Re: [PR] HDDS-16327. Read the block file length once per WriteChunk instead of three fstat calls [ozone]

["smengcl (via GitHub)" <gi...@apache.org>]

smengcl commented on code in PR #11150:
URL: https://github.com/apache/ozone/pull/11150#discussion_r4222748734


##########
hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/keyvalue/impl/FilePerBlockStrategy.java:
##########
@@ -157,31 +156,32 @@ public void writeChunk(Container container, BlockID blockID, ChunkInfo info,
     HddsVolume volume = containerData.getVolume();
 
     FileChannel channel = null;
-    boolean overwrite;
     try {
       channel = files.getChannel(chunkFile, doSyncWrite);
-      overwrite = validateChunkForOverwrite(channel, info);
     } catch (IOException e) {
       onFailure(volume);
       throw e;
     }
 
+    // Read the block file length once and reuse it for the overwrite check,
+    // the offset validation and the space accounting below.
+    long fileLengthBeforeWrite;
+    try {
+      fileLengthBeforeWrite = channel.size();
+    } catch (IOException e) {
+      throw new UncheckedIOException("Encountered an error while getting the file size for " + chunkFile.getName(), e);

Review Comment:
   It looks to me that this code keeps the response code for a failure in the first file size read.
   
   The original call in `isOverWriteRequested()` threw `UncheckedIOException` if `channel.size()` failed. `KeyValueHandler.handle()` then returned `CONTAINER_INTERNAL_ERROR`.
   
   The later file size reads used `CHUNK_FILE_INCONSISTENCY` if they failed after the first read succeeded. This patch removes those reads. The suggested change would therefore change the response code for a failure in the first read.



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