Incident: Slack Outage Disrupts Service for Millions of Users.

Published Date: 2021-01-04

Postmortem Analysis
Timeline 1. The software failure incident with Slack occurred on Monday, as mentioned in the article [110272]. 2. The article was published on 2021-01-04. 3. Estimating the date of the incident: - Step 1: The article mentions that the incident happened on Monday, which was the day many employees in the United States returned to work after the holidays. - Step 2: The article was published on 2021-01-04, which was a Monday. - Step 3: Therefore, the software failure incident with Slack occurred on 2021-01-04.
System 1. Slack messaging platform [110272]
Responsible Organization 1. The software failure incident experienced by Slack was caused by internal issues within the Slack platform itself, leading to disruptions in service for users [110272].
Impacted Organization 1. Slack users, including more than 10 million daily users, experienced disruptions in accessing the platform, sending messages, loading channels, making calls, logging in, and using calendar apps and email notifications [110272]. 2. Companies and organizations relying on Slack as an essential workplace tool, including media organizations and those working remotely due to the pandemic, were affected by the outage [110272].
Software Causes 1. Unknown
Non-software Causes 1. Increased demand due to employees returning to work after the holidays [110272]. 2. Spike in reported problems with Slack at about 10 a.m. Eastern time [110272]. 3. Intense competition in the market for workplace software leading to potential acquisitions [110272]. 4. Outages becoming more rare due to tech giants building networks of interconnected data centers [110272].
Impacts 1. Users of Slack experienced disruptions such as not being able to send messages, load channels, make calls, or log in to the service during the outage [110272]. 2. Some users had issues with their calendars and notifications as a result of the software failure incident [110272]. 3. The outage led many individuals to switch to alternative communication tools like Google or Zoom's video services, or resort to traditional methods like phone calls and emails [110272]. 4. The disruption caused inconvenience to employees who had become accustomed to the convenience and immediacy of using Slack for work, especially while working remotely due to the COVID-19 pandemic [110272]. 5. Service began to resume for some users around 12:20 p.m. Eastern, but with degraded performance [110272].
Preventions 1. Implementing robust monitoring systems to quickly detect and respond to any issues before they escalate [110272]. 2. Conducting regular load testing and capacity planning to ensure the platform can handle peak usage times without disruptions [110272]. 3. Enhancing redundancy and failover mechanisms to minimize the impact of any potential outages [110272]. 4. Improving communication with users by providing timely updates and transparent information during incidents to manage expectations and reduce frustration [110272].
Fixes 1. Implementing redundancy and failover mechanisms in the infrastructure to prevent service disruptions [110272]. 2. Conducting a thorough root cause analysis to identify the specific issue that caused the outage and implementing measures to prevent its recurrence [110272]. 3. Enhancing monitoring and alerting systems to quickly detect and respond to any service degradation or failures [110272]. 4. Improving communication with users during incidents to provide timely updates and transparency on the status of the service restoration process [110272].
References 1. Slack's official statement on its website [110272] 2. Slack representative [110272] 3. Downdetector website [110272]

