Monthly Archives: June 2020

Devops Pipeline Checklist

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  1. Ready the Sourcecode
  2. Upload Sourcecode to Azure Repo
  3. Create a build pipeline in azure – Creation of YAML Pipeline
  4. Creating service connection for the project
  5. Building release pipeline for deployment
  6. Compliancy check for build and release pipeline

There are two pipelines. Build and release pipeline. Build pipeline would be mostly one and there would be multiple release pipelines. There would be multiple config files appended to the release pipeline. These are basically Yaml files that are displayed in stages. In artifact there would be no details regarding the environment and DB config details. The Environment and config details are picked from the Stages which has multiple YAML file containing details of various envs and config which would be appended to the artifact at the time of deployment.

Creating a New Build Pipeline for Project

  1. Create a new repository and add readme.txt file which creates a master branch. Add simple spring boot project
  2. Create a new pipeline. While creating pipeline it asks to select repo.On Successful creation of pipeline new azure-pipeline.yml would be created and added as new file along with project file in repo.
  3. Make below changes in azure-pipeline.yml file(applicable for basic spring boot project)
    1. Step to Create Revision number mostly from environment variables
    2. Step to Build Spring boot project
    3. Step to Copy the JAR file and manifest.yml created at end of build
    4. Step to publish artifact and put in location drop

Creating a New Build Pipeline for Project

  1. From the Drop location the files would be picked by release pipeline. This is configured in manifest.yml.The name of the JAR created should be same as one specified in manifest or else it would complain as file not found error
  2. Release pipleine contains 2 things Artifact and Stages
  3. Artifact is the one copied from Build Pipeline. Azure Devops would be configured to pick the latest artifact from Branch
  4. The Trigger attached to Artifact tells from which branch the arifact should be copied and whether new release should be created
  5. Stages contains Jobs and Tasks. For running jobs we need agent. This is again configurable. By Default it would be set to some Ubuntu Linux agent
  6. The Artifact available in previous step now needs to be pushed in PCF, which would be done by creating new task. For this Clound Foundary endpoint and commands would be defined.Incase you are using PCF you can use Cloud Foundary CLI. In the arguments the location of the manifest.yml should be specified. Reading this manifest helps to locate the
    name of the JAR file which should be pushed into cloud environment. For the same reason we copy both JAR and Manifest in Step 3(3) in build pipeline. Now this would be picked from drop location
  7. There would be predeployment condition which checks for the availability of Artifact. This is again similar to trigger which runs checking for the availability of new release(artifact) for deployment

Javascript Function Basics

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  1. Function is represented as Object in Javascript
  2. Has 2 phases – Function Definition and Function Execution
  3. Two ways of defining function
    Function Declaration / Named Function – Function object would get created at scope creation phase
    Function Expression / Anonymous Function – Function object would get created at execution phase – Interepreter would throw error incase the function is called before anonymous definition.

      
  //Named Function
 displayAge(); 
 
 function displayAge(){
  console.log('My Age is 33')
 } 
 
 //Anonymous Function 
 var age = function(){ //Context/scope execution phase
   console.log('My Age is 33')
 } 
 age();
  4. No concept of function overloading. Function with near matching argument would be called.In the below code getSum has 2 arguments but still it gets called. 
    function getSum(num1, num2) {
  console.log('Function overloading is not possible');
}	
getSum();

      Function overloading is not possible
  5. Function namespace context would be created with the samename as the function namespace
  6. In the below code the getLunch appears to be overloaded but there would be only one namespace in context with name getLunch
  7. So you may expect the output to be different but all the times getLunch(buffey, paid) would be called in below code 
    function getLunch() {
  console.log('Free Lunch');
}

function getLunch(paidLunch) {
  console.log('paidLunch');
}

function getLunch(buffey, paid) {
  console.log('paidLunch buffey');
}
getLunch();
getLunch(5);
getLunch(5,10);

    Output

    paidLunch buffey
paidLunch buffey
paidLunch buffey
  8. So what would be the workaround. Check the code as below 
     
  function getLunch() {
  if(arguments.length === 0)
    console.log('Free Lunch');
  
  if(arguments.length === 1)
    console.log('paidLunch');
    
  if(arguments.length === 2)
    console.log('paidLunch buffey');
  }
  
   getLunch();
   getLunch(5);
   getLunch(5,10);

    Output

    Free Lunch
paidLunch
paidLunch buffey
  9. Using Restparameter feature from ECMAScript6 
     
function getLunch(bill, space, ...menu) {
  console.log(bill);
  console.log(space);
  console.log(menu);
}

getLunch(150, 'Open Terrace', 'idly', 'dosa', 'vada');

    Output

    150
Open Terrace
["idly", "dosa", "vada"]
Posted in JS.

Everything about pH

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Everything about pH – Acidic or Alkaline

  1. pH is the measure of acidity or alkalinity of soil.pH varies between 1 to 14. 1 being most acidic and 14 being most alkaline. 6.5 to 7 is considered as neutral
  2. pH varies between 1 to 14. 1 being most acidic and 14 being most alkaline. 6.5 to 7 is considered as neutral
  3. Plants extract iron from the soil by roots. If the soil is alkaline irons bound to the soil.Depending on soil pH mineral bound to soil particle or make it soluble for uptake by plant
  4. Hydrogen ions are found at very low level. 0.0000001 Molar which is (log10 -7) pH7.pH is concentration of hydrogen ions. The more hydrogen ions are loosely available the lower the pH. The soil would be more acidic not alkaline.

