C-JDBC(Java 數(shù)據(jù)庫連接群集)作為開發(fā)源碼的數(shù)據(jù)庫群集中間件，可以讓任何應(yīng)用程序通過JDBC能夠透明的訪問數(shù)據(jù)庫群集。數(shù)據(jù)庫可以分布在多個(gè)節(jié)點(diǎn)并可以進(jìn)行數(shù)據(jù)復(fù)制，C-JDBC能夠均衡在這些節(jié)點(diǎn)之間的查詢負(fù)載。 C-JDBC通過軟件來實(shí)現(xiàn)RAIDb(廉價(jià)數(shù)據(jù)庫冗余陣列)。C-JDBC是GNU LGPL許可證下的ObjectWeb項(xiàng)目。
http://c-jdbc.objectweb.org/網(wǎng)站上的C-JDBC-Brochure-EN.pdf寫的內(nèi)容挺好。(C-JDBC)tutorial.pdf內(nèi)容也挺翔實(shí)。
大型應(yīng)用隨著用戶量訪問越來越大，增加數(shù)據(jù)庫存儲和做好數(shù)據(jù)庫冗余可以增加系統(tǒng)的可靠性和性能。
無需修改客戶端應(yīng)用程序，無需變更應(yīng)用服務(wù)器或數(shù)據(jù)庫服務(wù)器軟件。C-JDBC的JDBC driver把SQL請求轉(zhuǎn)給C-JDBC controller(負(fù)責(zé)在databases之間做負(fù)載均衡）
The database is distributed and replicated among several nodes and C-JDBC load balances the queries between these nodes.
就這一句話就太誘人了！
上周的某一個(gè)上午，搞定C-JDBC的安裝配置啦~
主要根據(jù)官方的user guide和這篇好文: http://huaronghu.spaces.live.com/blog/cns!B9A68E1C1CA857AD!288.entry
準(zhǔn)備工作：
環(huán)境：windows,postgreSQL,JDK
建立數(shù)據(jù)庫“們”，安裝若干db在若干server上，所以如果使用商業(yè)數(shù)據(jù)庫的話，就會需要好幾套的錢哪。
安裝C-JDBC：
下載了binary版的c-jdbc-2.0.2-bin.zip，解壓到作為C-JDBC server的機(jī)器上（e.g. C:\software\c-jdbc-2.0.2-bin），
設(shè)置環(huán)境變量,新增系統(tǒng)變量:CJDBC_HOME =C:\software\c-jdbc-2.0.2-bin
把實(shí)際使用的數(shù)據(jù)庫的JDBC driver（例如mysql-connector-java-3.1.12-bin.jar ，postgresql-8.0.309.jdbc2.jar）拷貝到c-jdbc/drivers 中
配置文件：
在c-jdbc-2.0.2-bin/config/virtualdatabase目錄中創(chuàng)建虛擬數(shù)據(jù)庫配置文件。
里面DatabaseBackend 標(biāo)簽中定義的就是被集群的數(shù)據(jù)庫。
試驗(yàn)時(shí)，創(chuàng)建了文件：postgresql-raidb1-distribution.xml，使用了2個(gè)postgreSQL數(shù)據(jù)庫，采用了全復(fù)制的方法。
注意，如果采用全復(fù)制，所以在2個(gè)數(shù)據(jù)庫上建庫、建表的全部腳本都要完全相同，否則將會報(bào)出mismatch的錯(cuò)誤。
目前感覺配置里面最有用的配置就是<AuthenticationManager>，<DatabaseBackend>和<LoadBalancer>（還沒有仔細(xì)看）。
配置時(shí)可以參考已經(jīng)提供的例子，c-jdbc-2.0.2-bin/config/RAIDb-1-full-example.xml，里面對每一個(gè)屬性都有比較詳細(xì)的注釋，DatabaseBackend中還有各個(gè)開源數(shù)據(jù)庫連接的例子，挺貼心的。
<?
xml?version="1.0"?encoding="UTF8"
?>
<!
DOCTYPE?C-JDBC?PUBLIC?"-//ObjectWeb//DTD?C-JDBC?2.0.2//EN"?"http://c-jdbc.objectweb.org/dtds/c-jdbc-2.0.2.dtd"
>
<
C-JDBC
>
??
??
<
VirtualDatabase?
name
="myDB"
?maxNbOfConnections
="20"
?minNbOfThreads
="1"
?maxNbOfThreads
="20"
?blobEncodingMethod
="hexa"
>
????
<
AuthenticationManager
>
??????
