Add support for stats via Nebulex.Telemetry.StatsHandler (#29)

Add support for stats via `Nebulex.Telemetry.StatsHandler`

Author: simoncocking

lib/nebulex_redis_adapter.ex

@@ -300,7 +300,12 @@ defmodule NebulexRedisAdapter do
   import Nebulex.Helpers
   import NebulexRedisAdapter.Encoder
 
+  use Nebulex.Adapter.Stats
+
   alias Nebulex.Adapter
+  alias Nebulex.Adapter.Stats
+  alias Nebulex.Telemetry
+  alias Nebulex.Telemetry.StatsHandler
   alias NebulexRedisAdapter.{ClientCluster, Command, Connection, RedisCluster}
 
   ## Nebulex.Adapter
@@ -361,6 +366,9 @@ defmodule NebulexRedisAdapter do
         {node_name, Keyword.get(node_opts, :pool_size, System.schedulers_online())}
       end
 
+    # init stats
+    stats_counter = Stats.init(opts)
+
     child_spec =
       Nebulex.Adapters.Supervisor.child_spec(
         name: normalize_module_name([name, Supervisor]),
@@ -374,14 +382,29 @@ defmodule NebulexRedisAdapter do
       keyslot: keyslot,
       nodes: nodes,
       pool_size: pool_size,
+      stats_counter: stats_counter,
+      started_at: DateTime.utc_now(),
       default_dt: Keyword.get(opts, :default_data_type, :object),
       telemetry: Keyword.fetch!(opts, :telemetry),
       telemetry_prefix: Keyword.fetch!(opts, :telemetry_prefix)
     }
 
+    _ = maybe_attach_stats_handler(meta)
+
     {:ok, child_spec, meta}
   end
 
+  defp maybe_attach_stats_handler(%{stats_counter: nil}), do: :ok
+
+  defp maybe_attach_stats_handler(%{stats_counter: stats_counter} = meta) do
+    Telemetry.attach_many(
+      stats_counter,
+      [meta.telemetry_prefix ++ [:command, :stop]],
+      &StatsHandler.handle_event/4,
+      stats_counter
+    )
+  end
+
   defp do_init(:standalone, name, pool_size, opts) do
     {:ok, children} = Connection.init(name, pool_size, opts)
     {children, ClientCluster.Keyslot}
@@ -622,6 +645,13 @@ defmodule NebulexRedisAdapter do
     )
   end
 
+  @impl Nebulex.Adapter.Stats
+  def stats(%{started_at: started_at} = adapter_meta) do
+    if stats = super(adapter_meta) do
+      %{stats | metadata: Map.put(stats.metadata, :started_at, started_at)}
+    end
+  end
+
   ## Private Functions
 
   defp with_pipeline(adapter_meta, key, pipeline) do

test/nebulex_redis_adapter/stats_test.exs

@@ -0,0 +1,42 @@
+defmodule NebulexRedisAdapter.StatsTest do
+  use ExUnit.Case, async: true
+
+  defmodule Cache do
+    use Nebulex.Cache,
+      otp_app: :nebulex,
+      adapter: NebulexRedisAdapter
+  end
+
+  setup do
+    {:ok, pid} = Cache.start_link(stats: true, conn_opts: [database: 1])
+
+    on_exit(fn ->
+      :ok = Process.sleep(100)
+      if Process.alive?(pid), do: Cache.stop(pid)
+    end)
+
+    {:ok, cache: Cache, name: Cache}
+  end
+
+  describe "c:NebulexRedisAdapter.stats/1" do
+    test "returns valid %Stats{}" do
+      size = Cache.count_all()
+      refute Cache.get("stats")
+      assert Cache.put("stats", "stats") == :ok
+      assert Cache.get("stats") == "stats"
+      assert Cache.put("stats", "stats") == :ok
+      assert Cache.take("stats") == "stats"
+      refute Cache.get("stats")
+      assert Cache.put_new("stats", "stats")
+      assert Cache.replace("stats", "stats stats")
+      assert Cache.delete_all() == size + 1
+
+      assert stats = Cache.stats()
+      assert stats.measurements.evictions == size + 2
+      assert stats.measurements.hits == 2
+      assert stats.measurements.misses == 2
+      assert stats.measurements.writes == 3
+      assert stats.measurements.updates == 1
+    end
+  end
+end