mohsenyz/ganjex

Passive Container With Runtime Lifecycle Management

Ganjex

There are situations when you want to serve lots of dynamic services by just one JVM(runtime), with the help of Ganjex you can define your own framework.When you are developing micro-services, usually every micro service need a dedicated JVM, and any changes in it need restarting JVM. Remember tomcat which contains webapps and you can change webapps by removing or changing WAR files without restarting tomcat itself, but tomcat forces you to define your application in webapp schema, tomcat searches for servlet you defined and route HTTP messages to them. So if you want your micro-services communicating with each other by a queue for example or using gRPC you can't use tomcat simply to serve your micro-services. Also if you want to develop your services in a different manner than webapp and servlet, you can't use tomcat. OSGi is another solution but its too complicated and has a high learning curve. Ganjex like tomcat can contain services, and each service has its own classloader and lifecycle, but unlike tomcat which searches for servlets in its containing webapps, Ganjex is oblivious to its holding services, so we say Ganjex is a passive container just facilitating the management of the containing elements' alterations and lifecycle at runtime. The way this container should behave with its services (remember tomcat which searches for servlet and routes HTTP messages to them) should be defined by the client which uses Ganjex. So we say Ganjex is a platform layer container, which user must define their own framework based on their necessities and preferences properly. There are two types of elements Ganjex contains 1. Library and 2. Service.

Framework

It is expected that application framework, also called as client, would define how it plans to treat containing services. Ganjex container is started by framework with the code below:

Ganjex.run(ganjexConfiguration);

In the above code ganjexConfiguration is a configuration instance of GanjexConfiguration class which should be created by GanjexConfiguration.Builder. As an illustration:

	Ganjex ganjex = //you can save an instance of Ganjex container in Ganjex object
	    Ganjex.run(new GanjexConfiguration.Builder()
	        .libPath("/opt/ganjex/lib")         //location where libraries should be added
	        .servicePath("/opt/ganjex/service)  //location where services should be added
	        .watcherDelay(4)                    //how many seconds watchers should wait to retry
	        .hooks(new SomeHookContainer())     //list of all objects containing hooks
	        .build());

Please note that SomeHookContainer class in the above example may have methods annotated with @StartupHook or @ShutdownHook in order to manage the lifecycle of services. This is an example of this class:

public class SomeHookContainer {
    @StartupHook
    public void start(ServiceContext context){
        //consequent behavior changes mandated by the newly added service
    }
    
    @ShutdownHook
    public void destroy(ServiceContext context){
        //consequent fallback changes mandated by the newly added service
    }
} 

The service classLoader is required to surf the service code to manage business necessities defined by framework, so the service classLoader would be provided by the ServiceContext object. In other words, Ganjex would behave in a way that is defined in the framework by the client.

Service

Accomplishing specific jobs, services are interchangeable units typically implement a use case. As business use cases are being frequently changed, Ganjex services are supposed to be changed repetitively as well. As soon as a requirement is changed, the implementation of that requirement must be changed and deployed consequently. In Ganjex, also, services could be deployed or removed at runtime (on the fly). Soon after a service is added to Ganjex container, all of the @StartupHook methods
would be notified with the ServiceContext of the newly added service. Similarly, right after a service is removed from Ganjex container, all of the frameworks' methods annotated with @ShutdownHook would be notified with the ServiceContext of that service. This is framework's responsibility to treat each service properly, due to the fact that Ganjex knows nothing of the structure and pattern services utilize. Remember frameworks are not expected to be changed frequently.

Service manifest

Every service should have a file named manifest.properties in the root of its classpath. This is a manifest clearing the service identity. This should contain two keys: name and version

Library

There are cases when multiple services need a class, or a domain model class should be shared between services. As we can have many services, this might bring about having duplicate shared code in the services which would be inefficient and difficult to maintain. Here Libraries come to rescue, Libraries are typical jar files which can be changed and required to be accessible to the services. A service needing a library, should add the library's corresponding Maven dependency with <scope>provided</scope> because it would be provided by Ganjex at runtime.

Please note that changing the libraries is costly, meaning that soon after a library is changed (modified, added or removed), all of the services would be restarted in order to affect the consequent changes.

Dependency

To use ganjex library in your project add this dependency into your project pom:

<dependency>
    <groupId>com.piran-framework</groupId>
    <artifactId>ganjex</artifactId>
    <scope>0.4-RELEASE</scope>
</dependency>

Use Spring-Boot and Ganjex simultaneously

A Spring-boot-starter has been particularly designed for Ganjex which could be mounted on Spring-boot applications. By adding @EnableGanjexContainer class-level annotation on the Configuration class, Ganjex starts and scans all the beans with @GanjexHook annotation. Note that, if a class is marked with @GanjexHook, that class would be qualified to be a Spring component bean as well, so there would be no need to add @Component or @Service by doing so.

Spring-Boot properties

To add ganjex-starter to a spring-boot application, add three properties besides spring-boot properties:

• ganjex.lib-path
• ganjex.service-path
• ganjex.watch-delay

They are the same as GanjexConfiguration fields.

Sample Guide

There is a sample dynamic web framework developed using Spring and Ganjex, Full guide also available in its directory

Minimum Requirement

You need at least java 8 to use Ganjex container.

License

Copyright (c) 2018 Isa Hekmatizadeh.

Ganjex is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

Ganjex is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this program. If not, see http://www.gnu.org/licenses/.