Microservices Architecture with exmaple

Microservices are a way to break down a monolithic application into small, simple and independent services that work together, where each is responsible fro a specific function. This brings scalability

The basic concept of microservices also talks about the

Features of MicroServices:
- Service Oriented Approach
- Componentization via Services
- Organized around business capabilities
- Products not projects
- Smart end point dump pipes
- Decentralized governance
- Decentralized data management
- Infrastructure automation
- Design for failure
- Evolutionary design

Tools for building Micro Services

- Scriptable cloud infrastructire to automate continuos delivery release pipelines
- Reliable Messaging Infrastructire to allow service chirography
- Highly productive development framework
- Containerless runtime to allow deployment of one executable per service

Spring Boot

- It makes it easy to create stand-alone, production-grade Spring based Applications.
- Embed Tomcat or Jetty Directly (no need to deploy WAR files)
- Automatically configure Spring whenever possible
- Provide production ready features such as metrics, health checks and externalized configuration.

Create a Spring Boot Application :

References :

This is an example to package and run a spring boot application as a microservice. It will bring up the spring application with an embedded web server.  The executable jar includes all the required libraries to run this as an independent service. Following are the details :

• The code can be downloaded from github:

https://github.com/SanjayIngole/demo-microservice-springboot/archive/master.zip

• There is runnable microservice jar as well that can be downloaded from following location:

https://github.com/SanjayIngole/demo-microservice-springboot/blob/master/DemoMicroServices/target/demo-0.0.1.jar

• To run this microservic. It will bring up the spring application with an embedded web server. 

java -jar demo.jar

• A test page can be used to upload the sample xml and obtain JSON response.

https://github.com/SanjayIngole/demo-microservice-springboot/blob/master/DemoMicroServices/src/main/resources/testpage.html

• You can use a docker or boxfuse to deploy this on cloud. I use boxfuse to deploy my microservices to aws. You can setup a boxfuse account (https://console.boxfuse.com/) and configure your aws instance, and then download boxfuse command line client.
• 
  
• Package your project using maven, which will package all dependent jars in one file.
• mvn package
• And then deploy it using boxfuse command, this deploy this application on configured aws instance. 
• boxfuse run demo:0.0.1

aws mysql connection issues

I just set up a new spring mvc + hibernate application on aws instance via elastic beanstalk.

I created a new MySql db and was able to access it through my localhost, but I couldn't connect to mysql through my beanstalk application deployed on aws instance. 

I was able to fix these issues, and thought its worth sharing the solution as many others developers might be facing the same issue.  The connectivity issue could happen for different reasons, but in my 

case it was security groups that caused the issue.

First thing to make sure you correctly created you db instance, try to ping it from console.

>>>  nc -zv test.xxxxxxxxx.us-west-2.rds.amazonaws.com 3306

Connection to mgdb.czivgxrqpb9q.us-west-2.rds.amazonaws.com port 3306 [tcp/mysql] succeeded!

The aws troubleshooting guide is helpful and I would recommend to read it first.

http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_Troubleshooting.html#CHAP_Troubleshooting.Connecting

Here is my spring-hibernate configuration file just for the reference:

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://www.springframework.org/schema/beans 

http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">

<bean id="appDataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource" >

    <property name="driverClassName" value="com.mysql.jdbc.Driver"/>

    <property name="url" value="jdbc:mysql://xxxxxxx.us-west1.rds.amazonaws.com:3306/mgdb?zeroDateTimeBehavior=convertToNull"/>

    <property name="username" value="xxxxxx"/>

    <property name="password" value="xxxxxx"/>

</bean>

<bean id="appSessionFactory" 

class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">

    <property name="dataSource" ref="appDataSource"/>

    <property name="mappingResources">

        <list>

            <value>employee.hbm.xml</value>        

        </list>

    </property>

    <property name="hibernateProperties">

        <value>hibernate.dialect=org.hibernate.dialect.HSQLDialect</value>

    </property>

</bean>

<bean id="hibernateTemplate" 

class="org.springframework.orm.hibernate3.HibernateTemplate">

    <property name="sessionFactory">

        <ref bean="appSessionFactory"/>

    </property>

</bean>

</beans>

• First Connectivity issue:

28-Nov-2015 23:58:47.504 ERROR [localhost-startStop-1] <unknown>.<unknown> Unable obtain JDBC Connection

 com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.

Caused by: java.net.ConnectException: Connection refused

Fix:

Initially I was getting Connection refused exception but this was gone once I updated the security group to enable all traffic to my ElasticBeanstalk application. 

I have updated the security group to accept All traffic with default IP as shown here. 

(This is okay for testing if you are troubleshooting the connectivity issue, but its a good idea to set specific protocols and destination for more security)

• Second Connectivity issue :

org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection

Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.

Caused by: java.net.ConnectException: Connection timed out

Fix :

After resolving first issue I was still getting Connection timed out error. Going further in aws documentation I found that we also need to enable the DB Security group to make it accessible from EC2. 

As per aws docs - A DB security group controls network access to a DB instance that is not inside a VPC. By default, network access is turned off to a DB instance. You can specify rules in a security group that allows access from an IP address range, port, or EC2 security group. 

More can be found at this link:

http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_WorkingWithSecurityGroups.html

To change this, go to you DB instance and select "See Details" from "Instance Actions" dropdown.

On the details page click on the security group for your db instance.

Check the inbound and outbound settings for your DB security group. For testing purpose I am setting it to accept All traffic but its always recommended to configure more specific protocols and ip addresses, specially if its production database.

Inbound:

Outbound: