[Cassandra Wiki] Update of "ArchitectureAntiEntropy" by JingguoYao

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The "ArchitectureAntiEntropy" page has been changed by JingguoYao.
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http://wiki.apache.org/cassandra/ArchitectureAntiEntropy?action=diff&rev1=3&rev2=4

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  == Anti-entropy Overview ==
  
- AntiEntropyService generates MerkleTrees for column families during major compactions. These trees are then exchanged with remote nodes via a TreeRequest/TreeResponse conversation, and when ranges in the trees disagree, the 'org.apache.cassandra.streaming' package is used to repair those ranges.
+ !AntiEntropyService generates !MerkleTrees for column families during major compactions. These trees are then exchanged with remote nodes via a !TreeRequest/!TreeResponse conversation, and when ranges in the trees disagree, the 'org.apache.cassandra.streaming' package is used to repair those ranges.
  
  Tree comparison and repair triggering occur in the single threaded AE_SERVICE_STAGE.
  
  The steps taken to enact a repair are as follows:
  
  1. A major compaction is triggered either via nodeprobe, or automatically:
-   * Nodeprobe sends TreeRequest messages to all neighbors of the target node: when a node receives a TreeRequest, it will perform a readonly compaction to immediately validate the column family.
+   * Nodeprobe sends !TreeRequest messages to all neighbors of the target node: when a node receives a !TreeRequest, it will perform a readonly compaction to immediately validate the column family.
-   * Automatic compactions will also validate a column family and broadcast TreeResponses, but since TreeRequest messages are not sent to neighboring nodes, repairs will only occur if two nodes happen to perform automatic compactions within TREE_STORE_TIMEOUT of one another.
+   * Automatic compactions will also validate a column family and broadcast !TreeResponses, but since !TreeRequest messages are not sent to neighboring nodes, repairs will only occur if two nodes happen to perform automatic compactions within TREE_STORE_TIMEOUT of one another.
  2. The compaction process validates the column family by:
-   * Calling getValidator() (which can return a NoopValidator if validation should not be performed),
+   * Calling getValidator() (which can return a !NoopValidator if validation should not be performed),
    * Calling IValidator.prepare(), which samples the column family to determine key distribution,
    * Calling IValidator.add() in order for every row in the column family,
    * Calling IValidator.complete() to indicate that all rows have been added.
-     * If getValidator decided that the column family should be validated, calling complete() indicates that a valid MerkleTree has been created for the column family.
+     * If getValidator decided that the column family should be validated, calling complete() indicates that a valid !MerkleTree has been created for the column family.
-     * The valid tree is broadcast to neighboring nodes via TreeResponse, and stored locally.
+     * The valid tree is broadcast to neighboring nodes via !TreeResponse, and stored locally.
- 3. When a node receives a TreeResponse, it passes the tree to rendezvous(), which checks for trees to rendezvous with / compare to:
+ 3. When a node receives a !TreeResponse, it passes the tree to rendezvous(), which checks for trees to rendezvous with / compare to:
    * If the tree is local, it is cached, and compared to any trees that were received from neighbors.
    * If the tree is remote, it is immediately compared to a local tree if one is cached. Otherwise, the remote tree is cached in case a local tree is generated within TREE_STORE_TIMEOUT.
    * A Differencer object is enqueued for each comparison.
@@ -28, +28 @@

  === TODO ===
  Repairs currently require 2 major compactions: one to validate a column family, and then another to send the disagreeing ranges.
  
- One possible fix to this problem would be to use something like a [[http://comonad.com/reader/2008/linear-bloom-filters/|Linear Bloom Filter]] to store a summary of every SSTable on disk, where each sub-bloom is partitioned using 'midpoint()' like the current MerkleTree. Then, to validate a column family, you could OR together the bloom filters for each SSTable, and send it to neighbors without performing a compaction.
+ One possible fix to this problem would be to use something like a [[http://comonad.com/reader/2008/linear-bloom-filters/|Linear Bloom Filter]] to store a summary of every SSTable on disk, where each sub-bloom is partitioned using 'midpoint()' like the current !MerkleTree. Then, to validate a column family, you could OR together the bloom filters for each SSTable, and send it to neighbors without performing a compaction.