Software Taxonomy of Faults

Category Option Rationale
Recurring one_organization, multiple_organization (a) The software failure incident having happened again at one_organization: - The article mentions that in September, Google services, Slack, and a suite of Microsoft services experienced outages [110272]. - In December, Google suffered another outage with its apps [110272]. (b) The software failure incident having happened again at multiple_organization: - The article highlights that in August, an outage involving the video service Zoom caused problems for several hours [110272]. - It also mentions that in September, Google services, Slack, and a suite of Microsoft services experienced outages [110272].
Phase (Design/Operation) design, operation (a) The software failure incident related to the design phase can be inferred from the article as Slack experienced a major disruption that led to an outage affecting users' ability to send messages, load channels, make calls, log in, and access calendar apps and email notifications. The disruption was significant enough to prompt users to switch to alternative communication tools like Google or Zoom [110272]. (b) The software failure incident related to the operation phase is evident from the article as users faced issues with their calendars and notifications during the outage. Additionally, some users experienced degraded performance even after service began to resume for some around 12:20 p.m. Eastern time [110272].
Boundary (Internal/External) within_system (a) The software failure incident with Slack was primarily within the system. The disruption experienced by Slack users was due to issues within the Slack platform itself, leading to users being unable to send messages, load channels, make calls, log in, or access calendar apps and email notifications [110272]. (b) Additionally, the article mentions that outages like the one experienced by Slack have become more rare as tech giants like Google and Facebook have built networks of interconnected data centers, indicating that failures originating from outside the system (external factors) were not the primary cause of the Slack outage [110272].
Nature (Human/Non-human) non-human_actions (a) The software failure incident related to non-human actions was the outage experienced by Slack, as reported in Article 110272. The disruption occurred as many employees returned to work after the holidays, causing issues with loading channels, connecting to Slack, sending messages, making calls, and logging in to the service. The outage also affected calendar apps and email notifications. The company mentioned improvements with error rates on their side, and service began to resume for some users around 12:20 p.m. Eastern [110272]. (b) The software failure incident related to human actions was not explicitly mentioned in the provided article.
Dimension (Hardware/Software) software (a) The software failure incident reported in the articles does not seem to be attributed to hardware issues. The incident with Slack was primarily related to service disruptions and outages within the software itself, affecting users' ability to send messages, load channels, make calls, log in, and access calendar apps and email notifications [110272]. (b) The software failure incident with Slack was caused by issues within the software itself, leading to disruptions in service for users. The company acknowledged the problem as an "incident" initially and then upgraded it to an outage, indicating that the root cause was within the software system. Users experienced difficulties in using various features of the platform, and the company's representatives mentioned improvements in error rates on their side as they worked to resolve the issue [110272].
Objective (Malicious/Non-malicious) non-malicious (a) The software failure incident reported in the articles does not indicate any malicious intent or actions contributing to the failure. It appears to be a non-malicious failure caused by technical issues or disruptions in the service [110272].
Intent (Poor/Accidental Decisions) accidental_decisions (a) The software failure incident related to Slack's outage does not seem to be directly linked to poor decisions. The outage was primarily due to technical issues causing disruptions in service, leading to users being unable to send messages, load channels, make calls, or log in to the platform [110272]. The incident was described as a disruption that affected many users, and the company was working on resolving the issues to restore service [110272]. (b) The software failure incident appears to be more aligned with accidental decisions or technical issues rather than intentional poor decisions. The outage was likely caused by technical glitches or faults within the system, leading to disruptions in service for users. The company was focused on investigating and resolving the issues to minimize the impact on users [110272].
Capability (Incompetence/Accidental) accidental (a) The software failure incident related to development incompetence is not explicitly mentioned in the provided article. Therefore, it is unknown if the Slack outage was due to factors introduced by lack of professional competence. (b) The software failure incident related to accidental factors is evident in the article. The outage experienced by Slack was not intentional but rather an unexpected disruption that affected users' ability to send messages, load channels, make calls, log in, and use calendar apps and email notifications [110272].
Duration temporary (a) The software failure incident reported in the articles was temporary. The incident with Slack experiencing a major disruption was resolved within the same day. Service began to resume for some users around 12:20 p.m. Eastern, and by the afternoon, the spike in reported problems had subsided [110272].
Behaviour crash, omission, other (a) crash: The software failure incident in the article can be categorized as a crash as users were unable to send messages, load channels, make calls, or even log in to the service during the outage, indicating a complete disruption of the system's intended functions [110272]. (b) omission: The incident can also be classified as an omission as users experienced trouble loading channels or connecting to Slack, indicating that the system omitted to perform its intended functions at that instance [110272]. (c) timing: The timing of the incident can be considered a factor as it occurred at a critical time when many employees in the United States were returning to work after the holidays, causing disruption to their workflow [110272]. (d) value: There is no specific mention of the system performing its intended functions incorrectly, so this option is unknown based on the provided article. (e) byzantine: The incident does not exhibit characteristics of a byzantine failure where the system behaves erroneously with inconsistent responses and interactions, so this option is unknown based on the provided article. (f) other: The other behavior observed during the incident was users resorting to alternative communication tools like phone calls and emails, which could be considered an adaptation to the failure of the Slack platform [110272].

IoT System Layer

Layer Option Rationale
Perception None None
Communication None None
Application None None

Other Details

Category Option Rationale
Consequence property, delay (property) The software failure incident involving Slack resulted in users experiencing disruptions in their work activities, such as not being able to send messages, load channels, make calls, or log in to the service. Additionally, some users faced issues with their calendars and notifications [110272].
Domain information, finance (a) The software failure incident reported in the articles affected the information industry, specifically impacting the popular messaging platform Slack used by millions of people worldwide [110272]. (h) The incident also had implications for the finance industry as Salesforce, a company that sells marketing and sales software, had announced in December that it would buy Slack for $27.7 billion in cash and stock [110272]. (m) The software failure incident did not directly relate to any other industry not covered in the options provided.

Sources

Back to List