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TimesTen 數據庫復制學習：8. 管理Active Standby Pair（帶緩存組）

來源：程序員人生發布時間：2016-07-15 08:44:42 閱讀次數：4610次

帶緩存組的Active standby pairs(ASP)

在不帶緩存組的ASP中，復制產生在TimesTen的表間；而在帶緩存組的ASP中，復制產生在cache table之間。帶緩沖組的復制僅支持只讀和AWT緩存組。對只讀緩存組，復制的意義在于保持狀態的連續，而對AWT，復制可以保證數據不丟失。

設置帶只讀緩存組的ASP(例)

假定active master為cachedb1，standby master為cachedb2

在active上創建dynamic readonly緩存組

cachedb1>
CREATE DYNAMIC READONLY CACHE GROUP "RO" 
 AUTOREFRESH MODE INCREMENTAL INTERVAL 5 SECONDS
 STATE PAUSED
 FROM
  "TTHR"."A" (
    "ID"   NUMBER(38)        NOT NULL,
    "NAME" VARCHAR2(32 BYTE),
    PRIMARY KEY("ID")
  )

cachedb1> cachegroups;

Cache Group TTHR.RO:

  Cache Group Type: Read Only (Dynamic)
  Autorefresh: Yes
  Autorefresh Mode: Incremental
  Autorefresh State: Paused <- 確保此狀態是paused
  Autorefresh Interval: 5 Seconds
  Autorefresh Status: ok
  Aging: LRU on

  Root Table: TTHR.A
  Table Type: Read Only

緩存組的狀態必須為paused，否則后續操作會報錯，可使用alter cache group命令修改狀態

5166: Autorefresh state ON for TTHR.RO is incompatible with replication store state Idle.  Autorefresh state should be PAUSED. Alter the autorefresh state and reexecute statement.
cachedb1> alter cache group ro set autorefresh state paused;

創建active standby pair，缺省是異步的傳輸

cachedb1> CREATE ACTIVE STANDBY PAIR cachedb1, cachedb2;

設置active數據庫的狀態為ACTIVE

cachedb1> call ttRepStateSet('ACTIVE');
cachedb1> call ttRepStateGet;
< ACTIVE, NO GRID >

啟動復制代理并動態加載1條數據

cachedb1> call ttrepstart;

cachedb1> select * from a;
cachedb1> select * from a where id = 1;
< 1, beijing >

從active復制出standby, 注意-keepCG選項

cachedb1>create user repadmin identified by timesten;
cachedb1> grant admin to repadmin;

$ ttRepAdmin -duplicate -from cachedb1 -host $(hostname)  -uid repadmin -pwd timesten -keepCG cachedb2
Enter cache administrator UID: cacheadm
Enter cache administrator password: oracle
Waiting for the Duplicate operation to complete ...

登錄cachedb2，啟動緩存和復制代理，狀態自動變成STANDBY

$ ttisql -v1 -e "set prompt 'cachedb2> '" "dsn=cachedb2;uid=tthr;pwd=timesten;oraclepwd=oracle"
cachedb2> call ttCacheStart;
cachedb2> call ttRepStateGet;
< IDLE, NO GRID >
cachedb2> call ttRepStart;
cachedb2> call ttRepStateGet;
< STANDBY, NO GRID >

緩存組的數據已復制到standby，但standby是只讀的，不能運行LOAD操作

cachedb2> select * from a;
< 1, beijing >
cachedb2> select * from a where id = 2; <-只讀
 8151: TTHR.RO's replication role disallows the requested operation

cachedb1> select * from a where id = 2;
< 2, shanghai >

cachedb2> select * from a;
< 1, beijing >
< 2, shanghai > <- 可以看到cache group的數據已復制過來
目前1切正常

設置帶AWT緩存組的ASP(例)

建立AWT緩存組, 這時候active是cachedb2, standby是cachedb1, 全部進程以下：

cachedb2>
CREATE DYNAMIC ASYNCHRONOUS WRITETHROUGH CACHE GROUP "AWT" 
 FROM
  "TTHR"."A" (
    "ID"   NUMBER(38)        NOT NULL,
    "NAME" VARCHAR2(32 BYTE),
    PRIMARY KEY("ID")
  )
  AGING LRU ON
cachedb2> cachegroups;

Cache Group TTHR.AWT:

