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https://github.com/relaxdiego/charm-k8s-cassandra

Last synced: 13 days ago
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Host: GitHub
URL: https://github.com/relaxdiego/charm-k8s-cassandra
Owner: relaxdiego
License: apache-2.0
Created: 2020-06-23T12:58:25.000Z (over 4 years ago)
Default Branch: master
Last Pushed: 2021-04-20T20:19:02.000Z (over 3 years ago)
Last Synced: 2024-12-17T19:01:23.558Z (16 days ago)
Language: Python
Size: 23.4 KB
Stars: 0
Watchers: 3
Forks: 0
Open Issues: 2
Metadata Files:
- Readme: README.md
- License: LICENSE.txt

Awesome Lists containing this project

README

Cassandra Operator Charm
========================

CI Badges
---------

Click on each badge for more details.

| Branch | Build Status | Coverage |
|--------|--------------|----------|
| master | [![Build Status (master)](https://travis-ci.org/relaxdiego/cassandra-operator-charm.svg?branch=master)](https://travis-ci.org/relaxdiego/cassandra-operator-charm) | [![Coverage Status](https://coveralls.io/repos/github/relaxdiego/cassandra-operator-charm/badge.svg?branch=master)](https://coveralls.io/github/relaxdiego/cassandra-operator-charm?branch=master) |

Quick Start
-----------

git submodule update --init --recursive
sudo snap install --channel=2.7/stable juju --classic
sudo snap install microk8s --classic
sudo microk8s.enable dns registry storage ingress
sudo usermod -a -G microk8s $(whoami)

Log out then log back in so that the new group membership is applied to
your shell session.

juju bootstrap microk8s mk8s

Optional: Grab coffee/beer/tea or do a 5k run. Once the above is done, do:

juju create-storage-pool operator-storage kubernetes storage-class=microk8s-hostpath
juju add-model lma
juju deploy . --resource cassandra-image=cassandra:3.11.6

Wait until `juju status` shows that cassandra has a status of active.

This Charm's Architecture
-------------------------

To learn how to navigate this charm's code and become an effective contributor,
please read the [Charmed LMA Operators Architecture](https://docs.google.com/document/d/1V5cA9D1YN8WGEClpLhUwQt2dYrg5VZEY99LZiE6Mx_A/edit?usp=sharing)
reference doc.

Preparing Your Workstation for Local Development
------------------------------------------------

1. Install pyenv so that you can test with different versions of Python

```
curl -L https://raw.githubusercontent.com/yyuu/pyenv-installer/master/bin/pyenv-installer | bash
```

2. Append the following to your ~/.bashrc then log out and log back in

```
export PATH="/home/mark/.pyenv/bin:$PATH"
eval "$(pyenv init -)"
eval "$(pyenv virtualenv-init -)"
```

Exit the current shell session and start a new one

3. Install development packages. These are needed by pyenv to compile Python

```
sudo apt install build-essential libssl-dev zlib1g-dev libbz2-dev \
libreadline-dev libsqlite3-dev wget curl llvm libncurses5-dev libncursesw5-dev \
xz-utils tk-dev libffi-dev liblzma-dev python3-openssl git
```

4. Install Python 3.6.x and 3.7.x

NOTE: Replace X with the correct minor version as shown in `pyenv install --list`

```
pyenv install 3.6.X
pyenv install 3.7.X
```

7. Test if tox is able to run tests against all declared environments

```
tox
```

8. Upgrade pip and install pip tools

```
python3 -m pip install --upgrade pip
python3 -m pip install "pip-tools>=5.2.1,<5.3"
```

9. Install development requirements

```
pip-sync dev-requirements.txt --pip-args '--require-hashes'
```

Running the Unit Tests on Your Workstation
------------------------------------------

To run the test using the default interpreter as configured in `tox.ini`, run:

tox

If you want to specify an interpreter that's present in your workstation, you
may run it with:

tox -e py37

To view the coverage report that gets generated after running the tests above,
run:

make coverage-server

The above command should output the port on your workstation where the server is
listening on. If you are running the above command on [Multipass](https://multipass.io),
first get the Ubuntu VM's IP via `multipass list` and then browse to that IP and
the abovementioned port.

NOTE: You can leave that static server running in one session while you continue
to execute `tox` on another session. That server will pick up any new changes to
the report automatically so you don't have to restart it each time.