<
Admin
>
???????
<
User?
username
="admin"
?password
="c-jdbc"
/>
??????
</
Admin
>
?
??????
<
VirtualUsers
>
????????
<
VirtualLogin?
vLogin
="boss"
?vPassword
="boss"
/>
??????
</
VirtualUsers
>
????
</
AuthenticationManager
>
???
<
DatabaseBackend?
name
="postgreSQLNode114"
?driver
="org.postgresql.Driver"
?url
="jdbc:postgresql://10.10.0.114:5432/clusterdb"
?connectionTestStatement
="select?now()"
>
?
<
DatabaseSchema?
dynamicPrecision
="column"
/>
??????
<
ConnectionManager?
vLogin
="boss"
?rLogin
="postgres9"
?rPassword
="12345"
>
?
<
RandomWaitPoolConnectionManager?
poolSize
="20"
/>
??????
</
ConnectionManager
>
????
</
DatabaseBackend
>
????
<
DatabaseBackend?
name
="postgreSQLNode155"
?driver
="org.postgresql.Driver"
?url
="jdbc:postgresql://10.10.0.155:5432/clusterdb"
?connectionTestStatement
="select?now()"
>
?
<
DatabaseSchema?
dynamicPrecision
="column"
/>
??????
<
ConnectionManager?
vLogin
="boss"
?rLogin
="postgres"
?rPassword
="abcde"
>
?
<
RandomWaitPoolConnectionManager?
poolSize
="20"
/>
??????
</
ConnectionManager
>
????
</
DatabaseBackend
>
????
<
RequestManager
>
??????
<
RequestScheduler
>
?????????
<
RAIDb-1Scheduler?
level
="passThrough"
/>
???
??????
</
RequestScheduler
>
??????
<
RequestCache
>
?????????
<
MetadataCache?
maxNbOfMetadata
="10000"
?maxNbOfField
="0"
/>
?????????
<
ParsingCache?
backgroundParsing
="false"
?maxNbOfEntries
="5000"
/>
???
?????????
<
ResultCache?
granularity
="table"
?maxNbOfEntries
="100000"
?pendingTimeout
="0"
>
???????
<
ResultCacheRule?
queryPattern
="default"
?timestampResolution
="1000"
>
?????????????
<
EagerCaching
/>
?????????
</
ResultCacheRule
>
?????????
</
ResultCache
>
??????
</
RequestCache
>
??????
<
LoadBalancer
>
?????????
<
RAIDb-1
>
?????????
<
RAIDb-1-LeastPendingRequestsFirst
/>
??
?????????
</
RAIDb-1
>
??????
</
LoadBalancer
>
????????
????
</
RequestManager
>
??
</
VirtualDatabase
>
</
C-JDBC
>
?
在c-jdbc-2.0.2-bin/config/controller目錄中創(chuàng)建一個(gè)c-jdbc controller的配置文件。
試驗(yàn)時(shí)，創(chuàng)建的配置文件為：uud-controller-distributed.xml
<?
xml?version="1.0"?encoding="UTF8"?
?>
<!
DOCTYPE?C-JDBC-CONTROLLER?PUBLIC?"-//ObjectWeb//DTD?C-JDBC-CONTROLLER?2.0.2//EN"??"http://c-jdbc.objectweb.org/dtds/c-jdbc-controller-2.0.2.dtd"
>
<
C-JDBC-CONTROLLER
>
??
<
Controller?
port
="25322"
>
????
<
Report
/>
????
<
JmxSettings
>
??????
<
RmiJmxAdaptor?
port
="1091"
/>
????
</
JmxSettings
>
????
<
VirtualDatabase?
configFile
="postgresql-raidb1-distribution.xml"
?virtualDatabaseName
="myDB"
?autoEnableBackends
="true"
?checkpointName
="Initial_empty_recovery_log"
/>
??
</
Controller
>
</
C-JDBC-CONTROLLER
>
?
注意：Controller和VirtualMachine的配置文件不能采用相同的文件名
啟動(dòng)：
在c-jdbc-2.0.2-bin\bin目錄下，運(yùn)行controller.bat -f ../config/controller/uud-controller-distributed.xml
unix用戶使用controller.sh來啟動(dòng)controller
截圖：（下回補(bǔ)）
湊合看一下吧，控制臺的正常輸出：
C:\software\c-jdbc-2.0.2-bin\bin>controller.bat -f ../config/controller/uud-cont
roller-distributed.xml
2007-03-07 15:16:44,017 INFO? controller.core.Controller C-JDBC controller (2.0.
