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This edge release adds refinements to the Linkerd multicluster implementation,
adds new health checks for the tracing add-on, and addresses an issue in which
outbound requests from the proxy result in looping behavior.

* CLI
  * Added the `multicluster` command along with subcommands to configure and
    deploy Linkerd workloads which enable services to be mirrored across
    clusters
  * Added health-checks for tracing add-on
* Proxy
  * Added logic to prevent loops in outbound requests

* CLI
  * Fixed the display of the meshed pod column for non-selector services in
    `linkerd stat` output
  * Added an `addon-overwrite` upgrade flag which allows users to overwrite the
    existing addon config rather than merging into it
  * Added a `--close-wait-timeout` inject flag which sets the
    `nf_conntrack_tcp_timeout_close_wait` property which can be used to mitigate
    connection issues with application that hold half-closed sockets
* Controller
  * Restricted the service-mirror's RBAC permissions so that it no longer is
    able to read secrets in all namespaces
  * Moved many multicluster components into the `linkerd-multicluster` namespace
    by default
  * Added multicluster gateway mirror services to allow multicluster liveness
    probes to work in private networks
  * Fixed an issue where multicluster gateway mirror services could be
    incorrectly deleted during a resync
* Internal
  * Fixed many style issues in build scripts (thanks @joakimr-axis!)
* Helm
  * Added `global.grafanaUrl` variable to allow using an existing Grafana
    installation

## edge-20.5.3

* Controller
  * Added a Grafana dashboard for tracking multi-cluster traffic metrics
  * Added health checks for the Grafana add-on, under a separate section
  * Fixed issues when updating a remote multi-cluster gateway

* Proxy
  * Added special special handling for I/O errors in HTTP responses so that an
    `errno` label is included to describe the underlying errors in the proxy's
    metrics

* Internal
  * Started gathering stats of CI runs for aggregating CI health metrics

This edge release contains everything required to get up and running with
multicluster. For a tutorial on how to do that, check out the
[documentation](https://linkerd.io/2/features/multicluster_support/).

* CLI
  * Added a section to the `linkerd check` that validates that all
    clusters part of a multicluster setup have compatible trust anchors
  * Modified the `inkerd cluster export-service` command to work by
    transforming yaml instead of modifying cluster state
  * Added functionality that allows the `linkerd cluster export-service`
    command to operate on lists of services
* Controller
  * Changed the multicluster gateway to always require TLS on connections
    originating from outside the cluster
  * Removed admin server timeouts from control plane components, thereby
    fixing a bug that can cause liveness checks to fail
* Helm
  * Moved Grafana templates into a separate add-on chart
* Proxy
  * Improved latency under high-concurrency use cases.

* CLI
  * Fixed all commands to use kubeconfig's default namespace if specified
    (thanks @Matei207!)
  * Added multicluster checks to the `linkerd check` command
  * Hid development flags in the `linkerd install` command for release builds
* Controller
  * Added ability to configure Prometheus Altermanager as well as recording
    and alerting rules on the Linkerd Prometheus (thanks @naseemkullah!)
  * Added ability to add more commandline flags to the Prometheus command
    (thanks @naseemkullah!)
* Web UI
  * Fixed TrafficSplit detail page not loading
  * Added Jaeger links to the dashboard when the tracing addon is enabled
* Proxy
  * Modified internal buffering to avoid idling out services as a request
    arrives, fixing failures for requests that are sent exactly once per
    minute--such as Prometheus scrapes

This edge release includes several new CLI commands for use with multi-cluster
gateways, and adds liveness checks and metrics for gateways. Additionally, it
makes the proxy's gRPC error-handling behavior more consistent with other
implementations, and includes a fix for a bug in the web UI.

* CLI
  * Added `linkerd cluster setup-remote` command for setting up a multi-cluster
    gateway
  * Added `linkerd cluster gateways` command to display stats for multi-cluster
    gateways
  * Changed `linkerd cluster export-service` to modify a provided YAML file and
    output it, rather than mutating the cluster
* Controller
  * Added liveness checks and Prometheus metrics for multi-cluster gateways
  * Changed the proxy injector to configure proxies to do destination lookups
    for IPs in the private IP range
* Web UI
  * Fixed errors when viewing resource detail pages
* Internal
  * Created script and config to build a Linkerd CLI Chocolatey package for
    Windows users, which will be published with stable releases (thanks to
    @drholmie!)
* Proxy
  * Changed the proxy to set a `grpc-status: UNAVAILABLE` trailer when a gRPC
    response stream is interrupted by a transport error

This edge release fixes a packaging issue in `edge-20.4.3`.

