Enhance blocks handling in Staking DApp

apps/block_scout_web/assets/js/lib/queue.js

@@ -0,0 +1,72 @@
+/*
+
+Queue.js
+
+A function to represent a queue
+
+Created by Kate Morley - http://code.iamkate.com/ - and released under the terms
+of the CC0 1.0 Universal legal code:
+
+http://creativecommons.org/publicdomain/zero/1.0/legalcode
+
+*/
+
+/* eslint-disable */
+
+/* Creates a new queue. A queue is a first-in-first-out (FIFO) data structure -
+ * items are added to the end of the queue and removed from the front.
+ */
+module.exports = function Queue(){
+
+  // initialise the queue and offset
+  var queue  = [];
+  var offset = 0;
+
+  // Returns the length of the queue.
+  this.getLength = function(){
+    return (queue.length - offset);
+  }
+
+  // Returns true if the queue is empty, and false otherwise.
+  this.isEmpty = function(){
+    return (queue.length == 0);
+  }
+
+  /* Enqueues the specified item. The parameter is:
+   *
+   * item - the item to enqueue
+   */
+  this.enqueue = function(item){
+    queue.push(item);
+  }
+
+  /* Dequeues an item and returns it. If the queue is empty, the value
+   * 'undefined' is returned.
+   */
+  this.dequeue = function(){
+
+    // if the queue is empty, return immediately
+    if (queue.length == 0) return undefined;
+
+    // store the item at the front of the queue
+    var item = queue[offset];
+
+    // increment the offset and remove the free space if necessary
+    if (++ offset * 2 >= queue.length){
+      queue  = queue.slice(offset);
+      offset = 0;
+    }
+
+    // return the dequeued item
+    return item;
+
+  }
+
+  /* Returns the item at the front of the queue (without dequeuing it). If the
+   * queue is empty then undefined is returned.
+   */
+  this.peek = function(){
+    return (queue.length > 0 ? queue[offset] : undefined);
+  }
+
+}

apps/block_scout_web/assets/js/pages/stakes.js

@@ -5,6 +5,7 @@ import _ from 'lodash'
 import { subscribeChannel } from '../socket'
 import { connectElements } from '../lib/redux_helpers.js'
 import { createAsyncLoadStore, refreshPage } from '../lib/async_listing_load'
+import Queue from '../lib/queue'
 import Web3 from 'web3'
 import { openPoolInfoModal } from './stakes/validator_info'
 import { openDelegatorsListModal } from './stakes/delegators_list'
@@ -25,6 +26,7 @@ export const initialState = {
   blockRewardContract: null,
   channel: null,
   currentBlockNumber: 0, // current block number
+  finishRequestResolve: null,
   lastEpochNumber: 0,
   network: null,
   refreshBlockNumber: 0, // last page refresh block number
@@ -86,7 +88,8 @@ export function reducer (state = initialState, action) {
     }
     case 'PAGE_REFRESHED': {
       return Object.assign({}, state, {
-        refreshBlockNumber: action.refreshBlockNumber
+        refreshBlockNumber: action.refreshBlockNumber,
+        finishRequestResolve: action.finishRequestResolve
       })
     }
     case 'RECEIVED_UPDATE': {
@@ -108,6 +111,12 @@ export function reducer (state = initialState, action) {
     }
     case 'FINISH_REQUEST': {
       $(stakesPageSelector).fadeTo(0, 1)
+      if (state.finishRequestResolve) {
+        state.finishRequestResolve()
+        return Object.assign({}, state, {
+          finishRequestResolve: null
+        })
+      }
       return state
     }
     default:
@@ -139,10 +148,17 @@ if ($stakesPage.length) {
   const channel = subscribeChannel('stakes:staking_update')
   store.dispatch({ type: 'CHANNEL_CONNECTED', channel })
 
-  channel.on('staking_update', msg => {
+  let updating = false
+
+  async function onStakingUpdate (msg) { // eslint-disable-line no-inner-declarations
     const state = store.getState()
+
+    if (state.finishRequestResolve || updating) {
+      return
+    }
+    updating = true
+
     const firstMsg = (state.currentBlockNumber === 0)
-    const accountChanged = (msg.account !== state.account)
 
     store.dispatch({ type: 'BLOCK_CREATED', currentBlockNumber: msg.block_number })
 
@@ -153,7 +169,7 @@ if ($stakesPage.length) {
 
     $stakesTop.html(msg.top_html)
 
-    if (accountChanged) {
+    if (msg.account !== state.account) {
       store.dispatch({ type: 'ACCOUNT_UPDATED', account: msg.account })
       resetFilterMy(store)
     }
@@ -162,16 +178,15 @@ if ($stakesPage.length) {
       msg.staking_allowed !== state.stakingAllowed ||
       msg.epoch_number > state.lastEpochNumber ||
       msg.validator_set_apply_block !== state.validatorSetApplyBlock ||
-      (state.refreshInterval && msg.block_number >= state.refreshBlockNumber + state.refreshInterval)
+      (state.refreshInterval && msg.block_number >= state.refreshBlockNumber + state.refreshInterval) ||
+      msg.account !== state.account || msg.by_set_account
     ) {
-      if (firstMsg || accountChanged) {
+      if (firstMsg) {
         // Don't refresh the page for the first load
-        // as it is already refreshed by `initialize` function.
+        // as it is already refreshed by the `initialize` function.
-        // Also, don't refresh that after reconnect
-        // as it is already refreshed by `setAccount` function.
         msg.dont_refresh_page = true
       }
-      reloadPoolList(msg, store)
+      await reloadPoolList(msg, store)
     }
 
     const refreshBlockNumber = store.getState().refreshBlockNumber
@@ -185,13 +200,36 @@ if ($stakesPage.length) {
 
