chore(allsrv): add tracing to the database observer

The observer is updated with additional observability concerns. This
does violate single responsibility principles, but in this case it
encapsulates well. In my experience, it's rare that you have
metrics and tracing concerns that are required, and you only want one
or the other. Having a single observer for these makes it fairly simple.

Now that these are in place, add observability for metrics/tracing to
the http server.

allsrv/db_inmem.go

@@ -1,6 +1,7 @@
 package allsrv
 
 import (
+	"context"
 	"errors"
 )
 
@@ -9,7 +10,7 @@ type InmemDB struct {
 	m []Foo // 12)
 }
 
-func (db *InmemDB) CreateFoo(f Foo) error {
+func (db *InmemDB) CreateFoo(_ context.Context, f Foo) error {
 	for _, existing := range db.m {
 		if f.Name == existing.Name {
 			return errors.New("foo " + f.Name + " exists") // 8)
@@ -21,7 +22,7 @@ func (db *InmemDB) CreateFoo(f Foo) error {
 	return nil
 }
 
-func (db *InmemDB) ReadFoo(id string) (Foo, error) {
+func (db *InmemDB) ReadFoo(_ context.Context, id string) (Foo, error) {
 	for _, f := range db.m {
 		if id == f.ID {
 			return f, nil
@@ -30,7 +31,7 @@ func (db *InmemDB) ReadFoo(id string) (Foo, error) {
 	return Foo{}, errors.New("foo not found for id: " + id) // 8)
 }
 
-func (db *InmemDB) UpdateFoo(f Foo) error {
+func (db *InmemDB) UpdateFoo(_ context.Context, f Foo) error {
 	for i, existing := range db.m {
 		if f.ID == existing.ID {
 			db.m[i] = f
@@ -40,7 +41,7 @@ func (db *InmemDB) UpdateFoo(f Foo) error {
 	return errors.New("foo not found for id: " + f.ID) // 8)
 }
 
-func (db *InmemDB) DelFoo(id string) error {
+func (db *InmemDB) DelFoo(_ context.Context, id string) error {
 	for i, f := range db.m {
 		if id == f.ID {
 			db.m = append(db.m[:i], db.m[i+1:]...)

allsrv/observe_db.go

@@ -1,9 +1,11 @@
 package allsrv
 
 import (
+	"context"
 	"time"
 
 	"github.com/hashicorp/go-metrics"
+	"github.com/opentracing/opentracing-go"
 )
 
 const (
@@ -27,25 +29,37 @@ type dbMW struct {
 	met  *metrics.Metrics
 }
 
-func (d *dbMW) CreateFoo(f Foo) error {
+func (d *dbMW) CreateFoo(ctx context.Context, f Foo) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, d.name+"_foo_create")
+	defer span.Finish()
+
 	rec := d.record("create")
-	return rec(d.next.CreateFoo(f))
+	return rec(d.next.CreateFoo(ctx, f))
 }
 
-func (d *dbMW) ReadFoo(id string) (Foo, error) {
+func (d *dbMW) ReadFoo(ctx context.Context, id string) (Foo, error) {
+	span, ctx := opentracing.StartSpanFromContext(ctx, d.name+"_foo_read")
+	defer span.Finish()
+
 	rec := d.record("read")
-	f, err := d.next.ReadFoo(id)
+	f, err := d.next.ReadFoo(ctx, id)
 	return f, rec(err)
 }
 
-func (d *dbMW) UpdateFoo(f Foo) error {
+func (d *dbMW) UpdateFoo(ctx context.Context, f Foo) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, d.name+"_foo_update")
+	defer span.Finish()
+
 	rec := d.record("update")
-	return rec(d.next.UpdateFoo(f))
+	return rec(d.next.UpdateFoo(ctx, f))
 }
 
-func (d *dbMW) DelFoo(id string) error {
+func (d *dbMW) DelFoo(ctx context.Context, id string) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, d.name+"_foo_delete")
+	defer span.Finish()
+
 	rec := d.record("delete")
-	return rec(d.next.DelFoo(id))
+	return rec(d.next.DelFoo(ctx, id))
 }
 
 func (d *dbMW) record(op string) func(error) error {

allsrv/server.go

@@ -1,6 +1,7 @@
 package allsrv
 
 import (
+	"context"
 	"encoding/json"
 	"log"
 	"net/http"
@@ -51,10 +52,10 @@ import (
 type (
 	// DB represents the foo persistence layer.
 	DB interface {
-		CreateFoo(f Foo) error
-		ReadFoo(id string) (Foo, error)
-		UpdateFoo(f Foo) error
-		DelFoo(id string) error
+		CreateFoo(ctx context.Context, f Foo) error
+		ReadFoo(ctx context.Context, id string) (Foo, error)
+		UpdateFoo(ctx context.Context, f Foo) error
+		DelFoo(ctx context.Context, id string) error
 	}
 )
 
@@ -135,7 +136,7 @@ func (s *Server) createFoo(w http.ResponseWriter, r *http.Request) {
 
 	f.ID = s.idFn() // 11)
 
