# Challenges and Solution Directions of Microservice Architectures: A Systematic Literature Review
## 5 Identified Challenges and Solution Directions
### RQ2. What Are the Identified Solution Directions?
#### 5.2.1 Service Discovery
\begin{table}
\begin{tabular}{l c l} \hline \hline
**Primary Challenge** & \multicolumn{2}{c}{**Solution Direction**} \\ \hline  & - & An Approach That Provides Authentication and Decentralized Role-Based Authorization. \\  & - & A Platform for Identity and Access Control of Microservices. Study AC \\
**P7. Security** & - & Access Control Optimization Model. Study AJ \\  & - & Prototype Layered Security Framework (Hardware, Virtualization, Cloud, Communication, Application, and Orchestration). Study V \\  & - & An Approach for Handling Security as Security-as-a-Service. Study D \\  & - & Extended Role-Based Access Control Model. Study BT \\ \hline  & - & An Approach and Tool for Generating Service Dependency Graph. Study X \\  & - & A Tool for Generating Service Causal Graph. Study Z \\  & - & An Approach For Analyzing Architecture. Study AD \\  & - & A Tool For Handling Traversing Distinct Type of Logs. Study AS \\  & - & A Tool For Architecture Recovery. Study P \\  & - & A Root Cause Analysis Framework for Detecting Anomalies. Study AZ \\  & - & An Execution Trace-Based Root Cause Location Method. Study BG \\  & - & A Graph-based Trace Analysis Approach—Study BJ \\
**PS. Monitoring, Tracing** & - & An Offline Approach to Distributed Tracing—Study BL \\
**and Logging** & - & A Four Layered Framework for Detection and Diagnosis of Faulty Microservices—Study BN \\  & - & In-Kernel Transparent Monitoring Service—Study BO \\  & - & Microservice Fault Detection Method Based on Correlation Analysis—Study BQ \\  & - & A Fault Model-Based Root Cause Localization Framework—Study BR \\  & - & An Anomaly Detection Method based on Semi-Supervised Learning—Study BS \\  & - & A Root Cause Localization Approach—Study BU \\  & - & Lightweight Spectrum-Based Performance Diagnosis Tool—Study BV \\  & - & An Anomaly Detection Approach with Execution Trace Comparison—Study CE \\  & - & An Agent-Based Monitoring Platform to Detect Anomalies and Unexpected System \\  & - & Dependencies—Study CG \\ \hline  & - & A Conceptual Methodology for Deciding Right Size of Microservices. Study AB \\
**P9. Decomposition** & - & A Functional Decomposition Approach. Study U \\  & - & A Dataflow-Driven Decomposition. Study AP \\  & - & A Dependency Capturing and Clustering-Based Microservice Identification Approach. \\  & & Study CC \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Cont. Study [BC] argues that the unavailable states of services are useless and faulty interaction topics. The authors indicate that there should be a synchronization mechanism to support microservice communications. Hence, they offer a framework called Synchronizer. This framework achieves collecting health/state information of microservices by using distributed registries. This framework has been validated with multiple use cases and according to the result, it brings effectiveness to synchronization among microservices. To sum up, the corresponding solutions to the service discovery are based mainly on scalability and workload problems. To cope with these problems, the identified primary studies propose either a decision model helping to choose the best option within the existing solutions or a novel model for handling service discovery problems.