metrics: New feature module to track tor metrics

Related to #40063

Signed-off-by: David Goulet <dgoulet@torproject.org>

1 files changed, 66 insertions, 0 deletions

diff --git a/src/feature/metrics/metrics.c b/src/feature/metrics/metrics.c
new file mode 100644
index 0000000000..5f6fe776b7
--- /dev/null
+++ b/src/feature/metrics/metrics.c
@@ -0,0 +1,66 @@
+/* Copyright (c) 2007-2020, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * @file metrics.c
+ * @brief Metrics subsystem.
+ **/
+
+#include "orconfig.h"
+
+#include "lib/container/smartlist.h"
+#include "lib/log/util_bug.h"
+#include "lib/malloc/malloc.h"
+#include "lib/metrics/metrics_store.h"
+#include "lib/string/printf.h"
+
+#include "feature/metrics/metrics.h"
+
+#include "app/main/subsysmgr.h"
+
+/** Return newly allocated string containing the output of all subsystems
+ * having metrics.
+ *
+ * This is used to output the content on the MetricsPort. */
+char *
+metrics_get_output(const metrics_format_t fmt)
+{
+  char *data;
+  smartlist_t *chunks = smartlist_new();
+
+  /* Go over all subsystems that exposes a metrics store. */
+  for (unsigned i = 0; i < n_tor_subsystems; ++i) {
+    const smartlist_t *stores;
+    const subsys_fns_t *sys = tor_subsystems[i];
+
+    /* Skip unsupported subsystems. */
+    if (!sys->supported) {
+      continue;
+    }
+
+    if (sys->get_metrics && (stores = sys->get_metrics())) {
+      SMARTLIST_FOREACH_BEGIN(stores, const metrics_store_t *, store) {
+        smartlist_add(chunks, metrics_store_get_output(fmt, store));
+      } SMARTLIST_FOREACH_END(store);
+    }
+  }
+
+  data = smartlist_join_strings(chunks, "\n", 0, NULL);
+
+  SMARTLIST_FOREACH(chunks, char *, c, tor_free(c));
+  smartlist_free(chunks);
+
+  return data;
+}
+
+/** Initialize the subsystem. */
+void
+metrics_init(void)
+{
+}
+
+/** Cleanup and free any global memory of this subsystem. */
+void
+metrics_cleanup(void)
+{
+}