-	if err := s.db.CreateFoo(f); err != nil {
+	if err := s.db.CreateFoo(r.Context(), f); err != nil {
 		w.WriteHeader(http.StatusInternalServerError) // 9)
 		return
 	}
@@ -147,7 +148,7 @@ func (s *Server) createFoo(w http.ResponseWriter, r *http.Request) {
 }
 
 func (s *Server) readFoo(w http.ResponseWriter, r *http.Request) {
-	f, err := s.db.ReadFoo(r.URL.Query().Get("id"))
+	f, err := s.db.ReadFoo(r.Context(), r.URL.Query().Get("id"))
 	if err != nil {
 		w.WriteHeader(http.StatusNotFound) // 9)
 		return
@@ -165,14 +166,14 @@ func (s *Server) updateFoo(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if err := s.db.UpdateFoo(f); err != nil {
+	if err := s.db.UpdateFoo(r.Context(), f); err != nil {
 		w.WriteHeader(http.StatusInternalServerError) // 9)
 		return
 	}
 }
 
 func (s *Server) delFoo(w http.ResponseWriter, r *http.Request) {
-	if err := s.db.DelFoo(r.URL.Query().Get("id")); err != nil {
+	if err := s.db.DelFoo(r.Context(), r.URL.Query().Get("id")); err != nil {
 		w.WriteHeader(http.StatusNotFound) // 9)
 		return
 	}

allsrv/server_test.go

@@ -2,6 +2,7 @@ package allsrv_test
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"io"
 	"net/http"
@@ -65,7 +66,7 @@ func TestServer(t *testing.T) {
 	t.Run("foo read", func(t *testing.T) {
 		t.Run("when querying for existing foo id should pass", func(t *testing.T) {
 			db := allsrv.ObserveDB("inmem", newTestMetrics(t))(new(allsrv.InmemDB))
-			err := db.CreateFoo(allsrv.Foo{
+			err := db.CreateFoo(context.TODO(), allsrv.Foo{
 				ID:   "reader1",
 				Name: "read",
 				Note: "another note",
@@ -107,7 +108,7 @@ func TestServer(t *testing.T) {
 	t.Run("foo update", func(t *testing.T) {
 		t.Run("when updating an existing foo with valid changes should pass", func(t *testing.T) {
 			db := allsrv.ObserveDB("inmem", newTestMetrics(t))(new(allsrv.InmemDB))
-			err := db.CreateFoo(allsrv.Foo{
+			err := db.CreateFoo(context.TODO(), allsrv.Foo{
 				ID:   "id1",
 				Name: "first_name",
 				Note: "first note",
@@ -132,7 +133,7 @@ func TestServer(t *testing.T) {
 
 		t.Run("when provided invalid basic auth should fail", func(t *testing.T) {
 			db := new(allsrv.InmemDB)
-			err := db.CreateFoo(allsrv.Foo{
+			err := db.CreateFoo(context.TODO(), allsrv.Foo{
 				ID:   "id1",
 				Name: "first_name",
 				Note: "first note",
@@ -158,7 +159,7 @@ func TestServer(t *testing.T) {
 	t.Run("foo delete", func(t *testing.T) {
 		t.Run("when deleting an existing foo should pass", func(t *testing.T) {
 			db := allsrv.ObserveDB("inmem", newTestMetrics(t))(new(allsrv.InmemDB))
-			err := db.CreateFoo(allsrv.Foo{
+			err := db.CreateFoo(context.TODO(), allsrv.Foo{
 				ID:   "id1",
 				Name: "first_name",
 				Note: "first note",

go.mod

@@ -5,6 +5,7 @@ go 1.22
 require (
 	github.com/gofrs/uuid v4.4.0+incompatible
 	github.com/hashicorp/go-metrics v0.5.3
+	github.com/opentracing/opentracing-go v1.2.0
 	github.com/stretchr/testify v1.8.4
 )
 

go.sum

@@ -56,6 +56,8 @@ github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJ
 github.com/modern-go/reflect2 v0.0.0-20180701023420-4b7aa43c6742/go.mod h1:bx2lNnkwVCuqBIxFjflWJWanXIb3RllmbCylyMrvgv0=
 github.com/modern-go/reflect2 v1.0.1/go.mod h1:bx2lNnkwVCuqBIxFjflWJWanXIb3RllmbCylyMrvgv0=
 github.com/mwitkow/go-conntrack v0.0.0-20161129095857-cc309e4a2223/go.mod h1:qRWi+5nqEBWmkhHvq77mSJWrCKwh8bxhgT7d/eI7P4U=
+github.com/opentracing/opentracing-go v1.2.0 h1:uEJPy/1a5RIPAJ0Ov+OIO8OxWu77jEv+1B0VhjKrZUs=
+github.com/opentracing/opentracing-go v1.2.0/go.mod h1:GxEUsuufX4nBwe+T+Wl9TAgYrxe9dPLANfrWvHYVTgc=
 github.com/pascaldekloe/goe v0.1.0 h1:cBOtyMzM9HTpWjXfbbunk26uA6nG3a8n06Wieeh0MwY=
 github.com/pascaldekloe/goe v0.1.0/go.mod h1:lzWF7FIEvWOWxwDKqyGYQf6ZUaNfKdP144TG7ZOy1lc=
 github.com/pkg/diff v0.0.0-20210226163009-20ebb0f2a09e/go.mod h1:pJLUxLENpZxwdsKMEsNbx1VGcRFpLqf3715MtcvvzbA=