Low the soil pH
Soil that is too acid (having a low Ph between 1.0 and 6.0) will show the following symptoms caused by increased availability of aluminum and a
decreased availability of phosphorus

  1. wilting leaves
  2. stunted growth of plant and/or root
  3. yellow spots on the leaves that turn brown and lead to leaf death
  4. blighted leaf tips
  5. poor stem development

High the soil pH
Soil that is too alkaline (having a high Ph between 8.0 and 14.0) will show the following symptoms caused by the plants inability to absorb iron. Phosphorus is
also not readily available and the micronutrients zinc, copper and manganese are also in limited supply.

  1. Interveinal chlorosis- (light green or yellowing of the leaf with green veining)
  2. General leaf discoloration

From the ph scale below, certain plants thrive in slightly acidic or slightly alkaline conditions. If you see your asparagus, cauliflower, lettuce, parsley
and spinach thriving you may have more alkaline conditions if your plants like radishes, sweet potatoes, peppers, and carrots are
struggling since they thrive in more acidic conditions and vice versa.

Chlorosis in Plants

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Chlorosis is a yellowing of leaf tissue due to a lack of chlorophyll. Possible causes of chlorosis include poor drainage, damaged roots,
compacted roots, high alkalinity, and nutrient deficiencies in the plant. Nutrient deficiencies may occur because there is an insufficient amount in the soil or because the nutrients are unavailable due to a high pH (alkaline soil). Or the nutrients may not be absorbed due to injured roots or poor root growth.

Chlorosis can be because of iron deficiency(called just chlorosis) or nitrogen deficiency(interveinal chlorosis)

Iron deficiency or Intervenial Chlorosis
Interveinal chlorosis is a yellowing of the leaves between the veins with the veins remaining green. . A lack of iron in the soil can cause interveinal chlorosis but so will a number of other soil issues. Just because you have a plant with interveinal chlorosis does not mean you have an iron deficiency. Each of the following conditions can produce the same symptoms. Use Iron sulfate around the plant. This will add iron, in case you do have a deficiency. It will also add sulfur which might help lower your soil pH. You can also try just agricultural sulfur which will lower the pH. When the pH goes down, plants have an easier time getting at the existing iron.

  1. a high soil pH or Soil is alkaline
  2. manganese deficiency
  3. compacted soil
  4. plant competition

Nitrogen deficiency or Chlorisis
Nitrogen taken up by plants is used in the formation of amino acids which is the building block for proteins. Nitrogen is a structural component of chlorophyll. Urea, ammonium nitrate, calcium ammonium nitrate are common nitrogen-based fertilizers being used. When a plant is suffering from Nitrogen Chlorosis the older leaves of the plant will turn yellow rather than
younger leaves since younger leaves have nitrogen readily available from roots and more absorbing capacity than older leaves. Using azospirillum helps in fixing nitrogen in the soil.

Cross Origin Resource Sharing (CORS)

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Cross-Origin Resource Sharing (CORS)
The browser’s same-origin policy blocks reading a resource from a different origin. This mechanism stops a malicious site from reading another site’s data. The same-origin policy tells the browser to block cross-origin requests. When you want to get a public resource from a different origin, the resource-providing server needs to tell the browser “This origin where the request is coming from can access my resource”. The browser remembers that and allows cross-origin resource sharing.

In angular when front end request origin is different the browser stops processing response from the server.

Request has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header
is present on the requested resource.

Same-Origin Policy

  1. The same-origin policy fights one of the most common cyber-attacks out there: cross-site request forgery.
  2. If you have logged into FB your info would be stored in Cookie and would be tagged along when the request is made every time
  3. Every time you re-visit the FB tab and click around the app, you don’t have to sign in again. Instead, the API will recognize the stored session cookie upon further HTTP requests.
    The only trouble is that the browser automatically includes any relevant cookies stored for a domain when another request is made to that exact domain.
  4. Say you clicked on a particularly trick popup ad, opening evil-site.com.The evil site also has the ability to send a request to FB.com/api. Since the request is going to the FB.com domain, the browser includes the relevant cookies. Evil-site sends the session cookie, and gains authenticated access to FB. Your account has been successfully hacked with a cross-site request forgery attack.
  5. At this point, browser will step in and prevent the malicious code from making an API request like this. It will stop evil-site and say “Blocked by the same-origin policy.

How Browser works underhood?

  1. The browser checks for the request origins of the web application and the Server origins response match
  2. The origin is the combination of the protocol, host, and port. 
          For example, in https://www.FB.com, 
	   the protocol is https://, 
	   the host is www.FB.com, and 
	   the hidden port number is 5400 (the port number typically used for https).
  3. To conduct the same-origin check, the browser accompanies all requests with a special request header
    that sends the domain information to receiving server
  4. For example, for an app running on localhost:3000, the special request format looks like this: 
    Origin: http://localhost:3000

    Reacting to this special request, the server sends back a response header. This header contains an Access-Control-Allow-Origin key,
    to specify which origins can access the server’s resources. The key will have one of two values:

    One: the server can be really strict, and specify that only one origin can access it:
    Access-Control-Allow-Origin: http://localhost:3000

    Two: the server can let the gates go wide open, and specify the wildcard value to allow all domains to access its resources:
    Access-Control-Allow-Origin: *

  5. Once the browser receives this header information back, it compares the frontend domain with the Access-Control-Allow-Origin
    value from the server. If the frontend domain does not match the value, the browser raises the red flag and blocks the API
    request with the CORS policy error.

The above solution works for development. How about in production.

To address such issues, the proxy is used between client and server.

Request from Client -> Proxy Server -> Server 
Respose from Server -> Proxy Server(appends origin) -> Client

Now what the proxy does is it appends the s Access-Control-Allow-Origin: * in the header before the response is sent to the client browser