Add additional javadoc for SlaveLocksClient and for SlaveStatementLocks

after review
neo4j · Jul 17, 2017 · 556ce42 · 556ce42
1 parent b3c5aa2
commit 556ce42
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diff --git a/enterprise/ha/src/main/java/org/neo4j/kernel/ha/lock/SlaveLocksClient.java b/enterprise/ha/src/main/java/org/neo4j/kernel/ha/lock/SlaveLocksClient.java
@@ -228,6 +228,17 @@ public long activeLockCount()
         return client.activeLockCount();
     }
 
+    /**
+     * In order to prevent various indexes collisions on master during transaction commit that originate on one of the
+     * slaves we need to grab same locks on {@link ResourceTypes#LABEL} and {@link ResourceTypes#RELATIONSHIP_TYPE}
+     * that
+     * where obtained on origin. To be able to do that and also prevent shared locks to be propagates to master in cases
+     * of
+     * read only transactions we need to postpone obtaining them till we know that we participating in a
+     * transaction that performs modifications.
+     *
+     * @param tracer lock tracer
+     */
     void acquireDeferredSharedLocks( LockTracer tracer )
     {
         assertNotStopped();

diff --git a/enterprise/ha/src/main/java/org/neo4j/kernel/ha/lock/SlaveStatementLocks.java b/enterprise/ha/src/main/java/org/neo4j/kernel/ha/lock/SlaveStatementLocks.java
@@ -24,11 +24,20 @@
 import org.neo4j.kernel.impl.locking.ActiveLock;
 import org.neo4j.kernel.impl.locking.LockTracer;
 import org.neo4j.kernel.impl.locking.Locks;
+import org.neo4j.kernel.impl.locking.ResourceTypes;
 import org.neo4j.kernel.impl.locking.StatementLocks;
 
 /**
  * Slave specific statement locks that in addition to standard functionality provided by configured delegate
  * will grab selected shared locks on master during prepareForCommit phase.
+ * <p>
+ * In order to prevent various indexes collisions on master during transaction commit that originate on one of the
+ * slaves we need to grab same locks on {@link ResourceTypes#LABEL} and {@link ResourceTypes#RELATIONSHIP_TYPE} that
+ * where obtained on origin. To be able to do that and also prevent shared locks to be propagates to master in cases of
+ * read only transactions we will postpone obtaining them till we know that we participating in a
+ * transaction that performs modifications. That's why we will obtain them only as
+ * part of {@link #prepareForCommit(LockTracer)} call.
+ * </p>
  */
 public class SlaveStatementLocks implements StatementLocks
 {