Merge pull request #1848 from poanetwork/block_counter_cache

Add cache for block counter

apps/block_scout_web/lib/block_scout_web/controllers/chain_controller.ex

@@ -3,7 +3,7 @@ defmodule BlockScoutWeb.ChainController do
 
   alias BlockScoutWeb.ChainView
   alias Explorer.{Chain, PagingOptions, Repo}
-  alias Explorer.Chain.{Address, Block, Transaction}
+  alias Explorer.Chain.{Address, Block, BlockCountCache, Transaction}
   alias Explorer.Counters.AverageBlockTime
   alias Explorer.ExchangeRates.Token
   alias Explorer.Market
@@ -11,7 +11,7 @@ defmodule BlockScoutWeb.ChainController do
 
   def show(conn, _params) do
     transaction_estimated_count = Chain.transaction_estimated_count()
-    block_count = Chain.block_consensus_count()
+    block_count = BlockCountCache.count()
 
     exchange_rate = Market.get_exchange_rate(Explorer.coin()) || Token.null()
 

apps/explorer/config/config.exs

@@ -78,6 +78,9 @@ config :spandex_ecto, SpandexEcto.EctoLogger,
   tracer: Explorer.Tracer,
   otp_app: :explorer
 
+config :explorer, Explorer.Chain.BlockCountCache,
+  ttl: System.get_env("BLOCK_COUNT_CACHE_TTL")
+
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.
 import_config "#{Mix.env()}.exs"

apps/explorer/lib/explorer/application.ex

@@ -6,7 +6,7 @@ defmodule Explorer.Application do
   use Application
 
   alias Explorer.Admin
-  alias Explorer.Chain.{BlockNumberCache, TransactionCountCache}
+  alias Explorer.Chain.{BlockCountCache, BlockNumberCache, TransactionCountCache}
   alias Explorer.Repo.PrometheusLogger
 
   @impl Application
@@ -38,6 +38,7 @@ defmodule Explorer.Application do
     res = Supervisor.start_link(children, opts)
 
     BlockNumberCache.setup()
+    BlockCountCache.setup()
 
     res
   end

apps/explorer/lib/explorer/chain.ex

@@ -1042,7 +1042,7 @@ defmodule Explorer.Chain do
     end
   end
 
-  @spec fetch_min_and_max_block_numbers() :: {non_neg_integer(), non_neg_integer}
+  @spec fetch_min_and_max_block_numbers() :: {non_neg_integer, non_neg_integer}
   def fetch_min_and_max_block_numbers do
     query =
       from(block in Block,
@@ -1058,6 +1058,17 @@ defmodule Explorer.Chain do
     end
   end
 
+  @spec fetch_count_consensus_block() :: non_neg_integer
+  def fetch_count_consensus_block do
+    query =
+      from(block in Block,
+        select: count(block.hash),
+        where: block.consensus == true
+      )
+
+    Repo.one!(query)
+  end
+
   @doc """
   The number of `t:Explorer.Chain.InternalTransaction.t/0`.
 

apps/explorer/lib/explorer/chain/block_count_cache.ex

@@ -0,0 +1,84 @@
+defmodule Explorer.Chain.BlockCountCache do
+  @moduledoc """
+  Cache for count consensus blocks.
+  """
+
+  alias Explorer.Chain
+
+  @tab :block_count_cache
+  # 1 minutes
+  @cache_period 1_000 * 60
+  @key "count"
+  @opts_key "opts"
+
+  @spec setup() :: :ok
+  def setup do
+    if :ets.whereis(@tab) == :undefined do
+      :ets.new(@tab, [
+        :set,
+        :named_table,
+        :public,
+        write_concurrency: true
+      ])
+    end
+
+    setup_opts()
+    update_cache()
+
+    :ok
+  end
+
+  def count do
+    initial_cache = {_count, old_current_time} = cached_values()
+
+    {count, _current_time} =
+      if current_time() - old_current_time > cache_period() do
+        update_cache()
+
+        cached_values()
+      else
+        initial_cache
+      end
+
+    count
+  end
+
+  defp update_cache do
+    current_time = current_time()
+    count = count_from_db()
+    tuple = {count, current_time}
+
+    :ets.insert(@tab, {@key, tuple})
+  end
+
+  defp setup_opts do
+    cache_period = Application.get_env(:explorer, __MODULE__)[:ttl] || @cache_period
+
+    :ets.insert(@tab, {@opts_key, cache_period})
+  end
+
+  defp cached_values do
+    [{_, cached_values}] = :ets.lookup(@tab, @key)
+
+    cached_values
+  end
+
+  defp cache_period do
+    [{_, cache_period}] = :ets.lookup(@tab, @opts_key)
+
+    cache_period
+  end
+
+  defp count_from_db do
+    Chain.fetch_count_consensus_block()
+  rescue
+    _e ->
+      0
+  end
+
+  defp current_time do
+    utc_now = DateTime.utc_now()
+
+    DateTime.to_unix(utc_now, :millisecond)
+  end
+end

apps/explorer/test/explorer/chain/block_count_cache_test.exs

@@ -0,0 +1,45 @@
+defmodule Explorer.Chain.BlockCountCacheTest do
+  use Explorer.DataCase
+
+  alias Explorer.Chain.BlockCountCache
+
+  describe "count/0" do
+    test "return count" do
+      insert(:block, number: 1, consensus: true)
+      insert(:block, number: 2, consensus: true)
+      insert(:block, number: 3, consensus: false)
+
+      BlockCountCache.setup()
+
+      assert BlockCountCache.count() == 2
+    end
+
+    test "invalidates cache if period did pass" do
+      insert(:block, number: 1, consensus: true)
+
+      Application.put_env(:explorer, BlockCountCache, ttl: 2_00)
+      BlockCountCache.setup()
+
+      assert BlockCountCache.count() == 1
+
+      insert(:block, number: 2, consensus: true)
+
+      Process.sleep(2_000)
+
+      assert BlockCountCache.count() == 2
+    end
+
+    test "does not invalidate cache if period time did not pass" do
+      insert(:block, number: 1, consensus: true)
+
+      Application.put_env(:explorer, BlockCountCache, ttl: 2_00)
+      BlockCountCache.setup()
+
+      assert BlockCountCache.count() == 1
+
+      insert(:block, number: 2, consensus: true)
+
+      assert BlockCountCache.count() == 1
+    end
+  end
+end