Oracle RAC 客户端故障转移(failover) TAF
2015-10-23 17:26
531 查看
Oracle RAC
客户端故障转移(failover),当采用TAF方式时,对于已经建立连接的客户端,在连接的实例或节点出现故障时,客户端无需再次发出连接请求,仍然
可以继续之前的数据库操作,此称之为透明故障转移。本文描述基于Oracle 10g rac,客户端TAF方式的故障转移并给出示例。
下面是一些关于这方面的基础参考链接:
有关负监听配置,载均衡(load balance)以及Oracle service请参考
ORACLE RAC 监听配置 (listener.ora tnsnames.ora)
ORACLE RAC 下非缺省端口监听配置(listener.ora tnsnames.ora)
Oracle RAC 客户端连接负载均衡(Load Balance)
Oracle RAC 服务器端连接负载均衡(Load Balance)
Oracle RAC 负载均衡测试(结合服务器端与客户端)
有关Oracle RAC failover 连接时故障转移请参考
Oracle RAC failover 测试(连接时故障转移)
Oracle RAC failover 测试(Server TAF方式)
- 1、TAF描述
- #下面关于TAF来自Oracle 的官方描述 ID 453293.1
- Transparent Application Failover (TAF) is a feature of the Oracle Call Interface (OCI) driver at client side.
- It enables the application to automatically reconnect to a database, if the database instance to which the connection is
- made fails. In this case, the active transactions roll back.
- Tnsnames Parameter: FAILOVER_MODE
- When an instance to which a connection is established fails or is shutdown, the connection on the client side becomes
- stale and would throw exceptions to the caller trying to use it. TAF enables the application to transparently reconnect
- to a preconfigured secondary instance creating a fresh connection, but identical to the connection that was established
- on the first original instance.
- #简单一点来说,就是说对于那些已经成功连接到特定实例的客户端,如果该实例或节点异常宕机,客户端会自动重新发出到剩余实例的连
- #接请求。使得客户端感觉不到它所连接的实例或节点已经出现故障,这个就称之为透明转移。但其间的活动事务将被回滚。
- #通过在客户端的tnsnames.ora中配置FAILOVER_MODE项实现TAF
- 2、服务器端、客户端的环境
- #服务器端环境,host信息
- oracle@bo2dbp:~> cat /etc/hosts |grep vip
- 192.168.7.61 bo2dbp-vip.2gotrade.com bo2dbp-vip
- 192.168.7.62 bo2dbs-vip.2gotrade.com bo2dbs-vip
- #服务器端环境,集群信息
- oracle@bo2dbp:~> ./crs_stat.sh
- Resource name Target State
- -------------- ------ -----
- ora.GOBO4.GOBO4A.inst OFFLINE OFFLINE on bo2dbp #此时节点1上的实例被关闭
- ora.GOBO4.GOBO4B.inst ONLINE ONLINE on bo2dbs
- ora.GOBO4.db ONLINE ONLINE on bo2dbp
- ora.bo2dbp.ASM1.asm ONLINE ONLINE on bo2dbp
- ora.bo2dbp.LISTENER_BO2DBP.lsnr ONLINE ONLINE on bo2dbp
- ora.bo2dbp.LISTENER_ORA10G_BO2DBP.lsnr ONLINE ONLINE on bo2dbp
- ora.bo2dbp.gsd ONLINE ONLINE on bo2dbp
- ora.bo2dbp.ons ONLINE ONLINE on bo2dbp
- ora.bo2dbp.vip ONLINE ONLINE on bo2dbp
- ora.bo2dbs.ASM2.asm ONLINE ONLINE on bo2dbs
- ora.bo2dbs.LISTENER_BO2DBS.lsnr ONLINE ONLINE on bo2dbs
- ora.bo2dbs.LISTENER_ORA10G_BO2DBS.lsnr ONLINE ONLINE on bo2dbs
- ora.bo2dbs.gsd ONLINE ONLINE on bo2dbs
- ora.bo2dbs.ons ONLINE ONLINE on bo2dbs
- ora.bo2dbs.vip ONLINE ONLINE on bo2dbs
- ora.ora10g.db ONLINE ONLINE on bo2dbp
- #客户端环境
- robin@SZDB:~> cat /etc/issue
- Welcome to SUSE Linux Enterprise Server 10 SP3 (x86_64) - Kernel \r (\l).
