Quick Tutorial with Kubernetes Pod Lifecycle

What is Kubernetes ?

Kubernetes, also known as K8s, is an open-source system for automating deployment, scaling, and management of containerized applications.

What is a Pod in kubernetes ?

Pods are the smallest, most basic deployable objects in Kubernetes. A Pod represents a single instance of a running process in your cluster. Pods contain one or more containers, such as Docker containers. When a Pod runs multiple containers, the containers are managed as a single entity and share the Pod’s resources.

Pod Lifecycle

A pods follow a defined lifecycle, starting in the Pending phase, moving through Running if at least one of its primary containers starts OK, and then through either the Succeeded or Failed phases depending on whether any container in the Pod terminated in failure.

HI Readers, today we are going to have a discussion over Kubernetes Pod life cycle and the reason of each stage that a pod goes through in its life cycle.

The main stages through which a pod can go through are listed below.

  • Pending
  • ContainerCreating
  • Image pull
  • ErrImagePull
  • ImagePullBackOff
  • Running
  • CrashLoopBackOff
  • Terminating

Pending : If a Pod is stuck in Pending it means that it can not be scheduled onto a node.
Generally this is because there are insufficient resources of one type or another that prevent scheduling

command to check pod
#kubectl get events --all-namespaces --sort-by='.metadata.creationTimestamp'

ContainerCreating : starts creating container.

Image pull: if image pull succeed then container created
else
ErrImagePull : either image is not exist or login failed to registry

ImagePullBackOff: Here are some of the possible causes behind your pod getting stuck in the ImagePullBackOff state:

Image doesn't exist.
Image tag or name is incorrect.
Image is private, and there is an authentication failure.
Network issue.
Registry name is incorrect.
Container registry rate limits.

Running: The Running status indicates that a container is executing without issues.

CrashLoopBackOff : is a common error that you may have encountered when running
your first containers on Kubernetes. This error indicates that a pod failed to start,
Kubernetes tried to restart it, and it continued to fail repeatedly
your application crashed not started
if its API and trying to establish connection to external DB and connection is not established.

Terminating: Kubernetes marks the Pod state as “Terminating” and stops sending traffic to the Pod.
Kubernetes send a TERM signal to the Pod, indicating that the Pod should shut down.
When the grace period expires, Kubernetes issues a SIGKILL to any processes still running in the Pod.

Please refer this official link for more information.

Original article source at: https://blog.knoldus.com/

#kubernetes #lifecycle 

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Buddha Community

Quick Tutorial with Kubernetes Pod Lifecycle
Christa  Stehr

Christa Stehr

1602964260

50+ Useful Kubernetes Tools for 2020 - Part 2

Introduction

Last year, we provided a list of Kubernetes tools that proved so popular we have decided to curate another list of some useful additions for working with the platform—among which are many tools that we personally use here at Caylent. Check out the original tools list here in case you missed it.

According to a recent survey done by Stackrox, the dominance Kubernetes enjoys in the market continues to be reinforced, with 86% of respondents using it for container orchestration.

(State of Kubernetes and Container Security, 2020)

And as you can see below, more and more companies are jumping into containerization for their apps. If you’re among them, here are some tools to aid you going forward as Kubernetes continues its rapid growth.

(State of Kubernetes and Container Security, 2020)

#blog #tools #amazon elastic kubernetes service #application security #aws kms #botkube #caylent #cli #container monitoring #container orchestration tools #container security #containers #continuous delivery #continuous deployment #continuous integration #contour #developers #development #developments #draft #eksctl #firewall #gcp #github #harbor #helm #helm charts #helm-2to3 #helm-aws-secret-plugin #helm-docs #helm-operator-get-started #helm-secrets #iam #json #k-rail #k3s #k3sup #k8s #keel.sh #keycloak #kiali #kiam #klum #knative #krew #ksniff #kube #kube-prod-runtime #kube-ps1 #kube-scan #kube-state-metrics #kube2iam #kubeapps #kubebuilder #kubeconfig #kubectl #kubectl-aws-secrets #kubefwd #kubernetes #kubernetes command line tool #kubernetes configuration #kubernetes deployment #kubernetes in development #kubernetes in production #kubernetes ingress #kubernetes interfaces #kubernetes monitoring #kubernetes networking #kubernetes observability #kubernetes plugins #kubernetes secrets #kubernetes security #kubernetes security best practices #kubernetes security vendors #kubernetes service discovery #kubernetic #kubesec #kubeterminal #kubeval #kudo #kuma #microsoft azure key vault #mozilla sops #octant #octarine #open source #palo alto kubernetes security #permission-manager #pgp #rafay #rakess #rancher #rook #secrets operations #serverless function #service mesh #shell-operator #snyk #snyk container #sonobuoy #strongdm #tcpdump #tenkai #testing #tigera #tilt #vert.x #wireshark #yaml

