1 files changed, 129 insertions, 0 deletions
diff --git a/cpu.c b/cpu.c
new file mode 100644
index 0000000..f73e235
--- /dev/null
+++ b/cpu.c
@@ -0,0 +1,129 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "cpu.h"
+#include "util.h"
+
+// limits for CPU numbers
+#define MAX_CPU_ID 9999999
+#define MAX_CPU_DIGITS 7
+// size of input buffer for reading lines
+#define BUF_SIZE 256
+
+static void *cpu_init(int argc, char *argv[]);
+static void cpu_collect(scrape_req *req, void *ctx_ptr);
+
+const struct collector cpu_collector = {
+  .name = "cpu",
+  .collect = cpu_collect,
+  .init = cpu_init,
+};
+
+struct cpu_context {
+  long clock_tick;
+};
+
+void *cpu_init(int argc, char *argv[]) {
+  long clock_tick = sysconf(_SC_CLK_TCK);
+  if (clock_tick <= 0) {
+    perror("sysconf(_SC_CLK_TCK)");
+    return 0;
+  }
+
+  struct cpu_context *ctx = malloc(sizeof *ctx);
+  if (!ctx)
+    return 0;
+  ctx->clock_tick = clock_tick;
+  return ctx;
+}
+
+void cpu_collect(scrape_req *req, void *ctx_ptr) {
+  struct cpu_context *ctx = ctx_ptr;
+
+  // buffers
+
+  char cpu_label[MAX_CPU_DIGITS + 1] = "";
+  static const char *modes[] = {
+    "user", "nice", "system", "idle", "iowait", "irq", "softirq", "steal",
+    0,
+  };
+
+  const char *stat_labels[][2] = {
+    { "cpu", cpu_label },
+    { "mode", 0 },  // filled by code
+    { 0, 0 },
+  };
+  const char *freq_labels[][2] = {
+    { "cpu", cpu_label },
+    { 0, 0 },
+  };
+
+  char buf[BUF_SIZE];
+
+  FILE *f;
+
+  // collect node_cpu_seconds_total metrics from /proc/stat
+
+  f = fopen("/proc/stat", "r");
+  if (f) {
+    while (fgets_line(buf, sizeof buf, f)) {
+      if (strncmp(buf, "cpu", 3) != 0 || (buf[3] < '0' || buf[3] > '9'))
+        continue;
+
+      char *at = buf + 3;
+      char *sep = strchr(at, ' ');
+      if (!sep || sep - at + 1 > sizeof cpu_label)
+        continue;
+      *sep = '\0';
+      strcpy(cpu_label, at);
+
+      at = sep + 1;
+      for (const char **mode = modes; *mode; mode++) {
+        while (*at == ' ')
+          at++;
+        sep = strpbrk(at, " \n");
+        if (!sep)
+          break;
+        *sep = '\0';
+
+        char *endptr;
+        double value = strtod(at, &endptr);
+        if (*endptr != '\0')
+          break;
+        value /= ctx->clock_tick;
+
+        stat_labels[1][1] = *mode;
+        scrape_write(req, "node_cpu_seconds_total", stat_labels, value);
+
+        at = sep + 1;
+      }
+    }
+    fclose(f);
+  }
+
+  // collect node_cpu_frequency_hertz metrics from /sys/devices/system/cpu/cpu*/cpufreq
+
+  for (int cpu = 0; cpu <= MAX_CPU_ID; cpu++) {
+#define PATH_FORMAT "/sys/devices/system/cpu/cpu%d/cpufreq/scaling_cur_freq"
+    char path[sizeof PATH_FORMAT - 2 + MAX_CPU_DIGITS + 1];
+    snprintf(path, sizeof path, PATH_FORMAT, cpu);
+
+    f = fopen(path, "r");
+    if (!f)
+      break;
+
+    if (fgets(buf, sizeof buf, f)) {
+      char *endptr;
+      double value = strtod(buf, &endptr);
+      if (*endptr == '\0' || *endptr == '\n') {
+        value *= 1000;
+        snprintf(cpu_label, sizeof cpu_label, "%d", cpu);
+        scrape_write(req, "node_cpu_frequency_hertz", freq_labels, value);
+      }
+    }
+
+    fclose(f);
+  }
+}