pmReconnectContext - reconnect to a PMAPI context
int pmReconnectContext(int handle)
cc ... -lpcp
As a consequence of network, host or Performance Metrics Collector
Daemon (PMCD) failures, an applications connection to a PMCD may be
established and then subsequently lost.
The routine pmReconnectContext allows an application to request that
the context identified by handle should be re-established, provided the
associated PMCD is accessible.
To avoid flooding the system with reconnect requests,
pmReconnectContext will only attempt a reconnection after a suitable
delay from the previous unsuccessful attempt to reconnect this context.
This imposed restriction on the reconnect re-try time interval uses an
exponential back-off so that the initial delay is 5 seconds after the
first unsuccessful attempt, then 10 seconds, then 20 seconds, then 40
seconds and then 80 seconds thereafter.
The environment variable PMCD_RECONNECT_TIMEOUT may be used to redefine
the back-off intervals, see PMAPI(3).
If the reconnection succeeds, pmReconnectContext returns handle.
If handle identifies a context associated with an archive source of
metrics, pmReconnectContext does nothing and returns handle.
Calling pmReconnectContext with a handle identifying a currently
connected context will cause the connection to be broken before any
reconnection is attempted.
Note that even in the case of a successful reconnection,
pmReconnectContext does not change the current Performance Metrics
Application Programming Interface (PMAPI) context.
When attempting to connect to a remote pmcd(1) on a machine that is
booting, pmReconnectContext could potentially block for a long time
until the remote machine finishes its initialization.
pmReconnectContext will abort and return an error if the connection has
not been established after some specified interval has elapsed. The
default interval is 5 seconds. This may be modified by setting
PMCD_CONNECT_TIMEOUT in the environment to a real number of seconds for
the desired timeout. This is most useful in cases where the remote
host is at the end of a slow network, requiring longer latencies to
establish the connection correctly.
Timeout period (in seconds) for pmcd(1) connection attempts.
Redefines the back-off intervals - refer to PMAPI(3).
pmcd(1), PMAPI(3), pmNewContext(3) and pmUseContext(3).
handle does not identify a valid PMAPI context
The re-try time has not elapsed, or the reconnection is
attempted and fails.
Applications that use gethostbyname(3) should exercise caution because
the static fields in struct hostent may not be preserved across some
PMAPI(4) calls. In particular, pmNewContext(3) and
pmReconnectContext(3) both may call gethostbyname(3) internally.