From 56b6f79f97c6227eec960b5d7983277eca2d3d7d Mon Sep 17 00:00:00 2001
From: Mononaut <github@monospace.live>
Date: Wed, 7 Dec 2022 14:51:26 -0600
Subject: [PATCH] improve thread error handling

---
 backend/src/api/mempool-blocks.ts | 51 ++++++++++++++++++++++---------
 1 file changed, 37 insertions(+), 14 deletions(-)

diff --git a/backend/src/api/mempool-blocks.ts b/backend/src/api/mempool-blocks.ts
index 62bdc8f1b..d94ed77bd 100644
--- a/backend/src/api/mempool-blocks.ts
+++ b/backend/src/api/mempool-blocks.ts
@@ -158,8 +158,11 @@ class MempoolBlocks {
       };
     });
 
+    // (re)initialize tx selection worker thread
     if (!this.txSelectionWorker) {
       this.txSelectionWorker = new Worker(path.resolve(__dirname, './tx-selection-worker.js'));
+      // if the thread throws an unexpected error, or exits for any other reason,
+      // reset worker state so that it will be re-initialized on the next run
       this.txSelectionWorker.once('error', () => {
         this.txSelectionWorker = null;
       });
@@ -169,15 +172,25 @@ class MempoolBlocks {
     }
 
     // run the block construction algorithm in a separate thread, and wait for a result
-    const workerResultPromise = new Promise<{ blocks: ThreadTransaction[][], clusters: { [root: string]: string[] } }>((resolve) => {
-      this.txSelectionWorker?.once('message', (result): void => {
-        resolve(result);
+    let threadErrorListener;
+    try {
+      const workerResultPromise = new Promise<{ blocks: ThreadTransaction[][], clusters: { [root: string]: string[] } }>((resolve, reject) => {
+        threadErrorListener = reject;
+        this.txSelectionWorker?.once('message', (result): void => {
+          resolve(result);
+        });
+        this.txSelectionWorker?.once('error', reject);
       });
-    });
-    this.txSelectionWorker.postMessage({ type: 'set', mempool: strippedMempool });
-    const { blocks, clusters } = await workerResultPromise;
+      this.txSelectionWorker.postMessage({ type: 'set', mempool: strippedMempool });
+      const { blocks, clusters } = await workerResultPromise;
 
-    this.processBlockTemplates(newMempool, blocks, clusters);
+      this.processBlockTemplates(newMempool, blocks, clusters);
+
+      // clean up thread error listener
+      this.txSelectionWorker?.removeListener('error', threadErrorListener);
+    } catch (e) {
+      logger.err('makeBlockTemplates failed. ' + (e instanceof Error ? e.message : e));
+    }
   }
 
   public async updateBlockTemplates(newMempool: { [txid: string]: TransactionExtended }, added: TransactionExtended[], removed: string[]): Promise<void> {
@@ -199,15 +212,25 @@ class MempoolBlocks {
     });
 
     // run the block construction algorithm in a separate thread, and wait for a result
-    const workerResultPromise = new Promise<{ blocks: ThreadTransaction[][], clusters: { [root: string]: string[] } }>((resolve) => {
-      this.txSelectionWorker?.once('message', (result): void => {
-        resolve(result);
+    let threadErrorListener;
+    try {
+      const workerResultPromise = new Promise<{ blocks: ThreadTransaction[][], clusters: { [root: string]: string[] } }>((resolve, reject) => {
+        threadErrorListener = reject;
+        this.txSelectionWorker?.once('message', (result): void => {
+          resolve(result);
+        });
+        this.txSelectionWorker?.once('error', reject);
       });
-    });
-    this.txSelectionWorker.postMessage({ type: 'update', added: addedStripped, removed });
-    const { blocks, clusters } = await workerResultPromise;
+      this.txSelectionWorker.postMessage({ type: 'update', added: addedStripped, removed });
+      const { blocks, clusters } = await workerResultPromise;
 
-    this.processBlockTemplates(newMempool, blocks, clusters);
+      this.processBlockTemplates(newMempool, blocks, clusters);
+
+      // clean up thread error listener
+      this.txSelectionWorker?.removeListener('error', threadErrorListener);
+    } catch (e) {
+      logger.err('updateBlockTemplates failed. ' + (e instanceof Error ? e.message : e));
+    }
   }
 
   private processBlockTemplates(mempool, blocks, clusters): void {