osd: report pg stats to mon at least every N (=500) epochs

The mon needs a moderately accurate last_epoch_clean value in order to trim
old osdmaps.  To prevent a PG that hasn't peered or received IO in forever
from preventing this, send pg stats at some minimum frequency.  This will
increase the pg stat report workload for the mon over an idle pool, but
should be no worse that a cluster that is getting actual IO and sees these
updates from normal stat updates.

This makes the reported update a bit more aggressive/useful in that the epoch
is the last map epoch processed by this PG and not just one that is >= the
currenting interval.  Note that the semantics of this field are pretty useless
at this point.

See #5519

Signed-off-by: Sage Weil <sage@inktank.com>
(cherry picked from commit da81228cc73c95737f26c630e5c3eccf6ae1aaec)

2 files changed, 10 insertions, 1 deletions

diff --git a/src/common/config_opts.h b/src/common/config_opts.h
index d040c9b0d9b..c31282c1997 100644
--- a/src/common/config_opts.h
+++ b/src/common/config_opts.h
@@ -410,6 +410,7 @@ OPTION(osd_heartbeat_grace, OPT_INT, 20)         // (seconds) how long before we
 OPTION(osd_mon_heartbeat_interval, OPT_INT, 30)  // (seconds) how often to ping monitor if no peers
 OPTION(osd_mon_report_interval_max, OPT_INT, 120)
 OPTION(osd_mon_report_interval_min, OPT_INT, 5)  // pg stats, failures, up_thru, boot.
+OPTION(osd_pg_stat_report_interval_max, OPT_INT, 500)  // report pg stats for any given pg at least this often
 OPTION(osd_mon_ack_timeout, OPT_INT, 30) // time out a mon if it doesn't ack stats
 OPTION(osd_min_down_reporters, OPT_INT, 1)   // number of OSDs who need to report a down OSD for it to count
 OPTION(osd_min_down_reports, OPT_INT, 3)     // number of times a down OSD must be reported for it to count
diff --git a/src/osd/PG.cc b/src/osd/PG.cc
index 5e477ac31fe..fb8b26ff389 100644
--- a/src/osd/PG.cc
+++ b/src/osd/PG.cc
@@ -2303,7 +2303,7 @@ void PG::publish_stats_to_osd()
   pg_stats_publish_lock.Lock();
   if (is_primary()) {
     // update our stat summary
-    info.stats.reported.inc(info.history.same_primary_since);
+    info.stats.reported.inc(get_osdmap()->get_epoch());
     info.stats.version = info.last_update;
     info.stats.created = info.history.epoch_created;
     info.stats.last_scrub = info.history.last_scrub;
@@ -6665,6 +6665,14 @@ boost::statechart::result PG::RecoveryState::Active::react(const AdvMap& advmap)
       pg->state_set(PG_STATE_DEGRADED);
     pg->publish_stats_to_osd(); // degraded may have changed
   }
+
+  // if we haven't reported our PG stats in a long time, do so now.
+  if (pg->info.stats.reported.epoch + g_conf->osd_pg_stat_report_interval_max < advmap.osdmap->get_epoch()) {
+    dout(20) << "reporting stats to osd after " << (advmap.osdmap->get_epoch() - pg->info.stats.reported.epoch)
+	     << " epochs" << dendl;
+    pg->publish_stats_to_osd();
+  }
+
   return forward_event();
 }