Why did Slack suffer an outage on Friday?

On Friday, Slack, an instant messaging platform for work spaces confirmed news of the global outage. Millions of users reported disruption in services due to the outage which occurred early Friday afternoon. Slack experienced a performance degradation issue impacting users from all over the world, with multiple services being down.

Yesterday the Slack team posted a detailed incident summary report of the service restoration. The Slack status page read: “On June 28, 2019 at 4:30 a.m. PDT some of our servers became unavailable, causing degraded performance in our job processing system. This resulted in delays or errors with features such notifications, unfurls, and message posting.

At 1:05 p.m. PDT, a separate issue increased server load and dropped a large number of user connections. Reconnection attempts further increased the server load, slowing down customer reconnection. Server capacity was freed up eventually, enabling all customers to reconnect by 1:36 p.m. PDT.

Full service restoration was completed by 7:20 p.m. PDT. During this period, customers faced delays or failure with a number of features including file uploads, notifications, search indexing, link unfurls, and reminders.

Now that service has been restored, the response team is continuing their investigation and working to calculate service interruption time as soon as possible. We’re also working on preventive measures to ensure that this doesn’t happen again in the future. If you’re still running into any issues, please reach out to us at feedback@slack.com.”

https://twitter.com/SlackStatus/status/1145541218044121089

These were the various services which were affected due to outage:

• Notifications
• Calls
• Connections
• Search
• Messaging
• Apps/Integrations/APIs
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• Link Previews
• Workspace/Org Administration
• Posts/Files

Timeline of Friday’s Slack outage

According to user reports it was observed that some Slack messages were not delivered with users receiving an error message.

On Friday, at 2:54 PM GMT+3, Slack status page gave the initial signs of the issue,  "Some people may be having an issue with Slack. We’re currently investigating and will have more information shortly. Thank you for your patience,".

https://twitter.com/SlackStatus/status/1144577107759996928

According to the Down Detector, Slack users noted that message editing also appeared to be impacted by the latest bug. Comments indicated it was down around the world, including Sweden, Russia, Argentina, Italy, Czech Republic, Ukraine and Croatia.

The Slack team continued to give updates on the issue, and on Friday evening they reported of services getting back to normal.

https://twitter.com/SlackStatus/status/1144806594435117056

This news gained much attraction on Twitter, as many of them commented saying Slack is already preps up for the weekend.

https://twitter.com/RobertCastley/status/1144575285980999682

https://twitter.com/Octane/status/1144575950815932422

https://twitter.com/woutlaban/status/1144577117788790785

 

Users on Hacker News compared Slack with other messaging platforms like Mattermost, Zulip chat, Rocketchat etc.

One of the user comments read, “Just yesterday I was musing that if I were King of the (World|Company) I'd want an open-source Slack-alike that I could just drop into the Cloud of my choice and operate entirely within my private network, subject to my own access control just like other internal services, and with full access to all message histories in whatever database-like thing it uses in its Cloud. Sure, I'd still have a SPOF but it's game over anyway if my Cloud goes dark.

Is there such a project, and if so does it have any traction in the real world?”

To this another user responded, “We use this at my company - perfectly reasonable UI, don't know about the APIs/integrations, which I assume are way behind Slack…”

Another user also responded, “Zulip, Rocket.Chat, and Mattermost are probably the best options.”

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