     const $refreshInformerLink = $refreshInformer.find('a')
     $refreshInformerLink.off('click')
-    $refreshInformerLink.on('click', (event) => {
+    $refreshInformerLink.on('click', async (event) => {
       event.preventDefault()
-      $refreshInformer.hide()
+      if (!store.getState().finishRequestResolve) {
-      $stakesPage.fadeTo(0, 0.5)
+        $refreshInformer.hide()
-      delete msg.dont_refresh_page // refresh anyway
+        $stakesPage.fadeTo(0, 0.5)
-      reloadPoolList(msg, store)
+        delete msg.dont_refresh_page // refresh anyway
+        await reloadPoolList(msg, store)
+      }
     })
+
+    updating = false
+  }
+
+  const messagesQueue = new Queue()
+
+  setTimeout(async () => {
+    while (true) {
+      const msg = messagesQueue.dequeue()
+      if (msg) {
+        // Synchronously handle the message
+        await onStakingUpdate(msg)
+      } else {
+        // Wait for the next message
+        await new Promise(resolve => setTimeout(resolve, 10))
+      }
+    }
+  }, 0)
+
+  channel.on('staking_update', msg => {
+    messagesQueue.enqueue(msg)
   })
 
   channel.on('contracts', msg => {
@@ -298,10 +336,12 @@ async function checkNetworkAndAccount (store, web3) {
   const accounts = await web3.eth.getAccounts()
   const account = accounts[0] ? accounts[0].toLowerCase() : null
 
-  if (account !== state.account) {
+  if (account !== state.account && await setAccount(account, store)) {
-    setAccount(account, store)
+    refresh = false // because refreshing will be done by `onStakingUpdate`
-  } else if (refresh) {
+  }
-    refreshPageWrapper(store)
+
+  if (refresh) {
+    await refreshPageWrapper(store)
   }
 
   setTimeout(() => {
@@ -320,21 +360,29 @@ async function loginByMetamask () {
   }
 }
 
-function refreshPageWrapper (store) {
+async function refreshPageWrapper (store) {
+  while (store.getState().finishRequestResolve) {
+    // Don't let anything simultaneously refresh the page
+    await new Promise(resolve => setTimeout(resolve, 10))
+  }
+
   let currentBlockNumber = store.getState().currentBlockNumber
   if (!currentBlockNumber) {
     currentBlockNumber = $('[data-block-number]', $stakesTop).data('blockNumber')
   }
 
-  refreshPage(store)
+  await new Promise(resolve => {
-  store.dispatch({
+    store.dispatch({
-    type: 'PAGE_REFRESHED',
+      type: 'PAGE_REFRESHED',
-    refreshBlockNumber: currentBlockNumber
+      refreshBlockNumber: currentBlockNumber,
+      finishRequestResolve: resolve
+    })
+    $refreshInformer.hide()
+    refreshPage(store)
   })
-  $refreshInformer.hide()
 }
 
-function reloadPoolList (msg, store) {
+async function reloadPoolList (msg, store) {
   store.dispatch({
     type: 'RECEIVED_UPDATE',
     lastEpochNumber: msg.epoch_number,
@@ -343,7 +391,7 @@ function reloadPoolList (msg, store) {
     validatorSetApplyBlock: msg.validator_set_apply_block
   })
   if (!msg.dont_refresh_page) {
-    refreshPageWrapper(store)
+    await refreshPageWrapper(store)
   }
 }
 
@@ -353,24 +401,32 @@ function resetFilterMy (store) {
 }
 
 function setAccount (account, store) {
-  store.dispatch({ type: 'ACCOUNT_UPDATED', account })
+  return new Promise(resolve => {
-  if (!account) {
+    store.dispatch({ type: 'ACCOUNT_UPDATED', account })
-    resetFilterMy(store)
+    if (!account) {
-  }
+      resetFilterMy(store)
+    }
 
-  const errorMsg = 'Cannot properly set account due to connection loss. Please, reload the page.'
+    const errorMsg = 'Cannot properly set account due to connection loss. Please, reload the page.'
-  const $addressField = $('.stakes-top-stats-item-address .stakes-top-stats-value')
+    const $addressField = $('.stakes-top-stats-item-address .stakes-top-stats-value')
-  $addressField.html('Loading...')
+    $addressField.html('Loading...')
-  store.getState().channel.push(
+    store.getState().channel.push(
-    'set_account', account
+      'set_account', account
-  ).receive('ok', () => {
+    ).receive('ok', () => {
-    $addressField.html(account)
+      $addressField.html(`
-    refreshPageWrapper(store)
+        <div data-placement="bottom" data-toggle="tooltip" title="${account}">
-    hideCurrentModal()
+          ${account}
-  }).receive('error', () => {
+        </div>
-    openErrorModal('Change account', errorMsg, true)
+      `)
-  }).receive('timeout', () => {
+      hideCurrentModal()
-    openErrorModal('Change account', errorMsg, true)
+      resolve(true)
+    }).receive('error', () => {
+      openErrorModal('Change account', errorMsg, true)
+      resolve(false)
+    }).receive('timeout', () => {
+      openErrorModal('Change account', errorMsg, true)
+      resolve(false)
+    })
   })
 }
 
