Explanation
After a new version of Kubernetes has been released and when Container Engine for Kubernetes supports the new version, you can use Container Engine for Kubernetes to upgrade master nodes running older versions of Kubernetes. Because Container Engine for Kubernetes distributes the KubernetesControl Plane on multiple Oracle-managed master nodes (distributed across different availability domains in a region where supported) to ensure high availability, you're able to upgrade the Kubernetes version running on master nodes with zero downtime.
Having upgraded master nodes to a new version of Kubernetes, you can subsequently create new node pools running the newer version. Alternatively, you can continue to create new node pools that will run older versions of Kubernetes (providing those older versions are compatible with the Kubernetes version running on the master nodes).
Note that you upgrade master nodes by performing an 'in-place' upgrade, but you upgrade worker nodes by performing an 'out-of-place' upgrade. To upgrade the version of Kubernetesrunning on worker nodes in a node pool, you replace the original node pool with a new node pool that has new worker nodes running the appropriate Kubernetes version. Having 'drained' existing worker nodes in the original node pool to prevent new pods starting and to delete existing pods, you can then delete the original node pool.
Upgrading the Kubernetes Version on Worker Nodes in a Cluster:
After a new version of Kubernetes has been released and when Container Engine for Kubernetes supports the new version, you can use Container Engine for Kubernetes to upgrade master nodes running older versions of Kubernetes. Because Container Engine for Kubernetes distributes the Kubernetes Control Plane on multiple Oracle-managed master nodes (distributed across different availability domains in a region where supported) to ensure high availability, you're able to upgrade the Kubernetes version running on master nodes with zero downtime.
You can upgrade the version of Kubernetes running on the worker nodes in a clusterin two ways:
(A) Perform an 'in-place' upgrade of a node pool in the cluster, by specifying a more recent Kubernetes version for new worker nodes starting in the existing node pool. First, you modify the existing node pool's properties to specify the morerecent Kubernetes version. Then, you 'drain' existing worker nodes in the node pool to prevent new pods starting, and to delete existing pods. Finally, you terminate each of the worker nodes in turn.
When new worker nodes are started in the existing node pool, they run the more recent Kubernetes version you specified. See Performing an In-Place Worker Node Upgrade by Updating anExisting Node Pool.
(B) Perform an 'out-of-place' upgrade of a node pool in the cluster, by replacing the original node pool with a new node pool. First, you create a new node pool with a more recent Kubernetes version. Then, you 'drain' existing worker nodes in the original node pool to prevent new pods starting, and to delete existing pods.
Finally, you delete the original node pool. When new worker nodes are started in the new node pool, they run the more recent Kubernetes version you specified. See Performing an Out-of-Place Worker Node Upgrade by Replacing an Existing Node Pool with a New Node Pool.
Note that in both cases:
The more recent Kubernetes version you specify for the worker nodes in the node pool must be compatible with the Kubernetes version running on the master nodes in the cluster. See Upgrading Clusters to Newer Kubernetes Versions).
You must drain existing worker nodes in the original node pool. If you don't drain the worker nodes, workloads running onthe cluster are subject to disruption.
References:
https://docs.cloud.oracle.com/en-us/iaas/Content/ContEng/Tasks/contengupgradingk8sworkernode.htm

Explanation
You can invoke a function that you've deployed to Oracle Functions in different ways:
Using the Fn Project CLI.
Using the Oracle Cloud Infrastructure CLI.
Using the Oracle Cloud Infrastructure SDKs.
Making a signed HTTP request to the function's invoke endpoint. Every function has an invoke endpoint.
Each of the above invokes the function via requests to the API. Any request to the API must be authenticated by including a signature and the OCID of the compartmentto which the function belongs in the request header.
Such a request is referred to as a 'signed' request. The signature includes Oracle Cloud Infrastructure credentials in an encrypted form.

Explanation
Overviewof Functions:
The serverless and elastic architecture of Oracle Functions means there's no infrastructure administration or software administration for you to perform. You don't provision or maintain compute instances, and operating system softwarepatches and upgrades are applied automatically. Oracle Functions simply ensures your app is highly-available, scalable, secure, and monitored. With Oracle Functions, you can write code in Java, Python, Node, Go, and Ruby (and for advanced use cases, bringyour own Dockerfile, and Graal VM). You can then deploy your code, call it directly or trigger it in response to events, and get billed only for the resources consumed during the execution.
References:
https://docs.cloud.oracle.com/en-us/iaas/Content/Functions/Concepts/functionsoverview.htm

Explanation
Adding Stock Responses as an API Gateway Back End:
You'll often want to verify that an API has been successfully deployed on an API gateway without having to set up an actual back-end service. One approach is to define a route in the API deployment specification that has a path to a 'dummy' back end. Onreceiving a request to that path, the API gateway itself acts as the back end and returns a stock response you've specified.
Equally, there are some situations in a production deployment where you'll want a particular path for a route to consistentlyreturn the same stock response without sending a request to a back end. For example, when you want a call to a path to always return a specific HTTP status code in the response.
Using the API Gateway service, you can define a path to a stock response backend that always returns the same:
HTTP status code
HTTP header fields (name-value pairs)
content in the body of the response
"type": "STOCK_RESPONSE_BACKEND" indicates that the API gateway itself will act as the back end and return the stock response you define (the status code, the header fields and the body content).
References:
https://docs.cloud.oracle.com/en-us/iaas/Content/APIGateway/Tasks/apigatewayaddingstockresponses.htm

Explanation
distributed systems of native-cloud like functions that have a lot of benefit like Resiliency and availability Resiliency andavailability refers to the ability of a system to continue operating, despite the failure or sub-optimal performance of some of its components.
In the case of Oracle Functions:
The control plane is a set of components that manages function definitions.
Thedata plane is a set of components that executes functions in response to invocation requests.
For resiliency and high availability, both the control plane and data plane components are distributed across different availability domains and fault domains ina region. If one of the domains ceases to be available, the components in the remaining domains take over to ensure that function definition management and execution are not disrupted.
When functions are invoked, they run in the subnets specified for theapplication to which the functions belong.
For resiliency and high availability, best practice is to specify a regional subnet for an application (or alternatively, multiple AD-specific subnets in different availability domains). If an availability domainspecified for an application ceases to be available, Oracle Functions runs functions in an alternative availability domain.
Concurrency and Scalability
Concurrency refers to the ability of a system to run multiple operations in parallel using shared resources.
Scalability refers to the ability of the system to scale capacity (both up and down) to meet demand.
In the case of Functions, when a function is invoked for the first time, the function's image is run as a container on an instance in a subnetassociated with the application to which the function belongs. When the function is executing inside the container, the function can read from and write to other shared resources and services running in the same subnet (for example, Database as a Service).The function can also read from and write to other shared resources (for example, Object Storage), and other Oracle Cloud Services.
If Oracle Functions receives multiple calls to a function that is currently executing inside a running container, Oracle Functions automatically and seamlessly scales horizontally to serve all the incoming requests. Oracle Functions starts multiple Docker containers, up to the limit specified for your tenancy. The default limit is 30 GB of RAM reserved for function execution per availability domain, although you can request an increase to this limit. Provided the limit is not exceeded, there is no difference in response time (latency) between functions executing on the different containers.