Example: Call Rate Monitor in C

// Call Rate Monitor
#include <stdio.h>
#include <time.h>   // For time(), difftime()
#include <unistd.h> // For usleep() on Unix-like systems, or <windows.h> and Sleep() on Windows

// Global counter for calls (volatile to prevent compiler optimizations that might affect reads)
static volatile long long call_count = 0;
// Global variable to store the start time for rate calculation
static time_t monitor_start_time;

void monitored_function_with_rate() {
    call_count++;
    // Simulate some work done by the function
    // For a real scenario, this would be your actual function logic.
}

void initialize_call_rate_monitor() {
    call_count = 0;
    monitor_start_time = time(NULL); // Get current time in seconds
}

void report_current_call_rate() {
    time_t current_time = time(NULL);
    double elapsed_seconds = difftime(current_time, monitor_start_time);

    printf("--- Call Rate Report ---\n");
    printf("Current Call Count: %lld\n", call_count);
    if (elapsed_seconds > 0) {
        double rate = (double)call_count / elapsed_seconds;
        printf("Elapsed Time: %.0f seconds\n", elapsed_seconds);
        printf("Calculated Call Rate: %.2f calls/second\n", rate);
    } else {
        printf("Not enough time has elapsed (less than 1 second) to calculate a meaningful rate.\n");
    }
    printf("------------------------\n");
}

int main() {
    // Step 1: Initialize the monitoring system
    initialize_call_rate_monitor();

    // Step 2: Simulate calls to the monitored function over a duration
    printf("Simulating function calls for 5 seconds...\n");
    time_t simulation_start_wall = time(NULL);
    while (difftime(time(NULL), simulation_start_wall) < 5) { // Run for 5 wall-clock seconds
        monitored_function_with_rate();
        // A small delay to avoid excessive CPU usage if the function does very little.
        // For pushing maximum call rates, remove usleep.
        // usleep(1); // Sleep for 1 microsecond (requires unistd.h)
    }

    // Step 3: Report the call rate for the first interval
    report_current_call_rate();

    // Step 4: Reset and simulate for another interval
    printf("\nResetting monitor and simulating more calls for 3 seconds...\n");
    initialize_call_rate_monitor(); // Reset monitor for a new interval
    simulation_start_wall = time(NULL);
    while (difftime(time(NULL), simulation_start_wall) < 3) { // Run for another 3 wall-clock seconds
        monitored_function_with_rate();
        // usleep(1);
    }

    // Step 5: Report the call rate for the second interval
    report_current_call_rate();

    return 0;
}