[GitHub] sohami commented on a change in pull request #1296: DRILL-5365: Prevent plugin config from changing default fs. Make DrillFileSystem Immutable.

[GitBox <gi...@apache.org>]

sohami commented on a change in pull request #1296: DRILL-5365: Prevent plugin config from changing default fs. Make DrillFileSystem Immutable.
URL: https://github.com/apache/drill/pull/1296#discussion_r213507759
 
 

 ##########
 File path: exec/java-exec/src/main/java/org/apache/drill/exec/store/dfs/DrillFileSystem.java
 ##########
 @@ -79,32 +77,56 @@
 
   private final ConcurrentMap<DrillFSDataInputStream, DebugStackTrace> openedFiles = Maps.newConcurrentMap();
 
+  private final Configuration fsConf;
   private final FileSystem underlyingFs;
   private final OperatorStats operatorStats;
   private final CompressionCodecFactory codecFactory;
 
+  private boolean initialized = false;
+
   public DrillFileSystem(Configuration fsConf) throws IOException {
     this(fsConf, null);
   }
 
   public DrillFileSystem(Configuration fsConf, OperatorStats operatorStats) throws IOException {
-    this.underlyingFs = FileSystem.get(fsConf);
-    this.codecFactory = new CompressionCodecFactory(fsConf);
+    // Configuration objects are mutable, and the underlying FileSystem object may directly use a passed in Configuration.
+    // In order to avoid scenarios where a Configuration can change after a DrillFileSystem is created, we make a copy
+    // of the Configuration.
+    this.fsConf = new Configuration(fsConf);
+    this.underlyingFs = FileSystem.get(this.fsConf);
+    this.codecFactory = new CompressionCodecFactory(this.fsConf);
     this.operatorStats = operatorStats;
+    this.initialized = true;
+  }
+
+  private void throwUnsupported() {
+    throw new UnsupportedOperationException(DrillFileSystem.class.getCanonicalName() + " is immutable and should not be changed after creation.");
   }
 
+  /**
+   * This method should never be used on {@link DrillFileSystem} since {@link DrillFileSystem} is immutable.
+   * {@inheritDoc}
+   * @throws UnsupportedOperationException when called.
+   */
   @Override
   public void setConf(Configuration conf) {
-    // Guard against setConf(null) call that is called as part of superclass constructor (Configured) of the
-    // DrillFileSystem, at which point underlyingFs is null.
-    if (conf != null && underlyingFs != null) {
-      underlyingFs.setConf(conf);
+    if (!initialized) {
 
 Review comment:
   We can still use `(underlyingFs != null)` check and get rid of the `initialized` flag. New check can be:
   
   ```
   if (underlyingFs != null) {
      throwUnsupported();
   }
   ```

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