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zipkin.go
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zipkin.go
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// 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 zipkin // import "go.opentelemetry.io/otel/exporters/zipkin"
import (
"bytes"
"context"
"encoding/json"
"fmt"
"io"
"log"
"net/http"
"net/url"
"sync"
"github.com/go-logr/logr"
"github.com/go-logr/stdr"
sdktrace "go.opentelemetry.io/otel/sdk/trace"
)
const (
defaultCollectorURL = "http://localhost:9411/api/v2/spans"
)
// Exporter exports spans to the zipkin collector.
type Exporter struct {
url string
client *http.Client
logger logr.Logger
stoppedMu sync.RWMutex
stopped bool
}
var _ sdktrace.SpanExporter = &Exporter{}
var emptyLogger = logr.Logger{}
// Options contains configuration for the exporter.
type config struct {
client *http.Client
logger logr.Logger
}
// Option defines a function that configures the exporter.
type Option interface {
apply(config) config
}
type optionFunc func(config) config
func (fn optionFunc) apply(cfg config) config {
return fn(cfg)
}
// WithLogger configures the exporter to use the passed logger.
// WithLogger and WithLogr will overwrite each other.
func WithLogger(logger *log.Logger) Option {
return WithLogr(stdr.New(logger))
}
// WithLogr configures the exporter to use the passed logr.Logger.
// WithLogr and WithLogger will overwrite each other.
func WithLogr(logger logr.Logger) Option {
return optionFunc(func(cfg config) config {
cfg.logger = logger
return cfg
})
}
// WithClient configures the exporter to use the passed HTTP client.
func WithClient(client *http.Client) Option {
return optionFunc(func(cfg config) config {
cfg.client = client
return cfg
})
}
// New creates a new Zipkin exporter.
func New(collectorURL string, opts ...Option) (*Exporter, error) {
if collectorURL == "" {
// Use endpoint from env var or default collector URL.
collectorURL = envOr(envEndpoint, defaultCollectorURL)
}
u, err := url.Parse(collectorURL)
if err != nil {
return nil, fmt.Errorf("invalid collector URL %q: %v", collectorURL, err)
}
if u.Scheme == "" || u.Host == "" {
return nil, fmt.Errorf("invalid collector URL %q: no scheme or host", collectorURL)
}
cfg := config{}
for _, opt := range opts {
cfg = opt.apply(cfg)
}
if cfg.client == nil {
cfg.client = http.DefaultClient
}
return &Exporter{
url: collectorURL,
client: cfg.client,
logger: cfg.logger,
}, nil
}
// ExportSpans exports spans to a Zipkin receiver.
func (e *Exporter) ExportSpans(ctx context.Context, spans []sdktrace.ReadOnlySpan) error {
e.stoppedMu.RLock()
stopped := e.stopped
e.stoppedMu.RUnlock()
if stopped {
e.logf("exporter stopped, not exporting span batch")
return nil
}
if len(spans) == 0 {
e.logf("no spans to export")
return nil
}
models := SpanModels(spans)
body, err := json.Marshal(models)
if err != nil {
return e.errf("failed to serialize zipkin models to JSON: %v", err)
}
e.logf("about to send a POST request to %s with body %s", e.url, body)
req, err := http.NewRequestWithContext(ctx, http.MethodPost, e.url, bytes.NewBuffer(body))
if err != nil {
return e.errf("failed to create request to %s: %v", e.url, err)
}
req.Header.Set("Content-Type", "application/json")
resp, err := e.client.Do(req)
if err != nil {
return e.errf("request to %s failed: %v", e.url, err)
}
defer resp.Body.Close()
// Zipkin API returns a 202 on success and the content of the body isn't interesting
// but it is still being read because according to https://golang.org/pkg/net/http/#Response
// > The default HTTP client's Transport may not reuse HTTP/1.x "keep-alive" TCP connections
// > if the Body is not read to completion and closed.
_, err = io.Copy(io.Discard, resp.Body)
if err != nil {
return e.errf("failed to read response body: %v", err)
}
if resp.StatusCode != http.StatusAccepted {
return e.errf("failed to send spans to zipkin server with status %d", resp.StatusCode)
}
return nil
}
// Shutdown stops the exporter flushing any pending exports.
func (e *Exporter) Shutdown(ctx context.Context) error {
e.stoppedMu.Lock()
e.stopped = true
e.stoppedMu.Unlock()
select {
case <-ctx.Done():
return ctx.Err()
default:
}
return nil
}
func (e *Exporter) logf(format string, args ...interface{}) {
if e.logger != emptyLogger {
e.logger.Info(fmt.Sprintf(format, args...))
}
}
func (e *Exporter) errf(format string, args ...interface{}) error {
e.logf(format, args...)
return fmt.Errorf(format, args...)
}
// MarshalLog is the marshaling function used by the logging system to represent this exporter.
func (e *Exporter) MarshalLog() interface{} {
return struct {
Type string
URL string
}{
Type: "zipkin",
URL: e.url,
}
}