Bastions are a cluster of machines used as the unique entry point by operational teams to securely connect to devices using ssh.
The Bastion provides mechanisms for authentication, authorization, traceability and auditability for the whole infrastructure.

A single distribution of libraries that automatically collects traces and metrics from your app, displays them locally, and sends them to any analysis tool.

Zipkin is a distributed tracing system. It helps gather timing data needed to troubleshoot latency problems in microservice architectures. It manages both the collection and lookup of this data. Zipkin’s design is based on the Google Dapper paper.

Applications are instrumented to report timing data to Zipkin. The Zipkin UI also presents a Dependency diagram showing how many traced requests went through each application. If you are troubleshooting latency problems or errors, you can filter or sort all traces based on the application, length of trace, annotation, or timestamp. Once you select a trace, you can see the percentage of the total trace time each span takes which allows you to identify the problem application.

Jaeger, inspired by Dapper and OpenZipkin, is a distributed tracing system released as open source by Uber Technologies. It is used for monitoring and troubleshooting microservices-based distributed systems, including:

Distributed context propagation
Distributed transaction monitoring
Root cause analysis
Service dependency analysis
Performance / latency optimization