Track method call times/counts as a single metric

Previously we'd create a separate Metric instance for every method call
that would exceed the method call threshold. This is problematic because
it doesn't provide us with information to accurately get the _total_
execution time of a particular method. For example, if the method
"Foo#bar" was called 4 times with a runtime of ~10 milliseconds we'd end
up with 4 different Metric instances. If we were to then get the
average/95th percentile/etc of the timings this would be roughly 10
milliseconds. However, the _actual_ total time spent in this method
would be around 40 milliseconds.

To solve this problem we now create a single Metric instance per method.
This Metric instance contains the _total_ real/CPU time and the call
count for every instrumented method.

1 files changed, 4 insertions, 6 deletions

diff --git a/spec/lib/gitlab/metrics/instrumentation_spec.rb b/spec/lib/gitlab/metrics/instrumentation_spec.rb
index cdf641341cb..8809b7e3f12 100644
--- a/spec/lib/gitlab/metrics/instrumentation_spec.rb
+++ b/spec/lib/gitlab/metrics/instrumentation_spec.rb
@@ -78,9 +78,8 @@ describe Gitlab::Metrics::Instrumentation do
         allow(described_class).to receive(:transaction).
           and_return(transaction)
 
-        expect(transaction).to receive(:add_metric).
-          with(described_class::SERIES, hash_including(:duration, :cpu_duration),
-               method: 'Dummy.foo')
+        expect(transaction).to receive(:measure_method).
+          with('Dummy.foo')
 
         @dummy.foo
       end
@@ -158,9 +157,8 @@ describe Gitlab::Metrics::Instrumentation do
         allow(described_class).to receive(:transaction).
           and_return(transaction)
 
-        expect(transaction).to receive(:add_metric).
-          with(described_class::SERIES, hash_including(:duration, :cpu_duration),
-               method: 'Dummy#bar')
+        expect(transaction).to receive(:measure_method).
+          with('Dummy#bar')
 
         @dummy.new.bar
       end