add healthy block period checking query

apps/block_scout_web/lib/block_scout_web/controllers/api/v1/health_controller.ex

@@ -0,0 +1,9 @@
+defmodule BlockScoutWeb.API.V1.HealthController do
+  use BlockScoutWeb, :controller
+
+  alias Explorer.Chain
+
+  def last_block_status(conn, _) do
+    # Chain.last_block_status()
+  end
+end

apps/explorer/config/config.exs

@@ -14,7 +14,8 @@ config :explorer,
     System.get_env("ALLOWED_EVM_VERSIONS") ||
       "homestead,tangerineWhistle,spuriousDragon,byzantium,constantinople,petersburg",
   include_uncles_in_average_block_time:
-    if(System.get_env("UNCLES_IN_AVERAGE_BLOCK_TIME") == "false", do: false, else: true)
+    if(System.get_env("UNCLES_IN_AVERAGE_BLOCK_TIME") == "false", do: false, else: true),
+  healthy_blocks_period: System.get_env("HEALTHY_BLOCKS_PERIOD") || :timer.minutes(5)
 
 config :explorer, Explorer.Counters.AverageBlockTime, enabled: true
 

apps/explorer/lib/explorer/chain.ex

@@ -1769,6 +1769,32 @@ defmodule Explorer.Chain do
     Repo.one!(query)
   end
 
+  @spec last_block_status() :: {:ok, non_neg_integer()} | {:error, non_neg_integer | nil}
+  def last_block_status do
+    query =
+      from(block in Block,
+        select: {block.number, block.timestamp},
+        where: block.consensus == true,
+        order_by: [desc: block.number],
+        limit: 1
+      )
+
+    case Repo.one(query) do
+      nil ->
+        {:error, :no_blocks}
+
+      {_number, timestamp} ->
+        now = DateTime.utc_now()
+        last_block_period = DateTime.diff(now, timestamp, :millisecond)
+
+        if last_block_period > Application.get_env(:explorer, :healthy_blocks_period) do
+          {:error, last_block_period}
+        else
+          {:ok, last_block_period}
+        end
+    end
+  end
+
   @doc """
   Calculates the ranges of missing consensus blocks in `range`.
 

apps/explorer/test/explorer/chain_test.exs

@@ -50,6 +50,24 @@ defmodule Explorer.ChainTest do
     end
   end
 
+  describe "last_block_status/0" do
+    test "return no_blocks errors if db is empty" do
+      assert {:error, :no_blocks} = Chain.last_block_status()
+    end
+
+    test "returns {:ok, last_block_period} if block is in healthy period" do
+      insert(:block, consensus: true)
+
+      assert {:ok, _} = Chain.last_block_status()
+    end
+
+    test "return {:ok, last_block_period} if block is not in healthy period" do
+      insert(:block, consensus: true, timestamp: Timex.shift(DateTime.utc_now(), hours: -50))
+
+      assert {:error, _} = Chain.last_block_status()
+    end
+  end
+
   describe "address_to_logs/2" do
     test "fetches logs" do
       address = insert(:address)