CCM (Cassandra Cluster Manager)

WARNING - CCM configuration changes using updateconf does not happen according to CASSANDRA-17379

After CASSANDRA-15234, to support the Python upgrade tests CCM updateconf is replacing new key name and value in case the old key name and value is provided.
For example, if you add to config permissions_validity_in_ms, it will replace permissions_validity in default cassandra.yaml This was needed to ensure correct overloading as CCM cassandra.yaml has keys sorted lexicographically. CASSANDRA-17379 was opened to improve the user experience and deprecate the overloading of parameters in cassandra.yaml. In CASSANDRA 4.1+, by default, we refuse starting Cassandra with a config containing both old and new config keys for the same parameter. Start Cassandra with -Dcassandra.allow_new_old_config_keys=true to override. For historical reasons duplicate config keys in cassandra.yaml are allowed by default, start Cassandra with -Dcassandra.allow_duplicate_config_keys=false to disallow this. Please note that key_cache_save_period, row_cache_save_period, counter_cache_save_period will be affected only by -Dcassandra.allow_duplicate_config_keys. Ticket CASSANDRA-17949 was opened to decide the future of CCM updateconf post CASSANDRA-17379, until then - bear in mind that old replace new parameters' in cassandra.yaml when using updateconf even if -Dcassandra.allow_new_old_config_keys=false is set by default.

TLDR Do not exercise overloading of parameters in CCM if possible. Also, the mentioned changes are done only in master branch. Probably the best way to handle cassandra 4.1 in CCM at this point is to set -Dcassandra.allow_new_old_config_keys=false and -Dcassandra.allow_duplicate_config_keys=false to prohibit any kind of overloading when using CCM master and CCM released versions

CCM (Cassandra Cluster Manager)

A script/library to create, launch and remove an Apache Cassandra cluster on localhost.

The goal of ccm and ccmlib is to make it easy to create, manage and destroy a small Cassandra cluster on a local box. It is meant for testing a Cassandra cluster.

New to Python development?

Python has moved on since CCM started development. pip is the new easy_install, Python 3 is the new 2.7, and pyenv and virtualenv are strongly recommended for managing multiple Python versions and dependencies for specific Python applications.

A typical MacOS setup would be to install Homebrew, then brew install pyenv to manage Python versions and then use virtualenv to manage the dependencies for CCM. Make sure to add brew's bin directory to your path in your ~/.zshenv. This would be /usr/local for MacOS Intel and /opt/homebrew/ for MacOS on Apple Silicon.

Now you are ready to install Python using pyenv. To avoid getting a bleeding edge version that will fail with some aspect of CCM you can pyenv install 3.9.16.

To create the virtualenv run python3 -m venv --prompt ccm venv with your git repo as the current working directory to create a virtual environment for CCM. Then source venv/bin/activate to enable the venv for the current terminal and deactivate to exit.

Now you a ready to set up the venv with CCM and its test dependencies. pip install -e <path_to_ccm_repo> to install CCM, and its runtime dependencies from requirements.txt, so that the version of CCM you are running points to the code you are actively working on. There is no build or package step because you are editing the Python files being run every time you invoke CCM.

Almost there. Now you just need to add the test dependencies that are not in requirements.txt. pip install mock pytest to finish setting up your dev environment!

Another caveat that has recently appeared Cassandra versions 4.0 and below ship with a version of JNA that isn't compatible with Apple Silicon and there are no plans to update JNA on those versions. One work around if you are generally building Cassandra from source to use with CCM is to replace the JNA jar in your Maven repo with a newer one that supports Apple Silicon. Which you version you need to replace will vary depending on the Cassandra version, but it will normally be in ~/.m2/repository/net/java/dev/jna/jna/<someversion>. You can also replace the library in ~/.ccm/repository/<whatever>/lib.

Also don't forget to disable AirPlay Receiver on MacOS which also listens on port 7000.

Requirements

• A working python installation (tested to work with python 2.7).

• See requirements.txt for runtime requirements

• mock and pytest for tests

• ant (http://ant.apache.org/, on Mac OS X, brew install ant)

• Java, Cassandra currently builds with either 8 or 11 and is restricted to JDK 8 language features and dependencies. There are several sources for the JDK and Azul Zulu is one good option.

• If you want to create multiple node clusters, the simplest way is to use multiple loopback aliases. On modern linux distributions you probably don't need to do anything, but on Mac OS X, you will need to create the aliases with

  sudo ifconfig lo0 alias 127.0.0.2 up
  sudo ifconfig lo0 alias 127.0.0.3 up
  ...
  

  Note that the usage section assumes that at least 127.0.0.1, 127.0.0.2 and 127.0.0.3 are available.

