[FLINK-16191][state backends] Improve error message on Windows when R…

…ocksDB is give a too long path.

flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBOperationUtils.java

@@ -24,6 +24,7 @@
 import org.apache.flink.runtime.state.RegisteredStateMetaInfoBase;
 import org.apache.flink.util.FlinkRuntimeException;
 import org.apache.flink.util.IOUtils;
+import org.apache.flink.util.OperatingSystem;
 import org.apache.flink.util.Preconditions;
 import org.apache.flink.util.function.LongFunctionWithException;
 
@@ -80,6 +81,10 @@ public static RocksDB openDB(
  } catch (RocksDBException e) {
  IOUtils.closeQuietly(columnFamilyOptions);
  columnFamilyDescriptors.forEach((cfd) -> IOUtils.closeQuietly(cfd.getOptions()));
+
+ // improve error reporting on Windows
+ throwExceptionIfPathLengthExceededOnWindows(path, e);
+
  throw new IOException("Error while opening RocksDB instance.", e);
  }
 
@@ -207,4 +212,16 @@ public static OpaqueMemoryResource<RocksDBSharedResources> allocateSharedCachesI
  throw new IOException("Failed to acquire shared cache resource for RocksDB", e);
  }
  }
+
+ private static void throwExceptionIfPathLengthExceededOnWindows(String path, Exception cause) throws IOException {
+ // max directory path length on Windows is 247.
+ // the maximum path length is 260, subtracting one file name length (12 chars) and one NULL terminator.
+ final int maxWinDirPathLen = 247;
+
+ if (path.length() > maxWinDirPathLen && OperatingSystem.isWindows()) {
+ throw new IOException(String.format(
+ "The directory path length (%d) is longer than the directory path length limit for Windows (%d): %s",
+ path.length(), maxWinDirPathLen, path), cause);
+ }
+ }
 }

flink-state-backends/flink-statebackend-rocksdb/src/test/java/org/apache/flink/contrib/streaming/state/RocksDBOperationsUtilsTest.java

@@ -0,0 +1,88 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http:https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.contrib.streaming.state;
+
+import org.apache.flink.util.OperatingSystem;
+
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+import org.rocksdb.ColumnFamilyOptions;
+import org.rocksdb.DBOptions;
+import org.rocksdb.NativeLibraryLoader;
+import org.rocksdb.RocksDB;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.util.Collections;
+
+import static org.hamcrest.Matchers.containsString;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assume.assumeTrue;
+
+/**
+ * Tests for the {@link RocksDBOperationUtils}.
+ */
+public class RocksDBOperationsUtilsTest {
+
+ @ClassRule
+ public static final TemporaryFolder TMP_DIR = new TemporaryFolder();
+
+ @BeforeClass
+ public static void loadRocksLibrary() throws Exception {
+ NativeLibraryLoader.getInstance().loadLibrary(TMP_DIR.newFolder().getAbsolutePath());
+ }
+
+ @Test
+ public void testPathExceptionOnWindows() throws Exception {
+ assumeTrue(OperatingSystem.isWindows());
+
+ final File folder = TMP_DIR.newFolder();
+ final File rocksDir = new File(folder, getLongString(247 - folder.getAbsolutePath().length()));
+
+ Files.createDirectories(rocksDir.toPath());
+
+ try (DBOptions dbOptions = new DBOptions().setCreateIfMissing(true);
+ ColumnFamilyOptions colOptions = new ColumnFamilyOptions()) {
+
+ RocksDB rocks = RocksDBOperationUtils.openDB(
+ rocksDir.getAbsolutePath(),
+ Collections.emptyList(),
+ Collections.emptyList(),
+ colOptions, dbOptions);
+ rocks.close();
+
+ // do not provoke a test failure if this passes, because some setups may actually
+ // support long paths, in which case: great!
+ }
+ catch (IOException e) {
+ assertThat(e.getMessage(), containsString("longer than the directory path length limit for Windows"));
+ }
+ }
+
+ private static String getLongString(int numChars) {
+ final StringBuilder builder = new StringBuilder();
+ for (int i = numChars; i > 0; --i) {
+ builder.append('a');
+ }
+ return builder.toString();
+ }
+}