pmWebTimerRegister - Man Page

thread-safe timer list management

C Synopsis

#include <pcp/pmwebapi.h>

typedef void (*pmWebTimerCallBack)(void *data);
int pmWebTimerRegister(pmWebTimerCallBack callback, void *data);

int pmWebTimerRelease(int seq);
int pmWebTimerSetMetricRegistry(struct mmv_registry *registry); cc ... -lpcp_web


The pmWebTimerRegister and related API functions provide a convenient thread-safe API for applications to manage a list of timer driven callbacks. On the first call to pmWebTimerRegister or pmWebTimerSetMetricRegistry, an internal timer is set up and initialized to fire every 1.0 seconds. Each time the timer fires, all currently registered callback functions will be called serially with the opaque data pointer that was supplied when each function was registered. The pmWebTimerCallBack typedef provides a suitable callback function prototype.

All registered callback functions should be non-blocking and execute quickly and synchronously. Typical callback functions include refreshing instrumentation, calculating and updating performance metric values, periodic garbage collection and any other local function that requires regular execution.

The pmWebTimerSetMetricRegistry function provides a convenient way for an application to pass in a pointer to an libpcp_mmv(3) registry that has been suitably initialized by the calling application. This registry will be used to dynamically create six server resource metrics named NAME.mem.datasz, NAME.mem.maxrss,, NAME.cpu.sys, NAME.cpu.user and, where NAME is the root PCP PMNS(5) name set up by the calling application. These metrics should be reasonably self explanatory; they provide resource usage metrics from the calling application / server and use getrusage(2), times(2) and getpid(2).

Return Value

The pmWebTimerRegister function returns a positive integer handle that may be subsequently used in a call to pmWebTimerRelease to remove a timer from the internal timer list. When a timer is removed with a call to pmWebTimerRelease, the internal data structures are freed. The caller however, is responsible for freeing the associated data (since it may or may not be dynamically allocated).


On failure a negative PMAPI error code is returned in all cases.

See Also

pmproxy(1), mmv_stats_registry(3), PMAPI(3) and PMWEBAPI(3).

Referenced By

The man pages pmWebTimerRelease(3) and pmWebTimerSetMetricRegistry(3) are aliases of pmWebTimerRegister(3).

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