Added integration support for DataDog APM Tracing

vendor/gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer/transport.go

@@ -0,0 +1,120 @@
+package tracer
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"runtime"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var tracerVersion = "v1.0"
+
+const (
+	defaultHostname    = "localhost"
+	defaultPort        = "8126"
+	defaultAddress     = defaultHostname + ":" + defaultPort
+	defaultHTTPTimeout = time.Second             // defines the current timeout before giving up with the send process
+	traceCountHeader   = "X-Datadog-Trace-Count" // header containing the number of traces in the payload
+)
+
+// Transport is an interface for span submission to the agent.
+type transport interface {
+	send(p *payload) error
+}
+
+// newTransport returns a new Transport implementation that sends traces to a
+// trace agent running on the given hostname and port. If the zero values for
+// hostname and port are provided, the default values will be used ("localhost"
+// for hostname, and "8126" for port).
+//
+// In general, using this method is only necessary if you have a trace agent
+// running on a non-default port or if it's located on another machine.
+func newTransport(addr string) transport {
+	return newHTTPTransport(addr)
+}
+
+// newDefaultTransport return a default transport for this tracing client
+func newDefaultTransport() transport {
+	return newHTTPTransport(defaultAddress)
+}
+
+type httpTransport struct {
+	traceURL string            // the delivery URL for traces
+	client   *http.Client      // the HTTP client used in the POST
+	headers  map[string]string // the Transport headers
+}
+
+// newHTTPTransport returns an httpTransport for the given endpoint
+func newHTTPTransport(addr string) *httpTransport {
+	// initialize the default EncoderPool with Encoder headers
+	defaultHeaders := map[string]string{
+		"Datadog-Meta-Lang":             "go",
+		"Datadog-Meta-Lang-Version":     strings.TrimPrefix(runtime.Version(), "go"),
+		"Datadog-Meta-Lang-Interpreter": runtime.Compiler + "-" + runtime.GOARCH + "-" + runtime.GOOS,
+		"Datadog-Meta-Tracer-Version":   tracerVersion,
+		"Content-Type":                  "application/msgpack",
+	}
+	host, port, _ := net.SplitHostPort(addr)
+	if host == "" {
+		host = defaultHostname
+	}
+	if port == "" {
+		port = defaultPort
+	}
+	addr = fmt.Sprintf("%s:%s", host, port)
+	return &httpTransport{
+		traceURL: fmt.Sprintf("http://%s/v0.3/traces", addr),
+		client: &http.Client{
+			// We copy the transport to avoid using the default one, as it might be
+			// augmented with tracing and we don't want these calls to be recorded.
+			// See https://golang.org/pkg/net/http/#DefaultTransport .
+			Transport: &http.Transport{
+				Proxy: http.ProxyFromEnvironment,
+				DialContext: (&net.Dialer{
+					Timeout:   30 * time.Second,
+					KeepAlive: 30 * time.Second,
+					DualStack: true,
+				}).DialContext,
+				MaxIdleConns:          100,
+				IdleConnTimeout:       90 * time.Second,
+				TLSHandshakeTimeout:   10 * time.Second,
+				ExpectContinueTimeout: 1 * time.Second,
+			},
+			Timeout: defaultHTTPTimeout,
+		},
+		headers: defaultHeaders,
+	}
+}
+
+func (t *httpTransport) send(p *payload) error {
+	// prepare the client and send the payload
+	req, err := http.NewRequest("POST", t.traceURL, p)
+	if err != nil {
+		return fmt.Errorf("cannot create http request: %v", err)
+	}
+	for header, value := range t.headers {
+		req.Header.Set(header, value)
+	}
+	req.Header.Set(traceCountHeader, strconv.Itoa(p.itemCount()))
+	req.Header.Set("Content-Length", strconv.Itoa(p.size()))
+	response, err := t.client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer response.Body.Close()
+	if code := response.StatusCode; code >= 400 {
+		// error, check the body for context information and
+		// return a nice error.
+		msg := make([]byte, 1000)
+		n, _ := response.Body.Read(msg)
+		txt := http.StatusText(code)
+		if n > 0 {
+			return fmt.Errorf("%s (Status: %s)", msg[:n], txt)
+		}
+		return fmt.Errorf("%s", txt)
+	}
+	return nil
+}