This post will show how to configure a CentOS server for deploying a Springboot application build with Gradle. The networking is passed trough nginx which can be used to run multiple servers on the same host or serve static traffic faster.

Configure nginx

To configure nginx add the following server declaration to your /etc/nginx/conf.d/nginx.conf file.

server {
        listen 80;
        listen [::]:80;

        server_name <your-domain>;

        location / {
             proxy_pass http://localhost:8080/;
             proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
             proxy_set_header X-Forwarded-Proto $scheme;
             proxy_set_header X-Forwarded-Port $server_port;
        }
}

This will pass the traffic through to the locally running app server.

Then test the configuration and restart nginx.

sudo nginx -t # test the new configuration for valid syntax
sudo systemctl restart nginx

Configure deployment in Gradle

First off, we need to define the server information and credentials. Log into the server and create a user deployment. Assign the sudo privilege to the newly created user. Then generate a ssh key deployment locally and add it to the allowed keys on the server.

Edit the user gradle.properties file at ~/.gradle/gradle.properties (or create it if it doesn’t exist) and add the following:

server_key_deployment_passphrase=<deployment-ssh-key-passphrase>
server_user_deployment_passphrase=<deployment-user-passphrase>

Now we need to set up Gradle to deploy the application. To do so we add the org.hidetake.ssh plugin which allows us to perform ssh operations:

plugins {
    id 'org.hidetake.ssh' version '2.9.0'
}

Then we configure our server access properties:

remotes {
    webServer {
        host = '<your-ip>'
        user = 'deployment'
        port = <your-ssh-port>
        identity = file("${System.properties['user.home']}/.ssh/deployment")
        passphrase = server_key_deployment_passphrase
        sudoPassword = server_user_deployment_passphrase
        errorStream = System.err
        outputStream = System.out
    }
}

Note how the passphrases are loaded from the properties file, such that they do not end up in version control by accident.

Next we define the build and deployment directories:

def remote_dir = '/var/www/<yourapp>'        // server deployment location
def local_dir = 'build/libs'                 // local artefact output directory
def deploy_file = "<yourapp>-${version}.jar" // artefact name

Now we add a new task to perform the deployment. The task requires that the artefact is build and checked (i.e. test cases are ran). Then it connects to the server and pushes the newly built file. The deployed application versions exist all side by side. The currently active one is linked to <yourapp>.jar. Then the app server is restarted.

task('deploy') {
  dependsOn build, test, check
  doLast {
    ssh.run {
      session(remotes.webServer) {
        put from: "${projectDir}/${local_dir}/${deploy_file}", into: remote_dir
        execute "ln -sf ${remote_dir}/${deploy_file} ${remote_dir}/<yourapp>.jar"
        executeSudo('systemctl restart <yourapp>.service', pty: true)
      }
    }
  }
}

Register the application with systemd

The new application needs to be registered with systemd such that it can be controlled easily. To do so, create a unit file at /etc/systemd/system/<yourapp>.service and write the following content inside.

[Unit]
Description=Spring Boot Application
After=syslog.target
After=network.target[Service]
User=<serveruser>
Type=simple

[Service]
ExecStart=/usr/bin/java -jar /var/www/<yourapp>/<yourapp>.jar
Restart=always
StandardOutput=syslog
StandardError=syslog
SyslogIdentifier=<yourapp>

[Install]
WantedBy=multi-user.target

Then start the app server:

sudo systemctl start <yourapp>
sudo systemctl status <yourapp>

Perform a local test

Build the uber jar containing all of the necessary jars, including the app server (e.g. tomcat) by invoking

./gradlew build

Now run it with java -jar <yourapp>.jar and test it.

Perform the deployment

To perform a deployment to the server you need to invoke the new Gradle task deploy:

./gradlew deploy

References