Rupert  Beatty

Rupert Beatty

1666454701

Fully Customizable & Extensible Action Sheet Controller

XLActionController

By XMARTLABS.

XLActionController is an extensible library to quickly create any custom action sheet controller.

Examples

demo_spotify.gifdemo_twitter.gifdemo_tweetbot.gif
demo_periscope.gifdemo_youtube.gifdemo_skype.gif

The action sheet controllers shown above were entirely created using XLActionController and are included in the Examples. To run the Example project: clone XLActionController repository, open XLActionController workspace and run the Example project.

The code snippet below shows how to present the Tweetbot action sheet controller:

let actionController = TweetbotActionController()

actionController.addAction(Action("View Details", style: .default, handler: { action in
  // do something useful
}))
actionController.addAction(Action("View Retweets", style: .default, handler: { action in
  // do something useful
}))
actionController.addAction(Action("View in Favstar", style: .default, handler: { action in
  // do something useful
}))
actionController.addAction(Action("Translate", style: .default, executeImmediatelyOnTouch: true, handler: { action in
  // do something useful
}))

actionController.addSection(Section())
actionController.addAction(Action("Cancel", style: .cancel, handler:nil))

present(actionController, animated: true, completion: nil)

As you may have noticed, the library usage looks pretty similar to UIAlertController.

Actions' handlers are executed after the alert controller is dismissed from screen. If you want, you can change this passing true to the action's constructor to the argument executeImmediatelyOnTouch.

Behind the scenes XLActionController uses a UICollectionView to display the action sheet.

Usage

First create a custom action sheet view controller by extending from the ActionController generic class. For details on how to create a custom action sheet controller look at the Extensibility section.

For instance, let's suppose we've already created TwitterActionController.

// Instantiate custom action sheet controller
let actionSheet = TwitterActionController()
// set up a header title
actionSheet.headerData = "Accounts"
// Add some actions, note that the first parameter of `Action` initializer is `ActionData`.
actionSheet.addAction(Action(ActionData(title: "Xmartlabs", subtitle: "@xmartlabs", image: UIImage(named: "tw-xmartlabs")!), style: .default, handler: { action in
   // do something useful
}))
actionSheet.addAction(Action(ActionData(title: "Miguel", subtitle: "@remer88", image: UIImage(named: "tw-remer")!), style: .default, handler: { action in
   // do something useful
}))
// present actionSheet like any other view controller
present(actionSheet, animated: true, completion: nil)

As the code above illustrates, there are no relevant differences compared to the UIAlertController API.

The main difference is that XLActionController works with any header data type and not only the standard UIAlertController title and message properties. Similarly XLActionController's Action works with any data Type and not only the title string.

// XLActionController:
xlActionController.headerData = SpotifyHeaderData(title: "The Fast And The Furious Soundtrack Collection", subtitle: "Various Artists", image: UIImage(named: "sp-header-icon")!)

// vs UIAlertController:
uiActionController.title = "The Fast And The Furious Soundtrack Collection" // no way to pass an image
uiActionController.message = "Various Artists"
// XLActionController:
let xlAction = Action(ActionData(title: "Save Full Album", image: UIImage(named: "sp-add-icon")!), style: .default, handler: { action in })
// notice that we are able to pass an image in addition to the title
xlActionController.addAction(xlAction)

// vs UIAlertController:
let uiAction = UIAlertAction(title: "Xmartlabs", style: .default, handler: { action in }))
uiActionController.addAction(uiAction)

This can be accomplished because XLActionController is a generic type.

