Add polling support in the Eth1Monitor (extracted from the merge branch)

beacon_chain/conf.nim

@@ -128,6 +128,12 @@ type
       desc: "One or more Web3 provider URLs used for obtaining deposit contract data"
       name: "web3-url" }: seq[string]
 
+    web3ForcePolling* {.
+      hidden
+      defaultValue: false
+      desc: "Force the use of polling when determining the head block of Eth1"
+      name: "web3-force-polling" }: bool
+
     nonInteractive* {.
       desc: "Do not display interative prompts. Quit on missing configuration"
       name: "non-interactive" }: bool

beacon_chain/eth1/eth1_monitor.nim

@@ -96,11 +96,12 @@ type
     web3Urls: seq[string]
     eth1Network: Option[Eth1Network]
     depositContractAddress*: Eth1Address
+    forcePolling: bool
 
     dataProvider: Web3DataProviderRef
+    latestEth1Block: Option[FullBlockId]
 
     depositsChain: Eth1Chain
-    latestEth1BlockNumber: Eth1BlockNumber
     eth1Progress: AsyncEvent
 
     runFut: Future[void]
@@ -120,6 +121,10 @@ type
 
   Web3DataProviderRef* = ref Web3DataProvider
 
+  FullBlockId* = object
+    number: Eth1BlockNumber
+    hash: BlockHash
+
   DataProviderFailure* = object of CatchableError
   CorruptDataProvider* = object of DataProviderFailure
   DataProviderTimeout* = object of DataProviderFailure
@@ -243,14 +248,16 @@ template finalizedDepositsMerkleizer(m: Eth1Monitor): auto =
   m.depositsChain.finalizedDepositsMerkleizer
 
 proc fixupWeb3Urls*(web3Url: var string) =
-  let normalizedUrl = toLowerAscii(web3Url)
+  var normalizedUrl = toLowerAscii(web3Url)
   if not (normalizedUrl.startsWith("https://") or
           normalizedUrl.startsWith("http://") or
           normalizedUrl.startsWith("wss://") or
           normalizedUrl.startsWith("ws://")):
-    web3Url = "ws://" & web3Url
+    normalizedUrl = "ws://" & normalizedUrl
     warn "The Web3 URL does not specify a protocol. Assuming a WebSocket server", web3Url
-    return
+
+  # We do this at the end in order to allow the warning above to print the original value
+  web3Url = normalizedUrl
 
 template toGaugeValue(x: Quantity): int64 =
   toGaugeValue(distinctBase x)
@@ -796,7 +803,8 @@ proc init*(T: type Eth1Monitor,
            db: BeaconChainDB,
            web3Urls: seq[string],
            depositContractSnapshot: DepositContractSnapshot,
-           eth1Network: Option[Eth1Network]): T =
+           eth1Network: Option[Eth1Network],
+           forcePolling: bool): T =
   doAssert web3Urls.len > 0
 
   var web3Urls = web3Urls
@@ -810,7 +818,8 @@ proc init*(T: type Eth1Monitor,
     depositContractAddress: cfg.DEPOSIT_CONTRACT_ADDRESS,
     web3Urls: web3Urls,
     eth1Network: eth1Network,
-    eth1Progress: newAsyncEvent())
+    eth1Progress: newAsyncEvent(),
+    forcePolling: forcePolling)
 
 proc safeCancel(fut: var Future[void]) =
   if not fut.isNil and not fut.finished:
@@ -826,7 +835,7 @@ proc resetState(m: Eth1Monitor) {.async.} =
   safeCancel m.runFut
 
   m.depositsChain.clear()
-  m.latestEth1BlockNumber = 0
+  m.latestEth1Block = none(FullBlockId)
 
   if m.dataProvider != nil:
     await m.dataProvider.close()
@@ -844,11 +853,15 @@ proc stop*(m: Eth1Monitor) {.async.} =
 const
   votedBlocksSafetyMargin = 50
 
+func latestEth1BlockNumber(m: Eth1Monitor): Eth1BlockNumber =
+  if m.latestEth1Block.isSome:
+    Eth1BlockNumber m.latestEth1Block.get.number
+  else:
+    Eth1BlockNumber 0
+
 func earliestBlockOfInterest(m: Eth1Monitor): Eth1BlockNumber =
   m.latestEth1BlockNumber - (2 * m.cfg.ETH1_FOLLOW_DISTANCE) - votedBlocksSafetyMargin
 
-
-
 proc syncBlockRange(m: Eth1Monitor,
                     merkleizer: ref DepositsMerkleizer,
                     fromBlock, toBlock,
@@ -1017,6 +1030,9 @@ proc syncBlockRange(m: Eth1Monitor,
 
           m.signalGenesis m.createGenesisState(genesisBlock)
 
