ICU-23247 CLDR-to-ICU: using parallel sometimes fails on Windows

Author: mihnita

tools/cldr/cldr-to-icu/src/main/java/org/unicode/icu/tool/cldrtoicu/DependencyGraph.java

@@ -24,7 +24,7 @@ public DependencyGraph(String cldrVersion) {
         this.cldrVersion = checkNotNull(cldrVersion);
     }
 
-    void addParent(String localeId, String parentId) {
+    synchronized void addParent(String localeId, String parentId) {
         // Aliases take priority (since they can be forced and will replace empty files). Note
         // however that this only happens in a tiny number of places due to the somewhat "hacky"
         // forced aliases, and in future it's perfectly possibly that there would never be an

tools/cldr/cldr-to-icu/src/main/java/org/unicode/icu/tool/cldrtoicu/IcuTextWriter.java

@@ -46,7 +46,16 @@ static void writeToFile(
             IcuData icuData, Path outDir, List<String> header, boolean allowOverwrite) {
 
         try {
-            Files.createDirectories(outDir);
+            try {
+                Files.createDirectories(outDir);
+            } catch (IOException e) {
+                // On Windows, concurrent directory creation by parallel threads can transiently
+                // produce AccessDeniedException even when the directory already exists. If the
+                // directory is now present (created by another thread), treat it as success.
+                if (!Files.isDirectory(outDir)) {
+                    throw e;
+                }
+            }
             Path file = outDir.resolve(icuData.getName() + ".txt");
             OpenOption[] fileOptions = allowOverwrite ? OVERWRITE_FILES : ONLY_NEW_FILES;
             try (Writer w = Files.newBufferedWriter(file, UTF_8, fileOptions);

tools/cldr/cldr-to-icu/src/main/java/org/unicode/icu/tool/cldrtoicu/LdmlConverter.java

@@ -30,6 +30,7 @@
 import com.google.common.collect.LinkedListMultimap;
 import com.google.common.collect.ListMultimap;
 import com.google.common.collect.Maps;
+import com.google.common.collect.Multimaps;
 import com.google.common.collect.SetMultimap;
 import com.google.common.collect.Sets;
 import com.google.common.io.CharStreams;
@@ -287,7 +288,8 @@ private void processLdml() {
         Map<IcuLocaleDir, DependencyGraph> graphMetadata = new HashMap<>();
         splitDirs.forEach(d -> graphMetadata.put(d, new DependencyGraph(cldrVersion)));
 
-        SetMultimap<IcuLocaleDir, String> writtenLocaleIds = HashMultimap.create();
+        SetMultimap<IcuLocaleDir, String> writtenLocaleIds =
+                Multimaps.synchronizedSetMultimap(HashMultimap.create());
         Path baseDir = config.getOutputDir();
 
         System.out.println("processing standard ldml files");
@@ -650,7 +652,12 @@ private Path createDirectory(Path dir) {
         try {
             Files.createDirectories(dir);
         } catch (IOException e) {
-            throw new RuntimeException("cannot create directory: " + dir, e);
+            // On Windows, concurrent directory creation by parallel threads can transiently
+            // produce AccessDeniedException even when the directory already exists. If the
+            // directory is now present (created by another thread), treat it as success.
+            if (!Files.isDirectory(dir)) {
+                throw new RuntimeException("cannot create directory: " + dir, e);
+            }
         }
         return dir;
     }