports event records needs to track which clients are connected to it, in order that it can
       track which events have been sent to which clients so far.  Only once an event has been sent to all monitoring tools that registered an in-
       terest can the event be discarded and any memory reclaimed.

       The PMDA(3) library provides callback routines for PMDA developers to provide custom handling of client connections and disconnections.	If
       the PMDA is making use of the event queueing mechanism provided by pmdaEventNewQueue(3) and friends, client connections and  disconnections
       must  be tracked via calls to pmdaEventNewClient and pmdaEventEndClient respectively.  This allows the library to keep track of when events
       can be discarded from a queue, for example, for the context specified.  This parameter is passed into the e_endCallBack function  directly,
       and  for  other	callback  functions is available via the e_context field of the pmdaExt structure.  Additionally, it can be queried at any
       time using pmdaGetContext(3).

       Sometimes it is useful for the PMDA to export a metric indicating the current count of attached clients - this is available using  the  pm-
       daEventClients routine, which will fill in the avp pmAtomValue structure on behalf of a PMDA fetch callback routine.

SEE ALSO

       pmdaEventNewArray(3), pmdaEventNewQueue(3), PMAPI(3), PMDA(3) and pmEventFlagsStr(3).

Performance Co-Pilot							PCP							PMDAEVENTCLIENT(3)

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pmdaattribute(3) [centos man page]

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