Add go-kit instrumentation library (#456)

* Add go-kit instrumentation library

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

* Add missing dependabot check

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

* Improve test coverage

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

* Add otelkit example

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

* Add otelkit to documentation

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

* Add example to dependabot

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

* Use RecordError for load balancer retried errors

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

.github/dependabot.yml

@@ -456,3 +456,23 @@ updates:
     schedule:
       interval: "weekly"
       day: "sunday"
+  -
+    package-ecosystem: "gomod"
+    directory: "/instrumentation/github.com/go-kit/kit/otelkit"
+    labels:
+      - dependencies
+      - go
+      - "Skip Changelog"
+    schedule:
+      interval: "weekly"
+      day: "sunday"
+  -
+    package-ecosystem: "gomod"
+    directory: "/instrumentation/github.com/go-kit/kit/otelkit/example"
+    labels:
+      - dependencies
+      - go
+      - "Skip Changelog"
+    schedule:
+      interval: "weekly"
+      day: "sunday"

instrumentation/README.md

@@ -12,6 +12,7 @@ The following instrumentation packages are provided for popular Go packages and
 | [github.com/bradfitz/gomemcache](./github.com/bradfitz/gomemcache/memcache/otelmemcache) |  | ✓ |
 | [github.com/emicklei/go-restful](./github.com/emicklei/go-restful/otelrestful) |  | ✓ |
 | [github.com/gin-gonic/gin](./github.com/gin-gonic/gin/otelgin) |  | ✓ |
+| [github.com/go-kit/kit](./github.com/go-kit/kit/otelkit) |  | ✓ |
 | [github.com/gocql/gocql](./github.com/gocql/gocql/otelgocql) | ✓ | ✓ |
 | [github.com/gorilla/mux](./github.com/gorilla/mux/otelmux) |  | ✓ |
 | [github.com/labstack/echo](./github.com/labstack/echo/otelecho) |  | ✓ |

instrumentation/github.com/go-kit/kit/otelkit/config.go

@@ -0,0 +1,98 @@
+// 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.
+
+// Based on https://github.com/go-kit/kit/blob/3796a6b25f5c6c545454d3ed7187c4ced258083d/tracing/opencensus/endpoint_options.go
+
+package otelkit
+
+import (
+	"context"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/trace"
+)
+
+// config holds the options for tracing an endpoint.
+type config struct {
+	// TracerProvider provides access to instrumentation Tracers.
+	TracerProvider trace.TracerProvider
+
+	// IgnoreBusinessError if set to true will not treat a business error
+	// identified through the endpoint.Failer interface as a span error.
+	IgnoreBusinessError bool
+
+	// Operation identifies the current operation and serves as a span name.
+	Operation string
+
+	// GetOperation is an optional function that can set the span name based on the existing operation
+	// for the endpoint and information in the context.
+	//
+	// If the function is nil, or the returned operation is empty, the existing operation for the endpoint is used.
+	GetOperation func(ctx context.Context, operation string) string
+
+	// Attributes holds the default attributes for each span created by this middleware.
+	Attributes []attribute.KeyValue
+
+	// GetAttributes is an optional function that can extract trace attributes
+	// from the context and add them to the span.
+	GetAttributes func(ctx context.Context) []attribute.KeyValue
+}
+
+// Option configures an EndpointMiddleware.
+type Option func(*config)
+
+// WithTracerProvider specifies a tracer provider to use for creating a tracer.
+// If none is specified, the global provider is used.
+func WithTracerProvider(provider trace.TracerProvider) Option {
+	return func(o *config) {
+		o.TracerProvider = provider
+	}
+}
+
+// WithIgnoreBusinessError if set to true will not treat a business error
+// identified through the endpoint.Failer interface as a span error.
+func WithIgnoreBusinessError(val bool) Option {
+	return func(o *config) {
+		o.IgnoreBusinessError = val
+	}
+}
+
+// WithOperation sets an operation name for an endpoint.
+// Use this when you register a middleware for each endpoint.
+func WithOperation(operation string) Option {
+	return func(o *config) {
+		o.Operation = operation
+	}
+}
+
+// WithOperationGetter sets an operation name getter function in config.
+func WithOperationGetter(fn func(ctx context.Context, name string) string) Option {
+	return func(o *config) {
+		o.GetOperation = fn
+	}
+}
+
+// WithAttributes sets the default attributes for the spans created by the Endpoint tracer.
+func WithAttributes(attrs ...attribute.KeyValue) Option {
+	return func(o *config) {
+		o.Attributes = attrs
+	}
+}
+
+// WithAttributeGetter extracts additional attributes from the context.
+func WithAttributeGetter(fn func(ctx context.Context) []attribute.KeyValue) Option {
+	return func(o *config) {
+		o.GetAttributes = fn
+	}
+}

