opencensus

README

watermill-opencensus

OpenCensus tracing for Watermill.

Usage

Middleware

import (
    "contrib.go.opencensus.io/exporter/jaeger"
    "github.com/ThreeDotsLabs/watermill/message"
    "go.opencensus.io/trace"
    opencensus "github.com/czeslavo/watermill-opencensus"
)

...

// setup trace exporter (for example - jaeger)
exporter, _ := jaeger.NewExporter(jaeger.Options{
    AgentEndpoint:     "localhost:6831",
    CollectorEndpoint: "http://localhost:14268/api/traces",
    ServiceName:       "tracing-demo",
})
trace.RegisterExporter(exporter)

// create watermill router
router, _ := message.NewRouter(message.RouterConfig{}, logger)

// add opencensus middleware
router.AddMiddleware(
    opencensus.TracingMiddleware,
)

Publisher decorator

pubsub := gochannel.NewGoChannel(gochannel.Config{}, logger)
publisher := opencensus.PublisherDecorator(pubsub, logger)

Documentation

Overview

OpenCensus tracing for Watermill

Index

• func GetSpanContext(message *message.Message) (sc trace.SpanContext, ok bool)
• func PublisherDecorator(pub message.Publisher, logger watermill.LoggerAdapter) message.Publisher
• func SetSpanContext(sc trace.SpanContext, msg *message.Message)
• func TracingMiddleware(h message.HandlerFunc) message.HandlerFunc

Functions

func GetSpanContext

func GetSpanContext(message *message.Message) (sc trace.SpanContext, ok bool)

GetSpanContext gets and deserialize trace.SpanContext from a message's metadata.

func PublisherDecorator

func PublisherDecorator(pub message.Publisher, logger watermill.LoggerAdapter) message.Publisher

PublisherDecorator decorates `message.Publisher` with propagating span context in the published message's metadata.

Note: Please keep in mind that the span context needs to be passed as message's context, otherwise no action will be taken.

func SetSpanContext

func SetSpanContext(sc trace.SpanContext, msg *message.Message)

SetSpanContext serialize trace.SpanContext to binary format and sets it in a message's metadata.

func TracingMiddleware

func TracingMiddleware(h message.HandlerFunc) message.HandlerFunc

TracingMiddleware is a Watermill middleware providing OpenCensus tracing.

It creates a span with a name derived from the handler. The span is ended after message is handled. It tries to extract an existing span context from the incoming message and use it as a parent - if there's no such it creates a new one.

The span context is set as the message's context so message handlers' code can start children spans out of it.

spanCtx := trace.FromContext(message.Context())

Depending on a result of the message handling, the span's status is set.

All messages procuded by the handler have span context set so it gets propagated further. Span context is serialized to binary format and is transported in messages' metadata.