• Development

    Drupal 8 Migrate – Tips and Tricks

    This is an ongoing brain dump of quick tips for working with Drupal 8 Migrate. These items may seem true to me as I’m writing them today, but I’m constantly being reminded that things aren’t always as they seem with Migrate. It’s a wonderful system but can be tricky to understand. I recommend reading through my other Migrate-related posts, especially the post on debugging.

  • Development

    Extending the Migrate Plus JSON Parser in Drupal 8

    The migrate_plus module provides a great JSON parser for easy migration of JSON data. With a small amount of code in a new class you can tweak the parser a bit. In my case I wanted to make a few simple changes:

    1. Speed up initial processing of the data
      1. Almost all of my data is at the top level in the JSON structure (there is no “Members” wrapper, for example).
      2. The stock JSON parser runs a selectByDepth() method if you use a item_selector: 0 , which slows things down considerably; it loops through every record, which is a bear if you have 46,000 records.
    2. Make it easy to manipulate the data (think prepare row)
      1. Using my overridden JSON parser as a base for additional parser classes it became nice to implement a simple prepareRows method to massage the data for each particular migration.
      2. I have several migrations coming out of the same data source (content type + supporting paragraphs). It’s nice to create a parser that extracts only the paragraph data so that we maintain an accurate count of the records for the “child” migration.
  • Development

    Monitoring a Drupal 8 Migration Executed with Drush

    Update 2 is proving to be the most useful method.

    Update 1

    Somehow I missed the documentation regarding the --feedback  argument for the drush mi  command. It’s similar to the methods below in that it helps you see that the migration is working, though you don’t see the totals. You can ask for feedback in seconds or items.

    Update 2:

    Another method that is a bit dirty but very useful is to add a single line to core/modules/migrate/src/MigrateExecutable.php.

    Adding the highlighted line to \Drupal\migrate\MigrateExecutable::import will let you see exactly where the migration is (which row is being processed).

    If this is something you want permanently, consider posting an issue on d.o to request more verbose logging. This is my hackey solution for my immediate needs.

    The output (in your logs, and in the drush output) will be something like this (institution_node is my migration, inst_guid is the only id):

    As of Thursday, August 16, 2018 the counter() method is removed. So, you have to drop a counter variable in place like this:

    This method of monitoring execution is surprisingly effective as it’s fast and you don’t have to lift a finger for it to happen each time you run a migration.


    Original Post

    This isn’t exactly an ideal solution, but it will do in a pinch. I’m working on a migration of more than 46,000 nodes (in a single migration among many). I needed a way to monitor the progress but I wanted to do it as quickly as possible (no coding). Here’s what I came up with, which I run in a new iTerm window.

    All we’re doing is asking how many records are in the “member_node” migration map every 5 seconds. If we started at 6350 items we know that by the end of 20 seconds we have created 35 records.

    We could also query the target content type itself:

    Here we can analyze the data the same way to see how many records the migration is creating.

    I recognize that this is pretty crude, but it’s effective; you are able to see that it’s working, instead of just staring at an unchanging prompt and watching your CPU jump.

  • Development

    Alter Date Format in a Drupal 8 Migration

    Per https://www.drupal.org/node/2820490 you can now use the format_date plugin to alter date formats like this:

    I do always recommend using skip_on_empty before any other process plugins.

  • Development

    Quick and Dirty Debugging of Drupal 8 Migrations

    Introduction

    If you’re working on a migration in Drupal 8 and you’re finding yourself a little confused by the YAML-based configuration, I strongly recommend using a proper debugger so you can step through the code. You cannot step through the YAML, but you can step through the code that the YAML triggers. This blog post is my attempt to share a few tips/tricks I’ve learned along the way. This isn’t meant to be an exhaustive step-by-step debugging tutorial, so you may have to do some Googling to fill in the blanks.

    Disclaimer: Some of the information is PHPStorm-specific, but you should be able to adapt to whichever debugging tools you use.