@@ -395,6 +451,17 @@ function updateFilters (store, filterType) {
   const filterBanned = $stakesPage.find('[pool-filter-banned]')
   const filterMy = $stakesPage.find('[pool-filter-my]')
   const state = store.getState()
+
+  if (state.finishRequestResolve) {
+    if (filterType === 'my') {
+      filterMy.prop('checked', !filterMy.prop('checked'))
+    } else {
+      filterBanned.prop('checked', !filterBanned.prop('checked'))
+    }
+    openWarningModal('Still loading', 'The previous request to load pool list is not yet finished. Please, wait...')
+    return
+  }
+
   if (filterType === 'my' && !state.account) {
     filterMy.prop('checked', false)
     openWarningModal('Unauthorized', 'Please login with MetaMask')

apps/block_scout_web/assets/js/pages/stakes/utils.js

@@ -10,8 +10,8 @@ export async function makeContractCall (call, store, gasLimit, callbackFunc) {
   if (!callbackFunc) {
     callbackFunc = function (errorMessage) {
       if (!errorMessage) {
-        state.refreshPageFunc(store)
         openSuccessModal('Success', 'Transaction is confirmed.')
+        state.refreshPageFunc(store)
       } else {
         openErrorModal('Error', errorMessage)
       }

apps/block_scout_web/lib/block_scout_web/application.ex

@@ -8,6 +8,7 @@ defmodule BlockScoutWeb.Application do
   alias BlockScoutWeb.Counters.BlocksIndexedCounter
   alias BlockScoutWeb.{Endpoint, Prometheus}
   alias BlockScoutWeb.RealtimeEventHandler
+  alias BlockScoutWeb.StakingEventHandler
 
   def start(_type, _args) do
     import Supervisor.Spec
@@ -22,6 +23,7 @@ defmodule BlockScoutWeb.Application do
       supervisor(Endpoint, []),
       {Absinthe.Subscription, Endpoint},
       {RealtimeEventHandler, name: RealtimeEventHandler},
+      {StakingEventHandler, name: StakingEventHandler},
       {BlocksIndexedCounter, name: BlocksIndexedCounter}
     ]
 

apps/block_scout_web/lib/block_scout_web/channels/stakes_channel.ex

@@ -63,18 +63,22 @@ defmodule BlockScoutWeb.StakesChannel do
       |> assign(:mining_address, mining_address)
       |> push_contracts()
 
-    handle_out(
+    data =
-      "staking_update",
+      case Map.fetch(socket.assigns, :staking_update_data) do
-      %{
+        {:ok, staking_update_data} ->
-        block_number: BlockNumber.get_max(),
+          staking_update_data
-        dont_refresh_page: true,
+
-        epoch_number: ContractState.get(:epoch_number, 0),
+        _ ->
-        staking_allowed: ContractState.get(:staking_allowed, false),
+          %{
-        staking_token_defined: ContractState.get(:token, nil) != nil,
+            block_number: BlockNumber.get_max(),
-        validator_set_apply_block: ContractState.get(:validator_set_apply_block, 0)
+            epoch_number: ContractState.get(:epoch_number, 0),
-      },
+            staking_allowed: ContractState.get(:staking_allowed, false),
-      socket
+            staking_token_defined: ContractState.get(:token, nil) != nil,
-    )
+            validator_set_apply_block: ContractState.get(:validator_set_apply_block, 0)
+          }
+      end
+
+    handle_out("staking_update", Map.merge(data, %{by_set_account: true}), socket)
 
     {:reply, :ok, socket}
   end
@@ -399,16 +403,30 @@ defmodule BlockScoutWeb.StakesChannel do
   end
 
   def handle_out("staking_update", data, socket) do
-    dont_refresh_page =
+    by_set_account =
-      case Map.fetch(data, :dont_refresh_page) do
+      case Map.fetch(data, :by_set_account) do
         {:ok, value} -> value
         _ -> false
       end
 
+    socket =
+      if by_set_account do
+        # if :by_set_account is in the `data`,
+        # it means that this function was called by
+        # handle_in("set_account", ...), so we
+        # shouldn't assign the incoming data to the socket
+        socket
+      else
+        # otherwise, we should do the assignment
+        # to use the incoming data later by
+        # handle_in("set_account", ...) and StakesController.render_top
+        assign(socket, :staking_update_data, data)
+      end
+
     push(socket, "staking_update", %{
       account: socket.assigns[:account],
       block_number: data.block_number,
-      dont_refresh_page: dont_refresh_page,
+      by_set_account: by_set_account,
       epoch_number: data.epoch_number,
       staking_allowed: data.staking_allowed,
       staking_token_defined: data.staking_token_defined,

apps/block_scout_web/lib/block_scout_web/controllers/stakes_controller.ex

@@ -19,11 +19,21 @@ defmodule BlockScoutWeb.StakesController do
   # when a new block appears (see `staking_update` event handled in `StakesChannel`),
   # or when the page is loaded for the first time or reloaded by a user (i.e. it is called by the `render_template(filter, conn, _)`)
   def render_top(conn) do
-    active_pools_length = ContractState.get(:active_pools_length, 0)
+    staking_data =
-    block_number = BlockNumber.get_max()
+      case Map.fetch(conn.assigns, :staking_update_data) do
-    epoch_end_block = ContractState.get(:epoch_end_block, 0)
+        {:ok, data} ->
-    epoch_number = ContractState.get(:epoch_number, 0)
+          data
-    max_candidates = ContractState.get(:max_candidates, 0)
+
+        _ ->
+          %{
+            active_pools_length: ContractState.get(:active_pools_length, 0),
+            block_number: BlockNumber.get_max(),
+            epoch_end_block: ContractState.get(:epoch_end_block, 0),
+            epoch_number: ContractState.get(:epoch_number, 0),
+            max_candidates: ContractState.get(:max_candidates, 0)
+          }
+      end
+
     token = ContractState.get(:token, %Token{})
 
     account =
@@ -38,14 +48,17 @@ defmodule BlockScoutWeb.StakesController do
         })
       end
 
-    epoch_end_in = if epoch_end_block - block_number >= 0, do: epoch_end_block - block_number, else: 0
+    epoch_end_in =
+      if staking_data.epoch_end_block - staking_data.block_number >= 0,
+        do: staking_data.epoch_end_block - staking_data.block_number,
+        else: 0
 
