From c1f6c2ba30a0ed7d54b03f411fc8b3cb0d660ed1 Mon Sep 17 00:00:00 2001
From: Karsten Loesing <karsten.loesing@gmx.net>
Date: Sat, 4 Jul 2009 22:17:08 +0200
Subject: [PATCH] Estimate v2 and v3 shares as mean values over measurement
 interval.

---
 ChangeLog      |  2 ++
 src/or/geoip.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index 0d5af889da..c4cc07b311 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -17,6 +17,8 @@ Changes in version 0.2.2.1-alpha - 2009-??-??
       help debug some conceivable causes of bug 930.
     - Directories that are configured with the --enable-geoip-stats flag
       now write their GeoIP stats to disk exactly every 24 hours.
+      Estimated shares of v2 and v3 requests are determined as averages,
+      not at the end of a measurement period.
     - Exit nodes can write statistics on the number of exit streams and
       transferred bytes per port to disk every 24 hours.  To enable this,
       run configure with the --enable-exit-stats option, and set
diff --git a/src/or/geoip.c b/src/or/geoip.c
index 41c8f21cdb..e18230d8c3 100644
--- a/src/or/geoip.c
+++ b/src/or/geoip.c
@@ -298,6 +298,67 @@ HT_PROTOTYPE(clientmap, clientmap_entry_t, node, clientmap_entry_hash,
 HT_GENERATE(clientmap, clientmap_entry_t, node, clientmap_entry_hash,
             clientmap_entries_eq, 0.6, malloc, realloc, free);
 
+/** How often do we update our estimate which share of v2 and v3 directory
+ * requests is sent to us? We could as well trigger updates of shares from
+ * network status updates, but that means adding a lot of calls into code
+ * that is independent from geoip stats (and keeping them up-to-date). We
+ * are perfectly fine with an approximation of 15-minute granularity. */
+#define REQUEST_SHARE_INTERVAL (15 * 60)
+
+/** When did we last determine which share of v2 and v3 directory requests
+ * is sent to us? */
+static time_t last_time_determined_shares = 0;
+
+/** Sum of products of v2 shares times the number of seconds for which we
+ * consider these shares as valid. */
+static double v2_share_times_seconds;
+
+/** Sum of products of v3 shares times the number of seconds for which we
+ * consider these shares as valid. */
+static double v3_share_times_seconds;
+
+/** Number of seconds we are determining v2 and v3 shares. */
+static int share_seconds;
+
+/** Try to determine which fraction of v2 and v3 directory requests aimed at
+ * caches will be sent to us at time <b>now</b> and store that value in
+ * order to take a mean value later on. */
+static void
+geoip_determine_shares(time_t now)
+{
+  double v2_share = 0.0, v3_share = 0.0;
+  if (router_get_my_share_of_directory_requests(&v2_share, &v3_share) < 0)
+    return;
+  if (last_time_determined_shares) {
+    v2_share_times_seconds += v2_share *
+        ((double) (now - last_time_determined_shares));
+    v3_share_times_seconds += v3_share *
+        ((double) (now - last_time_determined_shares));
+    share_seconds += now - last_time_determined_shares;
+  }
+  last_time_determined_shares = now;
+}
+
+/** Calculate which fraction of v2 and v3 directory requests aimed at caches
+ * have been sent to us since the last call of this function up to time
+ * <b>now</b>. Set *<b>v2_share_out</b> and *<b>v3_share_out</b> to the
+ * fractions of v2 and v3 protocol shares we expect to have seen. Reset
+ * counters afterwards. Return 0 on success, -1 on failure (e.g. when zero
+ * seconds have passed since the last call).*/
+static int
+geoip_get_mean_shares(time_t now, double *v2_share_out,
+                         double *v3_share_out)
+{
+  geoip_determine_shares(now);
+  if (!share_seconds)
+    return -1;
+  *v2_share_out = v2_share_times_seconds / ((double) share_seconds);
+  *v3_share_out = v3_share_times_seconds / ((double) share_seconds);
+  v2_share_times_seconds = v3_share_times_seconds = 0.0;
+  share_seconds = 0;
+  return 0;
+}
+
 /** Note that we've seen a client connect from the IP <b>addr</b> (host order)
  * at time <b>now</b>. Ignored by all but bridges and directories if
  * configured accordingly. */
@@ -374,6 +435,10 @@ geoip_note_client_seen(geoip_client_action_t action,
       else
         ++country->n_v2_ns_requests[REQUEST_HIST_LEN-1];
     }
+
+    /* Periodically determine share of requests that we should see */
+    if (last_time_determined_shares + REQUEST_SHARE_INTERVAL < now)
+      geoip_determine_shares(now);
   }
 
   if (!client_history_starts) {
@@ -639,7 +704,7 @@ dump_geoip_stats(void)
               since,
               data_v3 ? data_v3 : "", data_v2 ? data_v2 : "") < 0)
     goto done;
-  if (!router_get_my_share_of_directory_requests(&v2_share, &v3_share)) {
+  if (!geoip_get_mean_shares(now, &v2_share, &v3_share)) {
     if (fprintf(out, "v2-ns-share %0.2lf%%\n", v2_share*100) < 0)
       goto done;
     if (fprintf(out, "v3-ns-share %0.2lf%%\n", v3_share*100) < 0)