Engineering and technology notes
Hide curl output
curl –silent –output /dev/null http://example.com
Deploying to App Stores – Expo Documentation
ios.supportsTablet: false configured, your app will still render at phone resolution on iPads and must be usable.- Add a splash screen, the very first thing your users see after they select your app.
- Use AppLoading to ensure your interface is ready before the user sees it.
- Preload and cache your assets so your app loads quickly, even with a poor internet connection.
- Configure the status bar so it doesn’t clash with your interface.
- Use native gestures whenever possible.
- Use interface elements that make sense on the device. For example, see the iOS Human Interface Guidelines.
- Add a great icon. Icon requirements between iOS and Android differ and are fairly strict, so be sure and familiarize yourself with that guide.
- Customize your primaryColor.
- Make sure your app has a valid iOS Bundle Identifier and Android Package. Take care in choosing these, as you will not be able to change them later.
app.json file to specify the version of your app, but there are a few different fields each with specific functionality.versionwill apply both to iOS and Android. For iOS, this corresponds toCFBundleShortVersionString, and for Android this corresponds toversionName. This is your user-facing version string for both platforms.android.versionCodefunctions as your internal Android version number. This will be used to distinguish different binaries of your app.ios.buildNumberfunctions as your internal iOS version number, and corresponds toCFBundleVersion. This will be used to distinguish different binaries of your app.
- Use
Constants.nativeAppVersionto access theversionvalue listed above. - Use
Constants.nativeBuildVersionto access eitherandroid.versionCodeorios.buildNumbervalues (depending on the current platform)
- Starting October 3, 2018, all new iOS apps and app updates will be required to have a privacy policy in order to pass the App Store Review Guidelines.
- Additionally, a number of developers have reported warnings from Google if their app does not have a privacy policy, since by default all Expo apps contain code for requesting the Android Advertising ID. Though this code may not be executed depending on which Expo APIs you use, we still recommend that all apps on the Google Play Store include a privacy policy as well.
- All apps in the iTunes Store must abide by the App Store Review Guidelines.
- Apple will ask you whether your app uses the IDFA, the answer is “yes.” This is because Expo contains the Facebook and Branch SDKs, which contain code for collecting the IDFA, and you’ll need to check a couple boxes on the Apple submission form. See Branch’s Guide for which specific boxes to fill in.
Note: No data is sent to Branch, Facebook, Segment, or Amplitude from your app unless you explicitly do so using the APIs. For more information on how Expo handles your data, and your end users’ data, take a look at our Privacy Explained page.
- Permissions are configured via the
android.permissionskey in yourapp.jsonfile - By default, your app will include all permissions supported by Expo. This is so that your standalone app will match its behavior in the Expo client and simply “work out of the box” no matter what permissions you ask for, with hardly any configuration needed on your part.
- There are some drawbacks to this. For example, let’s say your To-do list app requests
CAMERApermission upon installation. Your users may be wary of installing since nothing in the app seems to use the camera, so why would it need that permission? - To remedy this, simply add the
android.permissionskey in yourapp.jsonfile, and specify which permissions your app will use. A list of all Android permissions and configuration options can be found here. - To use only the minimum necessary permissions that Expo requires to run, set
"permissions" : []. To use those in addition toCAMERApermission, for example, you’d set"permissions" : ["CAMERA"].
- It’s helpful to glance over Common App Rejections.
- Binaries can get rejected for having poorly formatted icons, so double check the App Icon guide.
- Apple can reject your app if elements don’t render properly on an iPad, even if your app doesn’t target the iPad form factor. Be sure and test your app on an iPad (or iPad simulator).
- Occasionally people get a message from Apple which mentions an IPv6 network. Typically this is just Apple’s way of informing you what kind of network they tested on, and the actual “IPv6” detail is a red herring. All of Expo’s iOS code uses
NSURLSession, which is IPv6-compatible. More info.
app.json, for example:"infoPlist": {
"NSCameraUsageDescription": "This app uses the camera to scan barcodes on event tickets."
},
infoPlist configuration. Because these strings are configured at the native level, they will only be published when you build a new binary with expo build.ios.infoPlist.CFBundleAllowMixedLocalizations: true, then provide a list of file paths to locales. "expo" : {
...