Another important difference is that XLActionController provides a way to add action sections as illustrated in the code below:

  actionController.addSection(Section())

and also each section has a data property. This property is generic, so that it can hold any type. This data will be used to create this section's header view.

let section = actionController.addSection(Section())
section.data = "String" // assuming section data Type is String

Each section contains a set of actions. We typically use sections to show a header view above a set of actions.

Extensibility

ActionController uses a UICollectionView to show actions and headers on screen. Actions will be rendered as instances of UICollectionViewCell. You can use your own subclass of UICollectionViewCell by specifying it in the action controller declaration. Additionally, ActionController allows you to specify a global header and a section header. Headers are shown as collection view's supplementary views.

The ActionController class is a generic type that works with any cell, header, section header type and its associated data types.

Create your custom action sheet controller

XLActionController provides extension points to specify a whole new look and feel to our custom sheet controller and to tweak present and dismiss animations. Let's see an example:

// As first step we should extend the ActionController generic type
public class PeriscopeActionController: ActionController<PeriscopeCell, String, PeriscopeHeader, String, UICollectionReusableView, Void> {

    // override init in order to customize behavior and animations
    public override init(nibName nibNameOrNil: String? = nil, bundle nibBundleOrNil: Bundle? = nil) {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
        // customizing behavior and present/dismiss animations
        settings.behavior.hideOnScrollDown = false
        settings.animation.scale = nil
        settings.animation.present.duration = 0.6
        settings.animation.dismiss.duration = 0.5
        settings.animation.dismiss.options = .curveEaseIn
        settings.animation.dismiss.offset = 30

        // providing a specific collection view cell which will be used to display each action, height parameter expects a block that returns the cell height for a particular action.
        cellSpec = .nibFile(nibName: "PeriscopeCell", bundle: Bundle(for: PeriscopeCell.self), height: { _ in 60})
        // providing a specific view that will render each section header.
        sectionHeaderSpec = .cellClass(height: { _ in 5 })
        // providing a specific view that will render the action sheet header. We calculate its height according the text that should be displayed.
        headerSpec = .cellClass(height: { [weak self] (headerData: String) in
            guard let me = self else { return 0 }
            let label = UILabel(frame: CGRect(x: 0, y: 0, width: me.view.frame.width - 40, height: CGFloat.greatestFiniteMagnitude))
            label.numberOfLines = 0
            label.font = .systemFontOfSize(17.0)
            label.text = headerData
            label.sizeToFit()
            return label.frame.size.height + 20
        })

        // once we specify the views, we have to provide three blocks that will be used to set up these views.
        // block used to setup the header. Header view and the header are passed as block parameters
        onConfigureHeader = { [weak self] header, headerData in
            guard let me = self else { return }
            header.label.frame = CGRect(x: 0, y: 0, width: me.view.frame.size.width - 40, height: CGFloat.greatestFiniteMagnitude)
            header.label.text = headerData
            header.label.sizeToFit()
            header.label.center = CGPoint(x: header.frame.size.width  / 2, y: header.frame.size.height / 2)
        }
        // block used to setup the section header
        onConfigureSectionHeader = { sectionHeader, sectionHeaderData in
            sectionHeader.backgroundColor = UIColor(white: 0.95, alpha: 1.0)
        }
        // block used to setup the collection view cell
        onConfigureCellForAction = { [weak self] cell, action, indexPath in
            cell.setup(action.data, detail: nil, image: nil)
            cell.separatorView?.isHidden = indexPath.item == self!.collectionView.numberOfItems(inSection: indexPath.section) - 1
            cell.alpha = action.enabled ? 1.0 : 0.5
            cell.actionTitleLabel?.textColor = action.style == .destructive ? UIColor(red: 210/255.0, green: 77/255.0, blue: 56/255.0, alpha: 1.0) : UIColor(red: 0.28, green: 0.64, blue: 0.76, alpha: 1.0)
        }
    }
}

ActionController type declaration:

public class ActionController<ActionViewType: UICollectionViewCell, ActionDataType, HeaderViewType: UICollectionReusableView, HeaderDataType, SectionHeaderViewType: UICollectionReusableView, SectionHeaderDataType>

When extending ActionController we must specify the following view types ActionViewType, HeaderViewType, SectionHeaderViewType. These types are the cell type used to render an action, the view used to render the action sheet header and the view used to render the section header.

