English: On 27 October 2020, the Wikimedia Foundation switched between their two primary datacenters as part of routine testing and maintenance. This involves a brief read-only period for Wikipedia and other related projects. This video shows the logs of their operations/SRE chat channel, alongside the "Listen to Wikipedia" app, which visualizes and makes music out of edits as they are made on Wikipedia.
1:40 lead-up to the read-only interval
2:03 config change deployed to go read-only
2:12 all servers have received the change, sites are read-only
now, once read-only, changes are made to switch which datacenter would receive writes
3:41 config change deployed to go read-write
3:50 first edit received in the new primary datacenter
4:00 edits are again streaming in at their usual rate
The rest of the video shows SRE monitoring some elevated latency (which was expected, and fixes itself -- many layers of caches need to be "warmed up" again by user traffic).
This was the first time that we managed less than two minutes of read-only duration.
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