Dependencies between the modules are one of the greatest challenges of distributed architectures. Applications based on microservices are inherently distributed – they may often have to deal with dependency challenges, that is, dependency problems and concerns between different services.
Since monolithic applications follow a layered model, you would encounter less cyclical dependencies. In a monolithic application, a dependency is created between the modules of the application when you import dependencies from one part of the application to another; For example, you provide a module with the necessary dependency so that it can run successfully.
On the other hand, applications based on microservices follow a graph model, which means that cyclical dependencies occur more frequently. A typical microservice architecture has dependencies between components and services.
These services can be modeled as independent, isolated units, but still have to communicate with one another to exchange data and information. Ideally, there should be no cyclical dependency in a typical microservice-based application, since a microservice should not call another microservice directly – a microservice should be called via an event.
However, you may need the collaboration, collaboration, and integration of the parts into your microservices-based application, and thus the dependency problem would arise.
Read: Difficulties in monolithic architecture and microservices
Problems with modularity in software development
Modularity refers to the ability to break up an application into separate, interchangeable components that together form an integrated whole, each of which can serve a specific business function. Modularity helps to increase reusability and maintenance and enables low coupling and high cohesion.
Despite the advantages it offers, dependency issues are one of the major disadvantages of modular design. Dependencies are a consequence of modularity – there are dependencies between modules due to the modular structure of the applications.
What is cyclical addiction and why is it bad?
A circular dependency is described as a connection between two or more modules of an application, in which the modules are directly or indirectly dependent on one another and are therefore mutually recursive.
Modules that have a circular dependency are mutually exclusive. If you have cyclical dependencies in a microservices based application, your services would not be scalable and you could not provide the services independently. If you have cyclical dependencies between the modules of an application, it is said that these violate both the principle of acyclical dependencies and the principle of order.
If the abstractions are cyclically dependent on each other, you must change, test, and reuse them together. Cyclic dependencies make code difficult to understand, change, and maintain over time, which also makes your application code prone to errors.
When there are circular dependencies between the components of an application, the components are also difficult to test. A change in one module of an application that has cyclical dependencies between the modules can have a ripple effect on other modules. The reuse of individual, tightly coupled modules is extremely difficult. Excessive dependencies between modules in an application are an indicator of poor software design, mainly because such systems are difficult to understand, operate, and maintain over time.
Read: Serverless functions versus microservices
To reduce or eliminate such dependencies, your architecture must use loose coupling and problem locality. While the former is an approach to design systems in such a way that the components are as little interdependent as possible, the latter says that related problems should be grouped together. There are several ways to break dependency cycles – below is a list of strategies that can be followed to break the dependency chains.
- Strategy 1: You can use an interface to break the dependency chain. To do this, you can introduce the interface for one of the abstractions that were used in the dependency cycle.
- Strategy 2: You can remove the unnecessary dependencies by refactoring the application source code.
- Strategy 3: This is another approach where you can move the source code that introduces cyclic dependencies to a different abstraction.
- Strategy 4: If the abstractions involved in the cycle are a semantically single object, you can merge the abstractions into a single abstraction.
Let’s understand strategy # 1 in more detail. Consider two classes x and AND that are interdependent – that is, they form a cycle of dependency. So, class x depends on the class AND and great AND also depends on class X. We know the problem – how do you break this addiction?
To solve this dependency problem, extract the functionality of the class x into an interface I. Now leave class AND depending on the interface I and great x Expand class AND and implement the interface I. This would break the circular dependency. You can also have classes AND Extension class x and implement the interface I to break the circular dependency.
Quadratic dependency matrix
A Dependency Square Matrix (DSM) offers a simple and concise approach to map the dependencies between the modules of an application. It’s an adjacency matrix, which is essentially a visual representation of the dependencies in an application. The Dependency Matrix can help you with decision-making in test cases and the quick detection of data-related errors. In the DSM, the rows and columns are used to represent tasks.
The tasks are dependent on each other, as data or information or objects have to flow from one task to another. A cell either remains empty or contains a selection. If the cell has no marker, it means that the task has no dependency. In contrast, a cell that contains a marker means that there is a dependency between a task in the column and a task in the row. You can also apply the dependency matrix at the module level. In this case, the dependency matrix would map the dependencies between different modules of an application.
Tools for recognizing cyclical dependencies
There are several tools to recognize cyclical dependencies in an application and Lattix architect Is one of them. Lattix Architect is a nice tool to quickly identify architectural problems. You can use this tool to get a visual representation of the architecture of the application along with its dependencies – the dependencies are represented with the Dependency Structure Matrix. These dependencies would help you gain insight into how the various layers and modules of the application interact, as well as any undesirable relationships and dependencies in the source code.
Here’s a quick rundown of what Lattix Architect can do:
- Understand the application architecture
- Check the software quality
- Refactoring the application architecture
Stan4J is a popular tool available on both Windows and Mac OS and used for the development and quality assurance of applications written in Java. It integrates into the development process, can recognize code odor such as cyclical dependencies and offers a visual dependency analysis.
Structure 101 is another tool for C, C ++ and Java with support for visualization and dependency functions. You can use this tool for structural analysis, dependency analysis and impact analysis.
Summary of application dependency management
While loose coupling, high cohesion, and modularity are best practices in software development, they are not free from drawbacks. One such disadvantage is the cyclical dependency. The good news is that there are several ways you can eliminate circular dependency problems.
