Snackbar for Error Handling in Twitter Followers Insight loklak App

In this blog post am going to explain how the Twitter Followers Insight app handles error which occurs when when no query is passed to the “Search” function i.e., when the search is proceeded with an empty query.

How to handle the Exception

In such cases, I have used SNACKBAR / TOAST. Snackbar / Toast is used to popup an error notification on the screen when an exception occurs.

Script for Snackbar / Toast:

In the below script, initially the error is set to null i.e., no error. The “showError” function is which is being called when there occurs a situation of no query or an empty query. The function below helps to show an error popup which only shows till a time limit.

    $scope.error = null;

    $scope.showError = function() {
        $(".snackbar").addClass("show");
        setTimeout(function(){ $(".snackbar").removeClass("show") }, 3000);
    }

 

In this script, it checks whether the query passed is undefined or empty. If yes, then the error message which was null earlier is changed and that error is showed up on the screen to the end user. Snackbars animate upwards from the edge of the screen.

        if ($scope.query === '' || $scope.query === undefined) {
            $scope.spinner = false;
            $scope.error = "Please enter a valid Username";
            $scope.showError();
            return;
        }

 

Resources:

Twitter Followers Insight App for loklak Apps Site

Twitter Followers Insight, is an app for checking the followers and following lists of an account and as we click on a name, the chain continues. The app also helps to visualize the data, which is returned from the loklak user information API, where it shows the distribution of followers and following across the world in the form of pie chart.

Related issue: https://github.com/fossasia/apps.loklak.org/pull/291

Developing the App

In the initial stage of the app, the main challenge faced was to implement the clickable feature i.e., make the name of the users in the list which gets displayed should be clickable which navigates to the next list to display as the query changes. Well this was tricky but easy to solve as I had to take the Angular JS with input parameter.

Script for storing and displaying the data:

The script below shows how to details are being fetched from the JSON object which is returned by the loklak Userdata API. The data or details is then being stored into an list/array which is a scope variable. The array is then iterated in a particular fashion how I want to get it displayed.

Storing the data:

for (var i = 0; i < followers.length; i++) {
    user = followers[i].screen_name;
    name = followers[i].name;
    followers_count = followers[i].followers_count;
    pic = followers[i].profile_image_url;
    followers_loc.push(followers[i].location_country);
    followerslist.push([user, pic, name, followers_count]);
}

 

The below script shows how the array i.e., showed in the above code, being used and iterated over. Here in this script I used a “ng-repeat” angular function where the list/array is iterated till the limit. The script also display in which order the data is getting displayed on the screen. The clickable feature is set in the “ng-click” angular function, where we are calling the Search function with query as the input parameter.

Displaying the data with clickable feature:

<ul class="gallery-container" >
    <li class="gallery-item" style="list-style-type: none;" ng-repeat="value in followersStatus | limitTo: limitFollowers">
        <a href ng-click="Search(value[0])">
            
class="item-image"> src="{{ value[1] }}" style="height: 94px;width: 94px" />
class="item-desc">
class="item-name"> {{ value[2] }}
class="item-handle"> @{{ value[0] }}
class="item-followers"> class="item-label">Followers: class="item-content">{{ value[3] }}
</div> </a> </li> </ul>

 

Visualizing Followers and Following data using Pie Chart

In this app, the data of user’s followers and following is visualized on the basis of the location they live in. This data is visualized in the form of pie chart using Highcharts.

Script for displaying pie chart:

             $('.pie-chart').highcharts({
                chart: {
                    plotBackgroundColor: null,
                    plotBorderWidth: null,
                    plotShadow: false,
                    type: 'pie'
                },
                title: {
                    text: "Followers"
                },
                tooltip: {
                    pointFormat: '{series.name}: <b>{point.percentage:.1f}%</b>'
                },
                plotOptions: {
                    pie: {
                        allowPointSelect: true,
                        cursor: 'pointer',
                        dataLabels: {
                            enabled: true,
                            format : '',
                            style: {
                                color: (Highcharts.theme && Highcharts.theme.contrastTextColor) || 'black'
                            }
                        }
                    }
                },
                series: [{
                    name: "Followers",
                    colorByPoint: true,
                    data: $scope.locations
                }]
            });

 

Resources

  • Learn more about AngularJS here.
  • Learn more about Highcharts here.
  • Learn more about Loklak API here.

