MB-50389: Remove dirtyAge & dirtyAgeHighWat

EPStats::dirtyAge records the 'dirty age' of the last mutation to be flushed - i.e. the duration from when the item was queued into the CheckpointManger until it was processed by the flusher. In a live system the duration of the last mutation is pretty meaningless - it's basically just a single random sample. We already record a histogtram of the dirty age for _all_ mutations flushed to disk, which is much more useful. Similary, EPStats::dirtyAgeHighWat records the maxmimum value for dirtyAge - which the histogram also records for us. Remove these two statistics as they just duplicate information available elsewhere. Change-Id: Icaaf6c86c89dec5612921b49ee0846b4b328b260 Reviewed-on: https://review.couchbase.org/c/kv_engine/+/169326 Reviewed-by: Richard de Mellow <richard.demellow@couchbase.com> Tested-by: Build Bot <build@couchbase.com>
couchbase · Jan 26, 2022 · a7b9668 · a7b9668
1 parent 2fc8b05
commit a7b9668
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diff --git a/engines/ep/docs/stats.org b/engines/ep/docs/stats.org
@@ -27,9 +27,6 @@ For introductory information on stats within Couchbase, start with the
 |---------------------------------------+-----------------------------------------|
 | uuid                                  | The unique identifier for the bucket    |
 | ep_version                            | Version number of ep_engine             |
-| ep_storage_age                        | Milliseconds since most recently        |
-|                                       | stored object was initially queued      |
-| ep_storage_age_highwat                | ep_storage_age high water mark (us)     |
 | ep_startup_time                       | System-generated engine startup time    |
 | ep_data_age                           | Seconds since most recently             |
 |                                       | stored object was modified              |
@@ -1406,8 +1403,6 @@ Reset Stats:
 | ep_pending_ops_max                             |
 | ep_pending_ops_max_duration                    |
 | ep_pending_ops_total                           |
-| ep_storage_age                                 |
-| ep_storage_age_highwat                         |
 | ep_replication_throttled                       |
 | ep_vbucket_del_max_walltime                    |
 | pending_ops                                    |

diff --git a/engines/ep/src/ep_bucket.cc b/engines/ep/src/ep_bucket.cc
@@ -1169,9 +1169,6 @@ void EPBucket::flushOneDelOrSet(TransactionContext& txnCtx,
             std::chrono::duration_cast<std::chrono::milliseconds>(
                     std::chrono::steady_clock::now() - qi->getQueuedTime());
     stats.dirtyAgeHisto.add(dirtyAge);
-    stats.dirtyAge.store(static_cast<rel_time_t>(dirtyAge.count()));
-    stats.dirtyAgeHighWat.store(std::max(stats.dirtyAge.load(),
-                                         stats.dirtyAgeHighWat.load()));
 
     auto* rwUnderlying = getRWUnderlying(qi->getVBucketId());
     if (!deleted) {

diff --git a/engines/ep/src/ep_engine.cc b/engines/ep/src/ep_engine.cc
@@ -3273,8 +3273,6 @@ cb::engine_errc EventuallyPersistentEngine::doEngineStatsHighCardinality(
         collector.addStat(Key::ep_bg_load, epstats.bgLoad);
     }
 
-    collector.addStat(Key::ep_storage_age, epstats.dirtyAge);
-    collector.addStat(Key::ep_storage_age_highwat, epstats.dirtyAgeHighWat);
     collector.addStat(Key::ep_num_workers,
                       ExecutorPool::get()->getNumWorkersStat());
 

diff --git a/engines/ep/src/stats.cc b/engines/ep/src/stats.cc
@@ -46,8 +46,6 @@ EPStats::EPStats()
       expired_pager(0),
       beginFailed(0),
       commitFailed(0),
-      dirtyAge(0),
-      dirtyAgeHighWat(0),
       commit_time(0),
       vbucketDeletions(0),
       vbucketDeletionFail(0),
@@ -277,8 +275,6 @@ void EPStats::reset() {
     tooYoung.store(0);
     tooOld.store(0);
     totalPersistVBState.store(0);
-    dirtyAge.store(0);
-    dirtyAgeHighWat.store(0);
     commit_time.store(0);
     cursorsDropped.store(0);
     memFreedByCheckpointRemoval.store(0);

diff --git a/engines/ep/src/stats.h b/engines/ep/src/stats.h
@@ -287,10 +287,6 @@ class EPStats {
     Counter beginFailed;
     //! Number of times a commit failed.
     Counter commitFailed;
-    //! How long an object is dirty before written.
-    std::atomic<rel_time_t> dirtyAge;
-    //! Oldest enqueued object we've seen while persisting.
-    std::atomic<rel_time_t> dirtyAgeHighWat;
     //! Amount of time spent in the commit phase.
     std::atomic<rel_time_t> commit_time;
     //! Number of times we deleted a vbucket.

diff --git a/engines/ep/tests/ep_testsuite.cc b/engines/ep/tests/ep_testsuite.cc
@@ -7406,8 +7406,6 @@ static enum test_result test_mb19687_fixed(EngineIface* h) {
               "ep_rocksdb_uc_max_size_amplification_percent",
               "ep_rollback_count",
               "ep_startup_time",
-              "ep_storage_age",
-              "ep_storage_age_highwat",
               "ep_storedval_num",
               "ep_storedval_overhead",
               "ep_storedval_size",

diff --git a/include/statistics/stats.def.h b/include/statistics/stats.def.h
@@ -133,8 +133,6 @@ STAT(default_engine_maxbytes,
 // TODO: applying a "kv_" prefix globally would be consistent but lead to kv_ep_
 //  for some stats. Providing metric family names without ep_ would avoid this
 // "All" stats group (doEngineStats)
-STAT(ep_storage_age, , microseconds, , )
-STAT(ep_storage_age_highwat, , microseconds, , )
 STAT(ep_num_workers, , count, , )
 STAT(ep_bucket_priority,
      ,