Optional Requirements

• Paramiko (http://www.paramiko.org/): Paramiko adds the ability to execute CCM remotely; pip install paramiko

Note: The remote machine must be configured with an SSH server and a working CCM. When working with multiple nodes each exposed IP address must be in sequential order. For example, the last number in the 4th octet of a IPv4 address must start with 1 (e.g. 192.168.33.11). See Vagrantfile for help with configuration of remote CCM machine.

Known issues

Windows only:

• node start pops up a window, stealing focus.
• cqlsh started from ccm show incorrect prompts on command-prompt
• non nodetool-based command-line options fail (sstablesplit, scrub, etc)
• To install psutil, you must use the .msi from pypi. pip install psutil will not work
• You will need ant.bat in your PATH in order to build C* from source
• You must run with an Unrestricted Powershell Execution-Policy if using Cassandra 2.1.0+
• Ant installed via chocolatey will not be found by ccm, so you must create a symbolic link in order to fix the issue (as administrator):
  • cmd /c mklink C:\ProgramData\chocolatey\bin\ant.bat C:\ProgramData\chocolatey\bin\ant.exe

MaxOS only:

• Airplay listens for incoming connections on 7000 so disable Settings -> General -> AirDrop & Handoff -> AirPlay Receiver

Remote Execution only:

• Using --config-dir and --install-dir with create may not work as expected; since the configuration directory and the installation directory contain lots of files they will not be copied over to the remote machine like most other options for cluster and node operations
• cqlsh started from ccm using remote execution will not start properly (e.g.ccm --ssh-host 192.168.33.11 node1 cqlsh); however -x <CMDS> or --exec=CMDS can still be used to execute a CQLSH command on a remote node.

Installation

ccm uses python distutils so from the source directory run:

sudo ./setup.py install

ccm is available on the Python Package Index:

pip install ccm

There is also a Homebrew package available:

brew install ccm

Usage

Let's say you wanted to fire up a 3 node Cassandra cluster.

Short version

ccm create test -v 2.0.5 -n 3 -s

You will of course want to replace 2.0.5 by whichever version of Cassandra you want to test.

Longer version

ccm works from a Cassandra source tree (not the jars). There are two ways to tell ccm how to find the sources:

1. If you have downloaded and compiled Cassandra sources, you can ask ccm to use those by initiating a new cluster with:

   ccm create test --install-dir=<path/to/cassandra-sources>

   or, from that source tree directory, simply

    ccm create test
   

2. You can ask ccm to use a released version of Cassandra. For instance to use Cassandra 2.0.5, run

    ccm create test -v 2.0.5
   

   ccm will download the binary (from http://archive.apache.org/dist/cassandra), and set the new cluster to use it. This means that this command can take a few minutes the first time you create a cluster for a given version. ccm saves the compiled source in ~/.ccm/repository/, so creating a cluster for that version will be much faster the second time you run it (note however that if you create a lot of clusters with different versions, this will take up disk space).

Once the cluster is created, you can populate it with 3 nodes with:

ccm populate -n 3

For Mac OSX, create a new interface for every node besides the first, for example if you populated your cluster with 3 nodes, create interfaces for 127.0.0.2 and 127.0.0.3 like so:

sudo ifconfig lo0 alias 127.0.0.2
sudo ifconfig lo0 alias 127.0.0.3

Note these aliases will disappear on reboot. For permanent network aliases on Mac OSX see .

After that execute:

ccm start

That will start 3 nodes on IP 127.0.0.[1, 2, 3] on port 9160 for thrift, port 7000 for the internal cluster communication and ports 7100, 7200 and 7300 for JMX. You can check that the cluster is correctly set up with

ccm node1 ring

You can then bootstrap a 4th node with

ccm add node4 -i 127.0.0.4 -j 7400 -b

(populate is just a shortcut for adding multiple nodes initially)

ccm provides a number of conveniences, like flushing all of the nodes of the cluster:

ccm flush

or only one node:

ccm node2 flush

You can also easily look at the log file of a given node with:

ccm node1 showlog

Finally, you can get rid of the whole cluster (which will stop the node and remove all the data) with

ccm remove

The list of other provided commands is available through

ccm

Each command is then documented through the -h (or --help) flag. For instance ccm add -h describes the options for ccm add.

