получить значения показателей производительности (get performance metric values)
Окружение (Environment)
Many of the performance metrics exported from PCP agents have the
semantics of counter meaning they are expected to be
monotonically increasing. Under some circumstances, one value of
these metrics may be smaller than the previously fetched value.
This can happen when a counter of finite precision overflows, or
when the PCP agent has been reset or restarted, or when the PCP
agent is exporting values from some underlying instrumentation
that is subject to some asynchronous discontinuity.
The environment variable PCP_COUNTER_WRAP may be set to indicate
that all such cases of a decreasing ``counter'' should be treated
as a counter overflow, and hence the values are assumed to have
wrapped once in the interval between consecutive samples. This
``wrapping'' behavior was the default in earlier PCP versions,
but by default has been disabled in PCP version 1.3 and later.