- robin@SZDB:~> sqlplus -v
- SQL*Plus: Release 10.2.0.3.0 - Production
- #客户端tnsnames配置
- GOBO4_TAF =
- (DESCRIPTION =
- (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.7.61)(PORT = 1521))
- (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.7.62)(PORT = 1521))
- (LOAD_BALANCE = yes)
- (CONNECT_DATA =
- (SERVER = DEDICATED)
- (SERVICE_NAME = GOBO4)
- (FAILOVER_MODE = #FAILOVER_MODE项参数
- (TYPE = session)
- (METHOD = basic)
- (RETRIES = 180
- (DELAY = 5)
- )
- )
- )
- 3、FAILOVER_MODE项分析
- FAILOVER_MODE项是实现TAF的主要配置内容,下面对其进行描述.
- METHOD: 用户定义何时创建到其实例的连接,有BASIC 和 PRECONNECT 两种可选值
- BASIC: 客户端通过地址列表成功建立连接后,即仅当客户端感知到节点故障时才创建到其他实例的连接
- PRECONNECT: 预连接模式,是在最初建立连接时就同时建立到所有实例的连接,当发生故障时,立刻就可以切换到其他链路上
- 上述两种方式各有优劣,前者建立连接的开销相对较小,但failover时会产生延迟,而后者正好与前者相反
- TYPE: 用于定义发生故障时对完成的SQL 语句如何处理,其中有2种类型:session 和select
- select:使用select方式,Oracle net会跟踪事务期间的所有select语句,并跟踪每一个与当前select相关的游标已返回多少行给客户
- 端。此时,假定select查询已返回500行,客户端当前连接的节点出现故障,Oracle Net自动建立连接到幸存的实例上并继续返回
- 剩余的行数给客户端。假定总行数为1500,行,则1000行从剩余节点返回。
-
session: 使用session方式,所有select查询相关的结果在重新建立新的连接后将全部丢失,需要重新发布select命令。
-
Failover Type Events
The following are possible failover types in the OracleOCI Failover interface:-
FO_SESSION
Is equivalent to FAILOVER_MODE=SESSION in the tnsnames.ora file CONNECT_DATA flags. This means that only the user session is re-authenticated on the server-side while open cursors in the OCI application need to be re-executed. -
FO_SELECT
Is equivalent to FAILOVER_MODE=SELECT in tnsnames.ora file CONNECT_DATA flags. This means that not only the user session is re-authenticated on the server-side, but open cursors in the OCI can continue fetching. This implies that the client-side logic maintains fetch-state of each open cursor. -
FO_NONE
Is equivalent to FAILOVER_MODE=NONE in the tnsnames.ora file CONNECT_DATA flags. This is the default, in which no failover functionality is used. This can also be explicitly specified to prevent failover from happening. Additionally, FO_TYPE_UNKNOWN implies that a bad failover type was returned from the OCI driver - 上述两种方式适用于不同的情形,对于select方式,通常使用与OLAP数据库,而对于session方式则使用与OLTP数据库。因为select
- 方式,Oracle 必须为每个session保存更多的内容,包括游标,用户上下文等,需要更多的资源。
- 其次,两种方式期间所有未提交的DML事务将自动回滚且必须重启启动。alter session语句不会failover。
- 临时对象不会failover也不能被重新启动。
- RETRIES: 表示重试的次数
- DELAY:表示重试的间隔时间
- 4、测试TAF
- #首次建立连接,此时客户端从tnsnames配置的第一个IP建立连接,由于第一个VIP所在的实例已经关闭,故连接到192.168.7.62
- #VIP 192.168.7.62对应的hostname以及instance_name分别为bo2dbs,GOBO4B,所以我们获得如下返回结果
- #其次我们可以看到当前session failover的相关参数
- robin@SZDB:~> sqlplus <a href="mailto:fail_over/fail@gobo4_taf">fail_over/fail@gobo4_taf
- fail_over@GOBO4> get verify.sql
- 1 REM the following query is for TAF connection verification
- 2 col sid format 99999
- 3 col serial# format 9999999
- 4 col failover_type format a13
- 5 col failover_method format a15
- 6 col failed_over format a11
- 7 Prompt
- 8 Prompt Failover status for current user
- 9 Prompt ============================================
- 10 SELECT sid,
- 11 serial#,
- 12 failover_type,
- 13 failover_method,
- 14 failed_over
- 15 FROM v$session
- 16 WHERE username = 'FAIL_OVER';
- 17 REM the following query is for load balancing verification
- 18 col host_name format a20
