feat(containers): concepts improvements

Author: thomas-tacquet

serverless/containers/concepts.mdx

@@ -31,43 +31,83 @@ Refer to the [dedicated documentation](/serverless/containers/reference-content/
 
 ## Container
 
-A container is a package of software that includes all dependencies: code, runtime, configuration, and system libraries so that it can run on any host system. Scaleway provides custom Docker images that are entirely handled for you in the cloud. With Containers, you can rely on your favorite technologies such as Django, or Ruby on Rails.
+A container is a package of software that includes all dependencies: code, runtime, configuration, and system libraries so that it can run on any host system. Scaleway provides custom Docker images that are entirely handled for you in the cloud.
 
 ## Container Registry
 
-Container Registry is the place where your images are stored before being deployed.
+Container Registry is the place where your images are stored before being deployed, we recommend using Scaleway Container Registry for a better integration. [Migration guide](/serverless/containers/api-cli/migrate-external-image-to-scaleway-registry/).
 
 ## CRON trigger
 
-A CRON trigger is a mechanism used to automatically invoke a Serverless Function at a specific time on a recurring schedule. It works similarly to a traditional Linux [cron job](https://en.wikipedia.org/wiki/Cron), using the `* * * * *` format, and uses the **UTC** time zone. Refer to our [cron schedules reference](/serverless/containers/reference-content/cron-schedules/) for more information.
+A CRON trigger is a mechanism used to automatically invoke a Serverless Function at a specific time on a recurring schedule.
+
+It works similarly to a traditional Linux [cron job](https://en.wikipedia.org/wiki/Cron), using the `* * * * *` format, and uses the **UTC** time zone. Refer to our [cron schedules reference](/serverless/containers/reference-content/cron-schedules/) for more information.
+
+## Custom domain
+
+By default a generated endpoint is assigned to your Serverless ressource and custom domains allows you to use your own domain read [custom domain documentation](/serverless/containers/how-to/add-a-custom-domain-to-a-container).
+
+## Deployment
+
+Some parameters requires a new deployment of the Container to take affect and it creates a Deployment. Rollout of a deployment will not cause downtime and the traffic switches smoothly to the newest revision.
+
+## Endpoint
+
+An endpoint is the URL generated to access your ressource, it can be customised with Custom Domains.
 
 ## Environment variables
 
-An environment variable is a variable whose value is set outside the program, typically through functionality built into the operating system, or microservice. An environment variable is made up of a name/value pair, and any number may be created and available for reference at a point in time.
+Environment variables are key/value pairs injected in your container. It's useful to share informations such as configuration with your container. Some names are reserved [details about reserved names](/serverless/containers/reference-content/containers-limitations/#configuration-restrictions).
 
 ## Ephemeral storage
 
-In addition to vCPU and RAM, Serverless Containers also provide a storage volume for the duration of the task. This storage space allows to hold the data retrieved by the job, and disappears once the execution is complete. The maximum size of the ephemeral storage is tied to the allocated memory.
+In addition to vCPU and RAM, Serverless Containers also provide a storage volume for the duration of the task. This storage space allows to hold the data retrieved by the job, and disappears once the execution is complete.
+
+The maximum size of the ephemeral storage is tied to the allocated memory.
 
 ## GB-s
 
 Unit used to measure the resource consumption of a container. It reflects the amount of memory consumed over time.
 
-## Image
+## gRPC
+
+gRPC is supported on Serverless Containers, it requires to enable http2 (`h2c`) protocol.
+
+## Healthcheck
+
+To determine the `Status` of a Serverless Containers, default healthecks automatically checks if basic requirements are met to define the status as `ready`.
 
-An image is a blueprint from which an arbitrary number of brand-new containers can be started. You can start a container from an image, perform operations in it, and save another image based on the latest state of the container.
+It's possible to define custom healthecks rules with a specific endpoint via the API: [read API doc](https://www.scaleway.com/en/developers/api/serverless-containers/#path-containers-create-a-new-container).
+
+## Instance
+
+Depending incoming requests, min scale and max scale, a Serverless Container instance processes incoming requests.
 