_From `edge.20.4.3` release notes_:

This edge release adds functionality to the CLI to output more detail and
includes changes which support the multi-cluster functionality. Also, the helm
support has been expanded to make installation more configurable. Finally, the
HA reliability is improved by ensuring that control plane pods are restarted
with a rolling strategy

* CLI
  * Added output to the `linkerd check --proxy` command to list all data
    plane pods which are not up-to-date rather than just printing the first
    one it encounters
  * Added a `--proxy` flag to the `linkerd version` command which lists all
    proxy versions running in the cluster and the number of pods running
    each version
  * Lifted requirement of using --unmeshed for linkerd stat when querying
    TrafficSplit resources
  * Added support for multi-stage installs with Add-Ons
* Controller
  * Added a rolling update strategy to Linkerd deployments that have
    multiple replicas during HA deployments to ensure that at most
    one pod begins terminating before a new pod ready is ready
  * Added a new label for the proxy injector to write to the template,
    `linkerd.io/workload-ns` which indicates the namespace of the workload/pod
* Internal
  * Added a [security policy](https://help.github.com/en/github/managing-security-vulnerabilities/adding-a-security-policy-to-your-repository)
    to facilitate conversations around security
* Helm
  * Changed charts to use downwardAPI to mount labels to the proxy container
    making them easier to identify
* Proxy
  * Changed the Linkerd proxy endpoint for liveness to use the new `/live` admin
    endpoint instead of the `/metrics` endpoint, because the `/live` endpoint
    returns a smaller payload
  * Added a per-endpoint authority-override feature to support
    multi-cluster gateways

This edge release adds functionality to the CLI to output more detail and
includes changes which support the multi-cluster functionality. Also, the helm
support has been expanded to make installation more configurable. Finally, the
HA reliability is improved by ensuring that control plane pods are restarted
with a rolling strategy

* CLI
  * Added output to the `linkerd check --proxy` command to list all data
    plane pods which are not up-to-date rather than just printing the first
    one it encounters
  * Added a `--proxy` flag to the `linkerd version` command which lists all
    proxy versions running in the cluster and the number of pods running
    each version
  * Lifted requirement of using --unmeshed for linkerd stat when querying
    TrafficSplit resources
  * Added support for multi-stage installs with Add-Ons
* Controller
  * Added a rolling update strategy to Linkerd deployments that have
    multiple replicas during HA deployments to ensure that at most
    one pod begins terminating before a new pod ready is ready
  * Added a new label for the proxy injector to write to the template,
    `linkerd.io/workload-ns` which indicates the namespace of the workload/pod
* Internal
  * Added a [security policy](https://help.github.com/en/github/managing-security-vulnerabilities/adding-a-security-policy-to-your-repository)
    to facilitate conversations around security
* Helm
  * Changed charts to use downwardAPI to mount labels to the proxy container
    making them easier to identify
* Proxy
  * Changed the Linkerd proxy endpoint for liveness to use the new `/live` admin
    endpoint instead of the `/metrics` endpoint, because the `/live` endpoint
    returns a smaller payload
  * Added a per-endpoint authority-override feature to support
    mutli-cluster gateways

This release brings a number of CLI fixes and Controller improvements.

* CLI
  * Fixed a bug that caused pods to crash after upgrade if
    `--skip-outbound-ports` or `--skip-inbound-ports` were used
  * Added `unmeshed` flag to the `stat` command, such that unmeshed resources
    are only displayed if the user opts-in
  * Added a `--smi-metrics` flag to `install`, to allow installation of the
    experimental `linkerd-smi-metrics` component
  * Fixed a bug in `linkerd stat`, causing incorrect output formatting when using
    the `--o wide` flag
  * Fixed a bug, causing `linkerd uninstall` to fail when attempting to delete
    PSPs
* Controller
  * Improved the anti-affinity of `linkerd-smi-metrics` deployment to avoid
    pod scheduling problems during `upgrade`
  * Improved endpoints change detection in the `linkerd-destination` service, enabling
    mirrored remote services to change cluster gateways
  * Added `operationID` field to tap OpenAPI response to prevent issues during
    upgrade from 2.6 to 2.7
* Proxy
  * Added a new protocol detection timeout to prevent clients from consuming
    resources indefinitely when not sending any data

## edge-20.4.1

This release introduces some cool new functionalities, all provided by our
awesome community of contributors! Also two bugs were fixed that were introduced
since edge-20.3.2.