"ios" : {
"infoPlist": {
"CFBundleAllowMixedLocalizations": true
}
},
"locales": {
"ru": "./languages/russian.json"
}
}
locales should be the 2-letter language code of your desired language, and the value should point to a JSON file that looks something like this:// russian.json
{
"CFBundleDisplayName": "Привет",
"NSContactsUsageDescription": "Эти слова по русски"
}
Привет whenever it’s installed on a device with the language set to Russian.Building Standalone Apps – Expo Documentation
node.js – how to achieve an apache Alias with a proxy pass on the same domain – Stack Overflow
<VirtualHost *:80>
ServerName domain.org
ServerAlias www.domain.org
ProxyPass /blog !
Alias /blog /var/apache-vhosts/www.domain.org-blog
<Directory /var/apache-vhosts/www.domain.org-blog/>
Options Indexes FollowSymLinks MultiViews
AllowOverride All
Order allow,deny
allow from all
</Directory>
ErrorLog ${APACHE_LOG_DIR}/error.log
# Possible values include: debug, info, notice, warn, error, crit,
# alert, emerg.
LogLevel warn
CustomLog ${APACHE_LOG_DIR}/access.log combined
ProxyPass / http://localhost:8884/
ProxyPassReverse / http://localhost:8884/
ProxyPreserveHost on
LogLevel debug
</VirtualHost>
Source: node.js – how to achieve an apache Alias with a proxy pass on the same domain – Stack Overflow
Deploying a react app using pm2 and serve · LoginRadius Engineering
Yes, you have learned React and now you can develop a full-fledged front end application. The create-react-app helps you to set up and run a React project, including it code transpiling, basic linting, testing, and build systems. In short, you can start writing React code with minimal preparation. But once your application is done, it is time to deploy the same on the server, you are stuck and you will seek help from your backend or DevOps mates.
Wait!! Being a front end guy it seems to be difficult, but depolying your application on server is relatively easier than writing state management in redux.
In this post, we will learn how to deploy a React application on an Ubuntu 18.04 server using Node.js, serve, and pm2
pm2 is a process manager for the JavaScript runtime Node.js. This is an open-source daemon process manager that helps to manage and keep application 24/7
Prerequisites
To follow this tutorial, you’ll need the following:
- Latest Node.js version installed on your computer or the Linux server where are you going to deploy the application.
sudo apt-get update sudo apt-get install nodejs node -v or node –version npm -v or npm –version create-react-apptoolnpm install -g create-react-appDeploying the app
1.First of all, create the app using
npx create-react-appnpx create-react-app my-app2.Now you can run the app by running following command in the project directory root
npm start3.The default react app will run in http://localhost:3000
4.Now install serve and pm2 packages globally on the system/server
npm install -g serve npm install -g pm25.Since you are in the root directory of your project, run the following command to create a production build of your app. This will create a directory named
buildin the project root directorynpm run build6.Now we can run the following command to deploy the app
pm2 serve <path> <port> --spaIn our case, we can run the following command
pm2 serve build 8082 --spaPM2 can serve static files very easily with the pm2 serve feature. It supports serving raw files from a specified folder or you can serve a SPA (Single Page Application) with it.
Now you can see that your application is running on 8081 port while you have logged out from your ssh terminal of the browser.
- Check the status of the application following command in the shell.
pm2 list
Bonus: Below are some utility commands to manage the pm2 process
- Specify the app name
pm2 --name <app-name> - Delete all pm2 process
pm2 delete all - Delete specific process
pm2 delete <app-name> - Check the CPU and memory usage
pm2 monit
Reference links :-
Source: Deploying a react app using pm2 and serve · LoginRadius Engineering
Set Up a Node.js App for a Website With Apache on Ubuntu 16.04
Introduction
Node.js is a JavaScript runtime environment which lets you easily build server-side applications. This tutorial will explain how to set up a Cloud Server running Ubuntu 16.04 so that Node.js scripts run as a service, and configure the Apache server to make the script accessible from the web.