     View.render_to_string(StakesView, "_stakes_top.html",
       account: account,
-      block_number: block_number,
+      block_number: staking_data.block_number,
-      candidates_limit_reached: active_pools_length >= max_candidates,
+      candidates_limit_reached: staking_data.active_pools_length >= staking_data.max_candidates,
       epoch_end_in: epoch_end_in,
-      epoch_number: epoch_number,
+      epoch_number: staking_data.epoch_number,
       token: token
     )
   end

apps/block_scout_web/lib/block_scout_web/notifier.ex

@@ -7,13 +7,11 @@ defmodule BlockScoutWeb.Notifier do
   alias BlockScoutWeb.{AddressContractVerificationView, Endpoint}
   alias Explorer.{Chain, Market, Repo}
   alias Explorer.Chain.{Address, InternalTransaction, TokenTransfer, Transaction}
-  alias Explorer.Chain.Cache.BlockNumber
   alias Explorer.Chain.Supply.RSK
   alias Explorer.Chain.Transaction.History.TransactionStats
   alias Explorer.Counters.AverageBlockTime
   alias Explorer.ExchangeRates.Token
   alias Explorer.SmartContract.{Solidity.CodeCompiler, Solidity.CompilerVersion}
-  alias Explorer.Staking.ContractState
   alias Phoenix.View
 
   def handle_event({:chain_event, :addresses, type, addresses}) when type in [:realtime, :on_demand] do
@@ -107,16 +105,6 @@ defmodule BlockScoutWeb.Notifier do
     })
   end
 
-  def handle_event({:chain_event, :staking_update}) do
-    Endpoint.broadcast("stakes:staking_update", "staking_update", %{
-      block_number: BlockNumber.get_max(),
-      epoch_number: ContractState.get(:epoch_number, 0),
-      staking_allowed: ContractState.get(:staking_allowed, false),
-      staking_token_defined: ContractState.get(:token, nil) != nil,
-      validator_set_apply_block: ContractState.get(:validator_set_apply_block, 0)
-    })
-  end
-
   def handle_event({:chain_event, :internal_transactions, :realtime, internal_transactions}) do
     internal_transactions
     |> Stream.map(

apps/block_scout_web/lib/block_scout_web/realtime_event_handler.ex

@@ -28,7 +28,6 @@ defmodule BlockScoutWeb.RealtimeEventHandler do
     # Does not come from the indexer
     Subscriber.to(:exchange_rate)
     Subscriber.to(:transaction_stats)
-    Subscriber.to(:staking_update)
     {:ok, []}
   end
 

apps/block_scout_web/lib/block_scout_web/staking_event_handler.ex

@@ -0,0 +1,26 @@
+defmodule BlockScoutWeb.StakingEventHandler do
+  @moduledoc """
+  Subscribing process for broadcast events from staking app.
+  """
+
+  use GenServer
+
+  alias BlockScoutWeb.Endpoint
+  alias Explorer.Chain.Events.Subscriber
+
+  def start_link(_) do
+    GenServer.start_link(__MODULE__, [], name: __MODULE__)
+  end
+
+  @impl true
+  def init([]) do
+    Subscriber.to(:staking_update, :realtime)
+    {:ok, []}
+  end
+
+  @impl true
+  def handle_info({:chain_event, :staking_update, :realtime, data}, state) do
+    Endpoint.broadcast("stakes:staking_update", "staking_update", data)
+    {:noreply, state}
+  end
+end

apps/block_scout_web/test/block_scout_web/channels/stakes_channel_test.exs

@@ -1,13 +1,21 @@
 defmodule BlockScoutWeb.StakesChannelTest do
   use BlockScoutWeb.ChannelCase
 
-  alias BlockScoutWeb.Notifier
+  alias BlockScoutWeb.StakingEventHandler
 
   test "subscribed user is notified of staking_update event" do
     topic = "stakes:staking_update"
     @endpoint.subscribe(topic)
 
-    Notifier.handle_event({:chain_event, :staking_update})
+    data = %{
+      block_number: 76,
+      epoch_number: 0,
+      staking_allowed: false,
+      staking_token_defined: false,
+      validator_set_apply_block: 0
+    }
+
+    StakingEventHandler.handle_info({:chain_event, :staking_update, :realtime, data}, nil)
 
     receive do
       %Phoenix.Socket.Broadcast{topic: ^topic, event: "staking_update", payload: %{epoch_number: _}} ->

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 last_block_number 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 staking_update token_transfers transactions contract_verification_result)a
 
   def broadcast(_data, false), do: :ok
 

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

@@ -3,11 +3,11 @@ 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 last_block_number 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 staking_update token_transfers transactions contract_verification_result)a
 
   @allowed_broadcast_types ~w(catchup realtime on_demand contract_verification_result)a
 
-  @allowed_events ~w(exchange_rate transaction_stats staking_update)a
+  @allowed_events ~w(exchange_rate transaction_stats)a
 
   @type broadcast_type :: :realtime | :catchup | :on_demand
 

apps/explorer/lib/explorer/smart_contract/reader.ex

@@ -138,6 +138,32 @@ defmodule Explorer.SmartContract.Reader do
     end)
   end
 
+  @spec query_contract_by_block_number(
+          String.t(),
+          term(),
+          functions(),
+          non_neg_integer()
+        ) :: functions_results()
+  def query_contract_by_block_number(contract_address, abi, functions, block_number) do
+    requests =
+      functions
+      |> Enum.map(fn {method_id, args} ->
+        %{
+          contract_address: contract_address,
+          method_id: method_id,
+          args: args,
+          block_number: block_number
+        }
+      end)
+
+    requests
+    |> query_contracts(abi)
+    |> Enum.zip(requests)
+    |> Enum.into(%{}, fn {response, request} ->
+      {request.method_id, response}
+    end)
+  end
+
   @doc """
   Runs batch of contract functions on given addresses for smart contract with an expected ABI and functions.
 

