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https://issues.apache.org/jira/browse/HADOOP-19139?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17838466#comment-17838466
 ] 

ASF GitHub Bot commented on HADOOP-19139:
-----------------------------------------

saxenapranav commented on code in PR #6699:
URL: https://github.com/apache/hadoop/pull/6699#discussion_r1569999944


##########
hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/services/AbfsInputStream.java:
##########
@@ -376,32 +439,48 @@ private int readLastBlock(final byte[] b, final int off, 
final int len)
     // data need to be copied to user buffer from index bCursor,
     // AbfsInutStream buffer is going to contain data from last block start. In
     // that case bCursor will be set to fCursor - lastBlockStart
-    long lastBlockStart = max(0, contentLength - footerReadSize);
+    if (!fileStatusInformationPresent.get()) {
+      long lastBlockStart = max(0, (fCursor + len) - footerReadSize);
+      bCursor = (int) (fCursor - lastBlockStart);
+      return optimisedRead(b, off, len, lastBlockStart, min(fCursor + len, 
footerReadSize), true);
+    }
+    long lastBlockStart = max(0, getContentLength() - footerReadSize);
     bCursor = (int) (fCursor - lastBlockStart);
     // 0 if contentlength is < buffersize
-    long actualLenToRead = min(footerReadSize, contentLength);
-    return optimisedRead(b, off, len, lastBlockStart, actualLenToRead);
+    long actualLenToRead = min(footerReadSize, getContentLength());
+    return optimisedRead(b, off, len, lastBlockStart, actualLenToRead, false);
   }
 
   private int optimisedRead(final byte[] b, final int off, final int len,
-      final long readFrom, final long actualLen) throws IOException {
+      final long readFrom, final long actualLen,
+      final boolean isReadWithoutContentLengthInformation) throws IOException {
     fCursor = readFrom;
     int totalBytesRead = 0;
     int lastBytesRead = 0;
     try {
       buffer = new byte[bufferSize];
+      boolean fileStatusInformationPresentBeforeRead = 
fileStatusInformationPresent.get();
       for (int i = 0;
-           i < MAX_OPTIMIZED_READ_ATTEMPTS && fCursor < contentLength; i++) {
+           i < MAX_OPTIMIZED_READ_ATTEMPTS && 
(!fileStatusInformationPresent.get()
+               || fCursor < getContentLength()); i++) {

Review Comment:
   have added the comment
   ```
         /*
          * Content length would not be available for the first optimized read 
in case
          * of lazy head optimization in inputStream. In such case, read of the 
first optimized read
          * would be done without the contentLength constraint. Post first 
call, the contentLength
          * would be present and should be used for further reads.
          */
   ```





> [ABFS]: No GetPathStatus call for opening AbfsInputStream
> ---------------------------------------------------------
>
>                 Key: HADOOP-19139
>                 URL: https://issues.apache.org/jira/browse/HADOOP-19139
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/azure
>            Reporter: Pranav Saxena
>            Assignee: Pranav Saxena
>            Priority: Major
>              Labels: pull-request-available
>
> Read API gives contentLen and etag of the path. This information would be 
> used in future calls on that inputStream. Prior information of eTag is of not 
> much importance.



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