Background

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• The new platform needs to have the facility to schedule the running of code.
• The granularity of the schedule is typically weekly or yearly, but sometimes daily.
• It needs to be able to execute Python 3 code that will broadly follow this template.
• It should be able to read and write to external urls.
• Some disk space is needed for temporary files produced by scrapers, a maximum of 10Mb per scraper, but typically much less.
• Some disk space will be needed for the environment for each scraper, in the order of 300Mb for a Docker image.
• There should be the possibility to execute 2 scrapers simultaneously (rare but possible).
• It should support scrapers (1 currently) that may have to wait for new quota from servers, which means that they will run for many hours, but be mostly idle (eg. pinging the server once a minute).
• The platform should be able to cope with in the order of 10000 calls to the web in a 3 hour period. (This is a worst case based on the FTS scraper which makes in the order of 2500 reads from FTS and 1000 read/writes to HDX in a one hour period. Planning for the future, I've allowed for 2 more scrapers like this.)
• It needs to have a user interface where the status of scrapers can be determined.
• It would be nice to be able to start scrapers from the interface.
• The process for adding new scrapers should be technically simple and bureaucratically light.
• If the scrapers fail, it does not require a quick resolution. This is because the data they have uploaded previously to HDX will still be there.

Choice of platform

It was decided given these requirements (subject to approval) to use Jenkins on an OCHA IT server. Jenkins is typically used for running unit tests, but it has test scheduling capability and a user interface for looking at suites of tests. To use Jenkins, we need only treat each scraper like a suite of unit tests. Jenkins is already deployed on OCHA IT infrastructure which means that the software is already approved in another context and that the expertise to understand and support it exists.

Rather than each scraper executing within a Python virtualenv as currently, they will each be in a Docker container. The scraperscrapers' s Docker image images will build upon (inherit) a base image owned by OCHA IT. The draft base image is here. It inherits from unocha/alpine-base:3.8 and contains a Python 3 environment suitable for running scrapers - it includes HDX Python API library, awesome-slugify and Pandas (including its dependencies on Scipy and Numpy). The libraries that HDX Python API depends on are all open source. An example scraper that inherits this base image is the FTS scraper.

There is some private information that is needed by the scrapers to run. Currently it resides in a private OCHA GitHub repository, but it will be moved to Ansible.

The setup will comply with OCHA IT's Hosting in Shared Infrastructure: Project Requirements.