apps/explorer/lib/explorer/staking/contract_reader.ex

@@ -5,38 +5,38 @@ defmodule Explorer.Staking.ContractReader do
 
   alias Explorer.SmartContract.Reader
 
-  def global_requests do
+  def global_requests(block_number) do
     [
       # 673a2a1f = keccak256(getPools())
-      active_pools: {:staking, "673a2a1f", []},
+      active_pools: {:staking, "673a2a1f", [], block_number},
       # 8c2243ae = keccak256(stakingEpochEndBlock())
-      epoch_end_block: {:staking, "8c2243ae", []},
+      epoch_end_block: {:staking, "8c2243ae", [], block_number},
       # 794c0c68 = keccak256(stakingEpoch())
-      epoch_number: {:staking, "794c0c68", []},
+      epoch_number: {:staking, "794c0c68", [], block_number},
       # 7069e746 = keccak256(stakingEpochStartBlock())
-      epoch_start_block: {:staking, "7069e746", []},
+      epoch_start_block: {:staking, "7069e746", [], block_number},
       # df6f55f5 = keccak256(getPoolsInactive())
-      inactive_pools: {:staking, "df6f55f5", []},
+      inactive_pools: {:staking, "df6f55f5", [], block_number},
       # f0786096 = keccak256(MAX_CANDIDATES())
-      max_candidates: {:staking, "f0786096", []},
+      max_candidates: {:staking, "f0786096", [], block_number},
       # 5fef7643 = keccak256(candidateMinStake())
-      min_candidate_stake: {:staking, "5fef7643", []},
+      min_candidate_stake: {:staking, "5fef7643", [], block_number},
       # da7a9b6a = keccak256(delegatorMinStake())
-      min_delegator_stake: {:staking, "da7a9b6a", []},
+      min_delegator_stake: {:staking, "da7a9b6a", [], block_number},
       # 957950a7 = keccak256(getPoolsLikelihood())
-      pools_likelihood: {:staking, "957950a7", []},
+      pools_likelihood: {:staking, "957950a7", [], block_number},
       # a5d54f65 = keccak256(getPoolsToBeElected())
-      pools_to_be_elected: {:staking, "a5d54f65", []},
+      pools_to_be_elected: {:staking, "a5d54f65", [], block_number},
       # f4942501 = keccak256(areStakeAndWithdrawAllowed())
-      staking_allowed: {:staking, "f4942501", []},
+      staking_allowed: {:staking, "f4942501", [], block_number},
       # 2d21d217 = keccak256(erc677TokenContract())
-      token_contract_address: {:staking, "2d21d217", []},
+      token_contract_address: {:staking, "2d21d217", [], block_number},
       # 704189ca = keccak256(unremovableValidator())
-      unremovable_validator: {:validator_set, "704189ca", []},
+      unremovable_validator: {:validator_set, "704189ca", [], block_number},
       # b7ab4db5 = keccak256(getValidators())
-      validators: {:validator_set, "b7ab4db5", []},
+      validators: {:validator_set, "b7ab4db5", [], block_number},
       # b927ef43 = keccak256(validatorSetApplyBlock())
-      validator_set_apply_block: {:validator_set, "b927ef43", []}
+      validator_set_apply_block: {:validator_set, "b927ef43", [], block_number}
     ]
   end
 
@@ -199,10 +199,10 @@ defmodule Explorer.Staking.ContractReader do
   end
 
   # args = [staking_epoch, delegator_staked, validator_staked, total_staked, pool_reward \\ 10_00000]
-  def delegator_reward_request(args) do
+  def delegator_reward_request(args, block_number) do
     [
       # 5fba554e = keccak256(delegatorShare(uint256,uint256,uint256,uint256,uint256))
-      delegator_share: {:block_reward, "5fba554e", args}
+      delegator_share: {:block_reward, "5fba554e", args, block_number}
     ]
   end
 
@@ -234,76 +234,83 @@ defmodule Explorer.Staking.ContractReader do
     ]
   end
 
+  def mining_by_staking_request(staking_address, block_number) do
+    [
+      # 00535175 = keccak256(miningByStakingAddress(address))
+      mining_address: {:validator_set, "00535175", [staking_address], block_number}
+    ]
+  end
+
   def pool_staking_requests(staking_address, block_number) do
     [
       active_delegators: active_delegators_request(staking_address, block_number)[:active_delegators],
       # 73c21803 = keccak256(poolDelegatorsInactive(address))
-      inactive_delegators: {:staking, "73c21803", [staking_address]},
+      inactive_delegators: {:staking, "73c21803", [staking_address], block_number},
       # a711e6a1 = keccak256(isPoolActive(address))
-      is_active: {:staking, "a711e6a1", [staking_address]},
+      is_active: {:staking, "a711e6a1", [staking_address], block_number},
-      mining_address_hash: mining_by_staking_request(staking_address)[:mining_address],
+      mining_address_hash: mining_by_staking_request(staking_address, block_number)[:mining_address],
       # a697ecff = keccak256(stakeAmount(address,address))
-      self_staked_amount: {:staking, "a697ecff", [staking_address, staking_address]},
+      self_staked_amount: {:staking, "a697ecff", [staking_address, staking_address], block_number},
       # 5267e1d6 = keccak256(stakeAmountTotal(address))
-      total_staked_amount: {:staking, "5267e1d6", [staking_address]},
+      total_staked_amount: {:staking, "5267e1d6", [staking_address], block_number},
       # 527d8bc4 = keccak256(validatorRewardPercent(address))
-      validator_reward_percent: {:block_reward, "527d8bc4", [staking_address]}
+      validator_reward_percent: {:block_reward, "527d8bc4", [staking_address], block_number}
     ]
   end
 
