#How to make luigi series
#How to make luigi download

The idea is to have two directories: вЂqueriesвЂ™ and вЂresultsвЂ™. We will use SQLAlchemy to manage the connections to the databases because this offers the right level of abstraction here. This will be done via a pandas DataFrame, to focus on the luigi code. It will then be picked up by a Luigi Task and sent to an SQLite database located in that directory. The generated csv will be located in a folder called вЂdataвЂ™ in the same directory as the code.

#How to make luigi download

You can access the data on GithubВ or download it here. You want to automate that process, so that whenever you put a new SQL file in a dedicated folder (one per database), a report will be produced and dropped in an output folder, with the same name as the query file.ДЇor the sake of this exercise, we will use a csv file generated by means of the USGS earthquakes API, on a period between 15 September 2018 and 1 October 2018, worldwide, with all magnitudes.

#How to make luigi series

LetвЂ™s say you have a series of databases and that you need to produce Excel reports based on SQL queries ran against these databases. Now that we have presented the main principles, we will introduce a way to put a pipeline in place that will output an arbitrary number of reports based on SQL query files. The different Task instances will be run separately, unless one of these Parameters is set to be insignificant. Luigi will regard two Task instances with different Parameter values as different. Parameter objects are defined at class level, but their value is assigned at instance level. These can represent any type of object that can be passed on to a Task, and that will be used to perform the Task and verify dependencies. In addition, Luigi provides a way to pass on parameters to the Tasks to be run, under the form of Parameter objects. Many more can be found in the different contribution packages, depending on your preferred technology stack. LocalTarget, which represents a file on the system. Luigi already provides a few of them, i.e. Targets offer one method: exist() method, which should be overridden and should return True if the Target exists. WrapperTask has no run() nor output() method and is used to aggregate multiple Tasks that have to be run together.

For example, ExternalTask does not require a run() method and represent an external resource, i.e. In addition, there are special kinds of Tasks that do not require all three methods to be set.

run() to specify which operation the Task will perform and how it will create the Target from the output() method.

output() to specify the Target created by the Task.

requires() to specify the required dependencies, usually one Task or a list of Tasks.Tasks offer three different methods to override: It will then run the whole tree of dependencies to finish by the topmost Task. If these dependencies have dependencies themselves, luigi will verify them as well, and so on until it finds Tasks that are complete or that do not require dependencies. If not, luigi will verify whether the dependencies are complete (whether their Targets exist) and run them if they donвЂ™t. Luigi will first verify if the topmost TaskвЂ™s Target exists. This allows users to easily build entire schedules of Tasks that depend on each other. The premise is simple: a Task produces a Target, and the existence of this Target will be used by dependent Tasks to assess whether or not they can be run. For luigi, a process is called a Task and the output a Target. Therefore, if the output produced by the first process does not exist, the second process cannot be run. The idea behind luigi is that usually, a process produces an output, which is stored in a file or database before being picked up by another process to perform transformations and/or aggregations. Luigi is mainly based on two object types: Tasks and Targets. In this article, we present how luigi works and how you can set up a simple reporting pipeline based on an SQL database and query files. It is currently used by dozens, if not hundreds of companies around the world to process and transform data. It has been developed by Spotify, open-sourced in 2012, and expanded by hundreds of developers. From running SQL queries, dumping results into a database, storing intermediate results and more, luigi can manage thousands of jobs spanning several weeks. Luigi is an open source framework that has been designed to help you build, monitor and troubleshoot your data transformation pipeline.