add a trace log line (#37)

palantir · Jul 18, 2019 · f859494 · f859494
1 parent 36d74a3
commit f859494
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Showing 2 changed files with 24 additions and 2 deletions.
diff --git a/src/java/org/apache/cassandra/io/sstable/SSTableRewriter.java b/src/java/org/apache/cassandra/io/sstable/SSTableRewriter.java
@@ -126,7 +126,7 @@ public RowIndexEntry append(AbstractCompactedRow row)
                 boolean save = false;
                 for (SSTableReader reader : transaction.originals())
                 {
-                    if (reader.getCachedPosition(row.key, false) != null)
+                    if (reader.getCachedPosition(row.key, false, true) != null)
                     {
                         save = true;
                         break;

diff --git a/src/java/org/apache/cassandra/io/sstable/format/SSTableReader.java b/src/java/org/apache/cassandra/io/sstable/format/SSTableReader.java
@@ -1540,11 +1540,33 @@ public void cacheKey(DecoratedKey key, RowIndexEntry info)
 
     public RowIndexEntry getCachedPosition(DecoratedKey key, boolean updateStats)
     {
-        return getCachedPosition(new KeyCacheKey(metadata.ksAndCFName, descriptor, key.getKey()), updateStats);
+        return getCachedPosition(key, updateStats, false);
+    }
+
+    public RowIndexEntry getCachedPosition(DecoratedKey key, boolean updateStats, boolean isSstableRewrite)
+    {
+        return getCachedPosition(
+                new KeyCacheKey(metadata.ksAndCFName, descriptor, key.getKey()),
+                updateStats,
+                isSstableRewrite);
     }
 
     protected RowIndexEntry getCachedPosition(KeyCacheKey unifiedKey, boolean updateStats)
     {
+        return getCachedPosition(unifiedKey, updateStats, false);
+    }
+
+    protected RowIndexEntry getCachedPosition(KeyCacheKey unifiedKey, boolean updateStats, boolean isSstableRewrite)
+    {
+        //Lock contention in the cache causes unnecessary overhead during compactions that slows the overall compaction
+        //speed to a crawl. We don't need to update the cache on the basis of values read during a compaction anyway
+        //because they don't represent real read load.
+        if (isSstableRewrite && Boolean.getBoolean("palantir_cassandra.disable_sstablerewrite_keycache"))
+        {
+            logger.trace("Not returning cached position of row for SSTable rewrite");
+            return null;
+        }
+
         if (keyCache != null && keyCache.getCapacity() > 0 && metadata.getCaching().keyCache.isEnabled()) {
             if (updateStats)
             {