Some web-applications have to ingest an enormous amount of new data on a regular basis. Import scripts easily become an ever-growing procedural mess, annoying to maintain. In this post I show a bit of code which can be used to simplify and unify such import scripts.
Assume you have a pipeline of post-import steps to run. This can be organized in numerous ways. Simplest is to just have a bunch of methods called one after the other once you have the data loaded:
Now, assume once in a while one of the steps fail for an unexpected reason. You know, it’s rare data from external sources is as clean as we’d like. So you need to fix a few things and retry the import. However, as datasizes grow and with that the running time of the import, it can be a huge waste redoing all the work because of a misplaced comma made the final
deploy_hamsters step fail.
Exceptions are the obvious way to report fatal data-errors, and implicit or explicit transactions to ensure consistency of the import. But how can this easily be combined for a resume-friendly import mechanism?
Enter the bulk importer step runner with trivial progress reporting:
Notice you obviously have to change the model-name (
ImportModel above) and provide the actual implementation for these individual steps.
all_steps returns the list of methods to run,
run_import_step runs a single step with error-handling, and
import_updaters runs all the relevant updaters.
Easy performance statistics
As a bit of bonus-functionality, the following can be used for reporting import progress with timing-statistics after each step completes:
Usage is simple - just call
report_progress with a comment to print and a block of code, like this:
What do you use to make data-imports easier to manage?
Hi, I'm Laust Rud Jacobsen, an experienced webapp developer specializing in Ruby-based solutions. You can hire me to build awesome stuff for you. If you have any questions or comments, reach out at @laustrud or privately at email@example.com.
A current and exciting development: I'm in the process of writing
Effective Maintenance: taming messy code (Ruby edition).
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