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Tag: hadoop

Faster munging for the Wikidata Query Service using Hadoop

The Wikidata query service is a public SPARQL endpoint for querying all of the data contained within Wikidata. In a previous blog post I walked through how to set up a complete copy of this query service. One of the steps in this process is the munge step. This performs some pre-processing on the RDF dump that comes directly from Wikidata.

Back in 2019 this step took 20 hours and now takes somewhere between 1-2 days as Wikidata has continued to grow. The original munge step (munge.sh) makes use of only a single CPU. The WMF has been experimenting for some time with performing this step in their Hadoop cluster as part of their modern update mechanism (streaming updater). An additional patch has now also made this useful for the current default load process (using loadData.sh).

This post walks through using the new Hadoop based munge step with the latest Wikidata TTL dump on Google clouds Dataproc service. This cuts the munge time down from 1-2 days to just 2 hours using an 8 worker cluster. Even faster times can be expected with more workers, all the way down to ~20 minutes.

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Using Hue & Hive to quickly determine Wikidata API maxlag usage

Hue, or Hadoop User Experience is described by its documentation pages as “a Web application that enables you to easily interact with an Hadoop cluster”.

The Wikimedia Foundation has a Hue frontend for their Hadoop cluster, which contains various datasets including web requests, API usage and the MediaWiki edit history for all hosted sites. The install can be accessed at https://hue.wikimedia.org/ using Wikimedia LDAP for authentication.

Once logged in Hue can be used to write Hive queries with syntax highlighting, auto suggestions and formatting, as well as allowing users to save queries with names and descriptions, run queries from the browser and watch hadoop job execution state.

The Wikidata & maxlag bit

MediaWiki has a maxlag API parameter that can be passed alongside API requests in order to cause errors / stop writes from happening when the DB servers are lagging behind the master. Within MediaWiki this lag can also be raised when the JobQueue is very full. Recently Wikibase introduced the ability to raise this lag when the Dispatching of changes to client projects is also lagged behind. In order to see how effective this will be, we can take a look at previous API calls.

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WMDE: Metrics & Data Gatherings

Below you will find an internal WMDE presentation covering the general area of WMDE Metric & Data Gatherings from 2016.

This presentation follows on from the initial introduction to engineering analytics activities.

The presentation skims through:

  • WMDE Grafana dashboards
  • The Wikimedia Analytics landscape
  • Grafana & graphite
  • Hadoop, Kafka, Hive & Oozie
  • EventLogging, Mysql replicas & MediaWiki logs
  • Out Analytics scripts
  • How to get access

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