Deploy to Azure Button for loklak

In this blog post, am going to tell you about yet a new deployment method for loklak which is easy and quick with just one click. Deploying to Azure Websites from a Git repository just got a little easier with the Deploy to Azure Button. Simply place the button in README.md with a link to the loklak, and users who click on it will be directed to a streamlined deployment process. If we want to do something more advanced and customize this behavior, then add an ARM template called “azuredeploy.json” at the root of the repository which will cause users to be presented with different inputs and configure your services as specified.

I’m going to walk you through a workflow that I used to test them before checking them in to my repo, as well as describe some of the special behaviors that the “Deploy to Azure” site does

Adding a button

To add a deployment button, insert the following markdown to your README.md file:

[![Deploy to Azure](https://azuredeploy.net/deploybutton.svg)](https://deploy.azure.com/?repository=https://github.com/loklak/loklak_server)

How it works

When a user clicks on the button, a “referrer” header is sent to azuredeploy.net which contains the location of the Git repository of loklak_server to deploy from.

An Example Template

This is a blank template which shows, how the azure divides its inputs.

{
  "$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
  },
  "variables": {
  },
  "resources": [
  ],
  "outputs": {
  }
}

By following the above template, in the case of loklak server, the parameters used are name, image i.e., docker image, port , number of CPUs to be utilized and space i.e., memory required.

In the resources section we use container, the type of the container will be

"type": "Microsoft.ContainerInstance/containerGroups",

 

And as output, we expect a public IP address to access the azure cloud instance created by us.

Everything under the root “parameters” property will be inputs into our template. Then these parameter values feed into the resources defined later in the template with the “[parameters(‘paramName’)]” syntax.

Try the “Deploy to Azure” Button here:



Resources

Working of One Click Deployment Buttons in loklak

Today’s topic is deployment. It’s called one-click deployment for a reason: Developers are lazy. It’s hard to do less than clicking on one button, so that’s our goal to make use of one click button in loklak.

For one click buttons we only need a central build server, which is our loklak_server. Everything written here was based on Apache ant, but later on ant build was deprecated and loklak server started to use gradle build. We wanted to make the process of provisioning and setting up a complete infrastructure of your own, from server to continuous integration tasks, as easy as possible. These button allows you to do all of that in one click.

How does it work?

You can see the one click buttons in the README page of loklak_server repository.

These repositories may include a different files like scalingo.json for scalingo, docker-compose.yml and docker-cloud.yml for docker cloud etc files at their root, allowing them to define a few things like a name, description, logo and build environment (Gradle build in the case of loklak server). Once you’ve clicked on any of the buttons, you will be redirected to respective apps and prompted with this information for you to review before confirming the fork.

This will effectively fork the repository in your account. Once the repo is ready, you can click on it. You will then be asked to “activate” or “deploy” your branch, allowing it to provision actual servers and run tasks. At the same time, you will be asked to review and potentially modify a few variables that were defined in the predefined files (for eg: app.json for heroku) of the apps. These are usually things like the Git URL of the repo for loklak, or some of the details related to the cloud provider you want to use (eg: Digital Ocean).

Once you confirmed this last step, your branch i.e., most probably master branch of loklak server repo is activated and the button will start provisioning and configuring your servers, along with the tasks which may allow you to build and deploy your app. In most of the cases, you can go to the tasks/setup section and run the build task that will fetch loklak server’s code, build it and deploy it on your server, all configurations included and will get a public IP.

What’s next

In loklak we are also introducing new one click “AZURE” button, then the users can also start deploying loklak in azure platform.

Resources

One Click Deployment Button for loklak Using Heroku with Gradle Build

The one click deploy button makes it easy for the users of loklak to get their own cloud instance created and deployed in their heroku account and can be used according to their flexibility. Heroku uses an app.json manifest in the code repo to figure out what add-ons, config and other deployment steps are required to make the code run. This is used to configure and deploy the app.

Once you have provide the app name and then click on deploy button, Heroku will start deploying the loklak server to a new app on your account:

When setup is complete, you can open the deployed app in your browser or inspect it in Dashboard.

All these steps and requirements can now be encoded in an app.json file and placed in a repo alongside a button that kicks off the setup with a single click.

App.json is a manifest format for describing apps and specifying what their config requirements are. Heroku uses this file to figure out how code in a particular repo should be deployed on the platform. Here is the loklak’s app.json file which used gradle build pack:

{
	"name": "Loklak Server",
	"description": "Distributed Tweet Search Server",
	"logo": "https://raw.githubusercontent.com/loklak/loklak_server/master/html/images/loklak_anonymous.png",
	"website": "http://api.loklak.org",
	"repository": "https://github.com/loklak/loklak_server.git",
	"image": "loklak/loklak_server:latest-master",
	"env": {
		"BUILDPACK_URL": "https://github.com/heroku/heroku-buildpack-gradle.git"
	}
}

 

If you are interested you can try deploying the peer from here itself. Checkout how simple it can be to deploy.

