Let's Play With Zookeeper on DigitalOcean

Run Zookeeper Locally

You can get Zookeeper a few ways:

We're going to use the tar.gz from the Releases Page, and we're using version 3.6.x

Also, here's a semi-official guide.

Run Zookeeper on DigitalOcean

In the examples/zookeeper-digitalocean directory we have some Terraform scripts you can use to spin up 3 nodes, and a cloud-init Bash script you might find interesting.

Our goal with this exercise is to create 3 Zookeeper nodes, and to get them use TLS for following use cases:

  • Admin Server on port 8080
  • Quroum ports on ports 2888 & 3888
  • Client port on 2281

The nodes will only be accessible over the Private IP addresses because of how we'll configure the certificates.

Create the ZK Nodes

You'll need to use doctl to set up a DigitalOcean credential file. Then you'll need to create a DigitalOcean Personal Access Token. And finally you'll need valid, public addressable DNS Domain. For this tutorial we're using zkocean.hpy.dev but you'll need to supply your own, or create your own solution for dns.

You can edit the variable.tf to satisfy any of the requirements you might have.

Depending on whether or not you're on macOS, linux, or windows, you'll probably need to adjust the source of your doctl config file inside of data.tf or you'll need to adjust the DigitalOcean provider in providers.tf

Once that's ready, run the following Terraform commands:

cd ./examples/zookeeper-digitalocean/
terraform init
terraform plan -out tfout
terraform apply "tfout"

In a few moments you should have 3 nodes which you can start using immediately.

Validate that ZK works without SSL

Locally, get the SSH key out of terraform:


And then SSH to your nodes:

ssh -i ./outputs/ec2_key.pem root@zk-1.zkocean.hpy.dev
ssh -i ./outputs/ec2_key.pem root@zk-2.zkocean.hpy.dev
ssh -i ./outputs/ec2_key.pem root@zk-3.zkocean.hpy.dev

On each host start zookeeper:

sudo systemctl start zookeeper
sudo journalctl -f -u zookeeper.service

Once the logs get boring, validate each node agrees on the same leader:

curl -s localhost:8080/commands/leader | jq .

Now that we have validated a basic, working Zookeeper cluster, let's enable some TLS!

Create ZK Keystores


Most of this work is already done for you via cloudinit.sh on first boot.

Create SSL keystore JKS to store local credentials, one keystore should be created for each ZK instance.

In this example we generate a self-signed certificate and store it together with the private key in keystore.jks. This is suitable for testing purposes, but you probably need an official certificate to sign your keys in a production environment.


The alias (-alias) and the distinguished name (-dname) must match the hostname of the machine that is associated with, otherwise hostname verification won't work.

(This is already done for you in the cloudinit.sh on boot.)

keytool -genkeypair -alias zk-1.private.zkocean.hpy.dev \
-keyalg RSA -keysize 2048 -dname "cn=zk-1.private.zkocean.hpy.dev" \
-keypass password \
-keystore /opt/zookeeper/conf/keystore.jks \
-ext san=ip:,dns:zk-1.private.zkocean.hpy.dev,dns:localhost
-storepass password

We add the additional SAN addresses so that we can properly use this certificate with Curl later on when we want to access the Admin Server over HTTPS.

Extract the signed public key (certificate) from keystore, this step might only necessary for self-signed certificates.

(This is already done for you in the cloudinit.sh on boot.)

keytool -exportcert -alias zk-1.private.zkocean.hpy.dev \
-keystore /opt/zookeeper/conf/keystore.jks \
-file /opt/zookeeper/conf/zk-1.private.zkocean.hpy.dev.cer -rfc

Locally download the certs on to your developer computer:

mkdir certs
cd certs
scp -i ../outputs/ec2_key.pem root@zk-1.zkocean.hpy.dev:/opt/zookeeper/conf/zk-1.private.zkocean.hpy.dev.cer .
scp -i ../outputs/ec2_key.pem root@zk-2.zkocean.hpy.dev:/opt/zookeeper/conf/zk-2.private.zkocean.hpy.dev.cer .
scp -i ../outputs/ec2_key.pem root@zk-3.zkocean.hpy.dev:/opt/zookeeper/conf/zk-3.private.zkocean.hpy.dev.cer .