Each view type has its associated data: ActionDataType, HeaderDataType, SectionHeaderDataType respectively.

If your custom action sheet doesn't have a header view we can use UICollectionReusableView as HeaderViewType and Void as HeaderDataType. If it doesn't have a section header view you can use UICollectionReusableView as SectionHeaderViewType and Void as SectionHeaderDataType.

The code below shows how we specify these types for the action controllers provided in the example project:

class PeriscopeActionController: ActionController<PeriscopeCell, String, PeriscopeHeader, String, UICollectionReusableView, Void> { ... } // doesn't need to show a section header
class SpotifyActionController: ActionController<SpotifyCell, ActionData, SpotifyHeaderView, SpotifyHeaderData, UICollectionReusableView, Void> { ... } // doesn't need to show a section header
class TwitterActionController: ActionController<TwitterCell, ActionData, TwitterActionControllerHeader, String, UICollectionReusableView, Void> { ... } // doesn't need to show a section header
class YoutubeActionController: ActionController<YoutubeCell, ActionData, UICollectionReusableView, Void, UICollectionReusableView, Void>

Tweaking default style and animation parameters

By following the previous section steps you should already be able to play with your custom action controller. It happens quite often that we need some other customization such as zooming out the presenting view, changing the status bar color or customizing the default present and dismiss animation.

ActionController class defines the settings property of type ActionSheetControllerSettings to tweak all these.

UICollectionView's behavior

// Indicates if the action controller must be dismissed when the user taps the background view. `true` by default.
settings.behavior.hideOnTap: Bool
// Indicates if the action controller must be dismissed when the user scrolls down the collection view. `true` by default.
settings.behavior.hideOnScrollDown: Bool
// Indicates if the collectionView's scroll is enabled. `false` by default.
settings.behavior.scrollEnabled: Bool
// Controls whether the collection view scroll bounces past the edge of content and back again. `false` by default.
settings.behavior.bounces: Bool
// Indicates if the collection view layout will use UIDynamics to animate its items. `false` by default.
settings.behavior.useDynamics: Bool
// Determines whether the navigation bar is hidden when action controller is being presented. `true` by default
settings.hideCollectionViewBehindCancelView: Bool

UICollectionView Style

// Margins between the collection view and the container view's margins. `0` by default
settings.collectionView.lateralMargin: CGFloat
// Cells height when UIDynamics is used to animate items. `50` by default.
settings.collectionView.cellHeightWhenDynamicsIsUsed: CGFloat

Animation settings

Struct that contains all properties related to presentation & dismissal animations

// Used to scale the presenting view controller when the action controller is being presented. If `nil` is set, then the presenting view controller won't be scaled. `(0.9, 0.9)` by default.
settings.animation.scale: CGSize? = CGSize(width: 0.9, height: 0.9)

Present animation settings

// damping value for the animation block. `1.0` by default.
settings.animation.present.damping: CGFloat
// delay for the animation block. `0.0` by default.
settings.animation.present.delay: TimeInterval
// Indicates the animation duration. `0.7` by default.
settings.animation.present.duration: TimeInterval
// Used as `springVelocity` for the animation block. `0.0` by default.
settings.animation.present.springVelocity: CGFloat
// Present animation options. `UIViewAnimationOptions.curveEaseOut` by default.
settings.animation.present.options: UIViewAnimationOptions

Dismiss animation settings

// damping value for the animation block. `1.0` by default.
settings.animation.dismiss.damping: CGFloat
// Used as delay for the animation block. `0.0` by default.
settings.animation.dismiss.delay: TimeInterval
// animation duration. `0.7` by default.
settings.animation.dismiss.duration: TimeInterval
// springVelocity for the animation block. `0.0` by default
settings.animation.dismiss.springVelocity: CGFloat
// dismiss animation options. `UIViewAnimationOptions.curveEaseIn` by default
settings.animation.dismiss.options: UIViewAnimationOptions

