# How to Use Antithesis

## Context

Antithesis is a third party vendor with an environment that can perform network fuzzing. We can
upload images containing `docker-compose.yml` files, which represent various MongoDB topologies, to
the Antithesis Docker registry. Antithesis runs `docker-compose up` from these images to spin up
the corresponding multi-container application in their environment and run a test suite. Network
fuzzing is performed on the topology while the test suite runs & a report is generated by
Antithesis identifying bugs. Check out
https://github.com/mongodb/mongo/wiki/Testing-MongoDB-with-Antithesis to see an example of how we
use Antithesis today.

## Base Images

The `base_images` directory consists of the building blocks for creating a MongoDB test topology.
These images are uploaded to the Antithesis Docker registry weekly during the
`antithesis_image_push` task. For more visibility into how these images are built and uploaded to
the Antithesis Docker registry, please see that task.

### mongo_binaries

This image contains the latest `mongo`, `mongos` and `mongod` binaries. It can be used to
start a `mongod` instance, `mongos` instance or execute `mongo` commands. This is the main building
block for creating the System Under Test topology.

### workload

This image contains the latest `mongo` binary as well as the `resmoke` test runner. The `workload`
container is not part of the actual toplogy. The purpose of a `workload` container is to execute
`mongo` commands to complete the topology setup, and to run a test suite on an existing topology
like so:

```shell
buildscript/resmoke.py run --suite antithesis_concurrency_sharded_with_stepdowns_and_balancer
```

**Every topology must have 1 workload container.**

Note: During `workload` image build, `buildscripts/antithesis_suite.py` runs, which generates
"antithesis compatible" test suites and prepends them with `antithesis_`. These are the test suites
that can run in antithesis and are available from witihin the `workload` container.

## Topologies

The `topologies` directory consists of subdirectories representing various mongo test topologies.
Each topology has a `Dockerfile`, a `docker-compose.yml` file and a `scripts` directory.

### Dockerfile

This assembles an image with the necessary files for spinning up the corresponding topology. It
consists of a `docker-compose.yml`, a `logs` directory, a `scripts` directory and a `data`
directory. If this is structured properly, you should be able to copy the files & directories
from this image and run `docker-compose up` to set up the desired topology.

Example from `buildscripts/antithesis/topologies/sharded_cluster/Dockerfile`:

```Dockerfile
FROM scratch
COPY docker-compose.yml /
ADD scripts /scripts
ADD logs /logs
ADD data /data
ADD debug /debug
```

All topology images are built and uploaded to the Antithesis Docker registry during the
`antithesis_image_push` task. Some of these directories are created during the
`evergreen/antithesis_image_build.sh` script such as `/data` and `/logs`.

Note: These images serve solely as a filesystem containing all necessary files for a topology,
therefore use `FROM scratch`.

### docker-compose.yml

This describes how to construct the corresponding topology using the
`mongo-binaries` and `workload` images.

Example from `buildscripts/antithesis/topologies/sharded_cluster/docker-compose.yml`:

```yml
version: '3.0'

services:
        configsvr1:
                container_name: configsvr1
                hostname: configsvr1
                image: mongo-binaries:evergreen-latest-master
                volumes:
                  - ./logs/configsvr1:/var/log/mongodb/
                  - ./scripts:/scripts/
                  - ./data/configsvr1:/data/configdb/
                command: /bin/bash /scripts/configsvr_init.sh
                networks:
                        antithesis-net:
                                ipv4_address: 10.20.20.6
                                # Set the an IPv4 with an address of 10.20.20.130 or higher
                                # to be ignored by the fault injector
                                #

        configsvr2: ...
        configsvr3: ...
        database1: ...
                container_name: database1
                hostname: database1
                image: mongo-binaries:evergreen-latest-master
                volumes:
                  - ./logs/database1:/var/log/mongodb/
                  - ./scripts:/scripts/
                  - ./data/database1:/data/db/
                command: /bin/bash /scripts/database_init.sh Shard1
                networks:
                        antithesis-net:
                                ipv4_address: 10.20.20.3
                                # Set the an IPv4 with an address of 10.20.20.130 or higher
                                # to be ignored by the fault injector
                                #
        database2: ...
        database3: ...
        database4: ...
        database5: ...
        database6: ...
        mongos:
                container_name: mongos
                hostname: mongos
                image: mongo-binaries:evergreen-latest-master
                volumes:
                  - ./logs/mongos:/var/log/mongodb/
                  - ./scripts:/scripts/
                command: python3 /scripts/mongos_init.py
                depends_on:
                        - "database1"
                        - "database2"
                        - "database3"
                        - "database4"
                        - "database5"
                        - "database6"
                        - "configsvr1"
                        - "configsvr2"
                        - "configsvr3"
                networks:
                        antithesis-net:
                                ipv4_address: 10.20.20.9
                                # The subnet provided here is an example
                                # An alternative subnet can be used
        workload:
                container_name: workload
                hostname: workload
                image: workload:evergreen-latest-master
                volumes:
                  - ./logs/workload:/var/log/resmoke/
                  - ./scripts:/scripts/
                command: python3 /scripts/workload_init.py
                depends_on:
                        - "mongos"
                networks:
                        antithesis-net:
                                ipv4_address: 10.20.20.130
                                # The subnet provided here is an example
                                # An alternative subnet can be used
networks:
        antithesis-net:
                driver: bridge
                ipam:
                        config:
                        - subnet: 10.20.20.0/24
```

