Store bridged token price in the DB

apps/explorer/lib/explorer/chain/bridged_token.ex

@@ -24,7 +24,8 @@ defmodule Explorer.Chain.BridgedToken do
           home_token_contract_address: %Ecto.Association.NotLoaded{} | Address.t(),
           home_token_contract_address_hash: Hash.Address.t(),
           custom_metadata: String.t(),
-          type: String.t()
+          type: String.t(),
+          exchange_rate: Decimal.t()
         }
 
   @derive {Poison.Encoder,
@@ -49,6 +50,7 @@ defmodule Explorer.Chain.BridgedToken do
     field(:foreign_token_contract_address_hash, Hash.Address)
     field(:custom_metadata, :string)
     field(:type, :string)
+    field(:exchange_rate, :decimal)
 
     belongs_to(
       :home_token_contract_address,
@@ -63,7 +65,7 @@ defmodule Explorer.Chain.BridgedToken do
   end
 
   @required_attrs ~w(home_token_contract_address_hash)a
-  @optional_attrs ~w(foreign_chain_id foreign_token_contract_address_hash custom_metadata type)a
+  @optional_attrs ~w(foreign_chain_id foreign_token_contract_address_hash custom_metadata type exchange_rate)a
 
   @doc false
   def changeset(%BridgedToken{} = bridged_token, params \\ %{}) do

apps/explorer/lib/explorer/chain/cache/token_exchange_rate.ex

@@ -4,7 +4,12 @@ defmodule Explorer.Chain.Cache.TokenExchangeRate do
   """
   use GenServer
 
+  import Ecto.Query, only: [from: 2]
+
+  alias Ecto.Changeset
+  alias Explorer.Chain.BridgedToken
   alias Explorer.ExchangeRates.Source
+  alias Explorer.Repo
 
   @cache_name :token_exchange_rate
   @last_update_key "last_update"
@@ -50,14 +55,20 @@ defmodule Explorer.Chain.Cache.TokenExchangeRate do
     "token_symbol_exchange_rate_#{symbol}"
   end
 
-  def fetch(symbol) do
+  def fetch(token_hash, symbol) do
     if cache_expired?(symbol) || value_is_empty?(symbol) do
       Task.start_link(fn ->
-        update_cache(symbol)
+        update_cache(token_hash, symbol)
       end)
     end
 
-    fetch_from_cache(cache_key(symbol))
+    cached_value = fetch_from_cache(cache_key(symbol))
+
+    if is_nil(cached_value) || Decimal.cmp(cached_value, 0) == :eq do
+      fetch_from_db(token_hash)
+    else
+      cached_value
+    end
   end
 
   def cache_name, do: @cache_name
@@ -78,11 +89,12 @@ defmodule Explorer.Chain.Cache.TokenExchangeRate do
     is_nil(value) || value == 0
   end
 
-  defp update_cache(symbol) do
+  defp update_cache(token_hash, symbol) do
     put_into_cache("#{cache_key(symbol)}_#{@last_update_key}", current_time())
 
     exchange_rate = fetch_token_exchange_rate(symbol)
 
+    put_into_db(token_hash, exchange_rate)
     put_into_cache(cache_key(symbol), exchange_rate)
   end
 
@@ -106,12 +118,44 @@ defmodule Explorer.Chain.Cache.TokenExchangeRate do
     end
   end
 
+  defp fetch_from_db(nil), do: nil
+
+  defp fetch_from_db(token_hash) do
+    token = get_token(token_hash)
+
+    if token do
+      token.exchange_rate
+    else
+      nil
+    end
+  end
+
   def put_into_cache(key, value) do
     if cache_table_exists?() do
       :ets.insert(@cache_name, {key, value})
     end
   end
 
+  def put_into_db(token_hash, exchange_rate) do
+    token = get_token(token_hash)
+
+    if token do
+      token
+      |> Changeset.change(%{exchange_rate: exchange_rate})
+      |> Repo.update()
+    end
+  end
+
+  defp get_token(token_hash) do
+    query =
+      from(bt in BridgedToken,
+        where: bt.home_token_contract_address_hash == ^token_hash
+      )
+
+    query
+    |> Repo.one()
+  end
+
   defp current_time do
     utc_now = DateTime.utc_now()
 

apps/explorer/lib/explorer/chain/supply/token_bridge.ex

@@ -194,12 +194,13 @@ defmodule Explorer.Chain.Supply.TokenBridge do
     omni_bridge_market_cap
   end
 
-  def get_current_price_for_bridged_token(symbol) when is_nil(symbol), do: nil
+  def get_current_price_for_bridged_token(_token_hash, symbol) when is_nil(symbol), do: nil
+  def get_current_price_for_bridged_token(token_hash, _symbol) when is_nil(token_hash), do: nil
 
-  def get_current_price_for_bridged_token(symbol) do
+  def get_current_price_for_bridged_token(token_hash, symbol) do
     bridged_token_symbol_for_price_fetching = bridged_token_symbol_mapping_to_get_price(symbol)
 
-    TokenExchangeRateCache.fetch(bridged_token_symbol_for_price_fetching)
+    TokenExchangeRateCache.fetch(token_hash, bridged_token_symbol_for_price_fetching)
   end
 
   def get_bridged_mainnet_tokens_list do
@@ -221,7 +222,7 @@ defmodule Explorer.Chain.Supply.TokenBridge do
     bridged_mainnet_tokens_with_supply =
       bridged_mainnet_tokens_list
       |> Enum.map(fn {bridged_token_hash, bridged_token_symbol} ->
-        bridged_token_price_from_cache = TokenExchangeRateCache.fetch(bridged_token_symbol)
+        bridged_token_price_from_cache = TokenExchangeRateCache.fetch(bridged_token_hash, bridged_token_symbol)
 
         bridged_token_price =
           if bridged_token_price_from_cache && Decimal.cmp(bridged_token_price_from_cache, 0) == :gt do

apps/explorer/lib/explorer/counters/bridge.ex

@@ -166,8 +166,8 @@ defmodule Explorer.Counters.Bridge do
     bridged_mainnet_tokens_list = TokenBridge.get_bridged_mainnet_tokens_list()
 
     bridged_mainnet_tokens_list
-    |> Enum.each(fn {_bridged_token_hash, bridged_token_symbol} ->
-      bridged_token_price = TokenBridge.get_current_price_for_bridged_token(bridged_token_symbol)
+    |> Enum.each(fn {bridged_token_hash, bridged_token_symbol} ->
+      bridged_token_price = TokenBridge.get_current_price_for_bridged_token(bridged_token_hash, bridged_token_symbol)
       cache_key = TokenExchangeRate.cache_key(bridged_token_symbol)
       TokenExchangeRate.put_into_cache(cache_key, bridged_token_price)
     end)

apps/explorer/lib/explorer/market/market.ex

@@ -63,7 +63,7 @@ defmodule Explorer.Market do
           fetch_token_usd_value(matches_known_address, symbol)
 
         mainnet_bridged_token?(token) ->
-          TokenBridge.get_current_price_for_bridged_token(symbol)
+          TokenBridge.get_current_price_for_bridged_token(token.contract_address_hash, symbol)
 
         true ->
           nil

apps/explorer/priv/repo/migrations/20210226154732_add_exchange_rate_column_to_bridged_tokens.exs

@@ -0,0 +1,9 @@
+defmodule Explorer.Repo.Migrations.AddExchangeRateColumnToBridgedTokens do
+  use Ecto.Migration
+
+  def change do
+    alter table("bridged_tokens") do
+      add(:exchange_rate, :decimal)
+    end
+  end
+end