[GitHub] [hadoop] tomscut commented on a diff in pull request #4209: HDFS-16550. Improper cache-size for journal node may cause cluster crash

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

tomscut commented on code in PR #4209:
URL: https://github.com/apache/hadoop/pull/4209#discussion_r1034167277


##########
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/qjournal/server/TestJournaledEditsCache.java:
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@@ -221,6 +224,24 @@ public void testCacheMalformedInput() throws Exception {
     cache.retrieveEdits(-1, 10, new ArrayList<>());
   }
 
+  @Test
+  public void testCacheFraction() {
+    // Set dfs.journalnode.edit-cache-size.bytes.
+    Configuration config = new Configuration();
+    config.setInt(DFSConfigKeys.DFS_JOURNALNODE_EDIT_CACHE_SIZE_KEY, 1);
+    config.setFloat(DFSConfigKeys.DFS_JOURNALNODE_EDIT_CACHE_SIZE_FRACTION_KEY, 0.1f);
+    cache = new JournaledEditsCache(config);
+    assertEquals(1, cache.getCapacity(), 0.0);
+
+    // Don't set dfs.journalnode.edit-cache-size.bytes.
+    Configuration config1 = new Configuration();
+    config1.setFloat(DFSConfigKeys.DFS_JOURNALNODE_EDIT_CACHE_SIZE_FRACTION_KEY, 0.1f);
+    cache = new JournaledEditsCache(config1);
+    assertEquals(
+        memory * config1.getFloat(DFSConfigKeys.DFS_JOURNALNODE_EDIT_CACHE_SIZE_FRACTION_KEY, 0.0f),
+        cache.getCapacity(), 0.0);

Review Comment:
   There will be a loss of accuracy.



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