lib: Create simple block watcher without blockstream

.gitignore

@@ -314,7 +314,6 @@ develop-eggs/
 downloads/
 eggs/
 .eggs/
-lib/
 lib64/
 parts/
 sdist/

index.js

@@ -3,6 +3,7 @@ const ethers = require("ethers");
 const BlockWatcher = require("./lib/blockWatcher");
 const RoundInitializer = require("./lib/roundInitializer");
 const TxSigner = require("./lib/txSigner");
+const SimpleBlockWatcher = require("./lib/simpleBlockWatcher");
 
 const ROUNDS_MANAGER_ADDRESSES = {
   1: ["0x3984fc4ceeef1739135476f625d36d6c35c40dc3"],
@@ -23,9 +24,9 @@ const ROUNDS_MANAGER_ADDRESSES = {
 
 const argv = require("yargs")
   .usage(
-    "Usage: $0 --rinkeby --provider [provider URL] --account [Ethereum account] --password [Ethereum account password] --datadir [data directory] --roundsManagerAddr [RoundsManager addresses]"
+    "Usage: $0 --rinkeby --provider [provider URL] --account [Ethereum account] --password [Ethereum account password] --datadir [data directory] --roundsManagerAddr [RoundsManager addresses] --pollingInterval [block polling interval in ms] --noBlockstream"
   )
-  .boolean(["rinkeby"])
+  .boolean(["rinkeby", "noBlockstream"])
   .string(["provider", "account", "roundsManagerAddr", "password"])
   .default("roundsManagerAddr", "")
   .demandOption(["account", "datadir"])
@@ -58,7 +59,9 @@ const run = async () => {
     roundsManagerAddrs = ROUNDS_MANAGER_ADDRESSES[network.chainId];
   }
 
-  const blockWatcher = new BlockWatcher(provider);
+  const blockWatcher = argv.noBlockstream
+    ? new SimpleBlockWatcher(provider, argv.pollingInterval)
+    : new BlockWatcher(provider, argv.pollingInterval);
   const roundInitializer = new RoundInitializer(
     provider,
     roundsManagerAddrs,

lib/blockWatcher.js

@@ -8,7 +8,7 @@ module.exports = class BlockWatcher {
         pollingInterval
     ) {
         this.provider = provider
-        this.pollingInterval = pollingInterval === undefined ? DEFAULT_POLLING_INTERVAL_MS : pollingInterval
+        this.pollingInterval = pollingInterval || DEFAULT_POLLING_INTERVAL_MS
         this.blockAndLogStreamer = undefined
         this.onBlockAddedSubscriptionToken = undefined
         this.blockAndLogStreamerIntervalId = undefined

lib/simpleBlockWatcher.js

@@ -0,0 +1,64 @@
+const DEFAULT_POLLING_INTERVAL_MS = 13000
+
+/**
+ * Block watcher that just fetches the last block and triggers the callback if it changed. This is opposed to the
+ * blockstream implementation that fetches all blocks since the previous one. This is needed for some testnet providers
+ * that throttle their API response times, making the default blockstreamer not keep up with all blocks produced.
+ */
+module.exports = class SimpleBlockWatcher {
+    constructor(
+        provider,
+        pollingInterval
+    ) {
+        this.provider = provider
+        this.pollingInterval = pollingInterval || DEFAULT_POLLING_INTERVAL_MS
+
+        this.lastBlockNumber = undefined
+        this.intervalId = undefined
+    }
+
+    subscribe(cb) {
+        this.intervalId = this.setIntervalAsyncFn(async () => {
+            const latestBlock = await this.provider.getBlock("latest")
+
+            if (!this.lastBlockNumber || latestBlock.number > this.lastBlockNumber) {
+                this.lastBlockNumber = latestBlock.number
+
+                await cb(latestBlock)
+            }
+        }, this.pollingInterval, this.onError.bind(this))
+    }
+
+    unsubscribe() {
+        this.clearIntervalAsyncFn(this.intervalId)
+    }
+
+    onError(err) {
+        console.warn("Block watcher error:", err)
+    }
+
+    // Utilities
+
+    setIntervalAsyncFn(fn, intervalMs, onError) {
+        let isRunning = false
+        const intervalId = setInterval(async () => {
+            if (isRunning) {
+                return
+            } else {
+                isRunning = true
+                try {
+                    await fn()
+                } catch (err) {
+                    onError(err)
+                }
+                isRunning = false
+            }
+        }, intervalMs)
+
+        return intervalId
+    }
+
+    clearIntervalAsyncFn(intervalId) {
+        clearInterval(intervalId)
+    }
+}