- 開始: 用zookeeper协调分布式程序
-
- 单例操作
- 管理zookeeper存储
- 连接zookeeper
- 执行zookeeper
- 以复制模式执行zookeeper
- 其他优化
文章主要是针对0基础想尝试使用zookeeper的开发人员，当中包括了一些简单的样例。仅用一台zookeeperserver，一些命令确认server正在执行，一个简单的程序样例。
文章最后，为了方便，也有一些内容考虑到一些相对复杂些的样例。列如，以复制模式部署，优化事务。
可是假设想运用到商业项目中。请參阅 ZooKeeper Administrator's Guide.
这个时间好比是zookeeper的心跳时间，是最小会话单元的超时时间范围是这个时间的2倍。
假如进程执行失败，zookeeper服务就会挂掉。单例模式启动对于开发环境来说是最好的。假设想已复制模式启动请看Running Replicated ZooKeeper.
- Java: Use
bin/zkCli.sh -server 127.0.0.1:2181This lets you perform simple, file-like operations. -
C: compile cli_mt (multi-threaded) or cli_st (single-threaded) by running make cli_mt or make cli_st in the src/c subdirectory in the ZooKeeper sources. See the README contained within src/c for full details.
You can run the program from src/c using:
LD_LIBRARY_PATH=. cli_mt 127.0.0.1:2181or
LD_LIBRARY_PATH=. cli_st 127.0.0.1:2181This will give you a simple shell to execute file system like operations on ZooKeeper.
Once you have connected, you should see something like:
Connecting to localhost:2181
log4j:WARN No appenders could be found for logger (org.apache.zookeeper.ZooKeeper).
log4j:WARN Please initialize the log4j system properly.
Welcome to ZooKeeper!
JLine support is enabled
[zkshell: 0]
[zkshell: 0] help
ZooKeeper host:port cmd args
get path [watch]
ls path [watch]
set path data [version]
delquota [-n|-b] path
quit
printwatches on|off
create path data acl
stat path [watch]
listquota path
history
setAcl path acl
getAcl path
sync path
redo cmdno
addauth scheme auth
delete path [version]
deleteall path
setquota -n|-b val path
[zkshell: 9] create /zk_test my_data
Created /zk_test
[zkshell: 11] ls /
[zookeeper, zk_test]
你能够确认下和这个节点关联的数据通过执行
get命令。例如以下：
[zkshell: 12] get /zk_test
my_data
cZxid = 5
ctime = Fri Jun 05 13:57:06 PDT 2009
mZxid = 5
mtime = Fri Jun 05 13:57:06 PDT 2009
pZxid = 5
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0
dataLength = 7
numChildren = 0
[zkshell: 14] set /zk_test junk
cZxid = 5
ctime = Fri Jun 05 13:57:06 PDT 2009
mZxid = 6
mtime = Fri Jun 05 14:01:52 PDT 2009
pZxid = 5
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0
dataLength = 4
numChildren = 0
[zkshell: 15] get /zk_test
junk
cZxid = 5
ctime = Fri Jun 05 13:57:06 PDT 2009
mZxid = 6
mtime = Fri Jun 05 14:01:52 PDT 2009
pZxid = 5
cversion = 0
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0
dataLength = 4
numChildren = 0
[zkshell: 16] delete /zk_test
[zkshell: 17] ls /
[zookeeper]
[zkshell: 18]
Programming to ZooKeeper
ZooKeeper has a Java bindings and C bindings. They are functionally equivalent. The C bindings exist in two variants: single threaded and multi-threaded. These differ only in how the messaging loop is done. For more information, see the Programming Examples in the ZooKeeper Programmer's Guide for sample code using of the different APIs.
这个文件和上面介绍单例模式使用的配置文件和类似。仅仅是有一点小小的不同，例如以下：
tickTime=2000
dataDir=/var/lib/zookeeper
clientPort=2181
initLimit=5
syncLimit=2
server.1=zoo1:2888:3888
server.2=zoo2:2888:3888
server.3=zoo3:2888:3888
当server启动的时候，通过寻找在数据文件夹的myid文件知道是哪台server。这个文件含有以
ASCII编码的server编号。尤其在zookeeperserver依次连接到leader时候。当一个新的leader诞生时，小弟们会通过这个port号利用tcp协议连接到leader。由于默认leader也用tcp协议。我们必需要求另外一个port用于选举leader。就是属性server的第二个port号。
（在这个复制模式执行的样例里，每一个执行在单一的机器都有一个配置文件）