+func init(T: type FullBlockId, blk: Eth1BlockHeader|BlockObject): T =
+  FullBlockId(number: Eth1BlockNumber blk.number, hash: blk.hash)
+
 proc startEth1Syncing(m: Eth1Monitor, delayBeforeStart: Duration) {.async.} =
   if m.state == Failed:
     await m.resetState()
@@ -1052,19 +1068,30 @@ proc startEth1Syncing(m: Eth1Monitor, delayBeforeStart: Duration) {.async.} =
       quit 1
 
   m.state = Started
+  var mustUsePolling = m.forcePolling or
+                       web3Url.startsWith("http://") or
+                       web3Url.startsWith("https://")
 
-  await m.dataProvider.onBlockHeaders do (blk: Eth1BlockHeader)
-                                         {.raises: [Defect], gcsafe.}:
-    try:
-      if blk.number.uint64 > m.latestEth1BlockNumber:
-        eth1_latest_head.set blk.number.toGaugeValue
-        m.latestEth1BlockNumber = Eth1BlockNumber blk.number
-        m.eth1Progress.fire()
-    except Exception:
-      # TODO Investigate why this exception is being raised
-      raiseAssert "AsyncEvent.fire should not raise exceptions"
-  do (err: CatchableError):
-    debug "Error while processing Eth1 block headers subscription", err = err.msg
+  if not mustUsePolling:
+    proc newBlockHeadersHandler(blk: Eth1BlockHeader)
+                               {.raises: [Defect], gcsafe.} =
+      try:
+        if blk.number.uint64 > m.latestEth1BlockNumber:
+          eth1_latest_head.set blk.number.toGaugeValue
+          m.latestEth1Block = some FullBlockId.init(blk)
+          m.eth1Progress.fire()
+      except Exception:
+        # TODO Investigate why this exception is being raised
+        raiseAssert "AsyncEvent.fire should not raise exceptions"
+
+    proc subscriptionErrorHandler(err: CatchableError)
+                                 {.raises: [Defect], gcsafe.} =
+      warn "Failed to subscribe for block headers. Switching to polling",
+            web3Url, err = err.msg
+      mustUsePolling = true
+
+    await m.dataProvider.onBlockHeaders(newBlockHeadersHandler,
+                                        subscriptionErrorHandler)
 
   let startBlock = awaitWithRetries(
     m.dataProvider.getBlockByHash(m.depositsChain.finalizedBlockHash.asBlockHash))
@@ -1099,10 +1126,23 @@ proc startEth1Syncing(m: Eth1Monitor, delayBeforeStart: Duration) {.async.} =
     if m.depositsChain.hasConsensusViolation:
       raise newException(CorruptDataProvider, "Eth1 chain contradicts Eth2 consensus")
 
-    awaitWithTimeout(m.eth1Progress.wait(), 5.minutes):
-      raise newException(CorruptDataProvider, "No eth1 chain progress for too long")
+    if mustUsePolling:
+      let blk = awaitWithRetries(
+        m.dataProvider.web3.provider.eth_getBlockByNumber(blockId("latest"), false))
 
-    m.eth1Progress.clear()
+      let fullBlockId = FullBlockId.init(blk)
+
+      if m.latestEth1Block.isSome and
+         m.latestEth1Block.get == fullBlockId:
+        await sleepAsync(m.cfg.SECONDS_PER_ETH1_BLOCK.int.seconds)
+        continue
+
+      m.latestEth1Block = some fullBlockId
+    else:
+      awaitWithTimeout(m.eth1Progress.wait(), 5.minutes):
+        raise newException(CorruptDataProvider, "No eth1 chain progress for too long")
+
+      m.eth1Progress.clear()
 
     if m.latestEth1BlockNumber <= m.cfg.ETH1_FOLLOW_DISTANCE:
       continue
@@ -1182,7 +1222,8 @@ when hasGenesisDetection:
              web3Urls: seq[string],
              depositContractAddress: Eth1Address,
              depositContractDeployedAt: BlockHashOrNumber,
-             eth1Network: Option[Eth1Network]): Future[Result[T, string]] {.async.} =
+             eth1Network: Option[Eth1Network],
+             forcePolling: bool): Future[Result[T, string]] {.async.} =
     doAssert web3Urls.len > 0
     try:
       var urlIdx = 0
@@ -1226,7 +1267,8 @@ when hasGenesisDetection:
         web3Urls,
         depositContractAddress,
         depositContractSnapshot,
-        eth1Network)
+        eth1Network,
+        forcePolling)
 
       for i in 0 ..< db.genesisDeposits.len:
         monitor.produceDerivedData db.genesisDeposits.get(i)

beacon_chain/nimbus_beacon_node.nim

@@ -224,7 +224,8 @@ proc init*(T: type BeaconNode,
           db,
           config.web3Urls,
           depositContractDeployedAt,
-          eth1Network)
+          eth1Network,
+          config.web3ForcePolling)
 
         if eth1MonitorRes.isErr:
           fatal "Failed to start Eth1 monitor",
@@ -342,7 +343,8 @@ proc init*(T: type BeaconNode,
       db,
       config.web3Urls,
       genesisDepositsSnapshot,
-      eth1Network)
+      eth1Network,
+      config.web3ForcePolling)
 
   let rpcServer = if config.rpcEnabled:
     RpcServer.init(config.rpcAddress, config.rpcPort)