Although Node.js scripts can be run from the command line using screen, running the scripts as a service using the process manager PM2 gives the scripts a more robust set of behaviors. When run as a service this way, the scripts will automatically restart if the server is rebooted or the script crashes.
PM2 is a process manager for Node.js, with a wide range of features you can use to control and manage your Node.js scripts. Visit the official PM2 website for more information on using PM2.
Requirements
- A Cloud Server running Linux (Ubuntu 16.04).
- A working domain name which points to the server.
- Apache web server installed and running.
Install Node.js
Update your server’s packages and install curl with the following commands:
sudo apt-get update
sudo apt-get install curl
Download the Node.js PPA:
curl -sL https://deb.nodesource.com/setup_6.x -o nodesource_setup.sh
Run the nodesource_setup.sh command to add the PPA to your server’s package cache:
sudo bash nodesource_setup.sh
Note: This script will update the server automatically. There is no need to run apt-get update a second time.
Install Node.js:
sudo apt-get install nodejs
This will automatically install npm as well.
Finally, install the build-essential package for npm:
sudo apt-get install build-essential
Create a Sample Node.js Application
For this example we will begin by creating a separate directory in your website’s document root for housing Node.js applications:
sudo mkdir /var/www/html/nodejs
Create the file hello.js in this directory:
sudo nano /var/www/html/nodejs/hello.js
Put the following content into the file:
#!/usr/bin/env nodejs
var http = require('http');
http.createServer(function (request, response) {
response.writeHead(200, {'Content-Type': 'text/plain'});
response.end('Hello World! Node.js is working correctly.\n');
}).listen(8080);
console.log('Server running at http://127.0.0.1:8080/');
Save and exit the file.
Make the file executable:
sudo chmod 755 hello.js
Install PM2
Use npm to install PM2 with the command:
sudo npm install -g pm2
Start the hello.js example script with the command:
sudo pm2 start hello.js
As root add PM2 to the startup scripts, so that it will automatically restart if the server is rebooted:
sudo pm2 startup systemd
Configure Apache
To access the Node.js script from the web, install the Apache modules proxy and proxy_http with the commands:
sudo a2enmod proxy
sudo a2enmod proxy_http
Once the installation is complete, restart Apache for the changes to take effect:
sudo service apache2 restart
Next, you will need to add the Apache proxy configurations. These directives need to be inserted into the VirtualHost command block in the site’s main Apache configuration file.
By common convention, this Apache configuration file is usually /etc/apache2/sites-available/example.com.conf on Ubuntu.
Note: The location and filename of a site’s Apache configuration file can vary.
Edit this file with your editor of choice, for example with the command:
sudo nano /etc/apache2/sites-available/example.com.conf
Scroll through the file until you find the VirtualHost command block, which will look like:
<VirtualHost *:80>
ServerName example.com
<Directory "/var/www/example.com/html">
AllowOverride All
</Directory>
</VirtualHost>
Add the following to VirtualHost command block:
ProxyRequests Off
ProxyPreserveHost On
ProxyVia Full
<Proxy *>
Require all granted
</Proxy>
<Location /nodejs>
ProxyPass http://127.0.0.1:8080
ProxyPassReverse http://127.0.0.1:8080
</Location>
Be sure to put these lines outside any Directory command blocks. For example:
<VirtualHost *:80>
ServerName example.com
ProxyRequests Off
ProxyPreserveHost On
ProxyVia Full
<Proxy *>
Require all granted
</Proxy>
<Location /nodejs>
ProxyPass http://127.0.0.1:8080
ProxyPassReverse http://127.0.0.1:8080
</Location>
<Directory "/var/www/example.com/html">
AllowOverride All
</Directory>
</VirtualHost>
Save and exit the file, then restart Apache for the changes to take effect:
sudo services apache2 restart`
After Apache restarts, you can test the application by viewing it in a browser. You should see the message, “Hello World! Node.js is working correctly.”
Source: Set Up a Node.js App for a Website With Apache on Ubuntu 16.04 – IONOS
Set Up a Node.js App for a Website With Apache on Ubuntu 16.04 – IONOS
sudo pm2 start hello.js
Source: Set Up a Node.js App for a Website With Apache on Ubuntu 16.04 – IONOS