-  def pool_mining_requests(mining_address) do
+  def pool_mining_requests(mining_address, block_number) do
     [
       # a881c5fd = keccak256(areDelegatorsBanned(address))
-      are_delegators_banned: {:validator_set, "a881c5fd", [mining_address]},
+      are_delegators_banned: {:validator_set, "a881c5fd", [mining_address], block_number},
       # c9e9694d = keccak256(banReason(address))
-      ban_reason: {:validator_set, "c9e9694d", [mining_address]},
+      ban_reason: {:validator_set, "c9e9694d", [mining_address], block_number},
       # 5836d08a = keccak256(bannedUntil(address))
-      banned_until: {:validator_set, "5836d08a", [mining_address]},
+      banned_until: {:validator_set, "5836d08a", [mining_address], block_number},
       # 1a7fa237 = keccak256(bannedDelegatorsUntil(address))
-      banned_delegators_until: {:validator_set, "1a7fa237", [mining_address]},
+      banned_delegators_until: {:validator_set, "1a7fa237", [mining_address], block_number},
       # a92252ae = keccak256(isValidatorBanned(address))
-      is_banned: {:validator_set, "a92252ae", [mining_address]},
+      is_banned: {:validator_set, "a92252ae", [mining_address], block_number},
       # b41832e4 = keccak256(validatorCounter(address))
-      was_validator_count: {:validator_set, "b41832e4", [mining_address]},
+      was_validator_count: {:validator_set, "b41832e4", [mining_address], block_number},
       # 1d0cd4c6 = keccak256(banCounter(address))
-      was_banned_count: {:validator_set, "1d0cd4c6", [mining_address]}
+      was_banned_count: {:validator_set, "1d0cd4c6", [mining_address], block_number}
     ]
   end
 
-  def staker_requests(pool_staking_address, staker_address) do
+  def staker_requests(pool_staking_address, staker_address, block_number) do
     [
       # 950a6513 = keccak256(maxWithdrawOrderAllowed(address,address))
-      max_ordered_withdraw_allowed: {:staking, "950a6513", [pool_staking_address, staker_address]},
+      max_ordered_withdraw_allowed: {:staking, "950a6513", [pool_staking_address, staker_address], block_number},
       # 6bda1577 = keccak256(maxWithdrawAllowed(address,address))
-      max_withdraw_allowed: {:staking, "6bda1577", [pool_staking_address, staker_address]},
+      max_withdraw_allowed: {:staking, "6bda1577", [pool_staking_address, staker_address], block_number},
       # e9ab0300 = keccak256(orderedWithdrawAmount(address,address))
-      ordered_withdraw: {:staking, "e9ab0300", [pool_staking_address, staker_address]},
+      ordered_withdraw: {:staking, "e9ab0300", [pool_staking_address, staker_address], block_number},
       # a4205967 = keccak256(orderWithdrawEpoch(address,address))
-      ordered_withdraw_epoch: {:staking, "a4205967", [pool_staking_address, staker_address]},
+      ordered_withdraw_epoch: {:staking, "a4205967", [pool_staking_address, staker_address], block_number},
       # a697ecff = keccak256(stakeAmount(address,address))
-      stake_amount: {:staking, "a697ecff", [pool_staking_address, staker_address]}
+      stake_amount: {:staking, "a697ecff", [pool_staking_address, staker_address], block_number}
     ]
   end
 
-  def staking_by_mining_request(mining_address) do
+  def staking_by_mining_request(mining_address, block_number) do
     [
       # 1ee4d0bc = keccak256(stakingByMiningAddress(address))
-      staking_address: {:validator_set, "1ee4d0bc", [mining_address]}
+      staking_address: {:validator_set, "1ee4d0bc", [mining_address], block_number}
     ]
   end
 
-  def validator_min_reward_percent_request(epoch_number) do
+  def validator_min_reward_percent_request(epoch_number, block_number) do
     [
       # cdf7a090 = keccak256(validatorMinRewardPercent(uint256))
-      value: {:block_reward, "cdf7a090", [epoch_number]}
+      value: {:block_reward, "cdf7a090", [epoch_number], block_number}
     ]
   end
 
   # args = [staking_epoch, validator_staked, total_staked, pool_reward \\ 10_00000]
-  def validator_reward_request(args) do
+  def validator_reward_request(args, block_number) do
     [
       # 8737929a = keccak256(validatorShare(uint256,uint256,uint256,uint256))
-      validator_share: {:block_reward, "8737929a", args}
+      validator_share: {:block_reward, "8737929a", args, block_number}
     ]
   end
 

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

@@ -128,31 +128,50 @@ defmodule Explorer.Staking.ContractState do
   @doc "Handles new blocks and decides to fetch fresh chain info"
   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)
+      # read general info from the contracts (including pool list and validator list)
+      global_responses =
+        ContractReader.perform_requests(ContractReader.global_requests(block_number), state.contracts, state.abi)
+
+      epoch_very_beginning = global_responses.epoch_start_block == block_number + 1
+
+      if global_responses.epoch_number > get(:epoch_number) and not epoch_very_beginning and state.seen_block > 0 do
+        # if the previous staking epoch finished and we have blocks gap,
+        # call fetch_state in a loop until the blocks gap is closed
+        loop_block_start = state.seen_block + 1
+        loop_block_end = block_number - 1
+
+        if loop_block_end >= loop_block_start do
+          for bn <- loop_block_start..loop_block_end do
+            gr = ContractReader.perform_requests(ContractReader.global_requests(bn), state.contracts, state.abi)
+            fetch_state(state.contracts, state.abi, gr, bn, gr.epoch_start_block == bn + 1)
+          end
+        end
+      end
+
+      fetch_state(state.contracts, state.abi, global_responses, block_number, epoch_very_beginning)
       {:noreply, %{state | seen_block: block_number}}
     else
       {:noreply, state}
     end
   end
 
-  defp fetch_state(contracts, abi, block_number) do
+  defp fetch_state(contracts, abi, global_responses, block_number, epoch_very_beginning) do
-    # read general info from the contracts (including pool list and validator list)
+    validator_min_reward_percent =
-    global_responses = ContractReader.perform_requests(ContractReader.global_requests(), contracts, abi)
+      get_validator_min_reward_percent(global_responses.epoch_number, block_number, contracts, abi)
 