  Cache Group Type: Asynchronous Writethrough (Dynamic)
  Autorefresh: No
  Aging: LRU on

  Root Table: TTHR.A
  Table Type: Propagate

cachedb2> call ttcachestart;
cachedb2> CREATE ACTIVE STANDBY PAIR cachedb2, cachedb1;
cachedb2> call ttrepstart;
cachedb2> call ttrepstateset('active');
cachedb2> call ttrepstateget;
< ACTIVE, NO GRID >

cachedb2> insert into a values(1, 'beijing');
cachedb2> commit;
cachedb2> select * from a;
< 1, beijing >

$ ttRepAdmin -duplicate -from cachedb2 -host $(hostname)  -uid repadmin -pwd timesten -keepCG cachedb1
Enter cache administrator UID: cacheadm
Enter cache administrator password: 
Waiting for the Duplicate operation to complete ...

$ ttisql -v1 -e "set prompt 'cachedb1> '" "dsn=cachedb1;uid=tthr;pwd=timesten;oraclepwd=oracle"
cachedb1> call ttrepstart;
cachedb1> call ttcachestart;
cachedb1> call ttrepstateget;
< STANDBY, NO GRID >
cachedb1> select * from a;
< 1, beijing >
cachedb1> insert into a values(2, 'shanghai');
16265: This store is currently the STANDBY.  Change to TTHR.A not permitted.
cachedb2> insert into a values(2, 'shanghai');
cachedb1> select * from a;
< 1, beijing >
< 2, shanghai > <- 復制的數據


cachedb1> call ttrepstop;
cachedb1> call ttRepStateSet('ACTIVE');
cachedb1> call ttrepstateget;
< ACTIVE, NO GRID >
cachedb1> call ttRepStateSave('FAILED', 'cachedb2','timesten-hol');
$ ttdestroy cachedb2

$ ttRepAdmin -duplicate -from cachedb1 -host $(hostname)  -uid repadmin -pwd timesten -keepCG -recoveringNode cachedb2
$ ttisql -v1 -e "set prompt 'cachedb2> '" "dsn=cachedb2;uid=tthr;pwd=timesten;oraclepwd=oracle"
cachedb2> call ttrepstart;
cachedb2> call ttcachestart;
calcachedb2> call ttrepstateget;
< STANDBY, NO GRID >
cachedb2> select * from a;
< 1, beijing >
< 2, shanghai >
cachedb2> insert into a values(3, 'guangzhou');
16265: This store is currently the STANDBY.  Change to TTHR.A not permitted.
cachedb1> insert into a values(3, 'guangzhou');
cachedb2> select * from a;
< 1, beijing >
< 2, shanghai >
< 3, guangzhou >

active數據庫失效時的恢復

當傳輸模式為return receipt或異步時

停止復制代理來摹擬active失效，以下是緩存組為read-only的情形，如果是AWT，也是類似的

cachedb1> call ttrepstop;

將standby提升為active, 并標記之前的active為失效狀態

cachedb2> call ttRepStateSet('ACTIVE');

cachedb2> call ttRepStateSave('FAILED', 'cachedb1','timesten-hol');

這時候新的active可以LOAD數據了

cachedb2> select * from a;
< 1, beijing >
< 2, shanghai >
cachedb2> select * from a where id = 3;
< 3, guangzhou >

燒毀原來的active，正常的情況下直接用ttdestroy便可

cachedb1> call ttcachestop;
cachedb1> drop active standby pair;
cachedb1> drop cache group ro;
cachedb1> exit
$ ttdestroy cachedb1

重新的active克隆出standby，注意-keepCG -recoveringNode選項

$ ttRepAdmin -duplicate -from cachedb2 -host $(hostname)  -uid repadmin -pwd timesten -keepCG -recoveringNode cachedb1
Enter cache administrator UID: cacheadm
Enter cache administrator password: 
Waiting for the Duplicate operation to complete ...

啟動standby的復制和緩存代理

$ ttisql -v1 -e "set prompt 'cachedb1> '" "dsn=cachedb1;uid=tthr;pwd=timesten;oraclepwd=oracle"
cachedb1> call ttrepstart;
cachedb1> call ttcachestart;
cachedb1> call ttrepstateget;
< STANDBY, NO GRID >

數據已復制到standby，但standby的緩存組不能進行LOAD操作

cachedb1> select * from a;
< 1, beijing >
< 2, shanghai >
< 3, guangzhou >
cachedb1> unload cache group ro;
16265: This store is currently the STANDBY.  Change to TTHR.A not permitted.

