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Example Use Cases

The repository contains several examples that have been modelled with help of MoDMaCAO: a model for a distributed MongoDB, a model for a the popular LAMP stack, a model for the Apache Cassandra database, and a model for an Apache Spark cluster.

MongoDB

MongoDB is a NoSQL database that can be highly scaled and is often used in cloud environments. To achieve scalability, it supports the concept of sharding, i.e., the decomposition of and distributed storage of a data collection to several machines. Furthermore, replication sets can be used, to provide redundancy and high availability in case a machine experiences a failure. An overview of the MongoDB specific extension is shown below: MongoDB extension

  • The MongoDBComponent mixin type is the base type for all other MongoDB-specific mixin types. It defines the attributes mongodb.bindip, and mongodb.port, that specifies the IP address and port on which the mongodb service should be listening.

  • The ReplicableMongoDBComponent mixin type defines the base type for components that can be replicated. It defines the attribute mongodb.replication.set.name that is used to assign a component to a certain replication set. MongoDB components belonging to the same replication set are synchronized copies of each other.

  • The Router mixin type abstracts the notion of a router in the MongoDB cluster. A router implements the component to which the user connects. It forwards the requests of the user to the machines that actually hold the data

  • The ConfigServer mixin type abstracts the notion of a config server of a MongoDB cluster. A config server stores the metadata, including the state and organization of the data. It is also responsible to store authentication configuration information.

  • The Shard mixin type abstracts the notion of a shard in the MongoDB cluster. The shards are used to store the actual data of the database. Each shard holds a subset of the overall data.

  • The Cluster mixin type defines constraints for a MongoDB cluster: A cluster must contain at least one router (i.e., OneOrMoreRouters), at least one shard (i.e., OneOrMoreShards), and at least one config server (i.e., OneOrMoreConfigServer ).

  • The ConfigServerDependency mixin type abstracts the execution dependency between MongoDBComponents and a ConfigServer , to be able to ensure that the ConfigServer is started, before the other components get started.

An overview of a sample configuration using the defined MongoDB extension is shown below: Sample MongoDB configuration

For the sake of brevity, we omit the depiction of Attributes. The MongoDB-cluster cluster consists of the components router, configserver, and the three shards, shard1 to shard3. The router and shard1 to shard3 have an execution dependency to
the configserver. The components are placed on five different virtual machines, vm1 to vm5 , using PlacementLinks, which are connected to a network using NetworkInterfaces.

LAMP

An overview of the LAMP specific extension is shown below:

LAMP Extension

An overview of a LAMP configuration using the defined LAMP extension is shown below: Sample LAMP configuration

Apache Cassandra

An overview of the Apache Cassandra extension is shown below:

Apache Cassandra Extension

An overview of a sample Apache Cassandra configuration using the defined Apache Cassandra extension is shown below: Sample Cassandra configuration

Apache Spark

An overview of the Apache Spark extension is shown below: Apache Spark extension

An overview of a sample Apache Spark configuration using the defined extension is shown below: Sample Apache Spark configuration