In order to cope with these mini peaks, Slack's web layer is set to autoscale based on 'CPU usage' and 'Apache worker thread status', but in this failure, network failures occurred at the same time. This 'mini-peak' is an access pattern that is characteristic of Slack, and refers to the phenomenon in which access increases rapidly to '0 minutes per hour' and '30 minutes' due to the message transmission that is executed regularly. However, during the 'mini-peak' of 7am Pacific Standard Time, Slack's web layer couldn't handle access and began to lose packets, eventually downing the entire service. Since the cause was found to be an upstream network failure, Slack reported to the cloud provider AWS. were working properly, but the percentage of messages that failed to be sent on Slack was a little high. The internal console, status screen, logging infrastructure, metrics output infrastructure, etc. On January 4, 2021, Slack's infrastructure team observed an increase in service error rates and abnormalities in the monitoring system, and began investigating. The failure began around 6am on January 4th and continued to be inaccessible to Slack from 7am to 8:30 am. Slack suffered a major access failure on JanuPacific Standard Time. Slack's Outage on January 4th 2021 -Slack Engineering It seems that the 'start of work' after the long holidays during the year-end and New Year holidays was the root cause of the disability. Slack has released a report summarizing the causes of the major Slack failure that occurred at the beginning of 2021. 19:00:00 Slack's massive failure early in the year was caused by a 'start of work'

Slack starts massive outage