StatusBar Style

// Indicates if the status bar should be visible or hidden when the action controller is visible. Its default value is `true`
settings.statusBar.showStatusBar: Bool
// Determines the style of the device’s status bar when the action controller is visible. `UIStatusBarStyle.LightContent` by default.
settings.statusBar.style: UIStatusBarStyle
// Determines whether the action controller takes over control of status bar appearance from the presenting view controller. `true` by default.
settings.statusBar.modalPresentationCapturesStatusBarAppearance: Bool

Cancel view style

Sometimes we need to show a cancel view below the collection view. This is the case of the SpotifyActionController. These properties have nothing to do with the actions added to an action Controller nor with the actions with .Cancel as style value.

 // Indicates if the cancel view is shown. `false` by default.
settings.cancelView.showCancel: Bool
 // Cancel view's title. "Cancel" by default.
settings.cancelView.title: String?
 // Cancel view's height. `60` by default.
settings.cancelView.height: CGFloat
 // Cancel view's background color. `UIColor.black.withAlphaComponent(0.8)` by default.
settings.cancelView.backgroundColor: UIColor
// Indicates if the collection view is partially hidden by the cancelView when it is pulled down.
settings.cancelView.hideCollectionViewBehindCancelView: Bool

Advanced animations

If tweaking previous settings is not enough to make the animations work like you want, XLActionController allows you to change the present/dismiss animation by overriding some functions.

Presentation

open func presentView(_ presentedView: UIView, presentingView: UIView, animationDuration: Double, completion: ((_ completed: Bool) -> Void)?)

The function above is responsible for making the present animation. It encapsulates how the presentation is performed and invokes onWillPresentView, performCustomPresentationAnimation and onDidPresentView to allow you to change a specific point of the animation.

Typically we don't need to override presentView function because overriding either onWillPresentView, performCustomPresentationAnimation or onDidPresentView is enough.

open func onWillPresentView()

onWillPresentView is called before the animation block starts. Any change here won't be animated. It's intended to set the initial animated properties values.

open func performCustomPresentationAnimation(_ presentedView: UIView, presentingView: UIView)

performCustomPresentationAnimation is called from within the main animation block.

open func onDidPresentView()

After the present animation is completed, presentView calls onDidPresentView from within completion callback.

onWillPresentView, performCustomPresentationAnimation, onDidPresentView won't be invoked if you override presentView implementation.

Dismissal

Dismissal animation can be customized in the same way as presentation animation.

open func dismissView(_ presentedView: UIView, presentingView: UIView, animationDuration: Double, completion: ((_ completed: Bool) -> Void)?)

The function above is responsible for making the dismissal animation. It encapsulates how the dismissal animation is performed and invokes onWillDismissView, performCustomDismissingAnimation and onDidDismissView to allow you to change an specific point of the animation.

Typically we don't need to override dismissView method because overriding either onWillDismissView, performCustomDismissingAnimationoronDidDismissView` is enough.

open func onWillDismissView()

Overrides onWillDismissView to perform any set up before the animation begins.

open func performCustomDismissingAnimation(_ presentedView: UIView, presentingView: UIView)

performCustomDismissingAnimation function is invoked from within the main animation block.

open func onDidDismissView()

After the dismissal animation completes, dismissView calls onDidDismissView from within completion callback.

onWillDismissView, performCustomDismissingAnimation, onDidDismissView won't be invoked if you override dismissView implementation.

To show how simple and powerful XLActionController is and give several examples of how to extend ActionController we have mimicked the Skype, Tweetbot, Twitter, Youtube, Periscope and Spotify action controllers.

Requirements

  • iOS 9.3+
  • Xcode 10.2+
  • Swift 5.0+

Getting involved

  • If you want to contribute please feel free to submit pull requests.
  • If you have a feature request please open an issue.
  • If you found a bug or need help please check older issues before submitting an issue.

