From 37a7d49676f1fc96d3ef63f8efdc2c4c0b57efe2 Mon Sep 17 00:00:00 2001
From: Piotr Jastrzebski <piotr@scylladb.com>
Date: Fri, 15 Jul 2016 16:35:03 +0200
Subject: [PATCH] Add collectd counter for uncached wide partitions.

Keep track of every read of wide partition that's
not cached.

Signed-off-by: Piotr Jastrzebski <piotr@scylladb.com>
---
 row_cache.cc | 15 +++++++++++++++
 row_cache.hh |  3 +++
 2 files changed, 18 insertions(+)

diff --git a/row_cache.cc b/row_cache.cc
index 6daa1c1c6d..eb2ca182e8 100644
--- a/row_cache.cc
+++ b/row_cache.cc
@@ -119,6 +119,11 @@ cache_tracker::setup_collectd() {
                 , "total_operations", "misses")
                 , scollectd::make_typed(scollectd::data_type::DERIVE, _misses)
         ),
+        scollectd::add_polled_metric(scollectd::type_instance_id("cache"
+                , scollectd::per_cpu_plugin_instance
+                , "total_operations", "uncached_wide_partitions")
+                , scollectd::make_typed(scollectd::data_type::DERIVE, _uncached_wide_partitions)
+        ),
         scollectd::add_polled_metric(scollectd::type_instance_id("cache"
                 , scollectd::per_cpu_plugin_instance
                 , "total_operations", "insertions")
@@ -196,6 +201,10 @@ void cache_tracker::on_miss() {
     ++_misses;
 }
 
+void cache_tracker::on_uncached_wide_partition() {
+    ++_uncached_wide_partitions;
+}
+
 allocation_strategy& cache_tracker::allocator() {
     return _region.allocator();
 }
@@ -248,6 +257,7 @@ public:
                         }
                         return make_ready_future<streamed_mutation_opt>(streamed_mutation_opt());
                     } else {
+                        _cache.on_uncached_wide_partition();
                         auto reader = _underlying(_schema,
                                                   query::partition_range::make_singular(dht::ring_position(std::move(dk))),
                                                   _ck_filtering,
@@ -269,6 +279,10 @@ void row_cache::on_miss() {
     _tracker.on_miss();
 }
 
+void row_cache::on_uncached_wide_partition() {
+    _tracker.on_uncached_wide_partition();
+}
+
 class just_cache_scanning_reader final {
     schema_ptr _schema;
     row_cache& _cache;
@@ -457,6 +471,7 @@ public:
                     } else {
                         assert(bool(dk));
                         _last_key = std::experimental::optional<dht::ring_position>();
+                        _cache.on_uncached_wide_partition();
                         auto reader = _underlying(_schema,
                                                   query::partition_range::make_singular(dht::ring_position(std::move(*dk))),
                                                   _ck_filtering,
diff --git a/row_cache.hh b/row_cache.hh
index e04f1ca1f8..a8ba8ebbae 100644
--- a/row_cache.hh
+++ b/row_cache.hh
@@ -149,6 +149,7 @@ public:
 private:
     uint64_t _hits = 0;
     uint64_t _misses = 0;
+    uint64_t _uncached_wide_partitions = 0;
     uint64_t _insertions = 0;
     uint64_t _merges = 0;
     uint64_t _evictions = 0;
@@ -170,6 +171,7 @@ public:
     void on_merge();
     void on_hit();
     void on_miss();
+    void on_uncached_wide_partition();
     allocation_strategy& allocator();
     logalloc::region& region();
     const logalloc::region& region() const;
@@ -232,6 +234,7 @@ private:
                                          query::clustering_key_filtering_context ck_filtering);
     void on_hit();
     void on_miss();
+    void on_uncached_wide_partition();
     void upgrade_entry(cache_entry&);
     void invalidate_locked(const dht::decorated_key&);
     void invalidate_unwrapped(const query::partition_range&);