Deploy button:

Deploy

Resources:

Auto Deploying loklak Server on Google Cloud Using Travis

This is a setup for loklak server which want to check in only the source files, but have the development branch in Kubernetes deployment automatically updated with some compiled output every time the push using details from Travis build.

How to achieve it?

Unix commands and shell script is one of the best option to automate all deployment and build activities. I explored Kubernetes Gcloud which can be accessed through unix command.

1.Checking for Travis build details before deployment:

Firstly check whether the repository is loklak_server, pull request is available and branches are either master or development, and then decide to update the docker image or not. The code of the aforementioned things is as follows:

if [ "$TRAVIS_REPO_SLUG" != "loklak/loklak_server" ]; then
    echo "Skipping image update for repo $TRAVIS_REPO_SLUG"
    exit 0
fi

if [ "$TRAVIS_PULL_REQUEST" != "false" ]; then
    echo "Skipping image update for pull request"
    exit 0
fi

if [ "$TRAVIS_BRANCH" != "master" ] && [ "$TRAVIS_BRANCH" != "development" ]; then
    echo "Skipping image update for branch $TRAVIS_BRANCH"
    exit 0
fi

2. Setting up Tag and Decrypting the credentials:

For the Kubernetes deployment, each time the travis build is successful, it takes the commit details from travis and appended into tag details for deployment and gcloud credentials is decrypted from the json file.

openssl aes-256-cbc -K $encrypted_48d01dc243a6_key -iv $encrypted_48d01dc243a6_iv  -in kubernetes/gcloud-credentials.json.enc -out kubernetes/gcloud-credentials.json -d

3. Install, Authenticate and Configure GCloud details with Kubernetes:

In this step, initially Google Cloud SDK should be installed with Kubernetes-

curl https://sdk.cloud.google.com | bash > /dev/null
source ~/google-cloud-sdk/path.bash.inc
gcloud components install kubectl

 

Then, Authenticate Google Cloud using the above mentioned decrypted credentials and finally configure the Google Cloud with the details like zone, project name, cluster details, number of nodes etc.

4. Update the Kubernetes deployment:

Since, in this issue it is specific to the loklak_server/development branch, so in here it checks if the branch is development or not and then updates the deployment using following command:

if [ $TRAVIS_BRANCH == "development" ]; then
    kubectl set image deployment/server --namespace=web server=$TAG
fi

 

Conclusion:

In this post, how to write a script in such a way that with each successful push after travis build how to update the deployment on Kubernetes GCloud.

Resources:

Know the Usage of all Emoji’s on Twitter with loklak Emoji Heatmap

Loklak apps page now has a new app in its store, Emoji Heatmap. This app can be used to see the usage of all the emoji’s in the tweets all over the world in the form of heatmap. So, the major difference between the emoji heatmap and emoji heatmapper apps are heatmapper shows the tweets related to specific search query whereas this heatmapper app, it displays all the tweets which contains emojis.

How do the App fetches and stores the locations

The emoji heatmap uses the loklak search API . The search API needs a query in order to search and output the JSON data. But this app takes no input from the user end to search any query. To make the search dynamic, we are using an existing JSON file from emojiHeatmapper app and loklak-fetcher-client javascript file. From the emoji.json file, we collect the each query item and search it using loklak-fetcher-client. The output json file which we get from loklak-fetcher-client is retrieved into the emojiHeatmap and we extract the location parameter. The location parameter is then stored into the “feature” option of open layers 3 maps.

So, here in the emoji Heatmap app, we iterate over the emoji.json, get different search query each time when we search for it using loklak search API.

Code which adds the location retrieved into feature

  $.getJSON("../emojiHeatmapper/emoji.json", function(json) {
    for (var i = 0; i < json.data.length; i++){
      var query = json.data[i][1];
      // Fetch loklak API data, and fill the vector
      loklakFetcher.getTweets(query, function(tweets) {
        for(var i = 0; i < tweets.statuses.length; i++) {
          if(tweets.statuses[i].location_point !== undefined){
          // Creation of the point with the tweet's coordinates
          //  Coords system swap is required: OpenLayers uses by default
          //  EPSG:3857, while loklak's output is EPSG:4326
            var point = new ol.geom.Point(ol.proj.transform(tweets.statuses[i].location_point, 'EPSG:4326', 'EPSG:3857'));
            vector.addFeature(new ol.Feature({  // Add the point to the data vector
              geometry: point,
              weight: 20
            }));
          }
        }
      });
    }
  });

 

The above function gets has two variables query and point. The query variable stores the data that is being retrieved from the emoji.json file each time it iterates and that query is being sent into the loklak-fetcher-client. Then the point variable is in which the location tracked using the loklak search API is converted into the co-ordinates system followed by the Open Layers 3. Then the point is added as a feature to the map vector. The map vector is the place where all the features are stored and then appended onto the map as a heatmap.