Create a truststore.jks with all our certificates.

keytool -keystore truststore.jks -storepass password \
-importcert -alias zk-1.private.zkocean.hpy.dev -file zk-1.private.zkocean.hpy.dev.cer
keytool -keystore truststore.jks -storepass password \
-importcert -alias zk-2.private.zkocean.hpy.dev -file zk-2.private.zkocean.hpy.dev.cer
keytool -keystore truststore.jks -storepass password \
-importcert -alias zk-3.private.zkocean.hpy.dev -file zk-3.private.zkocean.hpy.dev.cer

Create a combined CA Cert to install system wide:

cat *.cer >> zk-all.crt

List certs:

keytool -list -v -keystore truststore.jks
# Enter keystore password:
# Keystore type: PKCS12
# Keystore provider: SUN
# Your keystore contains 3 entries
# ...

We can also use openssl to look at the .cer files, for example:

openssl x509 -text -noout -in ./zk-1.private.zkocean.hpy.dev.cer

Upload your truststore.jks to your nodes:

scp -i ../outputs/ec2_key.pem ./truststore.jks root@zk-1.zkocean.hpy.dev:/opt/zookeeper/conf/truststore.jks
scp -i ../outputs/ec2_key.pem ./truststore.jks root@zk-2.zkocean.hpy.dev:/opt/zookeeper/conf/truststore.jks
scp -i ../outputs/ec2_key.pem ./truststore.jks root@zk-3.zkocean.hpy.dev:/opt/zookeeper/conf/truststore.jks
scp -i ../outputs/ec2_key.pem ./zk-all.crt root@zk-1.zkocean.hpy.dev:/usr/local/share/ca-certificates/zk-all.crt
scp -i ../outputs/ec2_key.pem ./zk-all.crt root@zk-2.zkocean.hpy.dev:/usr/local/share/ca-certificates/zk-all.crt
scp -i ../outputs/ec2_key.pem ./zk-all.crt root@zk-3.zkocean.hpy.dev:/usr/local/share/ca-certificates/zk-all.crt

Configure our server with some new properties:

sudo -u zookeeper vim /opt/zookeeper/conf/zoo.cfg

Now you can uncomment the following configuration:


Then restart Zookeeper:

sudo systemctl restart zookeeper.service
journalctl -f -u zookeeper.service

Show that the certificates aren't installed system wide yet:

curl https://localhost:8080/commands
# curl: (60) SSL certificate problem: self signed certificate
# More details here: https://curl.haxx.se/docs/sslcerts.html
# curl failed to verify the legitimacy of the server and therefore could not
# establish a secure connection to it. To learn more about this situation and
# how to fix it, please visit the web page mentioned above.

Update your local CA Certs store:

sudo update-ca-certificates

Validate Leader on each node:

curl -s https://localhost:8080/commands/leader | jq .
curl -s https://zk-1.private.zkocean.hpy.dev:8080/commands/leader | jq .

Validate with openssl:

sudo netstat -nltpu | grep java
openssl s_client -connect localhost:2181
# no SSL cert found
openssl s_client -connect localhost:2281
# requires client cert
openssl s_client -connect localhost:8080
# has a server cert
openssl s_client -connect localhost:7000
# no SSL cert found

Now connect with zkCli.sh:

/opt/zookeeper/bin/zkCli.sh -server

Try setting ssl.clientAuth=none and then let's try connecting with only the keystore:

/opt/zookeeper/bin/zkCli.sh -server

We can see the server no longer sends a list of client certs:

openssl s_client -connect localhost:2281
# No client certificate CA names sent

If we set the configuration to: ssl.clientAuth=want we'll see that it asks for them but they still aren't required:

openssl s_client -connect localhost:2281
# Acceptable client certificate CA names
# CN = zk-2.private.zkocean.hpy.dev
# CN = zk-3.private.zkocean.hpy.dev
# CN = zk-1.private.zkocean.hpy.dev
# Client Certificate Types: RSA sign, DSA sign, ECDSA sign

Destroy our workshop

When you're ready you can destroy everything with:

terraform destroy