當傳輸模式為return twosafe時

這類情況比較簡單，由于復制時，數據是先到standby然后在active上提交的。因此很多操作都是自動的。
大不了，從standby升級為active后，再克隆出新的standby便可

standby數據庫失效時的恢復

如果復制是return twosafe, 以下是緩存組為read-only的情形

CREATE ACTIVE STANDBY PAIR cachedb1, cachedb2 return twosafe
cachedb2> unload cache group ro;
 8099: TWOSAFE operation not permitted with AutoCommit = 1.
cachedb2> set autocommit 0;
cachedb2> unload cache group ro;
cachedb2> commit;
cachedb2> select * from a;
cachedb2> select * from a where id = 1;
< 1, beijing >
cachedb1> call ttrepstateget;
< STANDBY, NO GRID >
cachedb1> select * from a;
< 1, beijing >
cachedb1> call ttrepstop;
cachedb2> select * from a where id = 2; <- HANG了1會，結果還是出來了，
< 2, shanghai >
cachedb1> select * from a;
< 1, beijing > <- 不過數據自然是不會復制過去的了

如果緩存組為AWT，并且傳輸模式為return twosafe，這時候會禁止active真個事務提交，這時候需要設置主端：

call ttRepSyncSet( null, null, 2);
commit;
ttRepStateSave('FAILED','standby_database','host_name')

然后再克隆standby

交換active和standby的角色

假定active為cachedb1，standby為cachedb2
首先停止利用更新數據庫。
cachedb1> call ttRepSubscriberWait(NULL, NULL, 'cachedb2', 'timesten-hol', 10);
< 00 > <- 返回值必須為00
call ttRepDeactivate();
cachedb1> call ttrepstop;
cachedb1> call ttRepDeactivate();
cachedb1> call ttrepstateget;
< IDLE, NO GRID >

cachedb2> call ttRepStateSet('ACTIVE');
cachedb2> call ttrepstateget;
< ACTIVE, NO GRID >

cachedb1> call ttrepstart;
cachedb1> call ttrepstateget;
< IDLE, NO GRID >
過1小會
cachedb1> call ttrepstateget;
< STANDBY, NO GRID >
好了，角色換過了了

修改復制的用戶名和口令

修改schema user的口令

這個比較簡單，如果DDLReplicationLevel 是2，則口令的修改會自動復制到standby。否則就必須手工在每個庫中修改。例如：

cachedb2> alter user tthr identified by oracle;

User altered.

[oracle@timesten-hol ~]$ ttisql -v1 -e "set prompt 'cachedb1> '" "dsn=cachedb1;uid=tthr;pwd=timesten;oraclepwd=oracle"
 7001: User authentication failed
[oracle@timesten-hol ~]$ ttisql -v1 -e "set prompt 'cachedb1> '" "dsn=cachedb1;uid=tthr;pwd=oracle;oraclepwd=oracle"

修改cache admin 用戶的口令

這個實際上是不常見的。
cache admin用戶名在Oracle和TimesTen中必須是1樣的，但口令可以不1樣
所以改口令沒甚么特別的，alter user便可。例如

Command> ALTER USER cacheadmin IDENTIFIED BY newpwd;
Command> passthrough 3; 
Command> ALTER USER cacheadm IDENTIFIED BY newpwd;

如果改用戶名，就比較麻煩了，必須先刪除掉所有的緩存組，因此不建議。

創建災備用的subscriber

目前為止，談的都是數據中心內部的HA場景，我們也能夠建立1個位于災備真個subscriber ，在故障時使其成可以繼續與Oracle同步數據，第2個Oracle 數據庫也位于災備端。

大致進程以下，由于需要建立第2個Oracle 數據庫，這里就不演示了。

在主點建立AWT緩存組的ASP
建立災備真個Oracle 數據庫
在災備端建立1個subscriber, 這里關鍵是有1個ttRepAdmin -duplicate的-initCacheDR選項

參考

http://www.oracledistilled.com/linux/configuring-an-oracle-timesten-logical-server-name-on-unix-based-systems/

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