Merge pull request #3576 from mempool/mononaut/fix-difficulty-adjustment

Fix difficulty adjustment bugs

backend/src/api/difficulty-adjustment.ts

@@ -24,12 +24,11 @@ export function calcDifficultyAdjustment(
   network: string,
   latestBlockTimestamp: number,
 ): DifficultyAdjustment {
-  const ESTIMATE_LAG_BLOCKS = 146; // For first 7.2% of epoch, don't estimate.
   const EPOCH_BLOCK_LENGTH = 2016; // Bitcoin mainnet
   const BLOCK_SECONDS_TARGET = 600; // Bitcoin mainnet
   const TESTNET_MAX_BLOCK_SECONDS = 1200; // Bitcoin testnet
 
-  const diffSeconds = nowSeconds - DATime;
+  const diffSeconds = Math.max(0, nowSeconds - DATime);
   const blocksInEpoch = (blockHeight >= 0) ? blockHeight % EPOCH_BLOCK_LENGTH : 0;
   const progressPercent = (blockHeight >= 0) ? blocksInEpoch / EPOCH_BLOCK_LENGTH * 100 : 100;
   const remainingBlocks = EPOCH_BLOCK_LENGTH - blocksInEpoch;
@@ -37,18 +36,16 @@ export function calcDifficultyAdjustment(
   const expectedBlocks = diffSeconds / BLOCK_SECONDS_TARGET;
 
   let difficultyChange = 0;
-  let timeAvgSecs = diffSeconds / blocksInEpoch;
-  // Only calculate the estimate once we have 7.2% of blocks in current epoch
-  if (blocksInEpoch >= ESTIMATE_LAG_BLOCKS) {
-    difficultyChange = (BLOCK_SECONDS_TARGET / timeAvgSecs - 1) * 100;
-    // Max increase is x4 (+300%)
-    if (difficultyChange > 300) {
-      difficultyChange = 300;
-    }
-    // Max decrease is /4 (-75%)
-    if (difficultyChange < -75) {
-      difficultyChange = -75;
-    }
+  let timeAvgSecs = blocksInEpoch ? diffSeconds / blocksInEpoch : BLOCK_SECONDS_TARGET;
+
+  difficultyChange = (BLOCK_SECONDS_TARGET / timeAvgSecs - 1) * 100;
+  // Max increase is x4 (+300%)
+  if (difficultyChange > 300) {
+    difficultyChange = 300;
+  }
+  // Max decrease is /4 (-75%)
+  if (difficultyChange < -75) {
+    difficultyChange = -75;
   }
 
   // Testnet difficulty is set to 1 after 20 minutes of no blocks,

backend/src/api/websocket-handler.ts

@@ -211,6 +211,7 @@ class WebsocketHandler {
     if (!_blocks) {
       _blocks = blocks.getBlocks().slice(-config.MEMPOOL.INITIAL_BLOCKS_AMOUNT);
     }
+    const da = difficultyAdjustment.getDifficultyAdjustment();
     return {
       'mempoolInfo': memPool.getMempoolInfo(),
       'vBytesPerSecond': memPool.getVBytesPerSecond(),
@@ -220,7 +221,7 @@ class WebsocketHandler {
       'transactions': memPool.getLatestTransactions(),
       'backendInfo': backendInfo.getBackendInfo(),
       'loadingIndicators': loadingIndicators.getLoadingIndicators(),
-      'da': difficultyAdjustment.getDifficultyAdjustment(),
+      'da': da?.previousTime ? da : undefined,
       'fees': feeApi.getRecommendedFee(),
       ...this.extraInitProperties
     };
@@ -278,7 +279,9 @@ class WebsocketHandler {
         response['mempoolInfo'] = mempoolInfo;
         response['vBytesPerSecond'] = vBytesPerSecond;
         response['transactions'] = newTransactions.slice(0, 6).map((tx) => Common.stripTransaction(tx));
-        response['da'] = da;
+        if (da?.previousTime) {
+          response['da'] = da;
+        }
         response['fees'] = recommendedFees;
       }
 
@@ -505,7 +508,7 @@ class WebsocketHandler {
       const response = {
         'block': block,
         'mempoolInfo': memPool.getMempoolInfo(),
-        'da': da,
+        'da': da?.previousTime ? da : undefined,
         'fees': fees,
       };
 

backend/src/mempool.interfaces.ts

@@ -309,9 +309,11 @@ export interface IDifficultyAdjustment {
   remainingBlocks: number;
   remainingTime: number;
   previousRetarget: number;
+  previousTime: number;
   nextRetargetHeight: number;
   timeAvg: number;
   timeOffset: number;
+  expectedBlocks: number;
 }
 
 export interface IndexedDifficultyAdjustment {