Resources

Utilizing Readiness Probes for loklak Dependencies in Kubernetes

When we use any application and fail to connect to it, we do not give up and retry connecting to it again and again. But in the reality we often face this kind of obstacles like application that break instantly or when connecting to an API or database that is not ready yet, the app gets upset and refuses to continue to work. So, something similar to this was happening with api.loklak.org.
In such cases we can’t really re-write the whole application again every time the problem occurs.So for this we need to define dependencies of some kind that can handle the situation rather than disappointing the users of loklak app.

Solution:

We will just wait until a dependent API or backend of loklak is ready and then only start the loklak app. For this to be done, we used Kubernetes Health Checks.

Kubernetes health checks are divided into liveness and readiness probes.
The purpose of liveness probes are to indicate that your application is running.
Readiness probes are meant to check if your application is ready to serve traffic.
The right combination of liveness and readiness probes used with Kubernetes deployments can:
Enable zero downtime deploys
Prevent deployment of broken images
Ensure that failed containers are automatically restarted

Pod Ready to be Used?

A Pod with defined readiness probe won’t receive any traffic until a defined request can be successfully fulfilled. This health checks are defined through the Kubernetes, so we don’t need any changes to be made in our services (APIs). We just need to setup a readiness probe for the APIs that loklak server is depending on. Here you can see the relevant part of the container spec you need to add (in this example we want to know when loklak is ready):

        readinessProbe:
          httpGet:
            path: /api/status.json
            port: 80
          initialDelaySeconds: 30
          timeoutSeconds: 3

 

Readiness Probes

Updating deployments of loklak when something pushed into development without readiness probes can result in downtime as old pods are replaced by new pods in case of Kubernetes deployment. If the new pods are misconfigured or somehow broken, that downtime extends until you detect the problem and rollback.
With readiness probes, Kubernetes will not send traffic to a pod until the readiness probe is successful. When updating a loklak deployment, it will also leave old one’s running until probes have been successful on new copy. That means that if loklak server new pods are broken in some way, they’ll never see traffic, instead old pods of loklak server will continue to serve all traffic for the deployment.

Conclusion

Readiness probes is a simple solution to ensure that Pods with dependencies do not get started before their dependencies are ready (in this case for loklak server). This also works with more than one dependency.

Resources

CSS Styling Tips Used for loklak Apps

Cascading Style Sheets (CSS) is one of the main factors which is valuable to create beautiful and dynamic websites. So we use CSS for styling our apps in apps.loklak.org.

In this blog post am going to tell you about few rules and tips for using CSS when you style your App:

1.Always try something new – The loklak apps website is very flexible according to the user whomsoever creates an app. The user is always allowed to use any new CSS frameworks to create an app.

2.Strive for Simplicity – As the app grows, we’ll start developing a lot more than we imagine like many CSS rules and elements etc. Some of the rules may also override each other without we noticing it. It’s good practice to always check before adding a new style rule—maybe an existing one could apply.

3.Proper Structured file –

  • Maintain uniform spacing.
  • Always use semantic or “familiar” class/id names.
  • Follow DRY (Don’t Repeat Yourself) Principle.

CSS file of Compare Twitter Profiles App:

#searchBar {
    width:500px;
}

table {
  border-collapse: collapse;
  width: 70%;
}

th, td {
  padding: 8px;
  text-align: center;
  border-bottom: 1px solid#ddd;
}

 

The output screen of the app:


Do’s and Don’ts while using CSS:

  • Pages must continue to work when style sheets are disabled. In this case this means that the apps which are written in apps.loklak.org should run in any and every case. Let’s say for instance, when a user uses a old browsers or bugs or either because of style conflicts.
  • Do not use the !important attribute to override the user’s settings. Using the !important declaration is often considered bad practice because it has side effects that mess with one of CSS’s core mechanisms: specificity. In many cases, using it could indicate poor CSS architecture.
  • If you have multiple style sheets, then make sure to use the same CLASS names for the same concept in all of the style sheets.
    Do not use more than two fonts. Using a lot of fonts simply because you can will result in a messy look.
  • A firm rule for home page design is more is less : the more buttons and options you put on the home page, the less users are capable of quickly finding the information they need.