-    validator_min_reward_percent = get_validator_min_reward_percent(global_responses, contracts, abi)
-
-    epoch_very_beginning = global_responses.epoch_start_block == block_number + 1
     is_validator = Enum.into(global_responses.validators, %{}, &{address_bytes_to_string(&1), true})
 
     start_snapshotting =
       global_responses.epoch_number > get(:snapshotted_epoch_number) && global_responses.epoch_number > 0 &&
         not get(:is_snapshotting)
 
+    active_pools_length = Enum.count(global_responses.active_pools)
+
     # save the general info to ETS (excluding pool list and validator list)
     settings =
       global_responses
       |> get_settings(validator_min_reward_percent, block_number)
-      |> Enum.concat(active_pools_length: Enum.count(global_responses.active_pools))
+      |> Enum.concat(active_pools_length: active_pools_length)
 
     :ets.insert(@table_name, settings)
 
@@ -162,11 +181,12 @@ defmodule Explorer.Staking.ContractState do
         start_snapshotting,
         global_responses,
         contracts,
-        abi
+        abi,
+        block_number
       )
 
     # miningToStakingAddress mapping
-    mining_to_staking_address = get_mining_to_staking_address(validators, contracts, abi)
+    mining_to_staking_address = get_mining_to_staking_address(validators, contracts, abi, block_number)
 
     # the list of all pools (validators + active pools + inactive pools)
     pools =
@@ -188,7 +208,14 @@ defmodule Explorer.Staking.ContractState do
     # call `BlockReward.validatorShare` function for each pool
     # to get validator's reward share of the pool (needed for the `Delegators` list in UI)
     candidate_reward_responses =
-      get_candidate_reward_responses(pool_staking_responses, global_responses, pool_staking_keys, contracts, abi)
+      get_candidate_reward_responses(
+        pool_staking_responses,
+        global_responses,
+        pool_staking_keys,
+        contracts,
+        abi,
+        block_number
+      )
 
     # call `BlockReward.delegatorShare` function for each delegator
     # to get their reward share of the pool (needed for the `Delegators` list in UI)
@@ -207,7 +234,8 @@ defmodule Explorer.Staking.ContractState do
         pool_staking_responses,
         global_responses,
         contracts,
-        abi
+        abi,
+        block_number
       )
 
     # calculate total amount staked into all active pools
@@ -265,8 +293,19 @@ defmodule Explorer.Staking.ContractState do
       )
     end
 
-    # notify the UI about new block
+    # notify the UI about a new block
-    Publisher.broadcast(:staking_update)
+    data = %{
+      active_pools_length: active_pools_length,
+      block_number: block_number,
+      epoch_end_block: global_responses.epoch_end_block,
+      epoch_number: global_responses.epoch_number,
+      max_candidates: global_responses.max_candidates,
+      staking_allowed: global_responses.staking_allowed,
+      staking_token_defined: get(:token, nil) != nil,
+      validator_set_apply_block: global_responses.validator_set_apply_block
+    }
+
+    Publisher.broadcast([{:staking_update, data}], :realtime)
   end
 
   defp get_settings(global_responses, validator_min_reward_percent, block_number) do
@@ -284,9 +323,11 @@ defmodule Explorer.Staking.ContractState do
     end
   end
 
-  defp get_mining_to_staking_address(validators, contracts, abi) do
+  defp get_mining_to_staking_address(validators, contracts, abi, block_number) do
     validators.all
-    |> Enum.map(&ContractReader.staking_by_mining_request/1)
+    |> Enum.map(fn mining_address ->
+      ContractReader.staking_by_mining_request(mining_address, block_number)
+    end)
     |> ContractReader.perform_grouped_requests(validators.all, contracts, abi)
     |> Map.new(fn {mining_address, resp} -> {mining_address, address_string_to_bytes(resp.staking_address).bytes} end)
   end
@@ -303,7 +344,12 @@ defmodule Explorer.Staking.ContractState do
     # read pool info from the contracts by its mining address
     pool_mining_responses =
       pools
-      |> Enum.map(&ContractReader.pool_mining_requests(pool_staking_responses[&1].mining_address_hash))
+      |> Enum.map(fn staking_address_hash ->
+        ContractReader.pool_mining_requests(
+          pool_staking_responses[staking_address_hash].mining_address_hash,
+          block_number
+        )
+      end)
       |> ContractReader.perform_grouped_requests(pools, contracts, abi)
 
     # get a flat list of all stakers in the form of {pool_staking_address, staker_address, is_active}
@@ -318,7 +364,7 @@ defmodule Explorer.Staking.ContractState do
     staker_responses =
       stakers
       |> Enum.map(fn {pool_staking_address, staker_address, _is_active} ->
-        ContractReader.staker_requests(pool_staking_address, staker_address)
+        ContractReader.staker_requests(pool_staking_address, staker_address, block_number)
       end)
       |> ContractReader.perform_grouped_requests(stakers, contracts, abi)
 
