api: add HashKV and test

jetcd-core/src/main/java/com/coreos/jetcd/Maintenance.java

@@ -20,6 +20,7 @@
 import com.coreos.jetcd.maintenance.AlarmMember;
 import com.coreos.jetcd.maintenance.AlarmResponse;
 import com.coreos.jetcd.maintenance.DefragmentResponse;
+import com.coreos.jetcd.maintenance.HashKVResponse;
 import com.coreos.jetcd.maintenance.MoveLeaderResponse;
 import com.coreos.jetcd.maintenance.StatusResponse;
 import java.io.Closeable;
@@ -83,6 +84,14 @@ public interface Maintenance extends CloseableClient {
    */
   CompletableFuture<StatusResponse> statusMember(String endpoint);
 
+
+  /**
+   * returns a hash of the KV state at the time of the RPC.
+   * If revision is zero, the hash is computed on all keys. If the revision
+   * is non-zero, the hash is computed on all keys at or below the given revision.
+   */
+  CompletableFuture<HashKVResponse> hashKV(String endpoint, long rev);
+
   /**
    * retrieves backend snapshot.
    *

jetcd-core/src/main/java/com/coreos/jetcd/internal/impl/MaintenanceImpl.java

@@ -26,6 +26,7 @@
 import com.coreos.jetcd.api.AlarmRequest;
 import com.coreos.jetcd.api.AlarmType;
 import com.coreos.jetcd.api.DefragmentRequest;
+import com.coreos.jetcd.api.HashKVRequest;
 import com.coreos.jetcd.api.MaintenanceGrpc;
 import com.coreos.jetcd.api.MoveLeaderRequest;
 import com.coreos.jetcd.api.SnapshotRequest;
@@ -34,6 +35,7 @@
 import com.coreos.jetcd.exception.ErrorCode;
 import com.coreos.jetcd.maintenance.AlarmResponse;
 import com.coreos.jetcd.maintenance.DefragmentResponse;
+import com.coreos.jetcd.maintenance.HashKVResponse;
 import com.coreos.jetcd.maintenance.MoveLeaderResponse;
 import com.coreos.jetcd.maintenance.SnapshotReaderResponseWithError;
 import com.coreos.jetcd.maintenance.StatusResponse;
@@ -156,6 +158,19 @@ public CompletableFuture<StatusResponse> statusMember(
     );
   }
 
+  @Override
+  public CompletableFuture<HashKVResponse> hashKV(String endpoint, long rev) {
+    return this.connectionManager.withNewChannel(
+        endpoint,
+        MaintenanceGrpc::newFutureStub,
+        stub -> Util.toCompletableFuture(
+            stub.hashKV(HashKVRequest.newBuilder().setRevision(rev).build()),
+            HashKVResponse::new,
+            this.connectionManager.getExecutorService()
+        )
+    );
+  }
+
   @Override
   public Snapshot snapshot() {
     SnapshotImpl snapshot = new SnapshotImpl();

jetcd-core/src/main/java/com/coreos/jetcd/maintenance/HashKVResponse.java

@@ -0,0 +1,44 @@
+/**
+ * Copyright 2017 The jetcd authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.coreos.jetcd.maintenance;
+
+import com.coreos.jetcd.Maintenance;
+import com.coreos.jetcd.data.AbstractResponse;
+
+/**
+ * HashKVResponse returned by {@link Maintenance#HashKV(String, long)}.
+ */
+public class HashKVResponse extends AbstractResponse<com.coreos.jetcd.api.HashKVResponse> {
+
+  public HashKVResponse(com.coreos.jetcd.api.HashKVResponse response) {
+    super(response, response.getHeader());
+  }
+
+  /**
+   * return the hash value computed from the responding member's MVCC keys up to a given revision.
+   */
+  public int getHash() {
+    return getResponse().getHash();
+  }
+
+  /**
+   * return compact_revision is the compacted revision of key-value store when hash begins.
+   */
+  public long getCompacted() {
+    return getResponse().getCompactRevision();
+  }
+}

jetcd-core/src/test/java/com/coreos/jetcd/internal/impl/MaintenanceTest.java

@@ -73,6 +73,11 @@ public void testNnapshot() throws IOException {
     }
   }
 
+  @Test
+  public void testHashKV() throws ExecutionException, InterruptedException {
+    maintenance.hashKV(TestConstants.endpoints[0], 0).get();
+  }
+
   /**
    * test alarm list function
    * TODO trigger alarm, valid whether listAlarms will work.