How to fix Kubernetes CrashLoopBackOff

 How to debug/troubleshoot and fix Kubernetes CrashLoopBackOff?

Step 1:

run kubectl describe pod <REPLACE YOUR POD NAME HERE> will give us more information on that pod:

kubectl describe pod nginx-5796d5bc7c-xsl6p --namespace nginx-crashloop

Name:           nginx-5796d5bc7c-xsl6p

Namespace:      nginx-crashloop

Node:           ip-10-0-9-132.us-east-2.compute.internal/10.0.9.132

Start Time:     Tue, 11 Aug 2021 19:11:05 +0200

Labels:         app=nginx-crashloop

                name=nginx

                pod-template-hash=1352816737

                role=app

Annotations:    kubernetes.io/created-by={"kind":"SerializedReference","apiVersion":"v1","reference":{"kind":"ReplicaSet","namespace":"nginx-crashloop","name":"nginx-5796d5bc7c","uid":"fb9e9518-f542-11e7-a8f2-065cff0...

Status:         Running

IP:             10.47.0.15

Controlled By:  ReplicaSet/nginx-5796d5bc7c

Containers:

  nginx:

    Container ID:   docker://513cab3de8be8754d054a4eff45e291d33b63e11b2143d0ff782dccc286ba05e

    Image:          nginx

    Image ID:       docker-pullable://nginx@sha256:c4ee0ecb376636258447e1d8effb56c09c75fe7acf756bf7c13efadf38aa0aca

    Port:           <none>

    State:          Waiting

      Reason:       CrashLoopBackOff

    Last State:     Terminated

      Reason:       Error

      Exit Code:    1

      Started:      Tue, 11 Aug 2021 19:13:15 +0200

That will help to understand the issue.

Most of the cases you will find are related to configuration issues in deployment.yaml file.

For I found the reference key for the database password was wrong in myapp.yaml file.

I fixed and redeployed I got fixed this issue. here is hilighted key that was wrong earlier.

apiVersion: apps/v1

kind: Deployment

metadata: 

  name: mongo-express

  labels:

    app: mongo-express

spec:

  replicas: 2

  selector:

    matchLabels:

      app: mongo-express    

  template:

    metadata:

      labels:

        app: mongo-express

    spec:

      containers:

      - image: mongo-express

        imagePullPolicy: IfNotPresent

        name: mongo-express

        ports:

        - containerPort: 8081

        env:

        - name: ME_CONFIG_MONGODB_ADMINUSERNAME

          valueFrom:

            secretKeyRef:

              name: mongodb-secrete

              key: mongo-root-username

        - name: ME_CONFIG_MONGODB_ADMINPASSWORD 

          valueFrom:

            secretKeyRef:

              name: mongodb-secrete

              key: mongo-root-password

        - name: ME_CONFIG_MONGODB_SERVER 

          valueFrom:

            configMapKeyRef:

              name: mongodb-map

              key: database_url

---

apiVersion: v1

kind: Service

metadata:  

  name: mongo-express-service

spec:

  selector:

    app: mongo-express

  type: LoadBalancer

  ports:

    - protocol: TCP

      port: 8081

      targetPort: 8081

      nodePort: 30002

Angular 10: Can't bind to 'ngIf' since it isn't a known property of 'div'

 Error: Angular 10: Can't bind to 'ngIf' since it isn't a known property of 'div'

or

can't bind to 'ngif' since it isn't a known property of 'ng-container' angular 11

Solutions:

Make sure to import CommonModule from the module that is providing your component. for me I had to import CommonMudel in the TestComponent

import { CommonModule } from '@angular/common';

import { BrowserModule } from '@angular/platform-browser';

@NgModule({

imports: [CommonModule],

declarations: [TestComponent]

})

class MyComponentModule {}

BrowserModule vs CommonModule

BrowserModule provides services that are essential to launch and run a browser app.

BrowserModule also re-exports CommonModule from @angular/common, which means that components in the AppModule module also have access to the Angular directives every app needs, such as NgIf and NgFor.

CommonModule (all the basics of Angular templating: bindings, *ngIf, *ngFor…), except in the first app module, because it’s already part of the BrowserModule

Flutter: How to fix “unexpected element found in ” error?

 All of a sudden, I am started getting this build error in my Android project:

Error: unexpected element <queries> found in <manifest>

Understanding  the Issue:

To understanding why this happens see the above @CommonsWare's answer

This is because <queries> tag was introduced with new package visibility options for Android 11 and upwards (SDK 30+). Because of that, you need to update your build.gradle with a version that includes this changes. Below is a list of supported gradle options.

The best solution to deal with these errors is to Upgrade your Android Gradle plugin and Update Gradle

You’ll have to update your Gradle version to one of the compatible versions that have the latest query tags (which were introduced with Android 11).

How to Fix it?

To Update the Android Gradle plugin

Specify the plugin version in the YourAppDirectory/android/build.gradle file. The plugin version applies to all modules built-in that Android Studio project. The following example sets the plugin to version 4.0.1:

buildscript {

    ext.kotlin_version = '1.3.50'

    repositories {

        google()

        jcenter()

    }

    dependencies {

        classpath 'com.android.tools.build:gradle:4.0.1'

        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"

        classpath 'com.google.gms:google-services:4.3.3'

        classpath 'com.google.firebase:firebase-crashlytics-gradle:2.2.0'

    }

}

Gradle downloads it the next time you build your project 

To Update Gradle

Specify the Gradle version by editing the Gradle distribution reference in the YourAppDirectory/android/gradle/wrapper/gradle-wrapper.properties file.

