fetch token counters in parallel

the slowest part of the token overview page is
fetching of total token transfers and total token
holders counters queries. Sometimes they even cause
page load failures.

Now we will start fetching these counters in parallel and
limiting query execution to 40 seconds. If they fail
to load, we won't show these counters.

apps/block_scout_web/lib/block_scout_web/controllers/tokens/holder_controller.ex

@@ -12,6 +12,8 @@ defmodule BlockScoutWeb.Tokens.HolderController do
       next_page_params: 3
     ]
 
+  import BlockScoutWeb.Tokens.TokenController, only: [fetch_token_counters: 2]
+
   def index(conn, %{"token_id" => address_hash_string, "type" => "JSON"} = params) do
     with {:ok, address_hash} <- Chain.string_to_address_hash(address_hash_string),
          {:ok, token} <- Chain.token_from_address_hash(address_hash),
@@ -47,13 +49,15 @@ defmodule BlockScoutWeb.Tokens.HolderController do
 
     with {:ok, address_hash} <- Chain.string_to_address_hash(address_hash_string),
          {:ok, token} <- Chain.token_from_address_hash(address_hash, options) do
+      {total_token_transfers, total_token_holders} = fetch_token_counters(token, address_hash)
+
       render(
         conn,
         "index.html",
         current_path: current_path(conn),
         token: Market.add_price(token),
-        total_token_holders: token.holder_count || Chain.count_token_holders_from_token_hash(address_hash),
-        total_token_transfers: Chain.count_token_transfers_from_token_hash(address_hash)
+        total_token_holders: total_token_holders,
+        total_token_transfers: total_token_transfers
       )
     else
       :error ->

apps/block_scout_web/lib/block_scout_web/controllers/tokens/inventory_controller.ex

@@ -7,6 +7,7 @@ defmodule BlockScoutWeb.Tokens.InventoryController do
   alias Phoenix.View
 
   import BlockScoutWeb.Chain, only: [split_list_by_page: 1, default_paging_options: 0]
+  import BlockScoutWeb.Tokens.TokenController, only: [fetch_token_counters: 2]
 
   def index(conn, %{"token_id" => address_hash_string, "type" => "JSON"} = params) do
     with {:ok, address_hash} <- Chain.string_to_address_hash(address_hash_string),
@@ -64,13 +65,15 @@ defmodule BlockScoutWeb.Tokens.InventoryController do
 
     with {:ok, address_hash} <- Chain.string_to_address_hash(address_hash_string),
          {:ok, token} <- Chain.token_from_address_hash(address_hash, options) do
+      {total_token_transfers, total_token_holders} = fetch_token_counters(token, address_hash)
+
       render(
         conn,
         "index.html",
         current_path: current_path(conn),
         token: Market.add_price(token),
-        total_token_transfers: Chain.count_token_transfers_from_token_hash(address_hash),
-        total_token_holders: token.holder_count || Chain.count_token_holders_from_token_hash(address_hash)
+        total_token_transfers: total_token_transfers,
+        total_token_holders: total_token_holders
       )
     else
       :error ->

apps/block_scout_web/lib/block_scout_web/controllers/tokens/read_contract_controller.ex

@@ -3,17 +3,21 @@ defmodule BlockScoutWeb.Tokens.ReadContractController do
 
   alias Explorer.{Chain, Market}
 
+  import BlockScoutWeb.Tokens.TokenController, only: [fetch_token_counters: 2]
+
   def index(conn, %{"token_id" => address_hash_string}) do
     options = [necessity_by_association: %{[contract_address: :smart_contract] => :optional}]
 
     with {:ok, address_hash} <- Chain.string_to_address_hash(address_hash_string),
          {:ok, token} <- Chain.token_from_address_hash(address_hash, options) do
+      {total_token_transfers, total_token_holders} = fetch_token_counters(token, address_hash)
+
       render(
         conn,
         "index.html",
         token: Market.add_price(token),
-        total_token_transfers: token.holder_count || Chain.count_token_transfers_from_token_hash(address_hash),
-        total_token_holders: Chain.count_token_holders_from_token_hash(address_hash)
+        total_token_transfers: total_token_transfers,
+        total_token_holders: total_token_holders
       )
     else
       :error ->

apps/block_scout_web/lib/block_scout_web/controllers/tokens/token_controller.ex

@@ -1,7 +1,41 @@
 defmodule BlockScoutWeb.Tokens.TokenController do
   use BlockScoutWeb, :controller
 