When Adding a Development Dependency
------------------------------------

echo 'foo==1.0.0' >> requirements/dev.in
pip-compile --generate-hashes requirements/dev.in

The `requirements/dev.txt` file should now be updated. Make sure to commit
that to the repo:

git add requirements/dev.*
git commit -m "Add foo to requirements/dev.txt"
git push origin

Then install the dev dependencies using `pip-sync`:

pip-sync requirements/dev.txt --pip-args '--require-hashes'

Troubleshooting
---------------

*This section was originally written by Vlad Grevstev ([email protected])*

Since Kubernetes charms are not supported by `juju debug-hooks`, the only
way to intercept code execution is to initialize the non-tty-bound
debugger session and connect to the session externally.

For this purpose, we chose the [rpdb](https://pypi.org/project/rpdb/), the
remote Python debugger based on pdb.

For example, given that you have already deployed an application named
`cassandra` in a Juju model named `lma` and you would like to debug your
`config-changed` handler, execute the following:

kubectl exec -it pod/cassandra-operator-0 -n lma -- /bin/sh

This will open an interactive shell within the operator pod. Then, install
the editor and the RPDB:

apt update
apt install telnet vim -y
pip3 install rpdb

Open the charm entry point in the editor:

vim /var/lib/juju/agents/unit-cassandra-0/charm/src/charm.py

Find the `on_config_changed_handler` function definition in the `charm.py` file.
Modify it as follows:

def on_config_changed_handler(event, fw_adapter):
import rpdb
rpdb.set_trace()
# < ... rest of the code ... >

Save the file (`:wq`). Do not close the current shell session!

Open another terminal session and trigger the `config-changed` hook as follows:

juju config cassandra external-labels='{"foo": "bar"}'

Do a `juju status`, until you will see the following:

Unit Workload Agent Address Ports Message
cassandra/0* active executing 10.1.28.2 9090/TCP (config-changed)

This message means, that unit has started the `config-changed` hook routine and
it was already intercepted by the rpdb.

Now, return back to the operator pod session.

Enter the interactive debugger:

telnet localhost 4444

You should see the debugger interactive console.

# telnet localhost 4444
Trying ::1...
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
> /var/lib/juju/agents/unit-cassandra-0/charm/hooks/config-changed(91)on_config_changed_handler()
-> set_juju_pod_spec(fw_adapter)
(Pdb) where
/var/lib/juju/agents/unit-cassandra-0/charm/hooks/config-changed(141)()
-> main(Charm)
/var/lib/juju/agents/application-cassandra/charm/lib/ops/main.py(212)main()
-> _emit_charm_event(charm, juju_event_name)
/var/lib/juju/agents/application-cassandra/charm/lib/ops/main.py(128)_emit_charm_event()
-> event_to_emit.emit(*args, **kwargs)
/var/lib/juju/agents/application-cassandra/charm/lib/ops/framework.py(205)emit()
-> framework._emit(event)
/var/lib/juju/agents/application-cassandra/charm/lib/ops/framework.py(710)_emit()
-> self._reemit(event_path)
/var/lib/juju/agents/application-cassandra/charm/lib/ops/framework.py(745)_reemit()
-> custom_handler(event)
/var/lib/juju/agents/unit-cassandra-0/charm/hooks/config-changed(68)on_config_changed()
-> on_config_changed_handler(event, self.fw_adapter)
> /var/lib/juju/agents/unit-cassandra-0/charm/hooks/config-changed(91)on_config_changed_handler()
-> set_juju_pod_spec(fw_adapter)
(Pdb)

From this point forward, the usual pdb commands apply. For more information on
how to use pdb, see the [official pdb documentation](https://docs.python.org/3/library/pdb.html)

Relying on More Comprehensive Unit Tests
----------------------------------------

To ensure that this charm is tested on the widest number of platforms possible,
we make use of Travis CI which also automatically reports the coverage report
to a publicly available Coveralls.io page. To get a view of what the state of
each relevant branch is, click on the appropriate badges found at the top of
this README.

References
----------

Much of how this charm is architected is guided by the following classic
references. It will do well for future contributors to read and take them to heart:

1. [Hexagonal Architecture](https://en.wikipedia.org/wiki/Hexagonal_architecture_(software)) by Alistair Cockburn
1. [Boundaries (Video)](https://pyvideo.org/pycon-us-2013/boundaries.html) by Gary Bernhardt
1. [Domain Driven Design (Book)](https://dddcommunity.org/book/evans_2003/) by Eric Evans