1. Install Java. sdkman is a very useful tool for this. JDK 11 is preferred as Jython doesn't seem to like JDK8 on Ubuntu 18+.

2. Install Jython. Download Jython Installer from here

java -jar jython-installer-2.7.0.jar Install it wherever you like.

3. Install gradle or you the existing gradlew executable in TAF

- Set of VMs with Couchbase-Server running with correct version. General practice: Keep Couchbase credentials as Administrator:password.
- ssh access for root user on the VMs.

One way of setting this up is: Clone vagrants

git clone https://github.com/couchbaselabs/vagrants.git

Choose one of those sub-folders, and run vagrant up in it.

Get the ip addresses of the node as we need to later in ini file. vagrant status

Change the password of the nodes for root user to password:

vagrant ssh node1
sudo passwd

Enable root login

cd /etc/ssh
vi sshd_config

Enable root login for the vagrant boxes. To do that, change this setting(It may be different on various linus flavors):

PermitRootLogin yes

Restart sshd:

sudo systemctl restart sshd or sudo service restart sshd, depending on your vagrant's Linux flavour.

When running Jython, you have to supply the CLASSPATH. For a typical Java program this is long, and typically project management tools like Gradle and Maven are used to automatically pull in all dependencies, produce the CLASSPATH, and run the Java app.

So a gradle project is included with a task, "testrunner", that runs Jython on the testrunner.py script, sorting out the CLASSPATH automatically (including downloading all dependencies).

Execute:

gradle --refresh-dependencies testrunner -P jython="/path/to/jython" -P args="-i <ini file path> -t <absolute path of test case>"```

Examples:
  gradle --refresh-dependencies testrunner -P jython="/path/to/jython" -P args="-i tmp/local.ini -t rebalance_new.rebalance_in.RebalanceInTests.test_rebalance_in_with_ops,nodes_in=3,GROUP=IN;P0;default -m rest"

The above command will run the test mentioned using -t option on the cluster defined in local.ini file.

NOTE: (The --refresh-dependencies isn't strictly required every run. It makes sure that the latest versions of any SNAPSHOT dependencies have been loaded - e.g. for transactions.)

[global]
username:root <ssh user>
password:couchbase <password>
index_port:9102
n1ql_port:8093

[membase]
rest_username:Administrator <Couchbase server console user>
rest_password:password <Couchbase server console password>

[servers]
1:_1
2:_2
3:_3
4:_4

[_1]
ip:<IP>
port:8091
services:kv

[_2]
ip:<IP>
port:8091
services:kv

[_3]
ip:<IP>
port:8091
services:kv

[_4]
ip:<IP>
port:8091
services:kv

TAF supports cluster_run with following additional params under the specified sections,

[global]:
cli:<cluster_run_repo>/build/kv_engine/

[_1]
port:9000
memcached_port: 12000

[_2]
port:9001
memcached_port: 12002

[_3]
port:9002
memcached_port: 12004

If Jython reports Exception in thread "main" java.lang.NoSuchMethodError: java.nio.ByteBuffer.limit(I)Ljava/nio/ByteBuffer;

Jython appears to be broken on Ubuntu 18+: https://bugs.launchpad.net/ubuntu/+source/jython/+bug/1771476

Resolved by changing to OpenJDK 11. With sdkman installed:

sdk use java 11.0.3-zulu