Eurosys 2011 Tutorial

To complete this tutorial you will need the ZooKeeper 3.3.3 "fat" jar. This has all you need to run zookeeper and develop against it.

Running the ZooKeeper server

The easiest way to run ZooKeeper, and the way that is often used for development is to use it in "standalone" mode. This starts up a single ZooKeeper server, so it is not fault tolerant. For example:

java -jar zookeeper-3.3.3-fatjar.jar server 2181 /tmp/zkdata

starts a ZooKeeper server running on port 2181. It is storing its data in /tmp, so this is obviously not a way you want to run in production.

Lets start up a ZooKeeper server cluster, so that we can experiment a bit more. To do this we need to create a configuration file for each server. Generally, we can share a configuration file across server, but since we are starting all three on the same machine, we need to have a configuration for each server:

dataDir=/tmp/1
clientPort=2181
initLimit=3
syncLimit=3
server.1:127.0.0.1:2221:3331
server.2:127.0.0.1:2222:3332
server.3:127.0.0.1:2223:3333

dataDir=/tmp/2
clientPort=2182
initLimit=3
syncLimit=3
server.1:127.0.0.1:2221:3331
server.2:127.0.0.1:2222:3332
server.3:127.0.0.1:2223:3333

dataDir=/tmp/3
clientPort=2183
initLimit=3
syncLimit=3
server.1:127.0.0.1:2221:3331
server.2:127.0.0.1:2222:3332
server.3:127.0.0.1:2223:3333

A ZooKeeper server figures out which server it is by looking in the dataDir for a file called myid that contains its identity, so lets set those up:

mkdir /tmp/1
echo 1 > /tmp/1/myid
mkdir /tmp/2
echo 2 > /tmp/2/myid
mkdir /tmp/3
echo 3 > /tmp/3/myid

now lets startup the 3 servers:

java -jar zookeeper-3.3.3-fatjar.jar server server1.cfg &
java -jar zookeeper-3.3.3-fatjar.jar server server2.cfg &
java -jar zookeeper-3.3.3-fatjar.jar server server3.cfg &

you will see a bunch of messages which will eventually stop with something along the lines of Snapshotting: 100000000.

Setting things up for the example application

We need to create two znodes on our server: /assign and /tasks. Conveniently, the client is also included in the "fat" jar. It even has a bit of a shell. We start up the client with:

java -jar zookeeper-3.3.3-fatjar.jar client -server 127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183

Now lets create the znodes. We have to supply initial data for them even though it isn't used:

[zk: 127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183(CONNECTED) 0] create /assign ""
Created /assign
[zk: 127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183(CONNECTED) 1] create /tasks ""
Created /tasks
[zk: 127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183(CONNECTED) 2] ls /
[assign, tasks, zookeeper]

Tutorial slides

• Part 1
• Part 2
• Part 3
• Part 4