Alerce Reflector Step

Copies one or more Kafka topics into a new one, essentially a custom made mirrormaker. Used to replicate messages from an external source into the current Kafka cluster.

This step does nothing with the data. Custom consumers/producers completely skip the (de)serialization stages and messages are copied just as they are. There is no database connection.

Environment variables

Unless noted, the following environment variables are required

Local installation

Install required packages using:

pip install -r requirements.txt

The step itself can be run with:

python scripts/run_step.py

Development and testing

Additional dependencies for testing without the deployment of the full infrastructure are required. these can be installed using:

pip install -r dev-requirements.txt

To run all tests, use:

pytest

Previous conditions

No special conditions, only connection to Kafka.

Version

• 1.0.0

Libraries used

• APF

Environment variables

Consumer setup

• CONSUMER_SERVER: Kafka host with ports, e.g., localhost:9092
• CONSUMER_GROUP_ID: Name for the consumer group, e.g., cmirrormaker-step
• CONSUME_TIMEOUT: Maximum time in seconds to wait for a message. Defaults to 10
• CONSUME_MESSAGES: Number of messages to consume per operation. Defaults to 1000
• TOPIC_STRATEGY_FORMAT: Format of topics that change daily, e.g., ztf_%s_programid1 or ztf_%s_programid1,ztf_%s_programid3. The {} will be replaced by the date formatted as %Y%m%d, set to change every day at 23:00 UTC
• CONSUMER_TOPICS: List of topics to consume as a string separated by commas, e.g., topic or topic1,topic2

Note that one of TOPIC_STRATEGY_FORMAT or CONSUMER_TOPICS must be set. If both are set, then CONSUMER_TOPICS will be ignored.

Producer setup

• PRODUCER_SERVER: Kafka host with ports, e.g., localhost:9092
• PRODUCER_TOPIC: Topic to which messages will be produced, e.g., topic. This is optional, if not provided, it will produce with the same topic as the incoming message.

Step metadata

• STEP_VERSION: Current version of the step, e.g., 1.0.0. Defaults to dev
• STEP_ID: Unique identifier for the step. Defaults to cmirrormaker
• STEP_NAME: Name of the step. Defaults to cmirrormaker
• STEP_COMMENTS: Comments on the specific version of the step

Stream

This step requires a consumer and a producer. Schemas are ignored and copied as they are from the source.

Build docker image

To run this step you must first build the Docker image:

docker build -t alerce_reflector_step:version .

Run step

Run Docker container

To run the Docker container all environment variables must be set:

docker run --name alerce_reflector_step -e CONSUMER_SERVER=host:port -e [... all env ...] -d alerce_reflector_step:version

Run docker-compose

Alternatively, the environment variables can be edited in the file docker-compose.yml. To run one container, use:

docker-compose up -d

In order to scale up the number of containers, use:

docker-compose up -d --scale alerce_reflector_step=n

Note: To stop all containers, use: docker-compose down.

Run released image

For each release an image is uploaded to ghcr.io that can be used instead of building your own. To do that, replace the commands above with:

docker pull ghcr.io/alercebroker/alerce_reflector_step:latest