[GitHub] [kafka-site] ableegoldman commented on a change in pull request #301: Redo 2.6 docs commit

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ableegoldman commented on a change in pull request #301:
URL: https://github.com/apache/kafka-site/pull/301#discussion_r485154723



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File path: 26/streams/developer-guide/memory-mgmt.html
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@@ -202,7 +202,10 @@ <h2><a class="toc-backref" href="#id3">RocksDB</a><a class="headerlink" href="#r
        <span class="o">}</span>
     <span class="o">}</span>
       </div>
-        <sup id="fn1">1. INDEX_FILTER_BLOCK_RATIO can be used to set a fraction of the block cache to set aside for "high priority" (aka index and filter) blocks, preventing them from being evicted by data blocks. See the full signature of the <a class="reference external" href="https://github.com/facebook/rocksdb/blob/master/java/src/main/java/org/rocksdb/LRUCache.java#L72">LRUCache constructor</a>. </sup>
+        <sup id="fn1">1. INDEX_FILTER_BLOCK_RATIO can be used to set a fraction of the block cache to set aside for "high priority" (aka index and filter) blocks, preventing them from being evicted by data blocks. See the full signature of the <a class="reference external" href="https://github.com/facebook/rocksdb/blob/master/java/src/main/java/org/rocksdb/LRUCache.java#L72">LRUCache constructor</a>.
+          NOTE: the boolean parameter in the cache constructor lets you control whether the cache should enforce a strict memory limit by failing the read or iteration in the rare cases where it might go larger than its capacity. Due to a
+          <a class="reference external" href="https://github.com/facebook/rocksdb/issues/6247">bug in RocksDB</a>, this option cannot be used
+          if the write buffer memory is also counted against the cache. If you set this to true, you should NOT pass the cache in to the <code>WriteBufferManager</code> and just control the write buffer and cache memory separately.</sup>

Review comment:
       Nope, this is correct. As far as I know this has always been the case in every RocksDB version we've depended on but didn't discover the bug until just recently. (I believe it actually is fixed in some newer versions, so we may be able to remove this again once we upgrade)




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