instrumentation/github.com/go-kit/kit/otelkit/doc.go

@@ -0,0 +1,22 @@
+// 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 otelkit instruments the github.com/go-kit/kit package.
+//
+// Compared to other instrumentation libraries provided by go-kit itself,
+// this package only provides instrumentation for the endpoint layer.
+// For instrumenting the transport layer,
+// look at the instrumentation libraries provided by go.opentelemetry.io/contrib.
+// Learn more about go-kit's layers at https://gokit.io/faq/#architecture-and-design.
+package otelkit // import "go.opentelemetry.io/contrib/instrumentation/github.com/go-kit/kit/otelkit"

instrumentation/github.com/go-kit/kit/otelkit/endpoint.go

@@ -0,0 +1,129 @@
+// 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.
+
+// Based on https://github.com/go-kit/kit/blob/3796a6b25f5c6c545454d3ed7187c4ced258083d/tracing/opencensus/endpoint.go
+
+package otelkit
+
+import (
+	"context"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/codes"
+	"go.opentelemetry.io/otel/trace"
+
+	otelcontrib "go.opentelemetry.io/contrib"
+
+	"github.com/go-kit/kit/endpoint"
+	"github.com/go-kit/kit/sd/lb"
+)
+
+const (
+	tracerName = "go.opentelemetry.io/contrib/instrumentation/github.com/go-kit/kit/otelkit"
+
+	// defaultSpanName is the default endpoint span name to use.
+	defaultSpanName = "gokit/endpoint"
+)
+
+// EndpointMiddleware returns an Endpoint middleware, tracing a Go kit endpoint.
+// This endpoint middleware should be used in combination with a Go kit Transport
+// tracing middleware, generic OpenTelemetry transport middleware or custom before
+// and after transport functions.
+func EndpointMiddleware(options ...Option) endpoint.Middleware {
+	cfg := &config{}
+
+	for _, o := range options {
+		o(cfg)
+	}
+
+	if cfg.TracerProvider == nil {
+		cfg.TracerProvider = otel.GetTracerProvider()
+	}
+
+	tracer := cfg.TracerProvider.Tracer(
+		tracerName,
+		trace.WithInstrumentationVersion(otelcontrib.SemVersion()),
+	)
+
+	return func(next endpoint.Endpoint) endpoint.Endpoint {
+		return func(ctx context.Context, request interface{}) (response interface{}, err error) {
+			operation := cfg.Operation
+			if cfg.GetOperation != nil {
+				if newOperation := cfg.GetOperation(ctx, operation); newOperation != "" {
+					operation = newOperation
+				}
+			}
+
+			spanName := operation
+			if spanName == "" {
+				spanName = defaultSpanName
+			}
+
+			opts := []trace.SpanOption{
+				trace.WithAttributes(cfg.Attributes...),
+				trace.WithSpanKind(trace.SpanKindServer),
+			}
+
+			if cfg.GetAttributes != nil {
+				opts = append(opts, trace.WithAttributes(cfg.GetAttributes(ctx)...))
+			}
+
+			ctx, span := tracer.Start(ctx, spanName, opts...)
+			defer span.End()
+
+			defer func() {
+				if err != nil {
+					if lberr, ok := err.(lb.RetryError); ok {
+						// Handle errors originating from lb.Retry.
+						for idx, rawErr := range lberr.RawErrors {
+							span.RecordError(rawErr, trace.WithAttributes(
+								attribute.Int("gokit.lb.retry.count", idx+1),
+							))
+						}
+
+						span.RecordError(lberr.Final)
+
+						return
+					}
+
+					// generic error
+					span.RecordError(err)
+
+					return
+				}
+
+				// Test for business error. Business errors are often
+				// successful requests carrying a business failure that
+				// the client can act upon and therefore do not count
+				// as failed requests.
+				if res, ok := response.(endpoint.Failer); ok && res.Failed() != nil {
+					span.RecordError(res.Failed())
+
+					if cfg.IgnoreBusinessError {
+						span.SetStatus(codes.Unset, "")
+					}
+
+					return
+				}
+
+				// no errors identified
+			}()
+
+			response, err = next(ctx, request)
+
+			return
+		}
+	}
+}