If you use XLActionController in your app we would love to hear about it! Drop us a line on twitter.

Installation

CocoaPods

CocoaPods is a dependency manager for Cocoa projects.

Specify XLActionController into your project's Podfile:

source 'https://github.com/CocoaPods/Specs.git'
use_frameworks!

target '<Your App Target>' do
  # This will install just the library's core, won't include any examples
  pod 'XLActionController'

  # Uncomment depending on the examples that you want to install
  #pod 'XLActionController/Periscope'
  #pod 'XLActionController/Skype'
  #pod 'XLActionController/Spotify'
  #pod 'XLActionController/Tweetbot'
  #pod 'XLActionController/Twitter'
  #pod 'XLActionController/Youtube'
end

Then run the following command:

$ pod install

Carthage

Carthage is a simple, decentralized dependency manager for Cocoa.

Specify XLActionController into your project's Carthage:

github "xmartlabs/XLActionController" ~> 5.1.0

Manually as Embedded Framework

Clone XLActionController as a git submodule by running the following command from your project root git folder.

$ git submodule add https://github.com/xmartlabs/XLActionController.git

Open XLActionController folder that was created by the previous git submodule command and drag the XLActionController.xcodeproj into the Project Navigator of your application's Xcode project.

Select the XLActionController.xcodeproj in the Project Navigator and verify the deployment target matches with your application deployment target.

Select your project in the Xcode Navigation and then select your application target from the sidebar. Next select the "General" tab and click on the + button under the "Embedded Binaries" section.

Select XLActionController.framework and we are done!

Download Details:

Author: xmartlabs
Source Code: https://github.com/xmartlabs/XLActionController 
License: MIT license

#swift #ios 

Maud  Rosenbaum

Maud Rosenbaum

1601051854

Kubernetes in the Cloud: Strategies for Effective Multi Cloud Implementations

Kubernetes is a highly popular container orchestration platform. Multi cloud is a strategy that leverages cloud resources from multiple vendors. Multi cloud strategies have become popular because they help prevent vendor lock-in and enable you to leverage a wide variety of cloud resources. However, multi cloud ecosystems are notoriously difficult to configure and maintain.

This article explains how you can leverage Kubernetes to reduce multi cloud complexities and improve stability, scalability, and velocity.

Kubernetes: Your Multi Cloud Strategy

Maintaining standardized application deployments becomes more challenging as your number of applications and the technologies they are based on increase. As environments, operating systems, and dependencies differ, management and operations require more effort and extensive documentation.

In the past, teams tried to get around these difficulties by creating isolated projects in the data center. Each project, including its configurations and requirements were managed independently. This required accurately predicting performance and the number of users before deployment and taking down applications to update operating systems or applications. There were many chances for error.

Kubernetes can provide an alternative to the old method, enabling teams to deploy applications independent of the environment in containers. This eliminates the need to create resource partitions and enables teams to operate infrastructure as a unified whole.

In particular, Kubernetes makes it easier to deploy a multi cloud strategy since it enables you to abstract away service differences. With Kubernetes deployments you can work from a consistent platform and optimize services and applications according to your business needs.

The Compelling Attributes of Multi Cloud Kubernetes

Multi cloud Kubernetes can provide multiple benefits beyond a single cloud deployment. Below are some of the most notable advantages.

Stability

In addition to the built-in scalability, fault tolerance, and auto-healing features of Kubernetes, multi cloud deployments can provide service redundancy. For example, you can mirror applications or split microservices across vendors. This reduces the risk of a vendor-related outage and enables you to create failovers.

#kubernetes #multicloud-strategy #kubernetes-cluster #kubernetes-top-story #kubernetes-cluster-install #kubernetes-explained #kubernetes-infrastructure #cloud

Quick Tutorial with Kubernetes Pod Lifecycle

What is Kubernetes ?

Kubernetes, also known as K8s, is an open-source system for automating deployment, scaling, and management of containerized applications.

What is a Pod in kubernetes ?

Pods are the smallest, most basic deployable objects in Kubernetes. A Pod represents a single instance of a running process in your cluster. Pods contain one or more containers, such as Docker containers. When a Pod runs multiple containers, the containers are managed as a single entity and share the Pod’s resources.

