STAC Task (stactask)

This Python library consists of the Task class, which is used to create custom tasks based on a "STAC In, STAC Out" approach. The Task class acts as wrapper around custom code and provides several convenience methods for modifying STAC Items, creating derived Items, and providing a CLI.

This library is currently under development and may not be a final standalone repo and may be merged into stactools, see #345. It is based on a branch of cirrus-lib except aims to be more generic.

Quickstart for Creating New Tasks

from stactask import Task

class MyTask(Task):
    name = 'my-task'
    description = 'this task does it all'

    def validate(self):
        assert len(self.items) == 1

    def process(self):
        item = self.items[0]
        
        # download a datafile
        item = self.download_item_assets(item, assets=['data'])
        
        # operate on the local file to create a new asset


        item = self.upload_item_assets_to_s3(item)

        # this task returns a single item
        return [item]

Task Input

ProcessDefinition Object

A STAC task can be provided additional configuration via the 'process' field in the input ItemCollection.

TaskConfig Object

A Task Configuration contains information for running a specific task.

collections

The collections dictionary provides a collection ID and JSONPath pattern for matching against STAC Items. At the end of processing, before the final STAC Items are returned, the Task class can be used to assign all of the Items to specific collection IDs. For each Item the JSONPath pattern for all collections will be compared. The first match will cause the Item's Collection ID to be set to the provided value.

Example

    "collections": {
        "landsat-c2l2": "$[?(@.id =~ 'LC08.*')]"
    }

In this example, the task will set any STAC Items that have an ID beginning with "LC08" to the landsat-c2l2 collection.

See Jayway JsonPath Evaluator to experiment with JSONpath and regex101 to experiment with regex.

tasks

The tasks field is a dictionary with an optional key for each task. If present, it contains a dictionary that is converted to a set of keywords and passed to the Task's process function. The documentation for each task will provide the list of available parameters.

{
    "tasks": [
        {
            "name": "task-a",
            "parameters": {
                "param1": "value1"
            }
        },
        {
            "name": "task-c",
            "parameters": {
                "param2": "value2"
            }
        }
    ]
}

In the example above a task named task-a would have the param1=value1 passed as a keyword, while task-c would have param2=value2 passed. If there were a task-b to be run it would not be passed any keywords.

UploadOptions Object

path_template

The path_template string is a way to control the output location of uploaded assets from a STAC Item using metadata from the Item itself. The template can contain fixed strings along with variables used for substitution. The following variables can be used in the template.

See [https://jsonpath.herokuapp.com/](Jayway JsonPath Evaluator) to experiment with JSONpath and https://regex101.com/ to experiment with regex

Full Payload Example

{
    "description": "My process configuration",
    "collections": {
        "landsat-c2l2": "$[?(@.id =~ 'LC08.*')]"
    },
    "upload_options": {
        "path_template": "s3://my-bucket/${collection}/${year}/${month}/${day}/${id}"
    },
    "tasks": {
        "task-name": {
            "param": "value"
        }
    }
}

Development

run tests

$ pytest -v -s tests