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Architecture.md

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Architecture

Patron has two basic concepts:

  • The Component, which defines a long-running task like a server e.g. HTTP, gRPC, Kafka consumer, etc.
  • The Service, which is responsible for running provided components and monitoring them for errors

Component

A Component implements the following interface:

type Component interface {
  Run(ctx context.Context) error  
}

This allows a Service to start and then gracefully shutdown a Component via context cancellation.
The framework distinguishes between two types of components:

  • synchronous, which are components that follow the request/response pattern and
  • asynchronous, which consume messages from a source but don't respond anything back

The following component implementations are available:

  • HTTP (sync)
  • gRPC
  • RabbitMQ consumer (async)
  • Kafka consumer (async)
  • AWS SQS (async)

Service

The Service has the role of gluing all the above together:

  • setting up logging, metrics and tracing
  • setting up a default HTTP component with the following endpoints configured:
    • profiling via pprof
    • liveness check
    • readiness check
  • setting up termination by an OS signal
  • setting up SIGHUP custom hook if provided by an option
  • starting and stopping components
  • handling component errors

The service has some default settings which can be changed via environment variables:

  • Service HTTP port, for setting the default HTTP components port to 50000 with PATRON_HTTP_DEFAULT_PORT
  • Service HTTP read and write timeout, use PATRON_HTTP_READ_TIMEOUT, PATRON_HTTP_WRITE_TIMEOUT respectively. For acceptable values check here.
  • Log level, for setting the logger with INFO log level with PATRON_LOG_LEVEL
  • Tracing, for setting up jaeger tracing with
    • agent host 0.0.0.0 with PATRON_JAEGER_AGENT_HOST
    • agent port 6831 with PATRON_JAEGER_AGENT_PORT
    • sampler type probabilisticwith PATRON_JAEGER_SAMPLER_TYPE
    • sampler param 0.0 with PATRON_JAEGER_SAMPLER_PARAM, which means that no traces are sent.

The service provides also the option to bypass the legacy created HTTP component and use the new v2 component. This will effectively disable the default legacy HTTP component.

err = service.WithRouter(router).WithSIGHUP(sig).Run(ctx)
    if err != nil {
    log.Fatalf("failed to create and run service %v", err)
}

This above builder extension is temporary until we fully replace the legacy HTTP component with our v2 component.