报错背景：
CDH未关闭的情况下，Linux断电，导致cloudera-scm-server无法启动。
报错现象：
输入启动命令之后：/opt/cm-5.15.1/etc/init.d/cloudera-scm-server start，
cloudera-scm-server 会启动，但是几秒中之后就会死掉，显示：cloudera-scm-server 已死，但 pid 文件存在。
于是查看日志文件：vim /opt/cm-5.15.1/log/cloudera-scm-server/cloudera-scm-server.log，
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.cloudera.server.cmf.TrialState': Cannot resolve reference to bean 'entityManagerFactoryBean' while setting constructor argument; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactoryBean': FactoryBean threw exception on object creation; nested exception is javax.persistence.PersistenceException: org.hibernate.exception.GenericJDBCException: Could not open connection
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:)
at org.springframework.beans.factory.support.ConstructorResolver.resolveConstructorArguments(ConstructorResolver.java:)
at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:)
at org.springframework.beans.factory.support.AbstractBeanFactory$.getObject(AbstractBeanFactory.java:)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:)
at com.cloudera.server.cmf.Main.bootstrapSpringContext(Main.java:)
at com.cloudera.server.cmf.Main.<init>(Main.java:)
at com.cloudera.server.cmf.Main.main(Main.java:)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactoryBean': FactoryBean threw exception on object creation; nested exception is javax.persistence.PersistenceException: org.hibernate.exception.GenericJDBCException: Could not open connection
at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:)
at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:)
at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:)
... more
Caused by: javax.persistence.PersistenceException: org.hibernate.exception.GenericJDBCException: Could not open connection
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:)
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:)
at org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:)
at org.hibernate.ejb.TransactionImpl.begin(TransactionImpl.java:)
at com.cloudera.enterprise.AbstractWrappedEntityManager.beginForRollbackAndReadonly(AbstractWrappedEntityManager.java:)
at com.cloudera.enterprise.dbutil.DbUtil.isInnoDbEnabled(DbUtil.java:)
at com.cloudera.server.cmf.bootstrap.EntityManagerFactoryBean.checkMysqlTableEngineType(EntityManagerFactoryBean.java:)
at com.cloudera.server.cmf.bootstrap.EntityManagerFactoryBean.getObject(EntityManagerFactoryBean.java:)
at com.cloudera.server.cmf.bootstrap.EntityManagerFactoryBean.getObject(EntityManagerFactoryBean.java:)
at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:)
... more
Caused by: org.hibernate.exception.GenericJDBCException: Could not open connection
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:)
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:)
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.getConnection(LogicalConnectionImpl.java:)
at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.doBegin(JdbcTransaction.java:)
at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.begin(AbstractTransactionImpl.java:)
at org.hibernate.internal.SessionImpl.beginTransaction(SessionImpl.java:)
at org.hibernate.ejb.TransactionImpl.begin(TransactionImpl.java:)
... more
Caused by: java.sql.SQLException: Connections could not be acquired from the underlying database!
at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:)
at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:)
at org.hibernate.service.jdbc.connections.internal.C3P0ConnectionProvider.getConnection(C3P0ConnectionProvider.java:)
at org.hibernate.internal.AbstractSessionImpl$NonContextualJdbcConnectionAccess.obtainConnection(AbstractSessionImpl.java:)
at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:)
... more
Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.
at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:)
at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:)
at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutAndMarkConnectionInUse(C3P0PooledConnectionPool.java:)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:)
... more
Caused by: java.sql.SQLException: Access denied for user 'scm'@'master' (using password: YES)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:)
at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:)
at sun.reflect.GeneratedConstructorAccessor5.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:)
at java.lang.reflect.Constructor.newInstance(Constructor.java:)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:)
at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:)
at com.mchange.v2.resourcepool.BasicResourcePool.access$(BasicResourcePool.java:)
at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:)
at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:)
报错原因：
日志里面写的很清楚，
原因：Access denied for user 'scm'@'master' (using password: YES)
翻译：用户“scm”@“主机”拒绝访问（使用密码：是）
为什么会拒绝访问呢？一头雾水啊！！！
分析以下，拒绝访问可能是没有权限访问，或者MySQL数据库没有启动。
首先排除MySQL数据库没有启动的原因，接下来就是寻找没有访问权限的原因了。
根据百度的结果，大部分造成此种结果的原因是没有提供MySQL的远程访问权限。
但是我很确定当时我已经设置了MySQL数据库开放远程访问权限。
走投无路，只能死马当作活马医了，重新开放权限。
报错解决：
[root@master sources]# mysql -uroot -proot
mysql> use mysql;
mysql> select host,user,password from user;
mysql> update user set password=password('root') where user='root';
mysql> grant all privileges on *.* to 'root'@'master' identified by 'root'; --'root'@'%'中 %代表所有主机
但是执行到上面这一步的时候又报错：
Access denied for user 'root'@'master' (using password: YES)
这次我是彻底懵逼了，为了解决权限的错误执行的命令竟然报出权限的错误。
在网上找了很长时间也没有找到解决方案，于是我只能重装数据库了。
重装完成数据库之后，再次执行赋予远程登录的权限就成功了。
mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A Database changed
mysql> select host,user,password from user;
+-----------+------+-------------------------------------------+
| host | user | password |
+-----------+------+-------------------------------------------+
| localhost | root | *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B |
| master | root | *D2338747885A51AACEED4A7276143CB759A5B844 |
| 127.0.0.1 | root | *D2338747885A51AACEED4A7276143CB759A5B844 |
| ::1 | root | *D2338747885A51AACEED4A7276143CB759A5B844 |
+-----------+------+-------------------------------------------+
4 rows in set (0.00 sec) mysql> update user set password=password('root') where user='root';
Query OK, 3 rows affected (0.00 sec)
Rows matched: 4 Changed: 3 Warnings: 0 mysql> grant all privileges on *.* to 'root'@'master' identified by 'root';
Query OK, 0 rows affected (0.00 sec) mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec) mysql> exit
Bye
然后再执行数据库初始化
/opt/cm-5.15.1/share/cmf/schema/scm_prepare_database.sh mysql cm -hmaster -uroot -proot --scm-host master scm scm scm
参数分别是: 数据库类型 数据库名称 -h数据库主机名 -u数据库用户名 -p数据库密码--scm-host cmserver主机名 scm scm scm
主节点：通过/bigdata/cm-5.15.1/etc/init.d/cloudera-scm-server start启动服务端
[root@master /]# /opt/cm-5.15.1/etc/init.d/cloudera-scm-server start
这个时候cloudera-scm-server就不会挂掉了