最近nodejs很火，我也忍不住随潮流去研究了下。
哎。都是英文文档看起来老吃力了，随便看了点，也没点具体印象。
最后看到mongodb的时候觉得挺有意思于是自己也试着接触下。
简单的CRUD就不说了，语法很好玩
db.news.find()
db.news.save({title:'testtitle',content:'testcontent',addTime:new Date()})
db.news.remove({title:'testtitle'})
db.news.update({title:'testtitle'},{$set:{title:'testtitle1'}})
简单点这样了。
下面进如主题mongodb集群（不分片，主要就是主从数据库备份，额，大概就是这么个意思）
step1：建立数据库存放地址以及日志文件
mkdir -p /root/mongo/database/r0 /root/mongo/database/r1 /root/mongo/database/r2
mkdir -p /root/mongo/log
vi /root/mongo/log/r0.log
vi /root/mongo/log/r1.log
vi /root/mongo/log/r2.log
step2:启动3个mongodb
我的mongodb路径是/root/mongodb/
/root/mongodb/bin/mongod -dbpath=/root/mongo/database/r0 -logpath=/root/mongo/log/r0.log -logappend -fork -rest -replSet mongoSet -port 27017 -directoryperdb
forked process: 1453
all output going to: /root/mongo/log/r0.log
child process started successfully, parent exiting
/root/mongodb/bin/mongod -dbpath=/root/mongo/database/r1 -logpath=/root/mongo/log/r1.log -logappend -fork -rest -replSet mongoSet -port 27018 -directoryperdb
forked process: 1517
all output going to: /root/mongo/log/r1.log
child process started successfully, parent exiting
/root/mongodb/bin/mongod -dbpath=/root/mongo/database/r2 -logpath=/root/mongo/log/r2.log -logappend -fork -rest -replSet mongoSet -port 27019 -directoryperdb
forked process: 1565
all output going to: /root/mongo/log/r2.log
child process started successfully, parent exiting
[root@nodeLinux bin]# ./mongo 127.0.0.1:27017
MongoDB shell version: 2.2.0
connecting to: 127.0.0.1:27017/test
> rs.initiate()
{
"info2" : "no configuration explicitly specified -- making one",
"me" : "nodeLinux:27017",
"info" : "Config now saved locally. Should come online in about a minute.",
"ok" : 1
}
> rs.add('127.0.0.1:27018') //这里这样不知道为什么不行
{
"errmsg" : "exception: can't use localhost in repl set member names except when using it for all members",
"code" : 13393,
"ok" : 0
}
mongoSet:PRIMARY> rs.add('localhost:27018')//这里也不行
{
"errmsg" : "exception: can't use localhost in repl set member names except when using it for all members",
"code" : 13393,
"ok" : 0
}
mongoSet:PRIMARY> rs.add('nodeLinux:27018')//只能用hostname，貌似就行了。这里也可以用rs.initiate({_id:'mongoSet',member: [{_id:0,host:'nodeLinux:27017'},{_id:1,host:'nodeLinux:27018'},{_id:2,host:'nodeLinux:27019'}]})什么的吧。我没去试，看mongodb的DOC用的add
{ "ok" : 1 }
mongoSet:PRIMARY> rs.add('nodeLinux:27019')
{ "ok" : 1 }
mongoSet:PRIMARY> rs.status()
{
"set" : "mongoSet",
"date" : ISODate("2012-09-04T05:23:32Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "nodeLinux:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 1011,
"optime" : Timestamp(1346735894000, 1),
"optimeDate" : ISODate("2012-09-04T05:18:14Z"),
"self" : true
},
{
"_id" : 1,
"name" : "nodeLinux:27018",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 318,
"optime" : Timestamp(1346735894000, 1),
"optimeDate" : ISODate("2012-09-04T05:18:14Z"),
"lastHeartbeat" : ISODate("2012-09-04T05:23:32Z"),
"pingMs" : 0
}
],
"ok" : 1
}
mongoSet:PRIMARY> use test;
switched to db test
mongoSet:PRIMARY> db.news.save({title:'testtitle',content:'testcontent',addTime:new Date()});
在另外一个窗口连接27018
[root@nodeLinux ~]# cd /root/mongodb/bin/
[root@nodeLinux bin]# ./mongo 127.0.0.1:27018
MongoDB shell version: 2.2.0
connecting to: 127.0.0.1:27018/test
mongoSet:SECONDARY> db.news.find()
error: { "$err" : "not master and slaveOk=false", "code" : 13435 }//这里会报错哦，从库不能读写滴。
mongoSet:SECONDARY>rs.slaveOk()//不过这样一下就可以读了
mongoSet:SECONDARY> db.news.save({title:'testtitle111',content:'testcontent111',addTime:new Date()})//还是不能写，哈哈哈
not master
mongoSet:SECONDARY>
这就搭建完毕了，至于后面怎么弄就以后再说吧。。。
哎，这么简单的过程我搞了好几天，主要是每次建好数据库以后，在配置的时候总是提示我“all members and seeds must be reachable to initiate set”，查了点资料，说是在配置的时候要用hostname，别用IP地址，结果我用hostname也不行，哎呀，linux基础不行啊，最后纠结了好几天，查了数据库的log文件才发现每次都有这样的提示："mongodb getaddrinfo("nodeLinxu") failed: Temporary failure in name resolution"，应该是hosts没设置的原因了。。。
vi /etc/hosts加上即可，不过迷糊的是为什么127.0.0.1 nodeLinux不行呢，只能用192.168.10.28 nodeLinux(我虚拟机的IP是这个)才行。
一波十八折总算也勉强跑起来了。
