connector

The Connector is the most fundamental construct of the framework, providing key capabilities to Microbus microservices:

• Startup and shutdown with corresponding callbacks
• Service hostname and a random instance ID, both used to address the microservice
• Connectivity to NATS
• HTTP-like communication over NATS, unicast (request/response) and multicast (pub/sub)
• Structured logging
• Configuration
• Tickers to execute jobs on a recurring basis
• Distributed cache
• Embedded resource files and strings
• Distributed tracing
• Authorization

The connector package includes a separate source file for each functional area of the microservice. All these source files implement the same Connector class.

• config.go is responsible for fetching config values from the configurator core microservice
• connector.go defines the Connector struct and provides a few getters and setters
• control.go deals with subscribing and handling the control messages on the reserved port :888
• fragment.go orchestrates the fragmentation and defragmentation of large requests and responses
• lifecycle.go implements the Startup and Shutdown logic, as well as Go and Parallel for running code in goroutines
• logger.go provides a JSON logger for the microservice
• metrics.go collects metrics with OpenTelemetry
• muffler.go is an OpenTelemetry span sampler that excludes noisy spans
• publish.go deals with outbound messaging
• res.go manages the loading of files and localized strings from a resource FS
• selectiveprocessor.go is an OpenTelemetry processor of tracing spans that exports only spans that are explicitly selected
• subjects.go crafts the NATS subjects (topics) that a microservice subscribes to or publishes to
• subscribe.go deals with inbound message handling
• time.go introduces tickers to the microservice
• tracer.go supports distributed tracing with OpenTelemetry