Setup docker transition

In this tutorial you will learn what is required and recommended practice when creating an automated transition. An automated transition is just a docker image, and for this tutorial we will use python as our programming language. There are no restrictions on which languages that are allowed here, but you will see that it is practical to use one that has a LAS SDK, that is (Java, JavaScript, C#, Python).

We will use the make-predictions-image to explain some of the key concepts. For a simple python-based docker image you only need 3 files:

  • Dockerfile: The instructions for how to make the image,

    see dockers own documentation for more information

  • This is where the code that does the work lives

  • requirements.txt: Required packages that needs to be installed


For a simple process like this the Dockerfile can look something like this:

FROM python:3.8 # Use the base image of your own choice
WORKDIR /root # Set a working directory
# These ID's will be provided runtime, and is necessary to keep track of which execution is being processed
ENV TRANSITION_ID not_provided
ENV EXECUTION_ID not_provided
# Copy in the files you need in your image
COPY requirements.txt .
# Install requirements
RUN pip install -r requirements.txt
# Set the entrypoint
ENTRYPOINT ["python", ""]

This is the module that does all the work, let us first give a brief description of the anatomy.

import ... # Remember to import the LAS SDK and other packages you need.
def handler(...): # This is where all the code specific for this process goes
# Whatever is returned here will be sent along to the next task in your workflow
return response
if __name__ == '__main__':
# This is the necessary code block that takes care of fetching variables,
# and returning the response to the API.

Our recommendation is that you re-use the last block of this file and just edit the handler to fit your needs.

Entry point

The last part of contains a few essential steps;

  • Get the input to the execution

  • Run the user-spesific code in the handler

  • Let the API know that you have completed successfully or failed.

The code below makes sure that all this happens safely.

if __name__ == '__main__':
las_client = Client()
transition_id = os.environ['TRANSITION_ID']
execution_id = os.environ['EXECUTION_ID']
try: # Get input and update execution
execution = las_client.get_transition_execution(transition_id, execution_id=execution_id)
event = execution['input']'event: {event}')
output = handler(las_client, event, environ=os.environ)
except Exception: # This exception-block is important for proper error handling in the API
'message': str(traceback.format_exc()),

The handler

This is the part where you as a user is free to write whatever you need to automate your workflow. Let us first take a look at the input:

  • las_client: The client from the python-sdk for an easy access to LAS API.

  • event: This is the output from the previous transition in the workflow.

    If this is the first transition in the workflow then the input to the workflow will be the input to this transition.

  • environ: The environment consists of some pre-defined variables, such as the TRANSITION_ID and the EXECUTION_ID.

    In addition to these you can also define variables by specifying them as parameters directly in your transition,

    or through secrets if the information is sensitive. See the example at the end of this tutorial.

def handler(las_client, event, environ):
'''A simple handler that uses the LAS API to make predictions on a document from a specified model.'''
document_id = event['documentId']
model_id = event.get('modelId', environ.get('MODEL_ID'))
if not model_id:
raise ValueError('A modelId is needed for prediction, input modelId directly or MODEL_ID to env')
response = las_client.create_prediction(
max_pages=event.get('maxPages', 1),
auto_rotate=event.get('autoRotate', False),
return response

Create the transition

When you have all the building blocks that you need, we are ready to create the docker transition.

Building and pushing your image

First step is to build a docker image and push it to some repository

$ docker build . -t <image-url> && docker push <image-url>

It is recommended to place the docker image in a private repository, if that is the case you need to store your credentials as a secret.

$ las secrets create username=<username> password=<password> --description 'docker credentials'

The next step is to create a json-file - let's call it params.json - that contains the parameters you need to run the docker image. The variables you define in environment and environmentSecrets will end up in the environ-variable in the handler in the example above.

"imageUrl": "<image-url>",
"secretId": "las:secret:<hex-uuid>"
"environment": {
"MODEL_ID": "las:model:<hex-uuid>",
"environmentSecrets": [

The secretId field is only needed if you are using a private image.

Now you are ready to create the automatic transition

las transitions create docker -p params.json --name MakePredictions