Each container must have a `command` in `docker-compose.yml` that runs an init script. The init
script belongs in the `scripts` directory, which is included as a volume. The `command` should be
set like so: `/bin/bash /scripts/[script_name].sh` or `python3 /scripts/[script_name].py`. This is
a requirement for the topology to start up properly in Antithesis.

When creating `mongod` or `mongos` instances, route the logs like so:
`--logpath /var/log/mongodb/mongodb.log` and utilize `volumes` -- as in `database1`.
This enables us to easily retrieve logs if a bug is detected by Antithesis.

The `ipv4_address` should be set to `10.20.20.130` or higher if you do not want that container to
be affected by network fuzzing. For instance, you would likely not want the `workload` container  
to be affected by network fuzzing -- as shown in the example above.

Use the `evergreen-latest-master` tag for all images. This is updated automatically in
`evergreen/antithesis_image_build.sh` during the `antithesis_image_build` task -- if needed.

### scripts

Take a look at `buildscripts/antithesis/topologies/sharded_cluster/scripts/mongos_init.py` to see
how to use util methods from `buildscripts/antithesis/topologies/sharded_cluster/scripts/utils.py`
to set up the desired topology. You can also use simple shell scripts as in the case of
`buildscripts/antithesis/topologies/sharded_cluster/scripts/database_init.py`. These init scripts
must not end in order to keep the underlying container alive. You can use an infinite while
loop for `python` scripts or you can use `tail -f /dev/null` for shell scripts.

## How do I create a new topology for Antithesis testing?

To create a new topology for Antithesis testing is easy & requires a few simple steps.

1. Add a new directory in `buildscripts/antithesis/topologies` to represent your desired topology.
   You can use existing topologies as an example.
2. Make sure that your workload test suite runs against your topology without any failures. This
   may require tagging some tests as `antithesis-incompatible`.
3. Update the `antithesis_image_push` task so that your new topology image is
   uploaded to the Antithesis Docker registry.
4. Reach out to #server-testing on Slack & provide the new topology image name as well as the
   desired test suite to run.
5. Include the Correctness team on the code review.

These are the required updates to `evergreen/antithesis_image_build.sh`:

- Add the following command for each of your `mongos` and `mongod` containers in your topology to
  create your log directories.

```shell
mkdir -p antithesis/topologies/[topology_name]/{logs,data}/[container_name]
```

- Build an image for your new topology ending in `-config`

```shell
cd [your_topology_dir]
sed -i s/evergreen-latest-master/$tag/ docker-compose.yml
sudo docker build . -t [your-topology-name]-config:$tag
```

These are the required updates to `evergreen/antithesis_image_push.sh`:

- Push your new image to the Antithesis Docker registry

```shell
sudo docker tag "[your-topology-name]-config:$tag" "us-central1-docker.pkg.dev/molten-verve-216720/mongodb-repository/[your-topology-name]-config:$tag"
sudo docker push "us-central1-docker.pkg.dev/molten-verve-216720/mongodb-repository/[your-topology-name]-config:$tag"
```

## Additional Resources

If you are interested in leveraging Antithesis feel free to reach out to #server-testing on Slack.
