pmaTryDeltaInDom - Man Page
try to translate a physical indom record from a “full indom” to a “delta indom”
C Synopsis
#include <pcp/pmapi.h>
#include <pcp/libpcp.h>
#include <pcp/archive.h>
int pmaTryDeltaInDom(__pmLogCtl *lcp, __int32_t **rbuf, __pmLogInDom *lidp);
cc ... -lpcp_archive -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
The input instance domain is passed in as either a physical metadata record via rbuf or in the “loaded” format identified by lidp. As these are alternate formats for the input instance domain, pmaTryDeltaInDom demands that exactly one of rbuf and lidp must be NULL, else the return value is -2.
The input instance domain is on the path to being written to the archive identified by lcp.
If possible, the instance domain will be converted to the “delta indom” format, and the converted instance domain returned via rbuf or lidp (whichever is not NULL). If conversion takes place, any storage associated with the input instance domain will have been free'd.
The “delta indom” format is only supported for Version 3 archives and it is the caller's responsibility to determine if calling pmaTryDeltaInDom is appropriate.
To determine if the “delta indom” format is the most efficient encoding, pmaTryDeltaInDom maintains a per-instance domain cache of the last seen “full” instance domain. To avoid data corruption, this means pmaTryDeltaInDom first copies the input instance domain. The copy and the cache are all managed privately by pmaTryDeltaInDom so the caller is unaware of this activity.
The caching scheme requires that the caller must call pmaTryDeltaInDom for every instance domain record, independent of whether the “delta indom” format is likely to be appropriate.
Diagnostics and Return Values
In several places, fatal errors will trigger an error message and force the application to exit.
A return value of -1 indicates that rbuf was not NULL and the physical record therein was not a TYPE_INDOM (Version 3 “full” instance domain) record as expected. A return value of 1 means rbuf or lidp has been rewritten, and is now a TYPE_INDOM_DELTA record. Otherwise the return value is 0.