Add convenience wrappers for http.Get/Post, etc. (#390)

* Add convenience wrappers for http.Get/Post, etc.

Add convenience wrappers for http.{Get,Post,Head,PostForm}
using the otelhttp transport and taking a context.Context directly.
Makes instrumenting code using the original http convenience methods a
one-line change instead of a multiline one.

* Update instrumentation/net/http/otelhttp/client.go

Co-authored-by: Anthony Mirabella <a9@aneurysm9.com>

* Update instrumentation/net/http/otelhttp/client.go

Co-authored-by: Anthony Mirabella <a9@aneurysm9.com>

* Update instrumentation/net/http/otelhttp/client.go

Co-authored-by: Anthony Mirabella <a9@aneurysm9.com>

* Update instrumentation/net/http/otelhttp/client.go

Co-authored-by: Anthony Mirabella <a9@aneurysm9.com>

* Document new convenience wrappers in CHANGELOG

* Add tests, don't use cached global client.

* code format

* Expose DefaultClient and use it for all convenience wrappers.

* Update instrumentation/net/http/otelhttp/client.go

Co-authored-by: Sam Xie <xsambundy@gmail.com>

* Update CHANGELOG.md

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

* Don't bother attempting to reset the global provider.

* Assert existence of 4 clients spans for 4 client operations

* Improve comment on DefaultClient.

* Improve span testing.

* Move release note to unreleased section

Co-authored-by: Anthony Mirabella <a9@aneurysm9.com>
Co-authored-by: Sam Xie <xsambundy@gmail.com>
Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

CHANGELOG.md

@@ -8,6 +8,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Added
+
+- `otelhttp.{Get,Head,Post,PostForm}` convenience wrappers for their `http` counterparts. (#390)
+
 ## Fixed
 
 - `/detectors/aws` no longer fails if instance metadata is not available (e.g. not running in AWS) (#401)

instrumentation/net/http/otelhttp/client.go

@@ -0,0 +1,61 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package otelhttp
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+)
+
+// DefaultClient is the default Client and is used by Get, Head, Post and PostForm.
+// Please be careful of intitialization order - for example, if you change
+// the global propagator, the DefaultClient might still be using the old one
+var DefaultClient = &http.Client{Transport: NewTransport(http.DefaultTransport)}
+
+// Get is a convenient replacement for http.Get that adds a span around the request.
+func Get(ctx context.Context, url string) (resp *http.Response, err error) {
+	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	return DefaultClient.Do(req)
+}
+
+// Head is a convenient replacement for http.Head that adds a span around the request.
+func Head(ctx context.Context, url string) (resp *http.Response, err error) {
+	req, err := http.NewRequestWithContext(ctx, "HEAD", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	return DefaultClient.Do(req)
+}
+
+// Post is a convenient replacement for http.Post that adds a span around the request.
+func Post(ctx context.Context, url, contentType string, body io.Reader) (resp *http.Response, err error) {
+	req, err := http.NewRequestWithContext(ctx, "POST", url, body)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", contentType)
+	return DefaultClient.Do(req)
+}
+
+// PostForm is a convenient replacement for http.PostForm that adds a span around the request.
+func PostForm(ctx context.Context, url string, data url.Values) (resp *http.Response, err error) {
+	return Post(ctx, url, "application/x-www-form-urlencoded", strings.NewReader(data.Encode()))
+}

instrumentation/net/http/otelhttp/client_test.go

@@ -0,0 +1,80 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package otelhttp
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+
+	"go.opentelemetry.io/otel/api/global"
+
+	"github.com/stretchr/testify/assert"
+
+	mocktrace "go.opentelemetry.io/contrib/internal/trace"
+)
+
+func TestConvenienceWrappers(t *testing.T) {
+	provider, tracer := mocktrace.NewTracerProviderAndTracer(instrumentationName)
+	global.SetTracerProvider(provider)
+
+	content := []byte("Hello, world!")
+
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if _, err := w.Write(content); err != nil {
+			t.Fatal(err)
+		}
+	}))
+	defer ts.Close()
+
+	context, span := tracer.Start(context.Background(), "parent")
+	defer span.End()
+
+	res, err := Get(context, ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+
+	res, err = Head(context, ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+
+	res, err = Post(context, ts.URL, "text/plain", strings.NewReader("test"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+
+	form := make(url.Values)
+	form.Set("foo", "bar")
+	res, err = PostForm(context, ts.URL, form)
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+
+	spans := tracer.EndedSpans()
+	assert.Equal(t, 4, len(spans))
+	assert.Equal(t, "GET", spans[0].Name)
+	assert.Equal(t, "HEAD", spans[1].Name)
+	assert.Equal(t, "POST", spans[2].Name)
+	assert.Equal(t, "POST", spans[3].Name)
+}