Better behavior on parallel downloads

ehmicky · Aug 11, 2019 · 2314791 · 2314791
1 parent b5fb483
commit 2314791
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Showing 2 changed files with 22 additions and 1 deletion.
diff --git a/src/download.js b/src/download.js
@@ -41,7 +41,7 @@ const safeDownload = async function(version, outputDir, nodePath) {
   await downloadRuntime(version, tmpFile)
 
   await createOutputDir(outputDir)
-  await pRename(tmpFile, nodePath)
+  await moveFile(tmpFile, nodePath)
 }
 
 // Retrieve the Node binary from the Node website and persist it.
@@ -61,3 +61,12 @@ const createOutputDir = async function(outputDir) {
 
   await makeDir(outputDir)
 }
+
+const moveFile = async function(tmpFile, nodePath) {
+  // Another parallel download might have been running
+  if (await pathExists(nodePath)) {
+    return
+  }
+
+  await pRename(tmpFile, nodePath)
+}
diff --git a/test/download.js b/test/download.js
@@ -44,6 +44,18 @@ test('Can re-use same outputDir', async t => {
   await removeOutputDir(nodePath)
 })
 
+test('Parallel downloads', async t => {
+  const outputDir = getOutputDir()
+  const [nodePath, nodePathA] = await Promise.all([
+    getNode(TEST_VERSION, outputDir),
+    getNode(TEST_VERSION, outputDir),
+  ])
+
+  t.is(nodePath, nodePathA)
+
+  await removeOutput(nodePath)
+})
+
 test('Writes atomically', async t => {
   const outputDir = getOutputDir()