Add last_block_number realtime chain event

CHANGELOG.md

@@ -15,6 +15,7 @@
 ### Fixes
 - [#3408](https://github.com/poanetwork/blockscout/pull/3408) - Fix (total) difficulty display
 - [#3401](https://github.com/poanetwork/blockscout/pull/3401) - Fix procedure of marking internal transactions as failed
+- [#3400](https://github.com/poanetwork/blockscout/pull/3400) - Add :last_block_number realtime chain event
 - [#3399](https://github.com/poanetwork/blockscout/pull/3399) - Fix Token transfers CSV export
 - [#3396](https://github.com/poanetwork/blockscout/pull/3396) - Handle exchange rates request throttled
 - [#3382](https://github.com/poanetwork/blockscout/pull/3382) - Check ets table exists for know tokens

apps/explorer/lib/explorer/chain/events/publisher.ex

@@ -3,7 +3,7 @@ defmodule Explorer.Chain.Events.Publisher do
   Publishes events related to the Chain context.
   """
 
-  @allowed_events ~w(addresses address_coin_balances address_token_balances blocks block_rewards internal_transactions token_transfers transactions contract_verification_result)a
+  @allowed_events ~w(addresses address_coin_balances address_token_balances blocks block_rewards internal_transactions last_block_number token_transfers transactions contract_verification_result)a
 
   def broadcast(_data, false), do: :ok
 

apps/explorer/lib/explorer/chain/events/subscriber.ex

@@ -3,7 +3,7 @@ defmodule Explorer.Chain.Events.Subscriber do
   Subscribes to events related to the Chain context.
   """
 
-  @allowed_broadcast_events ~w(addresses address_coin_balances address_token_balances blocks block_rewards internal_transactions token_transfers transactions contract_verification_result)a
+  @allowed_broadcast_events ~w(addresses address_coin_balances address_token_balances blocks block_rewards internal_transactions last_block_number token_transfers transactions contract_verification_result)a
 
   @allowed_broadcast_types ~w(catchup realtime on_demand contract_verification_result)a
 

apps/explorer/lib/explorer/staking/contract_state.ex

@@ -68,7 +68,7 @@ defmodule Explorer.Staking.ContractState do
       write_concurrency: true
     ])
 
-    Subscriber.to(:blocks, :realtime)
+    Subscriber.to(:last_block_number, :realtime)
 
     staking_abi = abi("StakingAuRa")
     validator_set_abi = abi("ValidatorSetAuRa")
@@ -126,12 +126,10 @@ defmodule Explorer.Staking.ContractState do
   end
 
   @doc "Handles new blocks and decides to fetch fresh chain info"
-  def handle_info({:chain_event, :blocks, :realtime, blocks}, state) do
-    latest_block = Enum.max_by(blocks, & &1.number, fn -> %{number: 0} end)
-
-    if latest_block.number > state.seen_block do
-      fetch_state(state.contracts, state.abi, latest_block.number)
-      {:noreply, %{state | seen_block: latest_block.number}}
+  def handle_info({:chain_event, :last_block_number, :realtime, block_number}, state) do
+    if block_number > state.seen_block do
+      fetch_state(state.contracts, state.abi, block_number)
+      {:noreply, %{state | seen_block: block_number}}
     else
       {:noreply, state}
     end

apps/explorer/test/explorer/staking/contract_state_test.exs

@@ -30,7 +30,7 @@ defmodule Explorer.Staking.ContractStateTest do
 
     start_supervised!(ContractState)
 
-    Publisher.broadcast([{:blocks, [%Explorer.Chain.Block{number: 76}]}], :realtime)
+    Publisher.broadcast([{:last_block_number, 76}], :realtime)
 
     Process.sleep(500)
 

apps/indexer/lib/indexer/block/realtime/fetcher.ex

@@ -28,6 +28,7 @@ defmodule Indexer.Block.Realtime.Fetcher do
   alias EthereumJSONRPC.{Blocks, FetchedBalances, Subscription}
   alias Explorer.Chain
   alias Explorer.Chain.Cache.Accounts
+  alias Explorer.Chain.Events.Publisher
   alias Explorer.Counters.AverageBlockTime
   alias Indexer.{Block, Tracer}
   alias Indexer.Block.Realtime.TaskSupervisor
@@ -85,6 +86,7 @@ defmodule Indexer.Block.Realtime.Fetcher do
       )
       when is_binary(quantity) do
     number = quantity_to_integer(quantity)
+    Publisher.broadcast([{:last_block_number, number}], :realtime)
     # Subscriptions don't support getting all the blocks and transactions data,
     # so we need to go back and get the full block
     start_fetch_and_import(number, block_fetcher, previous_number, max_number_seen)