vdiravka commented on a change in pull request #2463:
URL: https://github.com/apache/drill/pull/2463#discussion_r809090421



##########
File path: 
exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/compression/AirliftBytesInputCompressor.java
##########
@@ -159,13 +160,13 @@ public void decompress(ByteBuffer input, int 
compressedSize, ByteBuffer output,
 
   @Override
   public void release() {
-    logger.debug(
-        "will release {} allocated buffers.",
-        this.allocatedBuffers.size()
-    );
+    int bufCount  = allocatedBuffers.size();
 
-    while (!this.allocatedBuffers.isEmpty()) {
-      this.allocator.release(allocatedBuffers.pop());
+    // LIFO release order to try to reduce memory fragmentation.
+    while (!allocatedBuffers.isEmpty()) {
+      allocator.release(allocatedBuffers.pop());
     }
+
+    logger.debug("released {} allocated buffers", bufCount);

Review comment:
       We possibly can assert or log the actual `allocatedBuffers.size()` to 
make sure allocated buffers are released

##########
File path: 
exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/compression/DrillCompressionCodecFactory.java
##########
@@ -50,17 +52,31 @@
 
   // The set of codecs to be handled by aircompressor
   private static final Set<CompressionCodecName> AIRCOMPRESSOR_CODECS = new 
HashSet<>(
-      Arrays.asList(CompressionCodecName.LZ4, CompressionCodecName.LZO,
-          CompressionCodecName.SNAPPY, CompressionCodecName.ZSTD));
+      Arrays.asList(
+        CompressionCodecName.LZ4,
+        CompressionCodecName.LZO,
+        CompressionCodecName.SNAPPY,
+        CompressionCodecName.ZSTD
+      )
+  );
 
-  // pool of reused aircompressor compressors (parquet-mr's factory has its 
own)
+  // pool of reusable thread-safe aircompressor compressors (parquet-mr's 
factory

Review comment:
       ```suggestion
     // pool of reusable thread-safe aircompressor compressors (parquet-mr's 
factory has its own)
   ```
   

##########
File path: 
exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/compression/DrillCompressionCodecFactory.java
##########
@@ -50,17 +52,31 @@
 
   // The set of codecs to be handled by aircompressor
   private static final Set<CompressionCodecName> AIRCOMPRESSOR_CODECS = new 
HashSet<>(
-      Arrays.asList(CompressionCodecName.LZ4, CompressionCodecName.LZO,
-          CompressionCodecName.SNAPPY, CompressionCodecName.ZSTD));
+      Arrays.asList(
+        CompressionCodecName.LZ4,
+        CompressionCodecName.LZO,
+        CompressionCodecName.SNAPPY,
+        CompressionCodecName.ZSTD
+      )
+  );
 
-  // pool of reused aircompressor compressors (parquet-mr's factory has its 
own)
+  // pool of reusable thread-safe aircompressor compressors (parquet-mr's 
factory
+  // has its own)
   private final Map<CompressionCodecName, AirliftBytesInputCompressor> 
airCompressors = new HashMap<>();
 
   // fallback parquet-mr compression codec factory
-  private CompressionCodecFactory parqCodecFactory;
+  private final CompressionCodecFactory parqCodecFactory;
 
   // direct memory allocator to be used during (de)compression
-  private ByteBufferAllocator allocator;
+  private final ByteBufferAllocator allocator;
+
+  // Start: members for working around a gzip concurrency bug c.f. DRILL-8139
+  private final Deque<CompressionCodecFactory> singleUseFactories;
+

Review comment:
       ```suggestion
   ```

##########
File path: 
exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/compression/DrillCompressionCodecFactory.java
##########
@@ -80,38 +99,56 @@ public DrillCompressionCodecFactory(Configuration config, 
ByteBufferAllocator al
   }
 