Pod Lifecycle

A pods follow a defined lifecycle, starting in the Pending phase, moving through Running if at least one of its primary containers starts OK, and then through either the Succeeded or Failed phases depending on whether any container in the Pod terminated in failure.

HI Readers, today we are going to have a discussion over Kubernetes Pod life cycle and the reason of each stage that a pod goes through in its life cycle.

The main stages through which a pod can go through are listed below.

  • Pending
  • ContainerCreating
  • Image pull
  • ErrImagePull
  • ImagePullBackOff
  • Running
  • CrashLoopBackOff
  • Terminating

Pending : If a Pod is stuck in Pending it means that it can not be scheduled onto a node.
Generally this is because there are insufficient resources of one type or another that prevent scheduling

command to check pod
#kubectl get events --all-namespaces --sort-by='.metadata.creationTimestamp'

ContainerCreating : starts creating container.

Image pull: if image pull succeed then container created
else
ErrImagePull : either image is not exist or login failed to registry

ImagePullBackOff: Here are some of the possible causes behind your pod getting stuck in the ImagePullBackOff state:

Image doesn't exist.
Image tag or name is incorrect.
Image is private, and there is an authentication failure.
Network issue.
Registry name is incorrect.
Container registry rate limits.

Running: The Running status indicates that a container is executing without issues.

CrashLoopBackOff : is a common error that you may have encountered when running
your first containers on Kubernetes. This error indicates that a pod failed to start,
Kubernetes tried to restart it, and it continued to fail repeatedly
your application crashed not started
if its API and trying to establish connection to external DB and connection is not established.

Terminating: Kubernetes marks the Pod state as “Terminating” and stops sending traffic to the Pod.
Kubernetes send a TERM signal to the Pod, indicating that the Pod should shut down.
When the grace period expires, Kubernetes issues a SIGKILL to any processes still running in the Pod.

Please refer this official link for more information.

Original article source at: https://blog.knoldus.com/

#kubernetes #lifecycle 

Kubernetes Pods For Beginners | Multi Container Pods | Kubernetes Tutorial

If you are an Admin, Architect, or Tester, then attend the FREE Class for Docker & Kubernetes Administrator (CKA) at https://bit.ly/30ABX0A

If you are a Developer, Architect, or Tester, then attend the FREE Class: for Docker & Kubernetes Application Developer (CKAD) at https://bit.ly/2F40sMb

A pod is the smallest deployable artifact that is created and managed by Kubernetes. Pods are compromised of one or more containers working together symbiotically. The pod is a shared execution environment, which means the pod has a set of resources that are shared by every container which is a part of the Pod.

The primary purpose of a multi-container Pod is to support co-located, co-managed helper processes for the main program. There are some general patterns of using helper processes in Pods.

➤ Design-patterns of Multi Container Pods

➤ Sidecar Design Pattern
Sidecar Design Pattern Imagine a container having a use-case, where there is a web server with a log processor, the sidecar design pattern aims to resolve this kind of exact problem. The sidecar pattern consists of the main application, i.e. the web application, and a helper container with a responsibility that is vital for your application but is not necessarily a part of the application and might not be needed for the main container to work.

➤ Adapter Design Pattern
The adapter pattern is used to standardize the output by the primary container. Standardizing refers to format the output in a specific manner that fits the standards across your applications. For instance, an adapter container could expose a standardized monitoring interface to the application even though the application does not implement it in a standard way.

➤ Ambassador Design Pattern
The ambassador design pattern is used to connect containers with the outside world. In this design pattern, the helper container can send network requests on behalf of the main application. It is nothing but a proxy that allows other containers to connect to a port on the localhost.

To know more, check this video by K21Academy
Where we explain:
(00:00) Introduction Kubernetes Pods for Beginners
(00:40) Kubernetes pods Agenda
(01:40) Kubernetes pod
(04:06) Multi-Container Pods
(08:56) Multi Container Pattern
(13:05) Learning Path for Docker & Certified Kubernetes Administrator (CKA)
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