- 19 Prompt
- 20 Prompt Current instance name and host name
- 21 Prompt ========================================
- 22* SELECT instance_name,host_name FROM v$instance;
- 23
- fail_over@GOBO4> @verify
- Failover status for current user
- ============================================
- SID SERIAL# FAILOVER_TYPE FAILOVER_METHOD FAILED_OVER
- ------ -------- ------------- --------------- -----------
- 1063 1175 SESSION BASIC NO
- Current instance name and host name
- ========================================
- INSTANCE_NAME HOST_NAME
- ---------------- --------------------
- GOBO4B bo2dbs
- #此时启动第一个实例GOBO4A,并停止第二个实例
- oracle@bo2dbp:~> srvctl start instance -d GOBO4 -i GOBO4A
- oracle@bo2dbp:~> srvctl stop instance -d GOBO4 -i GOBO4B
- #查看两个实例的状态
- oracle@bo2dbp:~> ./crs_stat.sh | grep inst
- ora.GOBO4.GOBO4A.inst ONLINE ONLINE on bo2dbp
- ora.GOBO4.GOBO4B.inst OFFLINE OFFLINE
- #在客户端的session再次检查连接状态,即执行查询,结果如下,我们收到了ORA-25408
- fail_over@GOBO4> @verify
- Failover status for current user
- ============================================
- SELECT sid,
- *
- ERROR at line 1:
- ORA-25408: can not safely replay call
- Current instance name and host name
- ========================================
- INSTANCE_NAME HOST_NAME
- ---------------- --------------------
- GOBO4A bo2dbp
- #再次执行查询,此时客户端已经自动实现了重新连接,从查询返回得到的INSTANCE_NAME与HOST_NAME可知。
- #最重要的一个FAILED_OVER值为YES,表明当前的session是一个failover来的session。
- #关于METHOD使用PRECONNECT与TYPE使用SELECT的方式在此不作演示
- fail_over@GOBO4> @verify
- Failover status for current user
- ============================================
- SID SERIAL# FAILOVER_TYPE FAILOVER_METHOD FAILED_OVER
- ------ -------- ------------- --------------- -----------
- 1073 29 SESSION BASIC YES
- Current instance name and host name
- ========================================
- INSTANCE_NAME HOST_NAME
- ---------------- --------------------
- GOBO4A bo2dbp
- #Author : Robinson
- #Blog : http://blog.csdn.net/robinson_0612
- 5、小结:
- a、客户端TAF方式实现了Oracle客户端到服务器透明故障转移
- b、主要在客户端tnsnames.ora配置FAILOVER_MODE来实现基于客户端的TAF
- c、FAILOVER_MODE中基于连接方式(METHOD)可以分为BASIC与PRECONNECT两种方式,后者开销更大,延迟小,与前者相反
- d、FAILOVER_MODE中TYPE可以分为select与session两种方式,两者所有未提交的事务全部回滚,select方式会failover查询,
- session方式不会。select方式多用在OLAP类型数据库,而session多用在OLTP类型数据库
- e、一旦所在的实例发生故障,会自动failover,无需手动重新连接,这就是与连接时故障转移所不同的。
来自 “ ITPUB博客 ” ,链接:http://blog.itpub.net/29446986/viewspace-1815944/,如需转载,请注明出处,否则将追究法律责任。
转载于:http://blog.itpub.net/29446986/viewspace-1815944/
相关文章推荐
- Windows Server 2008 故障转移群集(Failover Cluster)简介
- ORACLE RAC安装问题解决记录(3)- SYS用户不支持TAF故障切换
- MySQL 自动故障转移工具--mysqlfailover
- Oracle RAC failover 测试(Server TAF方式)
- 连接时的故障转移和客户端负载均衡
- The Failover Transport(失败故障转移传输)
- Oracle RAC failover 测试(连接时故障转移)
- 站点与客户端的自动故障转移1
- 客户端负载均衡及透明应用切换(TAF)tnsnames failover=on
- Oracle RAC TAF 无缝failover
- Oracle RAC TAF 无缝failover
- DHCP FailOver 主备故障转移+多网段网络环境系统部署
- Oracle 10g RAC系列之 FAILOVER(故障转移)
- couchbase failover 集群故障自动转移方案研究!
- [转] 微软SQL Server 2008故障转移集群概述(Windows Server Failover Clustering (WSFC))
- keepalived+redis 实现高可用的自动故障转移failover
- hadoop 2.x之HDFS HA讲解之十一测试failover故障转移和隔离、使用sshfence隔离的配置ssh无密钥登陆
- couchbase failover 集群故障自动转移方案研究!
- Oracle RAC failover 测试(TAF方式)
- Oracle 10g RAC系列之 FAILOVER(故障转移)