1PMDACACHE(3) Library Functions Manual PMDACACHE(3)
2
6 pmdaCacheStore, pmdaCacheStoreKey, pmdaCacheLookup, pmdaCacheLookup‐
7 Name, pmdaCacheLookupKey, pmdaCacheOp, pmdaCachePurge, pmdaCachePurge‐
8 Callback, pmdaCacheResize - manage a cache of instance domain informa‐
9 tion for a PMDA
10
12 #include <pcp/pmapi.h>
13 #include <pcp/pmda.h>
14 int pmdaCacheStore(pmInDom indom, int flags, const char *name,
16 void *private);
17 int pmdaCacheStoreKey(pmInDom indom, int flags, const char *name,
18 int keylen, const void *key, void *private);
19 int pmdaCacheLookup(pmInDom indom, int inst, char **name,
20 void **private);
21 int pmdaCacheLookupName(pmInDom indom, const char *name, int *inst,
22 void **private);
23 int pmdaCacheLookupKey(pmInDom indom, const char *name, int keylen,
24 const void *key, char **oname, int *inst, void **private);
25 int pmdaCacheOp(pmInDom indom, int op);
26 int pmdaCachePurge(pmInDom indom, time_t recent);
27 int pmdaCachePurgeCallback(pmInDom indom, time_t recent, void
28 (*callback)(void *));
29 int pmdaCacheResize(pmInDom indom, int maximum);
30 cc ... -lpcp_pmda -lpcp
32
34 The pmdaCache family of routines provide services to support the main‐
35 tenance of complex instance domains for Performance Co-Pilot PMDAs.
36 There is potentially one cache of information for each instance domain,
37 and for each instance the cache maintains:
38 - external instance name (supplied by the PMDA)
39 - internal instance identifier (assigned by pmdaCacheStore or calculat‐
40 ed from a ``hint'' by pmdaCacheStoreKey)
41 - state, where active instances are visible and part of the current in‐
42 stance domain, and inactive instances are hidden, but not forgotten;
43 pmdaCacheStore or pmdaCacheStoreKey may be used to change the state
44 of an instance
45 - an optional opaque pointer to data that is associated with the in‐
46 stance, but maintained by the PMDA
47 - an optional opaque key that is used as a ``hint'' to pmdaCache‐
48 StoreKey when guessing the initial internal instance identifier
49 - the last time the cache was saved and the instance had been marked as
50 active at some point since the previous cache load or save operation
51 The semantics of a PCP instance domain require a number of rules to be
53 followed, namely:
54 1. Each internal instance identifier must be unique and in the range 0
55 to 2^31 - 1. This rule is enforced by the pmdaCache family of rou‐
56 tines.
57 2. The external instance name must be unique. When the instance name
58 contains a space, it is further constrained such that the name to
59 the left of the first space (the short name) must also be unique.
60 Refer to the INSTANCE NAME MATCHING section below. The PMDA must
61 honor this rule, the pmdaCache family of routines will detect at‐
62 tempts to violate this rule.
63 3. Where an external instance name corresponds to some object or enti‐
64 ty, there is an expectation that the association between the name
65 and the object is fixed, e.g. ``/dev/hda'' is always the name of the
66 same disk on a particular system