   @Override
-  public BytesInputCompressor getCompressor(CompressionCodecName codecName) {
+  public synchronized BytesInputCompressor getCompressor(CompressionCodecName 
codecName) {
     if (AIRCOMPRESSOR_CODECS.contains(codecName)) {
       return airCompressors.computeIfAbsent(
           codecName,
           c -> new AirliftBytesInputCompressor(codecName, allocator)
       );
+    } else if (codecName != CompressionCodecName.SNAPPY) {
+      // Work around PARQUET-2126: construct a new codec factory every time to
+      // avoid a concurrrency bug c.f. DRILL-8139. Remove once PARQUET-2126 is
+      // fixed.  Snappy is immune because of the thread safety in the Xerial 
lib.
+      CompressionCodecFactory ccf = 
CodecFactory.createDirectCodecFactory(config, allocator, pageSize);
+      // hold onto a reference for later release()
+      singleUseFactories.add(ccf);
+      return ccf.getCompressor(codecName);
     } else {
       return parqCodecFactory.getCompressor(codecName);
     }
   }
 
   @Override
-  public BytesInputDecompressor getDecompressor(CompressionCodecName 
codecName) {
+  public synchronized BytesInputDecompressor 
getDecompressor(CompressionCodecName codecName) {
     if (AIRCOMPRESSOR_CODECS.contains(codecName)) {
       return airCompressors.computeIfAbsent(
           codecName,
           c -> new AirliftBytesInputCompressor(codecName, allocator)
       );
+    } else if (codecName != CompressionCodecName.SNAPPY) {

Review comment:
       Looks like existed `else` block starts to be never reached:
   When `codecName` is SNAPPY or other from `AIRCOMPRESSOR_CODECS` we will pass 
through the first condition 
   and for all other cases we will pass through the new `else if` block. If 
that by design the logic can be simplified: `else if` -> `else`. `return 
parqCodecFactory.getDecompressor(codecName);` possibly can be commented.
   
   The same for `#getCompressor` method

##########
File path: 
exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/compression/DrillCompressionCodecFactory.java
##########
@@ -80,38 +99,56 @@ public DrillCompressionCodecFactory(Configuration config, 
ByteBufferAllocator al
   }
 
   @Override
-  public BytesInputCompressor getCompressor(CompressionCodecName codecName) {
+  public synchronized BytesInputCompressor getCompressor(CompressionCodecName 
codecName) {
     if (AIRCOMPRESSOR_CODECS.contains(codecName)) {
       return airCompressors.computeIfAbsent(
           codecName,
           c -> new AirliftBytesInputCompressor(codecName, allocator)
       );
+    } else if (codecName != CompressionCodecName.SNAPPY) {
+      // Work around PARQUET-2126: construct a new codec factory every time to
+      // avoid a concurrrency bug c.f. DRILL-8139. Remove once PARQUET-2126 is

Review comment:
       ```suggestion
        // avoid a concurrrency bug c.f. DRILL-8139. TODO: Remove once 
PARQUET-2126 is
   Write Preview
   ```

##########
File path: 
exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/compression/DrillCompressionCodecFactory.java
##########
@@ -50,17 +52,31 @@
 
   // The set of codecs to be handled by aircompressor
   private static final Set<CompressionCodecName> AIRCOMPRESSOR_CODECS = new 
HashSet<>(
-      Arrays.asList(CompressionCodecName.LZ4, CompressionCodecName.LZO,
-          CompressionCodecName.SNAPPY, CompressionCodecName.ZSTD));
+      Arrays.asList(
+        CompressionCodecName.LZ4,
+        CompressionCodecName.LZO,
+        CompressionCodecName.SNAPPY,
+        CompressionCodecName.ZSTD
+      )
+  );
 
-  // pool of reused aircompressor compressors (parquet-mr's factory has its 
own)
+  // pool of reusable thread-safe aircompressor compressors (parquet-mr's 
factory
+  // has its own)
   private final Map<CompressionCodecName, AirliftBytesInputCompressor> 
airCompressors = new HashMap<>();
 
   // fallback parquet-mr compression codec factory
-  private CompressionCodecFactory parqCodecFactory;
+  private final CompressionCodecFactory parqCodecFactory;
 
   // direct memory allocator to be used during (de)compression
-  private ByteBufferAllocator allocator;
+  private final ByteBufferAllocator allocator;
+
+  // Start: members for working around a gzip concurrency bug c.f. DRILL-8139
+  private final Deque<CompressionCodecFactory> singleUseFactories;
+
+  private final Configuration config;
+

Review comment:
       ```suggestion
   ```




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