启动HBase后遇到的一个问题 有好几次，启动Hadoop和HBase之后，执行jps命令，已经看到有HMaster的进程， 但是进入到HBase的shell，执行一个命令，会出现下面的错误： ERROR: org.apache.hadoop.hbase.MasterNotRunningException: Retried 7 times 进入到logs
启动HBase后遇到的一个问题
有好几次，启动Hadoop和HBase之后，执行jps命令，已经看到有HMaster的进程，
但是进入到HBase的shell，执行一个命令，会出现下面的错误：
ERROR: org.apache.hadoop.hbase.MasterNotRunningException: Retried 7 times
进入到logs目录查看master的日志：发现一直显示下面的内容：
2013-04-13 17:13:17,374 INFO org.apache.hadoop.hbase.util.FSUtils: Waiting for dfs to exit safe mode...
2013-04-13 17:13:27,377 INFO org.apache.hadoop.hbase.util.FSUtils: Waiting for dfs to exit safe mode...
2013-04-13 17:13:37,386 INFO org.apache.hadoop.hbase.util.FSUtils: Waiting for dfs to exit safe mode...
2013-04-13 17:13:47,393 INFO org.apache.hadoop.hbase.util.FSUtils: Waiting for dfs to exit safe mode...
2013-04-13 17:13:57,395 INFO org.apache.hadoop.hbase.util.FSUtils: Waiting for dfs to exit safe mode...
2013-04-13 17:14:07,409 INFO org.apache.hadoop.hbase.util.FSUtils: Waiting for dfs to exit safe mode...
原来是Hadoop在刚启动的时候，还处在安全模式造成的。
[coder@h1 hadoop-0.20.2]$ bin/hadoop dfsadmin -safemode get
Safe mode is ON
[coder@h1 hadoop-0.20.2]$
可等Hadoop退出安全模式后再执行HBase命令，或者手动退出Hadoop的安全模式
[coder@h1 hadoop-0.20.2]$ bin/hadoop dfsadmin -safemode leave
Safe mode is OFF
[coder@h1 hadoop-0.20.2]$
现在再执行HBase的命令就没有问题了：
[coder@h1 hbase-0.90.5]$ bin/hbase shell
HBase Shell; enter 'help
Type "exit
Version 0.90.5, r1212209, Fri Dec 9 05:40:36 UTC 2011
hbase(main):001:0> list
TABLE
student
user
2 row(s) in 0.7530 seconds
hbase(main):002:0>
Explain the InnoDB Buffer Pool and its importance for performance.Apr 19, 2025 am 12:24 AMInnoDBBufferPool reduces disk I/O by caching data and indexing pages, improving database performance. Its working principle includes: 1. Data reading: Read data from BufferPool; 2. Data writing: After modifying the data, write to BufferPool and refresh it to disk regularly; 3. Cache management: Use the LRU algorithm to manage cache pages; 4. Reading mechanism: Load adjacent data pages in advance. By sizing the BufferPool and using multiple instances, database performance can be optimized.
MySQL vs. Other Programming Languages: A ComparisonApr 19, 2025 am 12:22 AMCompared with other programming languages, MySQL is mainly used to store and manage data, while other languages such as Python, Java, and C are used for logical processing and application development. MySQL is known for its high performance, scalability and cross-platform support, suitable for data management needs, while other languages have advantages in their respective fields such as data analytics, enterprise applications, and system programming.
Learning MySQL: A Step-by-Step Guide for New UsersApr 19, 2025 am 12:19 AMMySQL is worth learning because it is a powerful open source database management system suitable for data storage, management and analysis. 1) MySQL is a relational database that uses SQL to operate data and is suitable for structured data management. 2) The SQL language is the key to interacting with MySQL and supports CRUD operations. 3) The working principle of MySQL includes client/server architecture, storage engine and query optimizer. 4) Basic usage includes creating databases and tables, and advanced usage involves joining tables using JOIN. 5) Common errors include syntax errors and permission issues, and debugging skills include checking syntax and using EXPLAIN commands. 6) Performance optimization involves the use of indexes, optimization of SQL statements and regular maintenance of databases.
MySQL: Essential Skills for Beginners to MasterApr 18, 2025 am 12:24 AMMySQL is suitable for beginners to learn database skills. 1. Install MySQL server and client tools. 2. Understand basic SQL queries, such as SELECT. 3. Master data operations: create tables, insert, update, and delete data. 4. Learn advanced skills: subquery and window functions. 5. Debugging and optimization: Check syntax, use indexes, avoid SELECT*, and use LIMIT.
MySQL: Structured Data and Relational DatabasesApr 18, 2025 am 12:22 AMMySQL efficiently manages structured data through table structure and SQL query, and implements inter-table relationships through foreign keys. 1. Define the data format and type when creating a table. 2. Use foreign keys to establish relationships between tables. 3. Improve performance through indexing and query optimization. 4. Regularly backup and monitor databases to ensure data security and performance optimization.
MySQL: Key Features and Capabilities ExplainedApr 18, 2025 am 12:17 AMMySQL is an open source relational database management system that is widely used in Web development. Its key features include: 1. Supports multiple storage engines, such as InnoDB and MyISAM, suitable for different scenarios; 2. Provides master-slave replication functions to facilitate load balancing and data backup; 3. Improve query efficiency through query optimization and index use.
The Purpose of SQL: Interacting with MySQL DatabasesApr 18, 2025 am 12:12 AMSQL is used to interact with MySQL database to realize data addition, deletion, modification, inspection and database design. 1) SQL performs data operations through SELECT, INSERT, UPDATE, DELETE statements; 2) Use CREATE, ALTER, DROP statements for database design and management; 3) Complex queries and data analysis are implemented through SQL to improve business decision-making efficiency.
MySQL for Beginners: Getting Started with Database ManagementApr 18, 2025 am 12:10 AMThe basic operations of MySQL include creating databases, tables, and using SQL to perform CRUD operations on data. 1. Create a database: CREATEDATABASEmy_first_db; 2. Create a table: CREATETABLEbooks(idINTAUTO_INCREMENTPRIMARYKEY, titleVARCHAR(100)NOTNULL, authorVARCHAR(100)NOTNULL, published_yearINT); 3. Insert data: INSERTINTObooks(title, author, published_year)VA
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
SublimeText3 English version
Recommended: Win version, supports code prompts!
mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),
SublimeText3 Mac version
God-level code editing software (SublimeText3)
MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.
Atom editor mac version download
The most popular open source editor