Remote Usage (SSH/Paramiko)

All the usage examples above will work exactly the same for a remotely configured machine; however remote options are required in order to establish a connection to the remote machine before executing the CCM commands:

Argument	Value	Description
--ssh-host	string	Hostname or IP address to use for SSH connection
--ssh-port	int	Port to use for SSH connection Default is 22
--ssh-username	string	Username to use for username/password or public key authentication
--ssh-password	string	Password to use for username/password or private key passphrase using public key authentication
--ssh-private-key	filename	Private key to use for SSH connection

Special Handling

Some commands require files to be located on the remote server. Those commands are pre-processed, file transfers are initiated, and updates are made to the argument value for the remote execution of the CCM command:

Parameter	Description
--dse-credentials	Copy local DSE credentials file to remote server
--node-ssl	Recursively copy node SSL directory to remote server
--ssl	Recursively copy SSL directory to remote server

Short Version

ccm --ssh-host=192.168.33.11 --ssh-username=vagrant --ssh-password=vagrant create test -v 2.0.5 -n 3 -i 192.168.33.1 -s

Note: -i is used to add an IP prefix during the create process to ensure that the nodes communicate using the proper IP address for their node

Source Distribution

If you'd like to use a source distribution instead of the default binary each time (for example, for Continuous Integration), you can prefix cassandra version with source:, for example:

ccm create test -v source:2.0.5 -n 3 -s

Automatic Version Fallback

If 'binary:' or 'source:' are not explicitly specified in your version string, then ccm will fallback to building the requested version from git if it cannot access the apache mirrors.

Git and GitHub

To use the latest version from the canonical Apache Git repository, use the version name git:branch-name, e.g.:

ccm create trunk -v git:trunk -n 5

and to download a branch from a GitHub fork of Cassandra, you can prefix the repository and branch with github:, e.g.:

ccm create patched -v github:jbellis/trunk -n 1

Bash command-line completion

ccm has many sub-commands for both cluster commands as well as node commands, and sometimes you don't quite remember the name of the sub-command you want to invoke. Also, command lines may be long due to long cluster or node names.

Leverage bash's programmable completion feature to make ccm use more pleasant. Copy misc/ccm-completion.bash to somewhere in your home directory (or /etc if you want to make it accessible to all users of your system) and source it in your .bash_profile:

. ~/scripts/ccm-completion.bash

Once set up, ccm sw<tab> expands to ccm switch , for example. The switch sub-command has extra completion logic to help complete the cluster name. So ccm switch cl<tab> would expand to ccm switch cluster-58 if cluster-58 is the only cluster whose name starts with "cl". If there is ambiguity, hitting <tab> a second time shows the choices that match:

$ ccm switch cl<tab>
    ... becomes ...
$ ccm switch cluster-
    ... then hit tab twice ...
cluster-56  cluster-85  cluster-96
$ ccm switch cluster-8<tab>
    ... becomes ...
$ ccm switch cluster-85

It dynamically determines available sub-commands based on the ccm being invoked. Thus, users running multiple ccm's (or a ccm that they are continuously updating with new commands) will automagically work.

The completion script relies on ccm having two hidden subcommands:

• show-cluster-cmds - emits the names of cluster sub-commands.
• show-node-cmds - emits the names of node sub-commands.

Thus, it will not work with sufficiently old versions of ccm.

Testing

Create a virtual environment i.e.:

python3 -m venv ccm

pip install all dependencies as well as mock and pytest. Run pytest from the repository root to run the tests.

Remote debugging

If you would like to connect to your Cassandra nodes with a remote debugger you have to pass the -d (or --debug) flag to the populate command:

ccm populate -d -n 3

That will populate 3 nodes on IP 127.0.0.[1, 2, 3] setting up the remote debugging on ports 2100, 2200 and 2300. The main thread will not be suspended so you don't have to connect with a remote debugger to start a node.

Alternatively you can also specify a remote port with the -r (or --remote-debug-port) flag while adding a node

ccm add node4 -r 5005 -i 127.0.0.4 -j 7400 -b

Where things are stored

By default, ccm stores all the node data and configuration files under ~/.ccm/cluster_name/. This can be overridden using the --config-dir option with each command.

DataStax Enterprise

CCM 2.0 supports creating and interacting with DSE clusters. The --dse option must be used with the ccm create command. See the ccm create -h help for assistance.

CCM Lib

The ccm facilities are available programmatically through ccmlib. This could be used to implement automated tests against Cassandra. A simple example of how to use ccmlib follows:

import ccmlib.cluster

CLUSTER_PATH="."
cluster = ccmlib.cluster.Cluster(CLUSTER_PATH, 'test', cassandra_version='2.1.14')
cluster.populate(3).start()
[node1, node2, node3] = cluster.nodelist()

# do some tests on the cluster/nodes. To connect to a node through thrift,
# the host and port to a node is available through
#   node.network_interfaces['thrift']

cluster.flush()
node2.compact()

# do some other tests

# after the test, you can leave the cluster running, you can stop all nodes
# using cluster.stop() but keep the data around (in CLUSTER_PATH/test), or
# you can remove everything with cluster.remove()

-- Sylvain Lebresne sylvain@datastax.com