Removed dead code

-package org.onlab.onos.store.service;
-
-/**
- * Exception that indicates a optimistic lock failure.
- */
-@SuppressWarnings("serial")
-public class OptimisticLockException extends PreconditionFailedException {
-}

-package org.onlab.onos.store.service;
-
-/**
- * Exception that indicates a precondition failure.
- * Scenarios that can cause this exception:
- * <ul>
- * <li>An operation that attempts to write a new value iff the current value is equal
- * to some specified value.</li>
- * <li>An operation that attempts to write a new value iff the current version
- * matches a specified value</li>
- * </ul>
- */
-@SuppressWarnings("serial")
-public class PreconditionFailedException extends DatabaseException {
-}
\ No newline at end of file

 package org.onlab.onos.store.service;
 
+/**
+ * Status of completed read request.
+ */
 public enum ReadStatus {
+
+	/**
+	 * Read completed successfully.
+	 */
 	OK,
+
+    /**
+     * Read failed due to an invalid table name being specified.
+     */
     NO_SUCH_TABLE
 }

-package org.onlab.onos.store.service;
-
-
-/**
- * Exception that indicates a write operation is aborted.
- * Aborted operations do not mutate database state is any form.
- */
-@SuppressWarnings("serial")
-public class WriteAborted extends DatabaseException {
-}

 package org.onlab.onos.store.service;
 
+/**
+ * Status of completed write request.
+ */
 public enum WriteStatus {
+
+	/**
+	 * Write completed successfully.
+	 */
     OK,
+
+    /**
+     * Write was aborted (ex: if one or more write operations in a batch fail, others are aborted)
+     */
     ABORTED,
+
+    /**
+     * Write failed due to pre-condition failure. (ex: version or value mis-match)
+     */
     PRECONDITION_VIOLATION,
+
+    /**
+     * Write failed due to an invalid table name being specified.
+     */
     NO_SUCH_TABLE,
 }

@@ -111,16 +111,12 @@ public class ClusterMessagingProtocol
             .register(ReadRequest.class)
             .register(WriteRequest.class)
             .register(WriteRequest.Type.class)
-            .register(InternalReadResult.class)
-            .register(InternalWriteResult.class)
-            .register(InternalReadResult.Status.class)
             .register(WriteResult.class)
             .register(ReadResult.class)
             .register(BatchReadRequest.class)
             .register(BatchWriteRequest.class)
             .register(ReadStatus.class)
             .register(WriteStatus.class)
-            .register(InternalWriteResult.Status.class)
             .register(VersionedValue.class)
             .build();
 

@@ -11,7 +11,6 @@ import org.joda.time.DateTime;
 import org.onlab.onos.cluster.ClusterService;
 import org.onlab.onos.store.service.DatabaseService;
 import org.onlab.onos.store.service.Lock;
-import org.onlab.onos.store.service.OptimisticLockException;
 
 /**
  * A distributed lock implementation.
@@ -57,12 +56,10 @@ public class DistributedLock implements Lock {
 
     @Override
     public boolean tryLock(int leaseDurationMillis) {
-        try {
-            databaseService.putIfAbsent(DistributedLockManager.ONOS_LOCK_TABLE_NAME, path, lockId);
-            return true;
-        } catch (OptimisticLockException e) {
-            return false;
-        }
+        return databaseService.putIfAbsent(
+                DistributedLockManager.ONOS_LOCK_TABLE_NAME,
+                path,
+                lockId);
     }
 
     @Override

-package org.onlab.onos.store.service.impl;
-
-import java.io.Serializable;
-
-import org.onlab.onos.store.service.ReadResult;
-
-/**
- * Result of a read operation executed on the DatabaseStateMachine.
- */
-@SuppressWarnings("serial")
-public class InternalReadResult implements Serializable {
-
-    public enum Status {
-        OK,
-        NO_SUCH_TABLE
-    }
-
-    private final Status status;
-    private final ReadResult result;
-
-    public InternalReadResult(Status status, ReadResult result) {
-        this.status = status;
-        this.result = result;
-    }
-
-    public Status status() {
-        return status;
-    }
-
-    public ReadResult result() {
-        return result;
-    }
-
-    @Override
-    public String toString() {
-        return "InternalReadResult [status=" + status + ", result=" + result
-                + "]";
-    }
-}
\ No newline at end of file

-package org.onlab.onos.store.service.impl;
-
-import org.onlab.onos.store.service.WriteResult;
-
-import com.google.common.base.MoreObjects;
-
-/**
- * Result of a write operation executed on the DatabaseStateMachine.
- */
-public class InternalWriteResult {
-
-    public enum Status {
-        OK,
-        ABORTED,
-        NO_SUCH_TABLE,
-        PREVIOUS_VERSION_MISMATCH,
-        PREVIOUS_VALUE_MISMATCH
-    }
-
-    private final Status status;
-    private final WriteResult result;
-
-    public static InternalWriteResult ok(WriteResult result) {
-        return new InternalWriteResult(Status.OK, result);
-    }
-
-    public InternalWriteResult(Status status, WriteResult result) {
-        this.status = status;
-        this.result = result;
-    }
-
-    public Status status() {
-        return status;
-    }
-
-    public WriteResult result() {
-        return result;
-    }
-
-    @Override
-    public String toString() {
-        return MoreObjects.toStringHelper(getClass())
-                .add("status", status)
-                .add("result", result)
-                .toString();
-    }
-}