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+/**
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+ * Licensed to the Apache Software Foundation (ASF) under one
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+ * or more contributor license agreements. See the NOTICE file
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+ * distributed with this work for additional information
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+ * regarding copyright ownership. The ASF licenses this file
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+ * to you under the Apache License, Version 2.0 (the
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+ * "License"); you may not use this file except in compliance
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+ * with the License. You may obtain a copy of the License at
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+ *
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+ * http://www.apache.org/licenses/LICENSE-2.0
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+ *
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+ * Unless required by applicable law or agreed to in writing, software
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+ * distributed under the License is distributed on an "AS IS" BASIS,
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+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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+ * See the License for the specific language governing permissions and
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+ * limitations under the License.
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+ */
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+
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+/**
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+ * These .proto interfaces are private and unstable.
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+ * Please see http://wiki.apache.org/hadoop/Compatibility
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+ * for what changes are allowed for a *unstable* .proto interface.
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+ */
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+
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+option java_package = "org.apache.hadoop.ozone.protocol.proto";
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+
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+option java_outer_classname = "StorageContainerDatanodeProtocolProtos";
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+
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+option java_generic_services = true;
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+
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+option java_generate_equals_and_hash = true;
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+
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+package hadoop.hdfs;
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+import "hdfs.proto";
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+import "HdfsServer.proto";
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+import "DatanodeProtocol.proto";
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+import "DatanodeContainerProtocol.proto";
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+
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+
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+/**
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+* This message is send by data node to indicate that it is alive or it is
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+* registering with the node manager.
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+*/
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+message SCMHeartbeatRequestProto {
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+ required DatanodeIDProto datanodeID = 1;
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+}
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+
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+
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+/**
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+ * Request for version info of the software stack on the server.
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+ */
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+message SCMVersionRequestProto {
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+
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+}
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+
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+/**
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+* Generic response that is send to a version request. This allows keys to be
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+* added on the fly and protocol to remain stable.
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+*/
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+message SCMVersionResponseProto {
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+ required uint32 softwareVersion = 1;
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+ repeated hadoop.hdfs.ozone.KeyValue keys = 2;
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+}
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+
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+/**
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+ * Datanode ID returned by the SCM. This is similar to name node
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+ * registeration of a datanode.
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+ */
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+message RegisteredCmdResponseProto {
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+ required string datanodeUUID = 1;
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+ required string clusterID = 2;
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+}
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+
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+/*
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+ * These are commands returned by SCM for to the datanode to execute.
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+ */
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+
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+message SCMHeartbeatResponseProto {
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+ enum Type {
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+ nullCmd = 1;
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+ registeredCmd = 2; // Returns the datanode ID after registeration.
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+ }
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+
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+ required Type cmdType = 1; // Type of the command
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+ optional RegisteredCmdResponseProto registerNode = 2;
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+
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+}
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+
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+
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+
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+/**
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+ * Protocol used from a datanode to StorageContainerManager.
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+ *
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+ * Please see the request and response messages for details of the RPC calls.
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+ *
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+ * Here is a simple state diagram that shows how a datanode would boot up and
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+ * communicate with SCM.
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+ *
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+ * +-----------------------+
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+ * | Start |
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+ * +----------+------------+
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+ * |
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+ * |
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+ * |
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+ * |
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+ * |
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+ * |
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+ * |
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+ * +----------v-------------+
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+ * | Searching for SCM +------------+
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+ * +----------+-------------+ |
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+ * | |
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+ * | |
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+ * | +----------v-------------+
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+ * | | Register if needed |
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+ * | +-----------+------------+
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+ * | |
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+ * v |
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+ * +-----------+----------------+ |
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+ * +---------+ Heartbeat state <--------+
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+ * | +--------^-------------------+
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+ * | |
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+ * | |
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+ * | |
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+ * | |
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+ * | |
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+ * | |
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+ * | |
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+ * +------------------+
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+ *
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+ *
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+ *
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+ * Here is how this protocol is used by the datanode. When a datanode boots up
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+ * it moves into a stated called SEARCHING_SCM. In this state datanode is
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+ * trying to establish communication with the SCM. The address of the SCMs are
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+ * retrieved from the configuration information.
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+ *
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+ * In the SEARCHING_SCM state, only rpc call made by datanode is a getVersion
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+ * call to SCM. Once any of the SCMs reply, datanode checks if it has a local
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+ * persisted datanode ID. If it has this means that this datanode is already
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+ * registered with some SCM. If this file is not found, datanode assumes that
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+ * it needs to do a registration.
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+ *
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+ * If registration is need datanode moves into REGISTERING_NODE state. It will
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+ * send a register call with datanodeID data structure, but with datanode UUID
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+ * will be set to an empty string.
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+ *
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+ * The response to the command contains the datanode UUID and clusterID. This
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+ * information is persisted by the datanode and moves into heartbeat state.
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+ *
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+ * Once in the heartbeat state, datanode sends heartbeats and container reports
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+ * to SCM and process commands issued by SCM until it is shutdown.
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+ *
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+ * For time being we are going to use SCMHeartbeatResponseProto as the return
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+ * type for register and sendheartbeat messages.
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+ */
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+service StorageContainerDatanodeProtocolService {
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+
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+ /**
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+ * Gets the version information from the SCM.
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+ */
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+ rpc getVersion(SCMVersionRequestProto) returns (SCMVersionResponseProto);
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+
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+ /**
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+ * Registers a data node with SCM.
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+ */
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+ rpc register(SCMHeartbeatRequestProto) returns (SCMHeartbeatResponseProto);
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+
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+ /**
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+ * Send heartbeat from datanode to SCM. HB's under SCM looks more
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+ * like life line protocol than HB's under HDFS. In other words, it is
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+ * extremely light weight and contains no data payload.
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+ */
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+ rpc sendHeartbeat(SCMHeartbeatRequestProto) returns (SCMHeartbeatResponseProto);
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+
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+}
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Anu Engineer