Configuring gradual roll-out of traffic to Revisions
If your traffic configuration points to a Configuration target instead of a Revision target, when a new Revision is created and ready, 100% of the traffic from the target is immediately shifted to the new Revision.
This might make the request queue too long, either at the QP or Activator, and cause the requests to expire or be rejected by the QP.
Knative provides a rollout-duration
parameter, which can be used to gradually shift traffic to the latest Revision, preventing requests from being queued or rejected. Affected Configuration targets are rolled out to 1% of traffic first, and then in equal incremental steps for the rest of the assigned traffic.
Note
rollout-duration
is time-based, and does not interact with the autoscaling subsystem.
This feature is available for tagged and untagged traffic targets, configured for either Knative Services or Routes without a service.
Procedure
You can configure the rollout-duration
parameter per Knative Service or Route by using an annotation.
Tip
For information about global, ConfigMap configurations for roll-out durations, see the Administration guide
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
name: helloworld-go
namespace: default
annotations:
serving.knative.dev/rolloutDuration: "380s"
Route status updates
During a rollout, the system updates the Route and Knative Service status conditions. Both the traffic
and conditions
status parameters are affected.
For example, for the following traffic configuration:
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
...
spec:
...
traffic:
- percent: 55
configurationName: config # Pinned to latest ready Revision
- percent: 45
revisionName: config-00005 # Pinned to a specific Revision.
Initially 1% of the traffic is rolled out to the Revisions:
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
...
spec:
...
traffic:
- percent: 54
revisionName: config-00008
- percent: 1
revisionName: config-00009
- percent: 45
revisionName: config-00005 # Pinned to a specific Revision.
Then the rest of the traffic is rolled out in increments of 18%:
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
...
spec:
...
traffic:
- percent: 36
revisionName: config-00008
- percent: 19
revisionName: config-00009
- percent: 45
revisionName: config-00005 # Pinned to a specific Revision.
The rollout continues until the target traffic configuration is reached:
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
...
spec:
...
traffic:
- percent: 55
revisionName: config-00009
- percent: 45
revisionName: config-00005 # Pinned to a specific Revision.
During the rollout, the Route and Knative Service status conditions are as follows:
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
...
spec:
...
status:
conditions:
...
- lastTransitionTime: "..."
message: A gradual rollout of the latest revision(s) is in progress.
reason: RolloutInProgress
status: Unknown
type: Ready
Multiple roll-outs
If a new revision is created while a rollout is in progress, the system begins to shift traffic immediately to the newest Revision, and drains the incomplete roll-outs from newest to oldest.