configuration-variables

Configuration Variables

You can get configuration variables into a function and make them available as environment variables.

The configuration-variables function creates a database connection string. This function has four variables: DB_URL, DB_DRIVER, DB_USER, and DB_PASSWORD.

The DB_URL, DB_DRIVER, DB_USER, and DB_PASSWORD environment variables are set on different configuration levels. For example, the value of the DB_DRIVER variable is read from the func.yaml file in the config key. The DB_URL and DB_USER environment variables are set in the application configuration level, and the DB_PASSWORD environment variable is set in the function configuration level.

Step by step: Set the configuration values

Ensure you have the Fn server running to host your function.

(1) Start the server.

$ fn start

(2) Go to the configuration-variables directory.

$ cd configuration-variables

(3) Create an app for the function.

$ fn create app connection-app

(4) At the application level, configure the DB_URL environment variable.

$ fn config app connection-app DB_URL jdbc:mysql

(5) At the application level, configure the DB_USER environment variable.

$ fn config app connection-app DB_USER superadmin

(6) Deploy the application.

$ fn deploy --app connection-app --local

(7) At the function level, configure the DB_PASSWORD environment variable.

$ fn config function connection-app connection DB_PASSWORD superadmin

(8) Invoke the connection function.

$ fn invoke connection-app connection
driver: mysqlDriver; url: jdbc:mysql; user: superadmin; password: superadmin

Code walkthrough

The entrypoint to the function is specified in func.yaml in the cmd key. It is set to com.example.fn.Connection::getConnection. The whole class Connection is shown below:

package com.example.fn;

import com.fnproject.fn.api.FnConfiguration;
import com.fnproject.fn.api.RuntimeContext;


public class Connection {			
	private String url;
	private String driver;
	private String user;
	private String password;  

	@FnConfiguration
    public void config(RuntimeContext ctx) {
		//Set value at the application configuration level
    	url = ctx.getConfigurationByKey("DB_URL")
    			.orElse("jdbc:oracle");
    	//Set value in the func.yaml
    	driver = ctx.getConfigurationByKey("DB_DRIVER")
    			.orElse("OracleDriver");
    	//Set value at the application configuration level
    	user = ctx.getConfigurationByKey("DB_USER")
    			.orElse("admin");
    }


    public String getUrl() {
    	return  url;
    }


    public String getDriver() {
    	return  driver;        
    }


    public String getUser() {
        return  user;        
    }

	//Set value at the function configuration level
    public String getPassword() {
        password = System.getenv().getOrDefault("DB_PASSWORD", "admin");
    	return  password;        
    }

    public String getConnection() {
    	return "driver: " + getDriver() + "; url: " + url + "; user: " + getUser() + "; password: " + getPassword();
    }
}

For more information see the configuration vars documentaion page.