org.apache.cassandra.service
Class AntiEntropyService

java.lang.Object
  org.apache.cassandra.service.AntiEntropyService

public class AntiEntropyService
extends java.lang.Object

AntiEntropyService encapsulates "validating" (hashing) individual column families, exchanging MerkleTrees with remote nodes via a TreeRequest/Response conversation, and then triggering repairs for disagreeing ranges. Every Tree conversation has an 'initiator', where valid trees are sent after generation and where the local and remote tree will rendezvous in rendezvous(cf, endpoint, tree). Once the trees rendezvous, a Differencer is executed and the service can trigger repairs for disagreeing ranges. Tree comparison and repair triggering occur in the single threaded Stage.ANTIENTROPY. The steps taken to enact a repair are as follows: 1. A major compaction is triggered via nodeprobe: * 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. 2. The compaction process validates the column family by: * Calling Validator.prepare(), which samples the column family to determine key distribution, * Calling Validator.add() in order for every row in the column family, * Calling Validator.complete() to indicate that all rows have been added. * Calling complete() indicates that a valid MerkleTree has been created for the column family. * The valid tree is returned to the requesting node via a TreeResponse. 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 stored until a local tree can be generated. * A Differencer object is enqueued for each comparison. 4. Differencers are executed in Stage.ANTIENTROPY, to compare the two trees, and perform repair via the streaming api.

Nested Class Summary

static class	AntiEntropyService.TreeRequest A tuple of table, cf, address and range that represents a location we have an outstanding TreeRequest for.
static class	AntiEntropyService.TreeRequestVerbHandler Handler for requests from remote nodes to generate a valid tree.
static class	AntiEntropyService.TreeResponseVerbHandler Handler for responses from remote nodes which contain a valid tree.
static class	AntiEntropyService.Validator A Strategy to handle building and validating a merkle tree for a column family.

Field Summary

static AntiEntropyService	instance
static long	REQUEST_TIMEOUT

Constructor Summary

protected

AntiEntropyService() Protected constructor.

Method Summary

org.apache.cassandra.service.AntiEntropyService.RepairSession

getRepairSession(Range range, java.lang.String tablename, java.lang.String... cfnames) Requests repairs for the given table and column families, and blocks until all repairs have been completed.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

instance

public static final AntiEntropyService instance

REQUEST_TIMEOUT

public static final long REQUEST_TIMEOUT

See Also:

Constant Field Values

Constructor Detail

AntiEntropyService

protected AntiEntropyService()

Protected constructor. Use AntiEntropyService.instance.

Method Detail

getRepairSession

public org.apache.cassandra.service.AntiEntropyService.RepairSession getRepairSession(Range range,
                                                                                      java.lang.String tablename,
                                                                                      java.lang.String... cfnames)

Requests repairs for the given table and column families, and blocks until all repairs have been completed. TODO: Should add retries: if nodes go offline before they respond to the requests, this could block forever.