Write .meteor-portable-2.json files synchronously.

Ben Newman · Ben Newman · commit 4e4e204ab089 · 2018-01-18T16:26:05.000-05:00
Previously these files were written asynchronously in an attempt to
improve performance, since the success of the write is not critical.
While I stand by my claim that it's acceptable for these writes to fail, I
noticed recently that the async write was failing very often (resulting in
an empty .meteor-portable-2.json file). Switching to sync semantics
eliminated that problem with no noticeable loss of performance. In fact,
overall performance is likely better because of the future work saved by a
successful write.
diff --git a/tools/isobuild/meteor-npm.js b/tools/isobuild/meteor-npm.js
@@ -528,21 +528,20 @@ const isPortable = Profile("meteorNpm.isPortable", dir => {
         isPortable(files.pathJoin(dir, itemName)));
 
   if (canCache) {
-    // Write the .meteor-portable file asynchronously, and don't worry
-    // if it fails, e.g. because the file system is read-only (#6591).
-    // Failing to write the file only means more work next time.
-    fs.writeFile(
-      portableFile,
-      JSON.stringify(result) + "\n",
-      error => {
-        // Once the asynchronous write finishes (successful or not), we no
-        // longer need to cache the written value in memory.
-        delete portableCache[portableFile];
-      },
-    );
+    try {
+      files.writeFile(
+        portableFile,
+        JSON.stringify(result) + "\n",
+        "utf8"
+      );
+    } catch (ignored) {
+      // Don't worry if the write fails, e.g. because the file system is
+      // read-only (#6591). Failing to write the file only means more work
+      // next time.
+    }
 
-    // Cache the result immediately in memory so that the asynchronous
-    // write won't confuse synchronous optimisticReadJsonOrNull calls.
+    // Cache the result immediately in memory so we don't have to wait for
+    // file change notifications to invalidate optimisticReadJsonOrNull.
     portableCache[portableFile] = result;
   }
 