@@ -329,15 +375,25 @@ defmodule Explorer.Staking.ContractState do
     }
   end
 
-  defp get_candidate_reward_responses(pool_staking_responses, global_responses, pool_staking_keys, contracts, abi) do
+  defp get_candidate_reward_responses(
+         pool_staking_responses,
+         global_responses,
+         pool_staking_keys,
+         contracts,
+         abi,
+         block_number
+       ) do
     pool_staking_responses
     |> Enum.map(fn {_pool_staking_address, resp} ->
-      ContractReader.validator_reward_request([
+      ContractReader.validator_reward_request(
-        global_responses.epoch_number,
+        [
-        resp.self_staked_amount,
+          global_responses.epoch_number,
-        resp.total_staked_amount,
+          resp.self_staked_amount,
-        1000_000
+          resp.total_staked_amount,
-      ])
+          1000_000
+        ],
+        block_number
+      )
     end)
     |> ContractReader.perform_grouped_requests(pool_staking_keys, contracts, abi)
   end
@@ -347,7 +403,8 @@ defmodule Explorer.Staking.ContractState do
          pool_staking_responses,
          global_responses,
          contracts,
-         abi
+         abi,
+         block_number
        ) do
     # to keep sort order when using `perform_grouped_requests` (see below)
     delegator_keys = Enum.map(delegator_responses, fn {key, _} -> key end)
@@ -356,13 +413,16 @@ defmodule Explorer.Staking.ContractState do
     |> Enum.map(fn {{pool_staking_address, _staker_address, _is_active}, resp} ->
       staking_resp = pool_staking_responses[pool_staking_address]
 
-      ContractReader.delegator_reward_request([
+      ContractReader.delegator_reward_request(
-        global_responses.epoch_number,
+        [
-        resp.stake_amount,
+          global_responses.epoch_number,
-        staking_resp.self_staked_amount,
+          resp.stake_amount,
-        staking_resp.total_staked_amount,
+          staking_resp.self_staked_amount,
-        1000_000
+          staking_resp.total_staked_amount,
-      ])
+          1000_000
+        ],
+        block_number
+      )
     end)
     |> ContractReader.perform_grouped_requests(delegator_keys, contracts, abi)
   end
@@ -385,9 +445,9 @@ defmodule Explorer.Staking.ContractState do
     end)
   end
 
-  defp get_validator_min_reward_percent(global_responses, contracts, abi) do
+  defp get_validator_min_reward_percent(epoch_number, block_number, contracts, abi) do
     ContractReader.perform_requests(
-      ContractReader.validator_min_reward_percent_request(global_responses.epoch_number),
+      ContractReader.validator_min_reward_percent_request(epoch_number, block_number),
       contracts,
       abi
     ).value
@@ -414,7 +474,8 @@ defmodule Explorer.Staking.ContractState do
          start_snapshotting,
          global_responses,
          contracts,
-         abi
+         abi,
+         block_number
        ) do
     if start_snapshotting do
       # eebc7a39 = keccak256(getPendingValidators())
@@ -424,10 +485,15 @@ defmodule Explorer.Staking.ContractState do
           "eebc7a39" => {:ok, [validators_pending]},
           "004a8803" => {:ok, [validators_to_be_finalized]}
         } =
-          Reader.query_contract(contracts.validator_set, abi, %{
+          Reader.query_contract_by_block_number(
-            "eebc7a39" => [],
+            contracts.validator_set,
-            "004a8803" => []
+            abi,
-          })
+            %{
+              "eebc7a39" => [],
+              "004a8803" => []
+            },
+            block_number
+          )
 
         validators_pending = Enum.uniq(validators_pending ++ validators_to_be_finalized)
 
@@ -613,6 +679,8 @@ defmodule Explorer.Staking.ContractState do
          mining_to_staking_address
        ) do
     # start snapshotting at the beginning of the staking epoch
+    :ets.insert(@table_name, is_snapshotting: true)
+
     cached_pool_staking_responses =
       if epoch_very_beginning do
         pool_staking_responses
@@ -659,7 +727,10 @@ defmodule Explorer.Staking.ContractState do
 
   defp fetch_token(address, address_hash) do
     # the token doesn't exist in DB, so try
-    # to read it from a contract and then write to DB
+    # to read it from a contract and then write to DB.
+    # Since the Staking DApp doesn't use the token fields
+    # which dinamically change (such as totalSupply),
+    # we don't pass the current block_number to the RPC request
     token_functions = MetadataRetriever.get_functions_of(address)
 
     if map_size(token_functions) > 0 do

apps/explorer/lib/explorer/staking/stake_snapshotting.ex

@@ -19,8 +19,6 @@ defmodule Explorer.Staking.StakeSnapshotting do
         mining_to_staking_address,
         block_number
       ) do
-    :ets.insert(ets_table_name, is_snapshotting: true)
-
     # get staking addresses for the pending validators
     pool_staking_addresses =
       pools_mining_addresses
@@ -89,12 +87,15 @@ defmodule Explorer.Staking.StakeSnapshotting do
     validator_reward_responses =
       pool_staking_responses
       |> Enum.map(fn {_pool_staking_address, resp} ->
-        ContractReader.validator_reward_request([
+        ContractReader.validator_reward_request(
-          epoch_number,
+          [
-          resp.snapshotted_self_staked_amount,
+            epoch_number,
-          resp.snapshotted_total_staked_amount,
+            resp.snapshotted_self_staked_amount,
-          1000_000
+            resp.snapshotted_total_staked_amount,
-        ])
+            1000_000
+          ],
+          block_number
+        )
       end)
       |> ContractReader.perform_grouped_requests(pool_staking_keys, contracts, abi)
 
@@ -116,13 +117,16 @@ defmodule Explorer.Staking.StakeSnapshotting do
       |> Enum.map(fn {{pool_staking_address, _staker_address}, resp} ->
         staking_resp = pool_staking_responses[pool_staking_address]
 
-        ContractReader.delegator_reward_request([
+        ContractReader.delegator_reward_request(
-          epoch_number,
+          [
-          resp.snapshotted_stake_amount,
+            epoch_number,
-          staking_resp.snapshotted_self_staked_amount,
+            resp.snapshotted_stake_amount,
-          staking_resp.snapshotted_total_staked_amount,
+            staking_resp.snapshotted_self_staked_amount,
-          1000_000
+            staking_resp.snapshotted_total_staked_amount,
-        ])
+            1000_000
+          ],
+          block_number
+        )
       end)
       |> ContractReader.perform_grouped_requests(delegator_keys, contracts, abi)