org.apache.hadoop.hdfs.server.namenode.startupprogress.package-info Maven / Gradle / Ivy
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
/**
* This package provides a mechanism for tracking {@link NameNode} startup
* progress. The package models NameNode startup as a series of {@link Phase}s,
* with each phase further sub-divided into multiple {@link Step}s. All phases
* are coarse-grained and typically known in advance, implied by the structure of
* the NameNode codebase (example: loading fsimage). Steps are more granular and
* typically only known at runtime after startup begins (example: loading a
* specific fsimage file with a known length from a particular location).
*
* {@link StartupProgress} provides a thread-safe data structure for
* recording status information and counters. Various parts of the NameNode
* codebase use this to describe the NameNode's activities during startup.
*
* {@link StartupProgressView} provides an immutable, consistent view of the
* current state of NameNode startup progress. This can be used to present the
* data to a user.
*
* {@link StartupProgressMetrics} exposes startup progress information via JMX
* through the standard metrics system.
*/
@InterfaceAudience.Private
package org.apache.hadoop.hdfs.server.namenode.startupprogress;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hdfs.server.namenode.NameNode;