Distributed KV Store with example python program (Using Python-evnconsul)

Example use case of using Consul KV to retrieve Configuration values to have a stateless micro service.

Environment:

•  

  • Consul agent running at <consul_ip>.

  • Django based micro service.

  • Manage DB configuration in settings.py of the micro service.

Steps:

Add database configuration key values to Consul:

curl -X PUT -d 'django.db.backends.mysql' http://<consul_ip>:8500/v1/kv/<service_name>/database/engine
curl -X PUT -d '<DB_NAME>' http://<consul_ip>:8500/v1/kv/<service_name>/database/name
curl -X PUT -d '<DB_IP>' http://<consul_ip>:8500/v1/kv/<service_name>/database/ip
curl -X PUT -d 3306 http://<consul_ip>8500/v1/kv/<service_name>/database/port
curl -X PUT -d '<DB_USERNAME>' http://<consul_ip>:8500/v1/kv/<service_name>/database/username
curl -X PUT -d '<DB_PASSWORD>' http://<consul_ip>:8500/v1/kv/<service_name>/database/password

In settings.py of Django, retrieve the DB configuration values as:

import envconsul

ENV_CONSUL = envconsul.EnvConsul(
service_name='<service_name>',
host='<consul_ip>',
port=8500,
)

DB_ENGINE = ENV_CONSUL.get_str('/database/engine')
DB_NAME = ENV_CONSUL.get_str('/database/name')
DB_IP = ENV_CONSUL.get_str('/database/ip')
DB_PORT = ENV_CONSUL.get('/database/port')
DB_USERNAME = ENV_CONSUL.get_str('/database/username')
DB_PASSWORD = ENV_CONSUL.get_str('/database/password')

# Use the values obtained from Consul in DATABASES config of Django.

DATABASES = {
'default': {
'ENGINE': DB_ENGINE,
'NAME': DB_NAME,
'HOST': DB_IP,
'PORT': DB_PORT,
'USER': DB_USERNAME,
'PASSWORD': DB_PASSWORD,
},
}

This way, DB configuration can easily be passed to all the micro services. 

Example shown is using python-envconsul to fetch KVs. Need to use better library such as python-consul which provides capabilities to fetch KV as notifications whenever there are changes in the values. 

<TODO>

Distributed KV Store with example python program (Using Python-Consul)

this is to experiment notification functionality and configuration reloading. 

Distributed KV Store with example Java program (Using cfg4J)

Environment:

•  

  • Consul agent running at <consul_ip>.

  • Java based micro service.

  • Manage DB configuration values in a ".configuration" file of a micro service.

Steps:

Add database configuration key values to Consul:

curl -X PUT -d '<DB_NAME>' http://<consul_ip>:8500/v1/kv/<service_name>/database/name
curl -X PUT -d '<DB_IP>' http://<consul_ip>:8500/v1/kv/<service_name>/database/ip
curl -X PUT -d 3306 http://<consul_ip>8500/v1/kv/<service_name>/database/port
curl -X PUT -d '<DB_USERNAME>' http://<consul_ip>:8500/v1/kv/<service_name>/database/username
curl -X PUT -d '<DB_PASSWORD>' http://<consul_ip>:8500/v1/kv/<service_name>/database/password

Example usage of cfg4j to retrieve the above Key Values from Consul:

import org.cfg4j.provider.ConfigurationProvider;
import org.cfg4j.provider.ConfigurationProviderBuilder;
import org.cfg4j.source.ConfigurationSource;
import org.cfg4j.source.consul.ConsulConfigurationSourceBuilder;
import org.cfg4j.source.context.environment.ImmutableEnvironment;
import org.cfg4j.source.reload.ReloadStrategy;
import org.cfg4j.source.reload.strategy.PeriodicalReloadStrategy;
import org.cfg4j.source.compose.MergeConfigurationSource;
import org.cfg4j.source.files.FilesConfigurationSource;

import java.lang.reflect.Field;
import java.util.Collections;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.HashMap;
import java.util.concurrent.TimeUnit;

public class Consulcf4j {

public interface ReadDBConfig {
String name();
String ip();
Integer port();
String username();
String password();
}

public static void main(String... args) throws Exception{

HashMap<String, Object> prev_map = new HashMap<String, Object>();
HashMap<String, Object> curr_map = new HashMap<String, Object>();

prev_map.put("name", "");
prev_map.put("ip", "");
prev_map.put("port", 0);
prev_map.put("username", "");
prev_map.put("password", "");

ConfigurationSource source = new ConsulConfigurationSourceBuilder()
.withHost("localhost")
.build();

ReloadStrategy reloadStrategy = new PeriodicalReloadStrategy(5, TimeUnit.SECONDS);

//ConfigurationSource localOverrideSource = new FilesConfigurationSource(() -> Collections.singletonList(Paths.get("appliction.properties")));

//MergeConfigurationSource mergeConfigurationSource = new MergeConfigurationSource(localOverrideSource, source);

ConfigurationProvider provider = new ConfigurationProviderBuilder()
.withConfigurationSource(source)
.withEnvironment(new ImmutableEnvironment("vfcnslcm"))
.withReloadStrategy(reloadStrategy)
.build();

ReadDBConfig conf = provider.bind("database", ReadDBConfig.class);

while(true){
curr_map.put("name", conf.name());
curr_map.put("ip", conf.ip());
curr_map.put("port", conf.port());
curr_map.put("username", conf.username());
curr_map.put("password", conf.password());

for(String key: curr_map.keySet()){
if(!prev_map.get(key).equals(curr_map.get(key))){
System.out.println("Values: ");
for(String k: curr_map.keySet()){
System.out.println(curr_map.get(k));
}
break;
}
}

prev_map.clear();
prev_map.putAll(curr_map);

}

// String value = provider.getProperty("engine", String.class);
// System.out.println(value);
}
}

This way, DB configuration can easily be passed to all the micro services.

This can be used in Spring Beans as shown in http://www.cfg4j.org/releases/latest/#configuration-provider

Distributed KV Store with one of ONAP Python Service 

Distributed KV Store with one of ONAP Java Service