+  require Logger
+
+  alias Explorer.Chain
+
   def show(conn, %{"id" => address_hash_string}) do
     redirect(conn, to: token_transfer_path(conn, :index, address_hash_string))
   end
+
+  def fetch_token_counters(token, address_hash) do
+    total_token_transfers_task =
+      Task.async(fn ->
+        Chain.count_token_transfers_from_token_hash(address_hash)
+      end)
+
+    total_token_holders_task =
+      Task.async(fn ->
+        token.holder_count || Chain.count_token_holders_from_token_hash(address_hash)
+      end)
+
+    [total_token_transfers_task, total_token_holders_task]
+    |> Task.yield_many(:timer.seconds(40))
+    |> Enum.map(fn {_task, res} ->
+      case res do
+        {:ok, result} ->
+          result
+
+        {:exit, reason} ->
+          Logger.warn("Query fetching token counters terminated: #{inspect(reason)}")
+          0
+
+        nil ->
+          Logger.warn("Query fetching token counters timed out.")
+          0
+      end
+    end)
+    |> List.to_tuple()
+  end
 end

apps/block_scout_web/lib/block_scout_web/controllers/tokens/transfer_controller.ex

@@ -6,6 +6,7 @@ defmodule BlockScoutWeb.Tokens.TransferController do
   alias Phoenix.View
 
   import BlockScoutWeb.Chain, only: [split_list_by_page: 1, paging_options: 1, next_page_params: 3]
+  import BlockScoutWeb.Tokens.TokenController, only: [fetch_token_counters: 2]
 
   def index(conn, %{"token_id" => address_hash_string, "type" => "JSON"} = params) do
     with {:ok, address_hash} <- Chain.string_to_address_hash(address_hash_string),
@@ -48,13 +49,15 @@ defmodule BlockScoutWeb.Tokens.TransferController do
 
     with {:ok, address_hash} <- Chain.string_to_address_hash(address_hash_string),
          {:ok, token} <- Chain.token_from_address_hash(address_hash, options) do
+      {total_token_transfers, total_token_holders} = fetch_token_counters(token, address_hash)
+
       render(
         conn,
         "index.html",
         current_path: current_path(conn),
         token: Market.add_price(token),
-        total_token_transfers: Chain.count_token_transfers_from_token_hash(address_hash),
-        total_token_holders: token.holder_count || Chain.count_token_holders_from_token_hash(address_hash)
+        total_token_transfers: total_token_transfers,
+        total_token_holders: total_token_holders
       )
     else
       :error ->

apps/block_scout_web/lib/block_scout_web/templates/tokens/overview/_details.html.eex

@@ -57,8 +57,12 @@
             </span>
             <div class="d-flex flex-row justify-content-start text-muted">
               <span class="mr-4"> <%= @token.type %> </span>
-              <span class="mr-4"><%= @total_token_holders %>  <%= gettext "Addresses" %></span>
-              <span class="mr-4"><%= @total_token_transfers %> <%= gettext "Transfers" %></span>
+              <%= if @total_token_holders > 0 do %>
+                <span class="mr-4"><%= @total_token_holders %>  <%= gettext "Addresses" %></span>
+              <% end %>
+              <%= if @total_token_transfers > 0 do %>
+                <span class="mr-4"><%= @total_token_transfers %> <%= gettext "Transfers" %></span>
+              <% end %>
               <%= if decimals?(@token) do %>
                 <span class="mr-4"><%= @token.decimals %> <%= gettext "Decimals" %></span>
               <% end %>