2)
2007-03-07 15:16:44,439 INFO? controller.core.Controller Loading configuration f
ile: ../config/controller/uud-controller-distributed.xml
2007-03-07 15:16:44,752 INFO? controller.core.Controller JMX is enabled
2007-03-07 15:16:44,830 INFO? controller.core.Controller Starting JMX server on
host: 10.10.0.155
2007-03-07 15:16:46,376 INFO? backend.DatabaseBackend.postgreSQLNode114 Adding c
onnection manager for virtual user "boss"
2007-03-07 15:16:46,501 INFO? backend.DatabaseBackend.postgreSQLNode155 Adding c
onnection manager for virtual user "boss"
2007-03-07 15:16:46,642 INFO? controller.RequestManager.myDB Request manager wil
l parse requests with the following granularity: TABLE
2007-03-07 15:16:46,657 WARN? controller.virtualdatabase.myDB No recovery log ha
s been configured, enabling backend without checkpoint.
2007-03-07 15:16:48,641 INFO? backend.DatabaseBackend.postgreSQLNode114 Detected
?backend as: PostgreSQL
2007-03-07 15:16:49,063 WARN? backend.DatabaseBackend.postgreSQLNode114 Statemen
t.getGeneratedKeys not supported.
2007-03-07 15:16:49,579 INFO? backend.DatabaseBackend.postgreSQLNode114 Gatherin
g database schema
2007-03-07 15:16:49,782 INFO? controller.RequestManager.myDB Setting new virtual
?database schema.
2007-03-07 15:16:49,782 INFO? cjdbc.controller.cache Setting new database schema
.
2007-03-07 15:16:49,782 INFO? controller.loadbalancer.RAIDb1 Adding blocking tas
k worker thread for backend postgreSQLNode114
2007-03-07 15:16:49,797 INFO? controller.loadbalancer.RAIDb1 Adding non blocking
?task worker thread for backend postgreSQLNode114
2007-03-07 15:16:49,797 INFO? controller.RequestManager.myDB Database backend po
stgreSQLNode114 is now enabled
2007-03-07 15:16:50,922 INFO? backend.DatabaseBackend.postgreSQLNode155 Detected
?backend as: PostgreSQL
2007-03-07 15:16:51,328 WARN? backend.DatabaseBackend.postgreSQLNode155 Statemen
t.getGeneratedKeys not supported.
2007-03-07 15:16:52,172 INFO? backend.DatabaseBackend.postgreSQLNode155 Gatherin
g database schema
2007-03-07 15:16:52,390 INFO? controller.RequestManager.myDB Virtual database sc
hema merged with new schema.
2007-03-07 15:16:52,390 INFO? cjdbc.controller.cache Merging new database schema
2007-03-07 15:16:52,390 INFO? controller.loadbalancer.RAIDb1 Adding blocking tas
k worker thread for backend postgreSQLNode155
2007-03-07 15:16:52,390 INFO? controller.loadbalancer.RAIDb1 Adding non blocking
?task worker thread for backend postgreSQLNode155
2007-03-07 15:16:52,406 INFO? controller.RequestManager.myDB Database backend po
stgreSQLNode155 is now enabled
2007-03-07 15:16:52,422 WARN? VirtualDatabaseWorkerThread.myDB.metadata Metadata
?key [getMaxColumnsInIndex] is not compatible. (Backends are: [jdbc:postgresql:/
/10.10.0.114:5432/clusterdb] and [jdbc:postgresql://10.10.0.155:5432/clu
sterdb] ; Values are:[32] and [0])
2007-03-07 15:16:52,422 INFO? controller.core.Controller Adding VirtualDatabase
myDB
2007-03-07 15:16:52,437 INFO? controller.core.Controller Waiting for connections
?on 0.0.0.0:25322
2007-03-07 15:16:52,469 INFO? controller.core.Controller Controller started on 2
007.03.07 10 at 03:16:52 下午 GMT+08:00
2007-03-07 15:16:52,484 INFO? controller.core.Controller Controller 10.10.0.
155:25322 ready, listening to requests ...
