rahulsh1 / zoocurator

Test recipes for Apache Zookeeper along with Apache Curator

zoocurator

Explore the various recipes for Apache Zookeeper along with Apache Curator.

Recipes covered

• Discovery

1. Registration and discovery
2. Service Listener

• Path Watch

1. Tree (all changes on a certain tree)
2. Path (only immediate level children changes)

• Cache

1. Set config on a path
2. Watch changes to this config

Discovery

We will be creating some mock services, registering them so that can be discovered by other services.

Note I am using Zookeeper 3.4.6 along with Curator 2.10.0. I installed everything latest just to find it was not working. I used Zookeeper 3.4.8 along with Curator 3.1.0 and that kept throwing

 2016-03-24 22:43:03,759 [myid:] - WARN  [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:2181:ZooKeeperServer@707] - Received packet at server of unknown type 15

just to realize Curator 3.1.0 was using an alpha version of Zookeeper from maven dependencies. Curator 2.10.0 is latest too but that works with Zookeeper 3.4.6 which was released quite some time back.

Pre-requisites

• Zookeeper 3.4.6
• JDK 1.7/1.8
• Maven 3.x

Build

Download all sources and build with maven. Maven will download the correct dependencies.

$ git clone https://github.com/rahulsh1/zoocurator.git
$ cd zoocurator
$ mvn install

Run

• Start ZooKeeper server from zookeeper directory. I start this in foreground to look for interesting messages on the console.

    $ bin/zkServer.sh start-foreground
  

• Start our program. This assumes our server is running on 127.0.0.1:2181.

    $ mvn install -Prun
  

  If your server is not running on localhost or port 2181, you can use:

     $ mvn install -Prun -Dzoo.server=<server>:<port>
  

Output

$ mvn install -Prun

> help
Supported commands at the prompt:

add <name> <description>: Adds a mock service with the given name and description
delete <name>: Deletes one of the mock services with the given name
listall: Lists all the currently registered services
list <name>: Lists an instance of the service with the given name
quit: Quit the program

> add orders
Service orders registered on port 437
> add orders
Service orders registered on port 1238
> listall
Looking up orders
	orders: http://192.168.0.102:1238
	orders: http://192.168.0.102:437

From another prompt and same directory as before, run

$ mvn install -Prun

> list orders
Looking up orders
	orders: http://192.168.0.102:1238
	orders: http://192.168.0.102:437
>

Set data on certain Path and watch for changes

> set /mycache "zoo.server=abc;zoo.port=5555"      
> listen /mycache
Added watch for /mycache
> Cache changed: "zoo.server=abc;zoo.port=5555"

> set /mycache2 value1
> Cache changed: value1

> set /mycache2 value2
> Cache changed: value2

Feel free to add/delete services and check from other terminal.

Also shutdown the ZooKeeper Server and bring it back up and see if you can still see all the services registered.

Checking results with ZooKeeper Client

$ bin/zkCli.sh -server 127.0.0.1:2181

[zk: 127.0.0.1:2181(CONNECTED) 1] ls /myapp
[services]
[zk: 127.0.0.1:2181(CONNECTED) 2] ls /myapp/services/orders
[92cd30ef-d015-43d0-a7c3-730eb088f158, 897a31a6-b862-41e4-a63c-2b4210f3147c]
[zk: 127.0.0.1:2181(CONNECTED) 3] get /myapp/services/orders/

92cd30ef-d015-43d0-a7c3-730eb088f158   897a31a6-b862-41e4-a63c-2b4210f3147c
[zk: 127.0.0.1:2181(CONNECTED) 3] get /myapp/services/orders/92cd30ef-d015-43d0-a7c3-730eb088f158
{"name":"orders","id":"92cd30ef-d015-43d0-a7c3-730eb088f158","address":"192.168.0.102","port":1238,"sslPort":null,"payload":{"@class":"poc.curator.InstanceDetails","description":"orders"},"registrationTimeUTC":1458925251363,"serviceType":"DYNAMIC","uriSpec":{"parts":[{"value":"scheme","variable":true},{"value":"://","variable":false},{"value":"address","variable":true},{"value":":","variable":false},{"value":"port","variable":true}]}}
cZxid = 0x48
ctime = Fri Mar 25 10:00:51 PDT 2016
mZxid = 0x48
mtime = Fri Mar 25 10:00:51 PDT 2016
pZxid = 0x48
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x153aeb83ec60000
dataLength = 438
numChildren = 0
[zk: 127.0.0.1:2181(CONNECTED) 4]

License

MIT