MySQL Targets in Luigi workflow

Question

My TaskB requires TaskA, and on completion TaskA writes to a MySQL table, and then TaskB is to take in this output to the table as its input.

I cannot seem to figure out how to do this in Luigi. Can someone point me to an example or give me a quick example here?

Answer 1

The existing MySqlTarget in luigi uses a separate marker table to indicate when the task is complete. Here's the rough approach I would take...but your question is very abstract, so it is likely to be more complicated in reality.

import luigi
from datetime import datetime
from luigi.contrib.mysqldb import MySqlTarget


class TaskA(luigi.Task):
    rundate = luigi.DateParameter(default=datetime.now().date())
    target_table = "table_to_update"
    host = "localhost:3306"
    db = "db_to_use"
    user = "user_to_use"
    pw = "pw_to_use"

    def get_target(self):
        return MySqlTarget(host=self.host, database=self.db, user=self.user, password=self.pw, table=self.target_table,
                           update_id=str(self.rundate))

    def requires(self):
        return []

    def output(self):
        return self.get_target()

    def run(self):
        #update table
        self.get_target().touch()


class TaskB(luigi.Task):
    def requires(self):
        return [TaskA()]

    def run(self):
        # reading from target_table