 ## JWT Token
 
-JWT (JSON Web Token) is an access token you can create from the console or API to enable an application to access your Private Container. Consult the [Developer documentation](https://www.scaleway.com/en/developers/api/serverless-containers/#path-tokens) for more details.
+JWT (JSON Web Token) is an access token you can create from the console or API to enable an application to access your Private Container. [More details about how to secure a Container](/serverless/containers/how-to/secure-a-container/#restrict-access-to-your-containers)
+
+## Load balancing
+
+Incoming request traffic is managed by the Serverless infrastructure. In some cases such as rapid traffic changes or load testing, depending max scale parameter the ressources are automatically allocated to manage the traffic.
+
+## Max scale
+
+It's the maximum number of instances of your Container. Define this parameter according to the traffic spikes of your Container. In some cases you may want to limit the max scale for cost control reasons.
+
+## Min scale
+
+Customizing min scale for Serverless can be useful to keep an instance warm and limit cold starts. It also have an impact on costs of your Serverless Container.
 
 ## mvCPU
 
 A [vCPU](#vcpu) (Virtual Central Processing Unit) is equivalent to 1000 mvCPU.
 
 ## Namespace
 
-A namespace is a project that allows you to [group your containers](/serverless/containers/how-to/create-manage-delete-containers-namespace/). Containers in the same namespace can share environment variables and access tokens, defined at the namespace level.
+A namespace is a project that allows you to [group your containers](/serverless/containers/how-to/create-manage-delete-containers-namespace/).
+
+Containers in the same namespace can share environment variables, secrets and access tokens, defined at the namespace level.
 
 ## NATS trigger
 
@@ -86,6 +126,10 @@ The value defined in the port parameter will then be passed to your container du
 
 A container's privacy policy defines whether a container may be invoked anonymously (**public**) or only via an authentication mechanism provided by the [Scaleway API](https://www.scaleway.com/en/developers/api/serverless-containers/#authentication) (**private**).
 
+## Registry endpoint
+
+Registry endpoint parameter is the ressource link to the container image used in the Serverless Container.
+
 ## Sandbox
 
 A sandbox is an isolation area for your container. Serverless Containers offer two sandboxing environments:
@@ -110,7 +154,11 @@ Serverless allows you to deploy your Functions (FaaS) and Containerized Applicat
 
 ## Serverless Framework
 
-Serverless.com (Serverless Framework) is a tool that allows you to deploy serverless applications without having to manage Serverless Container’s API call. Write and deploy a YAML configuration file, everything else is handled automatically, even the image building.
+Serverless.com (Serverless Framework) is a tool that allows you to deploy serverless applications without having to manage Serverless Container's API call. Write and deploy a YAML configuration file, everything else is handled automatically, even the image building.
+
+## Serverless Job
+
+Serverless Jobs are close to Serverless Containers but it's more adapted to run long workloads, see [comparaison between Serverless products](/serverless/containers/reference-content/difference-jobs-functions-containers.mdx).
 
 ## SQS trigger
 
@@ -123,6 +171,17 @@ The container can then process the message and perform any required actions, suc
 
 A stateless application is a computer program that does not save client data between sessions. Data generated in one session is not saved for use in the next session with that client. All applications deployed on Serverless Containers are stateless.
 
+## Status
+
+A Serverless Container can be:
+* **Ready**: your Serverless Container is operational to serve requests.
+* **Pending**: your ressource is under deployment.
+* **Error**: something failed in the deploymen process, [open troubleshooting documentation](/serverless/containers/troubleshooting/cannot-deploy-image.mdx).
+
+## Terraform
+
+Terraform is an infrastructure as code tool, [read terraform documentation of Serverless Containers](https://registry.terraform.io/providers/scaleway/scaleway/latest/docs/resources/container).
+
 ## Timeout
 
 The timeout is the maximum length of time your container can spend processing a request before being stopped. This value must be in the range 10s to 900s.
@@ -138,4 +197,4 @@ Unit used to measure the resource consumption of a container. It reflects the am
 
 ## Protocol
 
-Serverless Containers supports **http1** (default) and **http2** (`h2c`). Use HTTP/2 if your container application is configured to listen for HTTP/2 requests, such as a gRPC service or a web server that uses HTTP/2 features like multiplexing, otherwise HTTP/1 is recommended.
+Serverless Containers supports **http1** (default) and **http2** (`h2c`). Use HTTP/2 if your container application is configured to listen for HTTP/2 requests, such as a **gRPC** service or a web server that uses HTTP/2 features like multiplexing, otherwise HTTP/1 is recommended.