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Posted to commits@cassandra.apache.org by sl...@apache.org on 2013/06/27 11:08:25 UTC
git commit: Update some javadoc for repair
Updated Branches:
refs/heads/trunk c06244916 -> 93a03feac
Update some javadoc for repair
Project: http://git-wip-us.apache.org/repos/asf/cassandra/repo
Commit: http://git-wip-us.apache.org/repos/asf/cassandra/commit/93a03fea
Tree: http://git-wip-us.apache.org/repos/asf/cassandra/tree/93a03fea
Diff: http://git-wip-us.apache.org/repos/asf/cassandra/diff/93a03fea
Branch: refs/heads/trunk
Commit: 93a03feacebb34b639558b8e6400398b3ae26f37
Parents: c062449
Author: Sylvain Lebresne <sy...@datastax.com>
Authored: Thu Jun 27 11:08:18 2013 +0200
Committer: Sylvain Lebresne <sy...@datastax.com>
Committed: Thu Jun 27 11:08:18 2013 +0200
----------------------------------------------------------------------
.../apache/cassandra/repair/RepairSession.java | 33 ++++++++++++++++++-
.../org/apache/cassandra/repair/Validator.java | 2 +-
.../cassandra/service/ActiveRepairService.java | 34 ++++++--------------
3 files changed, 43 insertions(+), 26 deletions(-)
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/cassandra/blob/93a03fea/src/java/org/apache/cassandra/repair/RepairSession.java
----------------------------------------------------------------------
diff --git a/src/java/org/apache/cassandra/repair/RepairSession.java b/src/java/org/apache/cassandra/repair/RepairSession.java
index 7101b5a..5761597 100644
--- a/src/java/org/apache/cassandra/repair/RepairSession.java
+++ b/src/java/org/apache/cassandra/repair/RepairSession.java
@@ -37,7 +37,37 @@ import org.apache.cassandra.service.ActiveRepairService;
import org.apache.cassandra.utils.*;
/**
- * Triggers repairs with all neighbors for the given table, cfs and range.
+ * Coordinates the (active) repair of a token range.
+ *
+ * A given RepairSession repairs a set of replicas for a given range on a list
+ * of column families. For each of the column family to repair, RepairSession
+ * creates a RepairJob that handles the repair of that CF.
+ *
+ * A given RepairJob has the 2 main phases:
+ * 1. Validation phase: the job requests merkle trees from each of the replica involves
+ * (RepairJob.sendTreeRequests()) and waits until all trees are received (in
+ * validationComplete()).
+ * 2. Synchonization phase: once all trees are received, the job compares each tree with
+ * all the other using a so-called Differencer (started by submitDifferencers()). If
+ * differences there is between 2 trees, the concerned Differencer will start a streaming
+ * of the difference between the 2 endpoint concerned (Differencer.performStreamingRepair).
+ * The job is done once all its Differencer are done (i.e. have either computed no differences
+ * or the streaming they started is done (syncComplete())).
+ *
+ * A given session will execute the first phase (validation phase) of each of it's job
+ * sequentially. In other words, it will start the first job and only start the next one
+ * once that first job validation phase is complete. This is done so that the replica only
+ * create one merkle tree at a time, which is our way to ensure that such creation starts
+ * roughly at the same time on every node (see CASSANDRA-2816). However the synchronization
+ * phases are allowed to run concurrently (with each other and with validation phases).
+ *
+ * A given RepairJob has 2 modes: either sequential or not (isSequential flag). If sequential,
+ * it will requests merkle tree creation from each replica in sequence (though in that case
+ * we still first send a message to each node to flush and snapshot data so each merkle tree
+ * creation is still done on similar data, even if the actual creation is not
+ * done simulatneously). If not sequential, all merkle tree are requested in parallel.
+ * Similarly, if a job is sequential, it will handle one Differencer at a time, but will handle
+ * all of them in parallel otherwise.