遇到過的問題：
1、
剛啟動(dòng)沒一會兒，就看到config文件讀取錯(cuò)誤，控制臺信息也就此結(jié)束。
解決方法：controller.bat -f filename中filename的相對路徑和文件名竟然都寫錯(cuò)了，汗。。。。
2、
啟動(dòng)時(shí)，控制臺拋出ERROR以及exception，大意是connection failed, IP沒有配置到pg_hba.conf中
解決方法：雖然是連本機(jī)的一個(gè)數(shù)據(jù)庫，但是由于數(shù)據(jù)庫連接的url里面寫的是IP地址，所以仍然要把本機(jī)的IP地址配置到pg_hba.conf以允許其訪問。
3、
還是啟動(dòng)時(shí)拋錯(cuò)了，Connection test failed(org.postgresql.util.PSQLException:Backend start-up failed:FATAL:role "boss_user" does not exist.)
解決方法：原來是在自己寫的.xml配置文件中，DatabaseBackend標(biāo)簽里面寫的用戶名和密碼需要是真實(shí)數(shù)據(jù)庫的真實(shí)用戶名和密碼。
最后都整好了,但是遇到一個(gè)warn的log：
backend.DatabaseBackend.postgreSQLNode155 Statement.getGeneratedKeys not supported
至今不知道是什么問題,有什么影響.
代碼部分：
只需要修改應(yīng)用程序用到的jdbc driver的配置，把c-jdbc/drivers/目錄下的c-jdbc-driver.jar拷貝到應(yīng)用程序的工程里，并加入到class-path中。
之前是使用 Class.forName("com.somevendor.jdbcDriver.Driver") 去連接某特定的數(shù)據(jù)庫
現(xiàn)在是使用 Class.forName("org.objectweb.cjdbc.driver.Driver") 統(tǒng)一處理。
連接字符串：DriverManager.getConnection("jdbc:cjdbc://localhost:25322/mycjdbc") 取得數(shù)據(jù)庫連接。
c-jdbc server稱為c-jdbc controller，聆聽請求們
其他所有通過c-jdbc來訪問的DB們稱為db backends.
jdbc:cjdbc://host1:port1,host2:port2/database
host是指跑著c-jdbc controller的機(jī)器IP，port是指controller監(jiān)聽客戶端鏈接的端口，默認(rèn)端口號：25322
注意，不僅真正的DB安裝多個(gè)在多個(gè)機(jī)器上，c-jdbc controller也可以安在不同的機(jī)器上,這樣可以防止一個(gè)c-jdbc 壞掉帶來的風(fēng)險(xiǎn)。
例如：
Class.forName(
"
org.objectweb.cjdbc.driver.Driver
"
);?
DriverManager.getConnection(
"
jdbc:cjdbc://c1.objectweb.org,c2.objectweb.org/tpcw
"
);?
//
不驗(yàn)證用戶名密碼
DriverManager.getConnection(
"
jdbc:cjdbc://host/db?user=me&password=secret
"
)
//
驗(yàn)證用戶名密碼的寫法1
DriverManager.getConnection(
"
jdbc:cjdbc://host/db;user=me;password=secret
"
)
//
驗(yàn)證用戶名密碼的寫法2
然后可以在代碼中insert/update幾個(gè)記錄，再單獨(dú)到各個(gè)數(shù)據(jù)庫中去查一下，應(yīng)該都受到影響就對了。
問題：
1、管理C-JDBC，不知道C-JDBC需要啥管理，不過好像是已經(jīng)有一個(gè)簡單的 Desktop Application 可以控制相關(guān)的 administration 介面, 最重要的是, 他結(jié)合了 JMX , 可以讓整個(gè)監(jiān)控的環(huán)境更完整.. （等待嘗試）
2、不知道通過C-JDBC來操作速度如何
3、RAIdb的3種類型，采取哪個(gè)更好？把表分開在不同server上對聯(lián)表查應(yīng)該不會有影響吧？
其他：
1、Configuring C-JDBC with Jakarta Tomcat
Copy the c-jdbc-driver.jar file to the lib directory of your web application (for example: $TOMCAT_HOME/webapps/mywebapp/WEB-INF/lib).
There are many ways to obtain connections from a Tomcat application. Just ensure that you are using org.objectweb.cjdbc.driver.Driver as the driver class name and that the JDBC URL is a C-JDBC URL
2、Configuring C-JDBC with Hibernate
C-JDBC just has to be defined as any JDBC driver in Hibernate, leaving the syntax set to the proper database. Here is a configuration example to use Hibernate with a C-JDBC cluster made of Sybase backends:
## C-JDBC
hibernate.dialect???????????????? net.sf.hibernate.dialect.SybaseDialect
hibernate.connection.driver_class org.objectweb.cjdbc.driver.Driver
hibernate.connection.username???? user
hibernate.connection.password???? pass
hibernate.connection.url????????? jdbc:cjdbc://localhost:25322/test???????