HBASE-29099 Avoid expensive BlockCacheKey.toString() calls when tracing is disabled (#6642) (#6645)

Signed-off-by: Ray Mattingly <[email protected]>
Co-authored-by: jbewing <[email protected]>

Author: rmdmattingly

hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileReaderImpl.java

@@ -1289,11 +1289,15 @@ public HFileBlock readBlock(long dataBlockOffset, long onDiskBlockSize, final bo
 
     BlockCacheKey cacheKey =
       new BlockCacheKey(path, dataBlockOffset, this.isPrimaryReplicaReader(), expectedBlockType);
-    Attributes attributes = Attributes.of(BLOCK_CACHE_KEY_KEY, cacheKey.toString());
 
     boolean useLock = false;
     IdLock.Entry lockEntry = null;
     final Span span = Span.current();
+    // BlockCacheKey#toString() is quite expensive to call, so if tracing isn't enabled, don't
+    // record
+    Attributes attributes = span.isRecording()
+      ? Attributes.of(BLOCK_CACHE_KEY_KEY, cacheKey.toString())
+      : Attributes.empty();
     try {
       while (true) {
         // Check cache for block. If found return.