v1.2 release

A new version of Knative is now available across multiple components.

Follow the instructions in the documentation Installing Knative for the respective component.

Minimum Kubernetes version is now v1.21.
Serving added experimental support for PVC.
Eventing ConfigMap element names are standardized to kebab case. Use data-max-size and channel-template-spec instead of the previous camel case elements, which have been deprecated. For more information, see Eventing v1.2.
The kn client has added autocomplete for several commands. For more information, see CLI v1.2.

Improves the error message when a DomainMapping cannot be reconciled because autocreate-cluster-domain-claims is false and the CDC does not exist. (#12439)
Utilizes Kubernetes's immediate trigger of readiness probes after startup. Restores default periodSeconds for readiness probe to Kubernetes default (10s). (#12550)

Changes liveness probes to directly probe the user container rather than queue proxy. (#12479)

Adds PVC support behind the feature flags kubernetes.podspec-persistent-volume-claim and kubernetes.podspec-persistent-volume-write. (#12458)

Change default Broker delivery spec. (#6011)
Unify inconsistent ConfigMaps (#5875):
- The Channel template in the ConfigMap that Brokers use to declare the underlying channel must be located under the channel-template-spec element. The previous channelTemplateSpec element has been deprecated.
- PingSource's ConfigMap element for maximum size has been redefined as data-max-size. The previous dataMaxSize element has been deprecated.

Traces generated by PingSource includes some Kubernetes attributes: k8s.namespace, k8s.name, k8s.resource. (#5928)
Add new new-trigger-filters experimental feature. When enabled, Triggers support a new filters field that conforms to the filters API field defined in the CloudEvents Subscriptions API. It allows you to specify a set of powerful filter expressions, where each expression evaluates to either true or false for each event. (#5995)

Fixes the following vulnerabilities (#6057):
- github.com/knative/pkg contains a dependency that is subject to DoS attack.
- github.com/kubernetes/utils contains a security issue that was discovered where a user might be able to create a container with subpath volume mounts to access files and directories outside of the volume, including on the host filesystem.

An HTTP header will be supplied to your event consumers when the Broker it is communicating with supports reply events. This will always be sent while using this Kafka Broker since it supports handling reply events. (#1771)
Apply back-pressure by limiting the number of in-flight dispatch requests in the unordered event consumption. (#1750)
Support TLS for the metrics server. Now, the receiver and the dispatcher accept the following environment variables (#1707):
- METRICS_PEM_CERT_PATH: TLS cert path
- METRICS_PEM_KEY_PATH: TLS key path
- METRICS_HOST: metrics server host

Improved Broker's and Source's README docs, sample descriptions, and files. (#555)
Add publisher confirms to ingress. Return 200 only when RabbitMQ confirms receiving and storing the message. (#568)
Makefile-based workflow. Includes migrating GitHub Actions. (#525, #569, #579)
Various code refactoring and code health improvements. (#552, #572)
Source adapter trigger dispatcher homologation. Now the Source Adapter and Broker Dispatcher's Prefetch Count behavior is the same. Updated the Trigger's webhook to validate the following (#536):
- Has a default value of 1. FIFO behavior
- Have limits: 1 ≤ prefetchCount ≤ 1000
All core Knative Eventing RabbitMQ Pods should now be able to run in the restricted Pod security standard profile. (#541)

Removing the dead letter sink on a Trigger will now properly fall back to the Broker's dead letter sink, if one is defined. (#533)
Messages sent to RabbitMQ are now marked as Persistent (#560):
- Configuring messages sent into the RabbitMQ Broker to be persistent as the Queues used by the Broker are always durable.
- Now if the user set the configuration of the RabbitMQ Source Exchange and Queue to be durable, the messages are also durable.

Add the support of resources configuration based on deploy and container names. (#893)

Release leads: @dprotaso and @psschwei

Knative is an open source project that anyone in the community can use, improve, and enjoy. We'd love you to join us!