add more modes to stresstest

Author: tenox7

stresstest.c

@@ -20,18 +20,44 @@
 
 const char help[] =
     "Usage:\n"
-    "  stresstest [-2] [-c] [-g] [-n] [-r rate]\n"
+    "  stresstest [-2] [-c] [-g] [-m] [-n] [-R] [-r rate]\n"
     "  stresstest -h\n"
     "\n"
     "  -h       print this help message and exit\n"
     "  -2       output two waves\n"
     "  -c       randomly chunk the output\n"
     "  -g       occasionally output garbage\n"
+    "  -m       output realistic metrics (CPU/bandwidth-like, random spikes)\n"
     "  -n       output negative values\n"
+    "  -R       output uniformly random values across the full range\n"
     "  -r rate  sample rate in samples/s (default: 100)\n"
     "  -s seed  set random seed\n";
 
-const char optstring[] = "h2cgnr:s:";
+const char optstring[] = "h2cgmnRr:s:";
+
+// Return a uniformly random value in [lo, hi].
+static double rand_range(double lo, double hi) {
+    return lo + ((double)rand() / RAND_MAX) * (hi - lo);
+}
+
+// Generate one realistic metrics sample. Models a mean-reverting baseline
+// (Ornstein-Uhlenbeck-style random walk) with occasional sharp spikes that
+// rise instantly and decay exponentially -- resembling CPU/bandwidth load.
+// State is carried in *level and *spike so multiple series stay independent.
+static double metric_sample(double *level, double *spike) {
+    const double target = 20.0;  // baseline the walk reverts toward
+    const double theta = 0.02;   // reversion strength
+    const double sigma = 1.5;    // baseline jitter amplitude
+    const double decay = 0.85;   // spike decay per sample (~6 samples to 1/e)
+
+    double noise = ((double)rand() / RAND_MAX) * 2.0 - 1.0;  // -1..1
+    *level += theta * (target - *level) + sigma * noise;
+    *spike *= decay;
+    if (rand() < RAND_MAX / 100)               // ~1% chance of a new spike
+        *spike += 30.0 + (rand() % 50);        // magnitude 30..79
+    double value = *level + *spike;
+    return value < 0 ? 0 : value;              // load is never negative
+}
 
 int main(int argc, char *argv[]) {
     char buffer[1024];
@@ -40,6 +66,8 @@ int main(int argc, char *argv[]) {
     bool two_waves = false;
     bool chunked = false;
     bool add_garbage = false;
+    bool metrics = false;
+    bool super_random = false;
     bool output_negative = false;
     double rate = 100;
     unsigned int seed = time(NULL);
@@ -59,9 +87,15 @@ int main(int argc, char *argv[]) {
             case 'g':
                 add_garbage = true;
                 break;
+            case 'm':
+                metrics = true;
+                break;
             case 'n':
                 output_negative = true;
                 break;
+            case 'R':
+                super_random = true;
+                break;
             case 'r':
                 rate = atof(optarg);
                 break;
@@ -81,15 +115,31 @@ int main(int argc, char *argv[]) {
     const useconds_t delay = 1e6 / rate;
     srand(seed);
 
+    double level1 = 20.0, spike1 = 0.0;  // metrics state, series 1
+    double level2 = 20.0, spike2 = 0.0;  // metrics state, series 2
+    const double rmin = output_negative ? -100.0 : 0.0;  // -R range
+    const double rmax = 100.0;
+
     for (unsigned int n = 0;; n += 5) {
-        buffer_pos += sprintf(buffer + buffer_pos, "%.1f\n",
-                              (sin(n * M_PI / 180) * 5) + (output_negative ? 0 : 5));
+        double wave1;
+        if (metrics)
+            wave1 = metric_sample(&level1, &spike1);
+        else if (super_random)
+            wave1 = rand_range(rmin, rmax);
+        else
+            wave1 = (sin(n * M_PI / 180) * 5) + (output_negative ? 0 : 5);
+        buffer_pos += sprintf(buffer + buffer_pos, "%.1f\n", wave1);
         if (add_garbage && rand() <= RAND_MAX / 5)
             buffer_pos += sprintf(buffer + buffer_pos, "garbage ");
         if (two_waves) {
-            buffer_pos +=
-                sprintf(buffer + buffer_pos, "%.1f\n",
-                        (cos(n * M_PI / 180) * 5) + (output_negative ? 0 : 5));
+            double wave2;
+            if (metrics)
+                wave2 = metric_sample(&level2, &spike2);
+            else if (super_random)
+                wave2 = rand_range(rmin, rmax);
+            else
+                wave2 = (cos(n * M_PI / 180) * 5) + (output_negative ? 0 : 5);
+            buffer_pos += sprintf(buffer + buffer_pos, "%.1f\n", wave2);
             if (add_garbage && rand() <= RAND_MAX / 5)
                 buffer_pos += sprintf(buffer + buffer_pos, "garbage ");
         }