Merge pull request #6461 from NomicFoundation/add-mutex-compiler-list

Add mutex when downloading compiler list

Author: ChristopherDedominici

.changeset/polite-crabs-relax.md

@@ -0,0 +1,6 @@
+---
+"@nomicfoundation/hardhat-utils": patch
+"hardhat": patch
+---
+
+Added a mutex to synchronize compiler list downloads

v-next/hardhat-utils/src/synchronization.ts

@@ -4,8 +4,8 @@
 // ATTENTION: in the current implementation, there's still a risk of two processes running simultaneously.
 // For example, if processA has locked the mutex and is running, processB will wait.
 // During this wait, processB continuously checks the elapsed time since the mutex lock file was created.
-// If an excessive amount of time has passed, processB will assume ownership of the mutex to avoid stale locks.
-// However, there's a possibility that processB might take ownership because the mutex creation file is outdated, even though processA is still running
+// If an excessive amount of time has passed, processB will assume ownership of the mutex to prevent stale locks, even if processA is still running.
+// As a result, two processes will be running simultaneously in what is theoretically a mutex-locked section.
 
 import fs from "node:fs";
 import os from "node:os";

v-next/hardhat/src/internal/builtin-plugins/solidity/build-system/compiler/downloader.ts

@@ -138,7 +138,8 @@ export class CompilerDownloaderImplementation implements CompilerDownloader {
   readonly #compilersDir: string;
   readonly #downloadFunction: typeof download;
 
-  readonly #mutex = new MultiProcessMutex("compiler-download");
+  readonly #mutexCompiler = new MultiProcessMutex("compiler-download");
+  readonly #mutexCompilerList = new MultiProcessMutex("compiler-download-list");
 
   /**
    * Use CompilerDownloader.getConcurrencySafeDownloader instead
@@ -156,21 +157,23 @@ export class CompilerDownloaderImplementation implements CompilerDownloader {
   public async updateCompilerListIfNeeded(
     versions: Set<string>,
   ): Promise<void> {
-    if (await this.#shouldDownloadCompilerList(versions)) {
-      try {
-        log(
-          `Downloading the list of solc builds for platform ${this.#platform}`,
-        );
-        await this.#downloadCompilerList();
-      } catch (e) {
-        ensureError(e);
-
-        throw new HardhatError(
-          HardhatError.ERRORS.SOLIDITY.VERSION_LIST_DOWNLOAD_FAILED,
-          e,
-        );
+    await this.#mutexCompilerList.use(async () => {
+      if (await this.#shouldDownloadCompilerList(versions)) {
+        try {
+          log(
+            `Downloading the list of solc builds for platform ${this.#platform}`,
+          );
+          await this.#downloadCompilerList();
+        } catch (e) {
+          ensureError(e);
+
+          throw new HardhatError(
+            HardhatError.ERRORS.SOLIDITY.VERSION_LIST_DOWNLOAD_FAILED,
+            e,
+          );
+        }
       }
-    }
+    });
   }
 
   public async isCompilerDownloaded(version: string): Promise<boolean> {
@@ -186,7 +189,7 @@ export class CompilerDownloaderImplementation implements CompilerDownloader {
     // This is because the mutex blocks access until a compiler has been fully downloaded, preventing any new process
     // from checking whether that version of the compiler exists. Without mutex it might incorrectly
     // return false, indicating that the compiler isn't present, even though it is currently being downloaded.
-    return this.#mutex.use(async () => {
+    return this.#mutexCompiler.use(async () => {
       const isCompilerDownloaded = await this.isCompilerDownloaded(version);
 
       if (isCompilerDownloaded === true) {