* CLI
  * Added `linkerd uninstall` command to uninstall the control plane (thanks
    @Matei207!)
  * Fixed a bug causing `linkerd routes -o wide` to not show the proper actual
    success rate
* Controller
  * Fail proxy injection if the pod spec has `automountServiceAccountToken`
    disabled (thanks @mayankshah1607!)
* Web UI
  * Added a route dashboard to Grafana (thanks @lundbird!)
* Proxy
  * Fixed a bug causing the proxy's inbound to spuriously return 503 timeouts

This release introduces several fixes and improvements to the CLI.

* CLI
  * Added support for kubectl-style label selectors in many CLI commands (thanks
    @mayankshah1607!)
  * Fixed the path regex in service profiles generated from proto files without
    a package name (thanks @amariampolskiy!)
  * Fixed an error when injecting Cronjobs that have no metadata
  * Relaxed the clock skew check to match the default node heartbeat interval
    on Kubernetes 1.17 and made this check a warning
  * Fixed a bug where the linkerd-smi-metrics pod could not be created on
    clusters with pod security policy enabled
* Internal
  * Upgraded tracing components to more recent versions and improved resource
    defaults (thanks @Pothulapati!)

This release introduces new experimental CLI commands for querying metrics using
the Service Mesh Interface (SMI) and for multi-cluster support via service
mirroring.

If you would like to learn more about service mirroring or SMI, or are
interested in experimenting with these features, please join us in
[Linkerd Slack](https://slack.linkerd.io) for help and feedback.

* CLI
  * Added experimental `linkerd cluster` commands for managing multi-cluster
    service mirroring
  * Added the experimental `linkerd alpha clients` command, which uses the
    smi-metrics API to display client-side metrics from each of a resource's
    clients
  * Added retries to some `linkerd check` checks to prevent spurious failures
    when run immediately after cluster creation or Linkerd installation

This release introduces substantial proxy improvements as well as
new observability and security functionality.

* CLI
  * Added the `linkerd alpha stat` command, which uses the smi-metrics
    API; the latter enables access to metrics to be controlled with RBAC
* Controller
  * Added support for configuring service profile timeouts
    `(x-linkerd-timeout)` via OpenAPI spec (thanks @lewiscowper!)
* Web UI
  * Improved the Grafana dashboards to use a globing operator for Prometheus in
    order to avoid producing queries that are too large (thanks @mmiller1!)
* Helm
  * Improved the `linkerd2` chart README (thanks @lundbird!)
* Proxy
  * Fixed a bug that could cause log levels to be processed incorrectly

This release introduces new functionality mainly focused around
observability and multi-cluster support via `service mirroring`.

If you would like to learn more about `service mirroring` or are interested in
experimenting with this feature, please join us in
[Linkerd Slack](https://slack.linkerd.io) for help and feedback.

* CLI
  * Improved the `linkerd check` command to check for extension server
    certificate (thanks @christyjacob4!)
* Controller
  * Removed restrictions preventing Linkerd from injecting proxies into
    Contour (thanks @alfatraining!)
  * Added an experimental version of a service mirroring controller, allowing
    discovery of services on remote clusters.
* Web UI
  * Fixed a bug causing incorrect Grafana links to be rendered in the web
    dashboard.
* Proxy
  * Fixed a bug that could cause the proxy's load balancer to stop processing
    updates from service discovery.

This release introduces the first optional add-on `tracing`, added through the
new add-on model!

The existing optional `tracing` components Jaeger and OpenCensus can now be
installed as add-on components.

There will be more information to come about the new add-on model, but please
refer to the details of [#3955](https://github.com/linkerd/linkerd2/pull/3955) for how to get started.

* CLI
  * Added the `linkerd diagnostics` command to get metrics only from the
    control plane, excluding metrics from the data plane proxies (thanks
    @srv-twry!)
  * Added the `linkerd install --prometheus-image` option for installing a
    custom Prometheus image (thanks @christyjacob4!)
  * Fixed an issue with `linkerd upgrade` where changes to the `Namespace`
    object were ignored (thanks @supra08!)
* Controller
  * Added the `tracing` add-on which installs Jaeger and OpenCensus as add-on
    components (thanks @Pothulapati!!)
* Proxy
  * Increased the inbound router's default capacity from 100 to 10k to
    accommodate environments that have a high cardinality of virtual hosts
    served by a single pod
* Web UI
  * Fixed styling in the CallToAction banner (thanks @aliariff!)