Use of environment variables

Do you want to use configuration variables into a function and make them available as environment variables? You can set configuration variables using the Fn CLI or the func.yaml file.

By using the Fn CLI, your can set configuration variables on the application or function level.

Set environment variables

The following three examples shows you how to set the configuration variables on different levels using the connection-app sample application. The configuration examples are listed in order of precedent, the later examples override the previous ones. For example, adding a function key/value pair overrides an application key/value pair with the same name.

(1) Application level configuration

Configuration variables set at the application level apply to all functions contained in that application.

fn config app <app-name> <key> <value>

For example, set the DB_URL configuration variable with value of jdbc:mysql.

$ fn config app connection-app DB_URL jdbc:mysql

(2) Function configuration from func.yaml file

Use the func.yaml file to define your configuration variables in the config key. For example: set the DB_DRIVER configuration variable with value of mysqlDriver.

schema_version: 20180708
name: connection
version: 0.0.16
runtime: java
build_image: fnproject/fn-java-fdk-build:jdk11-1.0.99
run_image: fnproject/fn-java-fdk:jre11-1.0.99
cmd: com.example.fn.Connection::getConnection
config:
  DB_DRIVER: mysqlDriver

See Function file for more info.

(3) Function level configuration

After you deploy your function, you can set function level configuration variables. The variables only apply to the specific function identified.

fn config function <app-name> <fn-name> <key> <value>

For example, set the DB_PASSWORD configuration variable with value of superadmin.

$ fn config function connection-app connection DB_PASSWORD superadmin

Get environment variables

You can use your environment variable in your function by using a RuntimeContext instance or the getenv() method of the System class.

The following example shows the config function configuration method, which is used to get the values of the DB_URL,DB_DRIVER, and DB_USER configuration variables. The getPassword method gets the value of the DB_PASSWORD configuration variable by using the System class.

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) {
	url = ctx.getConfigurationByKey("DB_URL")
    			.orElse("jdbc:oracle");
    	driver = ctx.getConfigurationByKey("DB_DRIVER")
    			.orElse("OracleDriver");
    	user = ctx.getConfigurationByKey("DB_USER")
    			.orElse("admin");	
    }
    
  
    public String getUrl() {	
    	return  url;
    }

    
    public String getDriver() {
    	return  driver;        
    }
    
	
    public String getUser() {
        return  user;        
    }
    
	public String getPassword() {
        password = System.getenv().getOrDefault("DB_PASSWORD", "admin");
    	return  password;        
    }
    
    public String getConnection() {
    	return "driver: " + getDriver() + "; url: " + url + "; user: " + getUser() + "; password: " + getPassword();
    }
}

See configuration-variables example application for more info.