*/
public class RepairSession extends WrappedRunnable implements IEndpointStateChangeSubscriber, IFailureDetectionEventListener
{
@@ -223,6 +253,7 @@ public class RepairSession extends WrappedRunnable implements IEndpointStateChan
throw new IOException(message);
}
}
+
ActiveRepairService.instance.addToActiveSessions(this);
try
{
http://git-wip-us.apache.org/repos/asf/cassandra/blob/93a03fea/src/java/org/apache/cassandra/repair/Validator.java
----------------------------------------------------------------------
diff --git a/src/java/org/apache/cassandra/repair/Validator.java b/src/java/org/apache/cassandra/repair/Validator.java
index 97b4ca2..0a7f927 100644
--- a/src/java/org/apache/cassandra/repair/Validator.java
+++ b/src/java/org/apache/cassandra/repair/Validator.java
@@ -42,7 +42,7 @@ import org.apache.cassandra.utils.FBUtilities;
import org.apache.cassandra.utils.MerkleTree;
/**
- * A Strategy to handle building and validating a merkle tree for a column family.
+ * Handles the building of a merkle tree for a column family.
*
* Lifecycle:
* 1. prepare() - Initialize tree with samples.
http://git-wip-us.apache.org/repos/asf/cassandra/blob/93a03fea/src/java/org/apache/cassandra/service/ActiveRepairService.java
----------------------------------------------------------------------
diff --git a/src/java/org/apache/cassandra/service/ActiveRepairService.java b/src/java/org/apache/cassandra/service/ActiveRepairService.java
index 2bcf579..53460b9 100644
--- a/src/java/org/apache/cassandra/service/ActiveRepairService.java
+++ b/src/java/org/apache/cassandra/service/ActiveRepairService.java
@@ -38,32 +38,18 @@ import org.apache.cassandra.repair.messages.ValidationComplete;
import org.apache.cassandra.utils.FBUtilities;
/**
- * ActiveRepairService encapsulates "validating" (hashing) individual column families,
- * exchanging MerkleTrees with remote nodes via a tree request/response conversation,
- * and then triggering repairs for disagreeing ranges.
+ * ActiveRepairService is the starting point for manual "active" repairs.
*
- * The node where repair was invoked acts as the 'initiator,' where valid trees are sent after generation
- * and where the local and remote tree will rendezvous in rendezvous().
- * Once the trees rendezvous, a Differencer is executed and the service can trigger repairs
- * for disagreeing ranges.
+ * Each user triggered repair will correspond to one or multiple repair session,
+ * one for each token range to repair. On repair session might repair multiple
+ * column families. For each of those column families, the repair session will
+ * request merkle trees for each replica of the range being repaired, diff those
+ * trees upon receiving them, schedule the streaming ofthe parts to repair (based on
+ * the tree diffs) and wait for all those operation. See RepairSession for more
+ * details.
*
- * Tree comparison and repair triggering occur in the single threaded Stage.ANTI_ENTROPY.
- *
- * The steps taken to enact a repair are as follows:
- * 1. A repair is requested via JMX/nodetool:
- * * The initiator sends TreeRequest messages to all neighbors of the target node: when a node
- * receives a TreeRequest, it will perform a validation (read-only) compaction to immediately validate
- * the column family. This is performed on the CompactionManager ExecutorService.
- * 2. The validation process builds the merkle tree by:
- * * Calling Validator.prepare(), which samples the column family to determine key distribution,
- * * Calling Validator.add() in order for rows in repair range 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 tree response, it passes the tree to rendezvous() to see if all responses are
- * received. Once the initiator receives all responses, it creates Differencers on every tree pair combination.
- * 4. Differencers are executed in Stage.ANTI_ENTROPY, to compare the given two trees, and perform repair via the
- * streaming api.
+ * The creation of a repair session is done through the submitRepairSession that
+ * returns a future on the completion of that session.
*/
public class ActiveRepairService
{