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Adding Request Policies and Response Policies to API Deployment Specifications:

You can control thebehavior of an API deployment you create on an API gateway by adding request and response policies to the API deployment specification:

a request policy describes actions to be performed on an incoming request from a caller before it is sent to a back end

a response policy describes actions to be performed on a response returned from a back end before it is sent to a caller

You can use request policies to:

limit the number of requests sent to back-end services

enable CORS (Cross-Origin Resource Sharing) support

provide authentication and authorization

You can add request and response policies that apply globally to all routes in an API deployment specification, and also (in some cases) request and response policies that apply only to particular routes.

Notethe following:

No response policies are currently available.

API Gateway request policies and response policies are different to IAM policies, which control access to Oracle Cloud Infrastructure resources.

You can add request and response policies to anAPI deployment specification by:

using the Console

editing a JSON file

References:

ateway/Tasks/apigatewayaddingrequestpolicies.htm

Authorization Header

The Oracle Cloud Infrastructure signature uses the "Signature" Authentication scheme (with an Authorization header), and not the Signature HTTP header.

Required Credentials and OCIDs

You need an API signing key in the correct format. See Required Keys and OCIDs.

You also need the OCIDs for your tenancy and user. See Where to Get the Tenancy's OCID and User's OCID.

Summary of Signing Steps

In general, these are the steps required to sign a request:

Form the HTTPS request (SSL protocol TLS 1.2 is required).

Create the signingstring, which is based on parts of the request.

Create the signature from the signing string, using your private key and the RSA-SHA256 algorithm.

Add the resulting signature and other required information to the Authorization header in the request.

References:

https://docs.cloud.oracle.com/en-us/iaas/Content/API/Concepts/sdks.htm

After a new version of Kubernetes has been released and when Container Engine forKubernetes 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.

Having upgraded master nodes to a new version ofKubernetes, 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 Kubernetes running 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 thendelete 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 cluster in 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 more recent 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 an Existing 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 podsstarting, 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 on the cluster are subject to disruption.

References:

aas/Content/Streaming/Concepts/streamingoverview.htm

Building consumers to read and process messages from a stream using the GetMessages API .

How StreamingWorks:

The Streaming service provides a robust, scalable mechanism that you can use to produce and consume high volumes of data between application components.

Here's how Streaming works: a producer publishes messages to a stream, which is an append-only log. These messages are distributed among the partitions using the message's key.

Streams are divided into a number of partitions for scalability. Partitions allow you to distribute a stream by splitting messages across multiple nodes (or brokers). Each partition can be placed on a separate machine to allow multiple consumers to read a stream in parallel. Multiple consumers can read from any partition regardless of where the partition is hosted.

A consumer can read messages from one or more streams. Each message within a stream is marked with an offset value, so a consumer can pick up where it left off if it is interrupted.

You can use the Streaming service by:

A.Creating a stream using the Console or API.

B.Using a producer to publish data to the stream.

C.Building consumers to read and process messages from a stream using the GetMessages API . .

References:

distributed systems of native-cloud like functions that have a lot of benefit like

Resiliency and availability

Resiliency and availability refers to the ability of asystem 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.

The data plane is a set of components thatexecutes 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 in a region. If one of the domains ceasesto 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 the application 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 domain specified 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 subnet associated with the application to which thefunction 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 toother 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.

What Is Cloud Native?

Cloud native technologies arecharacterized by the use of containers, microservices, serverless functions, development pipelines, infrastructure expressed as code, event-driven applications, and Application Programming Interfaces (APIs). Cloud native enables faster software developmentand the ability to build applications that are resilient, manageable, observable, and dynamically scalable to global enterprise levels.

When constructing a cloud-native application, you'll want to be sensitive to how back-end services communicate with each other. Ideally, the less inter-service communication, the better. However, avoidance isn't always possible as back-end services often rely on one another to complete an operation.

While direct HTTP calls between microservices are relatively simple to implement, care should be taken to minimize this practice. To start, these calls are always synchronous and will block the operation until a result is returned or the request times outs. What were once self-contained, independent services, able to evolve independently and deploy frequently, now become coupled to each other. As coupling among microservices increase, their architectural benefits diminish.

Executing an infrequent request that makes a single direct HTTP call to another microservice might be acceptable for some systems. However, high-volume calls that invoke direct HTTP calls to multiple microservices aren't advisable. They can increase latency and negatively impact the performance, scalability, and availability of your system. Even worse, a longseries of direct HTTP communication can lead to deep and complex chains of synchronous microservices calls, shown in Figure 4-9:

A message queue is an intermediary construct through which a producer and consumer pass a message. Queues implement an asynchronous, point-to-point messaging pattern.

Events

Message queuing is an effective way to implement communication where a producer can asynchronously send a consumer a message.

References:

Oracle Cloud Infrastructure Events enables you to create automation based on the state changes of resourcesthroughout your tenancy. Use Events to allow your development teams to automatically respond when a resource changes its state.

Here are some examples of how you might use Events:

Send a notification to a DevOps team when a database backup completes.

Convert files of one format to another when files are uploaded to an Object Storage bucket.

You can only deliver events to certain Oracle Cloud Infrastructure services with a rule. Use the following services to create actions:

Notifications

Streaming

Functions

References:

on/Concepts/notificationoverview.htm

Using Remote Exec

With Resource Manager, you can use Terraform's remote exec functionality to execute scripts or commands on a remotecomputer. You can also use this technique for other provisioners that require access to the remote resource.

References:

om/en-us/iaas/Content/ResourceManager/Tasks/usingremoteexec.htm

Token-based authentication for the CLI:

Token-based authentication for the CLI allows customers to authenticate their session interactively, then use theCLI for a single session without an API signing key. This enables customers using an identity provider that is not SCIM-supported to use a federated user account with the CLI and SDKs.

Starting a Token-based CLI Session

To use token-based authenticationfor the CLI on a computer with a web browser:

1. In the CLI, run the following command. This will launch a web browser.

oci session authenticate

2. In the browser, enter your user credentials. This authentication information is saved to the .config file.

Validating a Token

To verify that a token is valid, run the following command:

oci session validate --config-file --profile --auth security_token

You should receive a message showing the expiration date for the session.If you receive an error, check your profile settings.

References: