OpenTelemetry Package for the Gorm ORM

This package is meant to simplify wrapping Gorm requests to databases with OpenTelemetry Tracing Spans. The functionality within the package is as of OpenTelemetry-go v0.2.1 and is subject to change fairly rapidly as the standard is evolved.

This package is B.Y.O.E. (Bring Your Own Exporter)

Metrics support coming soon!

Example Usage

Make sure you have the following:

• Docker
• Go 1.13
• cURL or Postman for testing

Run the following commands to create the testing environment:

• docker run -d -p 5432:5432 -e POSTGRES_USER=testuser -e POSTGRES_PASSWORD=password! -e POSTGRES_DB=test --name postgres postgres:alpine
• docker run -d --name jaeger -e COLLECTOR_ZIPKIN_HTTP_PORT=9411 -p 5775:5775/udp -p 6831:6831/udp -p 6832:6832/udp -p 5778:5778 -p 16686:16686 -p 14268:14268 -p 14250:14250 -p 9411:9411 jaegertracing/all-in-one:1.16

.env File

JAEGER_HOST=127.0.0.1
DB_USER=testuser
DB_PASS=password!
DB_HOST=127.0.0.1
DB_PORT=5432
DB_NAME=test
DB_SSLMODE=disable

Example App

package main

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"time"

	"github.com/jdefrank/otgorm"

	"github.com/go-chi/chi"
	"github.com/jinzhu/gorm"
	_ "github.com/jinzhu/gorm/dialects/postgres"
	_ "github.com/joho/godotenv/autoload"
	"go.opentelemetry.io/otel/api/global"
	"go.opentelemetry.io/otel/exporter/trace/jaeger"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
)

type user struct {
	ID        uint      `gorm:"primary_key" json:"id"`
	FirstName string    `json:"firstName"`
	LastName  string    `json:"lastName"`
	CreatedAt time.Time `json:"createdAt"`
	UpdatedAt time.Time `json:"updatedAt"`
}

func readBody(bodyreader io.ReadCloser) (data []byte, err error) {
	body, err := ioutil.ReadAll(io.LimitReader(bodyreader, 1048576))
	if err != nil {
		return nil, err
	}
	if err := bodyreader.Close(); err != nil {
		return nil, err
	}
	return body, nil
}

func httpTraceWrapper(h http.Handler) http.Handler {
	fn := func(w http.ResponseWriter, r *http.Request) {
		t := global.TraceProvider().Tracer("component-http")
		ctx, span := t.Start(r.Context(), r.URL.Path)
		r = r.WithContext(ctx)
		h.ServeHTTP(w, r)
		span.End()
	}
	return http.HandlerFunc(fn)
}

// NOTE: I've found that if you'd like to separate services in the Jaeger UI,
// you'll need to create multiple exporters which in turn will show you different colors
// per service.
func initTracer() func() {
	//Create Jaeger exporter
	exporter, err := jaeger.NewExporter(
		jaeger.WithCollectorEndpoint(fmt.Sprintf("http://%s:14268/api/traces", os.Getenv("JAEGER_HOST"))),
		jaeger.WithProcess(jaeger.Process{
			ServiceName: "go-otel-gorm",
		}),
	)
	if err != nil {
		log.Fatal(err)
	}
	// For demoing purposes, always sample. In a production application, you should
	// configure this to a trace.ProbabilitySampler set at the desired
	// probability.
	tp, err := sdktrace.NewProvider(
		sdktrace.WithConfig(sdktrace.Config{DefaultSampler: sdktrace.AlwaysSample()}),
		sdktrace.WithSyncer(exporter))
	if err != nil {
		log.Fatal(err)
	}
	global.SetTraceProvider(tp)
	return func() {
		exporter.Flush()
	}
}

func main() {
	//Setup the exporter and defer close until main exits
	fn := initTracer()
	defer fn()

	// Connect to database
	connString := fmt.Sprintf("host=%s port=%s user=%s dbname=%s password=%s sslmode=%s",
		os.Getenv("DB_HOST"),
		os.Getenv("DB_PORT"),
		os.Getenv("DB_USER"),
		os.Getenv("DB_NAME"),
		os.Getenv("DB_PASS"),
		os.Getenv("DB_SSLMODE"),
	)
	db, err := gorm.Open("postgres", connString)
	if err != nil {
		panic(err)
	}

	//Register callbacks for GORM, while also passing in config Opts
	otgorm.RegisterCallbacks(db,
		otgorm.WithTracer(global.TraceProvider().Tracer("component-gorm")),
		otgorm.Query(true),
		otgorm.AllowRoot(true),
	)

	//Run migration and create a record
	db.AutoMigrate(user{})
	newUser := user{
		FirstName: "John",
		LastName:  "Smith",
	}
	//Since this first DB call is outside of a parent,
	//lets set up empty context and the DB client with that context
	ctx := context.Background()
	orm := otgorm.WithContext(ctx, db)
	err = orm.Create(&newUser).Error
	if err != nil {
		log.Print(err)
	}

	//Create router
	r := chi.NewRouter()

	//Register Endpoints for the API
	r.Post("/user", func(w http.ResponseWriter, r *http.Request) {
		orm := otgorm.WithContext(r.Context(), db)
		var u user
		body, err := readBody(r.Body)
		if err != nil {
			log.Print(err)
			return
		}
		err = json.Unmarshal(body, &u)
		if err != nil {
			log.Print(err)
			return
		}
		err = orm.Create(&u).Error
		if err != nil {
			w.WriteHeader(http.StatusInternalServerError)
			json.NewEncoder(w).Encode("{\"Error\":\"" + err.Error() + "\"")
			return
		}
		w.WriteHeader(http.StatusOK)
		return
	})
	http.ListenAndServe(":3000", httpTraceWrapper(r))
}

License

The MIT License (MIT). Please see License File for more information.