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  1. IL-0588 AppOptics metrics APIs returned 5xx as Kafka partitions stayed leaderless after an AWS power event hit their ZooKeeper
    AppOptics2018
    Symptoms

    On May 31, 2018 from 21:53 UTC the metrics APIs of AppOptics and Librato returned a 5xx for a majority of incoming metric data. APM metrics and traces sent from AppOptics APM were affected, and many alert notifications were delayed.

    High error rateFailover failureMonitoring outage
    Trigger

    A power event in one of AWS's availability zones in us-east-1 cut off nodes in several critical parts of the AppOptics and Librato infrastructure, including the ZooKeeper node that was then the leader of the ensemble coordinating the Kafka brokers.

    Root cause
    Cloud provider outage
    Component
    Message brokerCoordination and key-value store
    Contributing factor
    Single point of failureExcessive blast radiusMonitoring blind spot
    Remediation
    • Restarted one ZooKeeper node by hand to force a leader election, after which the ensemble regained quorum
    • Restarted every Kafka broker in a rolling restart until all partitions were back online
    • Worked through the backlog, including the backlog of alerts, and resumed normal operations
    Action items
    • Isolate the Kafka clusters better across availability zones and regions
    • Stop sharing one ZooKeeper ensemble across Kafka clusters
    • Run game days on this failure and check whether newer Kafka versions fix it
    • Put in place more checks that notify the team earlier about subsystems that need extra help to recover
    Lessons

    Running services across several availability zones and more than one Kafka cluster did not isolate the pipeline from the failure of one zone, because partitions of different clusters sat in the same zones and the clusters shared one ZooKeeper ensemble. More operational monitoring of the subsystems that needed help to recover would have led to a faster recovery.

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By root cause1

Cloud provider outage1 case

Component
Coordination and key-value storeMessage broker
Contributing factor
Excessive blast radiusMonitoring blind spotSingle point of failure
Organisation
AppOptics
  1. IL-0588 AppOptics metrics APIs returned 5xx as Kafka partitions stayed leaderless after an AWS power event hit their ZooKeeper
    AppOptics2018