Resources:

How the Compare Twitter Profiles loklak App works

People usually have a tendency to compare their profiles with others, So this is what exactly this app is used for: To compare Twitter profiles. loklak provides so many API’s which serves different functionalities. One among those API’s which I am using to implement this app is loklak’s User Details API. This API actually help in getting all the details of the user we search giving the user name as the query. In this app am going to implement a comparison between two twitter profiles which is shown in the form of tables on the output screen.

Usage of loklak’s User Profile API in the app:

In this app when the user given in the user names in the search fields as seen below:

The queries entered into the search field are taken and used as query in the User Profile API. The query in the code is taken in the following form:

var userQueryCommand = 'http://api.loklak.org/api/user.json?' +
                       'callback=JSON_CALLBACK&screen_name=' +
                       $scope.query;

var userQueryCommand1 = 'http://api.loklak.org/api/user.json?' +
                        'callback=JSON_CALLBACK&screen_name=' +
                        $scope.query1;

The query return a json output from which we fetch details which we need. A simple query and its json output:

http://api.loklak.org/api/user.json?screen_name=fossasia

Sample json output:

{
  "search_metadata": {"client": "162.158.50.42"},
  "user": {
    "$P": "I",
    "utc_offset": -25200,
    "friends_count": 282,
    "profile_image_url_https": "https://pbs.twimg.com/profile_images/1141238022/fossasia-cubelogo_normal.jpg",
    "listed_count": 185,
    "profile_background_image_url": "http://pbs.twimg.com/profile_background_images/882420659/14d1d447527f8524c6aa0c568fb421d8.jpeg",
    "default_profile_image": false,
    "favourites_count": 1877,
    "description": "#FOSSASIA #OpenTechSummit 2017, March 17-19 in Singapore https://t.co/aKhIo2s1Ck #OpenTech community of developers & creators #Code #Hardware #OpenDesign",
    "created_at": "Sun Jun 20 16:13:15 +0000 2010",
    "is_translator": false,
    "profile_background_image_url_https": "https://pbs.twimg.com/profile_background_images/882420659/14d1d447527f8524c6aa0c568fb421d8.jpeg",
    "protected": false,
    "screen_name": "fossasia",
    "id_str": "157702526",
    "profile_link_color": "DD2E44",
    "is_translation_enabled": false,
    "translator_type": "none",
    "id": 157702526,
    "geo_enabled": true,
    "profile_background_color": "F50000",
    "lang": "en",
    "has_extended_profile": false,
    "profile_sidebar_border_color": "000000",
    "profile_location": null,
    "profile_text_color": "333333",
    "verified": false,
    "profile_image_url": "http://pbs.twimg.com/profile_images/1141238022/fossasia-cubelogo_normal.jpg",
    "time_zone": "Pacific Time (US & Canada)",
    "url": "http://t.co/eLxWZtqTHh",
    "contributors_enabled": false,
    "profile_background_tile": true,
}

 

I am getting data from the json outputs as shown above, I use different fields from the json output like screen_name, favourites_count etc.

Injecting data from loklak API response using Angular:

As the loklak’s user profile API returns a json format file, I am using Angular JS to align the data according to the needs in the app.

I am using JSONP to retrieve the data from the API. JSONP or “JSON with padding” is a JSON extension wherein a prefix is specified as an input argument of the call itself. This how it is written in code:

$http.jsonp(String(userQueryCommand)).success(function (response) {
    $scope.userData = response.user;
 });

Here the response is stored into a $scope is an application object here. Using the $scope.userData variable , we access the data and display it on the screen using Javascript, HTML and CSS.

<div id="contactCard" style="pull-right">
    <div class="panel panel-default">
        <div class="panel-heading clearfix">
            <h3 class="panel-title pull-left">User 1 Profile</h3>
        </div>
        <div class="list-group">
            <div class="list-group-item">
                <img src="{{userData.profile_image_url}}" alt="" style="pull-left">
                <h4 class="list-group-item-heading" >{{userData.name}}</h4>
            </div>

In this app am also adding keyboard action and validations of fields which will not allow users to search for an empty query using this simple line in the input field.

ng-keyup="$event.keyCode == 13 && query1 != '' && query != '' ? Search() : null"

 


Resources: