dora-metrics

DORA metrics

How it works

This controller watches deployments that present label dora-controller/enabled: 'true'.

It collects four metrics:

• deployment frequency
• failure rate
• cycle time
• mean time to recovery

These are the four metrics highlighted as worth measuring by the authors of Accelerate.

Different teams interpret the exact meaning of the four metrics in ways that make sense to them, which is exactly as it should be. This implementation applies the following:

• deployment frequency is based on the number of successful deployments in production
• failure rate is based on the number of unsuccessful deployments in production
• cycle time is elapsed time between pipeline start (typically triggered by a git commit) and successful rollout
• mean time to recovery (MTTR) is here defined narrowly as the time it takes the cluster to recover from an outage (no healthy pods available) to a healthy deployment

Flow

flowchart TD
    A("Watch deployment update stream")
    B["New deployment update matching label<br/>dora-controller/enabled: 'true'"]
    C{"Parse annotations"}
    D["Update gauge dora_cycle_time"]
    E["Increment counter dora_successful_deployment"]
    F["Increment counter dora_failed_deployment"]
    G{"Parse desired and ready<br/>replica counts"}
    H["Set downtime flag"]
    I{"Downtime flag set?"}
    K["Update gauge dora_time_to_recovery"]
    L["Clear downtime flag"]

    A --> B --> C
    C -->|dora-controller/success == true| D
    C -->|dora-controller/success == false| F
    D --> E
    E --> G
    F --> G
    G -->|desired > 0 but ready == 0| H
    G -->| desired == ready| I
    H --> A
    I -->|true| K
    I -->|false| A
    K --> L --> A

Approach

With the exception of MTTR, the best source for these metrics is the CI pipeline. The CI system knows how long the pipeline runs and crucially it can find out quite easily if a given deployment has completed successfully.

For MTTR, the controller distinguishes broadly between "unavailable" and "available", where availability is defined as a deployment whose number of healthy pods matches the desired count.

In addition to MTTR, there is an opportunity to measure the frequency of outages, but that falls outside the four metrics.

  labels:
    dora-controller/enabled: 'true'
  annotations:
    dora-controller/report-before: '1626600056'
    dora-controller/cycle-time: '125'
    dora-controller/success: 'true'

The label is used to identify deployments the controller should monitor for state changes.

report-before is used to prevent stale attributes being picked up when a deployment changes state (which often happens without a new deployment taking place). This is not necessary for the controller pod that originally picks up this update (as it maintains a map of the previously seen report-before value for each deployment), but it is necessary should the controller pod be rescheduled due to a spot instance eviction, for example.

cycle-time is the elapsed time, in seconds, from the moment the pipeline was triggered to the moment the deployment completed, successfully or otherwise. Note that time spent in approval stages is deducted from the total.

success specifies whether a given deployment was successful.

Crucially, the application itself does no work to expose these metrics.

They are made available to Prometheus by single-pod deployment dora-metrics in namespace kube-monitoring.

Building dashboards

The following metrics are exposed to Prometheus:

• dora_cycle_time_seconds
• dora_failed_deployments_total
• dora_successful_deployments_total
• dora_time_to_recovery_seconds