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PMDAATTRIBUTE(3)					     Library Functions Manual						  PMDAATTRIBUTE(3)

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)

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PMDAEVENTCLIENT(3)					     Library Functions Manual						PMDAEVENTCLIENT(3)

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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