Don't forget to update your ditributionUrl in your gradle-wrapper.properties as well. For example, for gradle 4.0.1, you should have:

#Fri Jun 23 08:50:38 CEST 2017

distributionBase=GRADLE_USER_HOME

distributionPath=wrapper/dists

zipStoreBase=GRADLE_USER_HOME

zipStorePath=wrapper/dists

distributionUrl=https\://services.gradle.org/distributions/gradle-6.1.1-all.zip

Flutter: mobX store code generate not working

 

 mobX store code generate not working

I had a same issue and I was able to solve with following steps.

I had this problem today and put these versions and it worked, in case anyone needs

You need to follow just couple of steps. Here is my pubspec.yaml package version for the mobx

Step 1:

• Flutter (Channel stable, 1.22.6)
• mobx: ^1.2.1+2
• build_runner: 1.10.1
• mobx_codegen: ^1.1.0+1

Step 2: run following commands

• flutter clean
• flutter pub get
• flutter packages upgrade
• flutter pub run build_runner watch --delete-conflicting-outputs

I trust it will help you :)

 How to downgrade flutter?

You can downgrade using following setups:

Git Hub Source Code: 

Flutter is versioned using git. Changing the Flutter version is as simple as changing git branch.

Using Flutter Channel:

flutter channel <branch> (example: flutter channel stable)

This command is used to change between branches – usually stable/dev/beta/master. We can also put a specific commit id from git.

Flutter Downgrade Command:

flutter downgrade <version> (example: flutter downgrade v1.22.6)

This command will use a specific version number. You can have the list of the available version numbers using flutter downgrade or here

Then run  flutter doctor and Flutter will take care of downloading/compiling everything required to run this version.

Angular: Cannot Get /

 

I was facing this issue, while visiting http://localhost:4200 **'.

Then, when I opened up a web browser, I navigated to localhost:4200 and a web page with the following text were shown:

Error:  Cannot Get /

Solutions: This is related to most of time is incorrect syntax 

Step 1: open terminal and run "ng build"

Step 2: See the command output and you must find some syntax issue related to your code. Go ahead and fix your issue that problem will be gone

 

Flutter Commands List

 

Command to check flutter version:

D:\>flutter --version

Output:

Flutter 1.20.4 • channel unknown • unknown source

Framework • revision fba99f6cf9 (3 months ago) • 2020-09-14 15:32:52 -0700

Engine • revision d1bc06f032

Tools • Dart 2.9.2

 To generate an app bundle, run:

        flutter build appbundle --target-platform android-arm,android-arm64,android-x64

        Learn more on: 

    To split the APKs per ABI, run:

        flutter build apk --target-platform android-arm,android-arm64,android-x64 --split-per-abi

        Learn more on:  

Resolve Conflicts: 

flutter packages pub run build_runner watch --delete-conflicting-outputs

Here is some useful command List:  run flutter help <command>  to get command related information

Command Name	Example	Comments
analyze	flutter analyze -d <DEVICE_ID>	Analyzes the project’s Dart source code.
		Use instead of dartanalyzer.
assemble	flutter assemble -o <DIRECTORY>	Assemble and build flutter resources.
attach	flutter attach -d <DEVICE_ID>	Attach to a running application.
bash-completion	flutter bash-completion	Output command line shell completion setup scripts.
build	flutter build <DIRECTORY>	Flutter build commands.
channel	flutter channel <CHANNEL_NAME>	List or switch flutter channels.
config	flutter config --build-dir=<DIRECTORY>	Configure Flutter settings. To remove a setting, configure it to an empty string.
create	flutter create <DIRECTORY>	Creates a new project.
devices	flutter devices -d <DEVICE_ID>	List all connected devices.
doctor	flutter doctor	Show information about the installed tooling.
downgrade	flutter downgrade	Downgrade Flutter to the last active version for the current channel.
drive	flutter drive	Runs Flutter Driver tests for the current project.
emulators	flutter emulators	List, launch and create emulators.
format	flutter format <DART_FILE>	Format one or more dart files.
gen-l10n	flutter gen-l10n <DIRECTORY>	Generate localizations for the Flutter project.
install	flutter install -d <DEVICE_ID>	Install a Flutter app on an attached device.
logs	flutter logs	Show log output for running Flutter apps.
format	flutter format <DIRECTORY|DART_FILE>	Formats Flutter source code.
		Use instead of dartfmt.
precache	flutter precache <ARGUMENTS>	Populates the Flutter tool’s cache of binary artifacts.
pub	flutter pub <PUB_COMMAND>	Works with packages.
		Use instead of pub.
run	flutter run <DART_FILE>	Runs a Flutter program.
symbolize	flutter symbolize --input=<STACK_TRACK_FILE>	Symbolize a stack trace from the AOT compiled flutter application.
test	flutter test [<DIRECTORY|DART_FILE>]	Runs tests in this package.
		Use instead of pub run test.
upgrade	flutter upgrade	Upgrade your copy of Flutter.