[GitHub] [accumulo] ctubbsii commented on a diff in pull request #3079: Wire up FSDataInputStream.setDropBehind, set to true in FileCompactor

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

ctubbsii commented on code in PR #3079:
URL: https://github.com/apache/accumulo/pull/3079#discussion_r1023132794


##########
core/src/main/java/org/apache/accumulo/core/file/blockfile/impl/CachableBlockFile.java:
##########
@@ -83,8 +84,24 @@ public CachableBuilder conf(Configuration hadoopConf) {
     }
 
     public CachableBuilder fsPath(FileSystem fs, Path dataFile) {
+      return fsPath(fs, dataFile, false);
+    }
+
+    public CachableBuilder fsPath(FileSystem fs, Path dataFile, boolean dropCacheBehind) {
       this.cacheId = pathToCacheId(dataFile);
-      this.inputSupplier = () -> fs.open(dataFile);
+      this.inputSupplier = () -> {
+        FSDataInputStream is = fs.open(dataFile);
+        if (dropCacheBehind) {
+          // Tell the DataNode that the write ahead log does not need to be cached in the OS page
+          // cache
+          try {
+            is.setDropBehind(Boolean.TRUE);
+          } catch (IOException | UnsupportedOperationException e) {
+            log.debug("setDropBehind not enabled for wal file: {}", dataFile);

Review Comment:
   I'm wondering if it's useful to show the message from the exception in this debug message, at least in the case of IOException.



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