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transport.go
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transport.go
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// Unless explicitly stated otherwise all files in this repository are licensed
// under the Apache License Version 2.0.
// This product includes software developed at Datadog (https://www.datadoghq.com/).
// Copyright 2016 Datadog, Inc.
package tracer
import (
"bytes"
"fmt"
"io"
"net"
"net/http"
"net/url"
"os"
"runtime"
"strconv"
"strings"
"sync/atomic"
"time"
traceinternal "gopkg.in/DataDog/dd-trace-go.v1/ddtrace/internal"
"gopkg.in/DataDog/dd-trace-go.v1/internal"
"gopkg.in/DataDog/dd-trace-go.v1/internal/version"
"github.com/tinylib/msgp/msgp"
)
const (
// headerComputedTopLevel specifies that the client has marked top-level spans, when set.
// Any non-empty value will mean 'yes'.
headerComputedTopLevel = "Datadog-Client-Computed-Top-Level"
)
var defaultDialer = &net.Dialer{
Timeout: 30 * time.Second,
KeepAlive: 30 * time.Second,
DualStack: true,
}
func defaultHTTPClient(timeout time.Duration) *http.Client {
if timeout == 0 {
timeout = defaultHTTPTimeout
}
return &http.Client{
Transport: &http.Transport{
Proxy: http.ProxyFromEnvironment,
DialContext: defaultDialer.DialContext,
MaxIdleConns: 100,
IdleConnTimeout: 90 * time.Second,
TLSHandshakeTimeout: 10 * time.Second,
ExpectContinueTimeout: 1 * time.Second,
},
Timeout: timeout,
}
}
const (
defaultHostname = "localhost"
defaultPort = "8126"
defaultAddress = defaultHostname + ":" + defaultPort
defaultURL = "http://" + defaultAddress
defaultHTTPTimeout = 10 * 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 communicating data to the agent.
type transport interface {
// send sends the payload p to the agent using the transport set up.
// It returns a non-nil response body when no error occurred.
send(p *payload) (body io.ReadCloser, err error)
// sendStats sends the given stats payload to the agent.
sendStats(s *statsPayload) error
// endpoint returns the URL to which the transport will send traces.
endpoint() string
}
type httpTransport struct {
traceURL string // the delivery URL for traces
statsURL string // the delivery URL for stats
client *http.Client // the HTTP client used in the POST
headers map[string]string // the Transport headers
}
// newTransport returns a new Transport implementation that sends traces to a
// trace agent at the given url, using a given *http.Client.
//
// In general, using this method is only necessary if you have a trace agent
// running on a non-default port, if it's located on another machine, or when
// otherwise needing to customize the transport layer, for instance when using
// a unix domain socket.
func newHTTPTransport(url string, client *http.Client) *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": version.Tag,
"Content-Type": "application/msgpack",
}
if cid := internal.ContainerID(); cid != "" {
defaultHeaders["Datadog-Container-ID"] = cid
}
if eid := internal.EntityID(); eid != "" {
defaultHeaders["Datadog-Entity-ID"] = eid
}
return &httpTransport{
traceURL: fmt.Sprintf("%s/v0.4/traces", url),
statsURL: fmt.Sprintf("%s/v0.6/stats", url),
client: client,
headers: defaultHeaders,
}
}
func (t *httpTransport) sendStats(p *statsPayload) error {
var buf bytes.Buffer
if err := msgp.Encode(&buf, p); err != nil {
return err
}
req, err := http.NewRequest("POST", t.statsURL, &buf)
if err != nil {
return err
}
resp, err := t.client.Do(req)
if err != nil {
return err
}
if code := resp.StatusCode; code >= 400 {
// error, check the body for context information and
// return a nice error.
msg := make([]byte, 1000)
n, _ := resp.Body.Read(msg)
resp.Body.Close()
txt := http.StatusText(code)
if n > 0 {
return fmt.Errorf("%s (Status: %s)", msg[:n], txt)
}
return fmt.Errorf("%s", txt)
}
return nil
}
func (t *httpTransport) send(p *payload) (body io.ReadCloser, err error) {
req, err := http.NewRequest("POST", t.traceURL, p)
if err != nil {
return nil, 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()))
req.Header.Set(headerComputedTopLevel, "yes")
if t, ok := traceinternal.GetGlobalTracer().(*tracer); ok {
if t.config.canComputeStats() {
req.Header.Set("Datadog-Client-Computed-Stats", "yes")
}
droppedTraces := int(atomic.SwapUint32(&t.droppedP0Traces, 0))
partialTraces := int(atomic.SwapUint32(&t.partialTraces, 0))
droppedSpans := int(atomic.SwapUint32(&t.droppedP0Spans, 0))
if stats := t.statsd; stats != nil {
stats.Count("datadog.tracer.dropped_p0_traces", int64(droppedTraces),
[]string{fmt.Sprintf("partial:%s", strconv.FormatBool(partialTraces > 0))}, 1)
stats.Count("datadog.tracer.dropped_p0_spans", int64(droppedSpans), nil, 1)
}
req.Header.Set("Datadog-Client-Dropped-P0-Traces", strconv.Itoa(droppedTraces))
req.Header.Set("Datadog-Client-Dropped-P0-Spans", strconv.Itoa(droppedSpans))
}
response, err := t.client.Do(req)
if err != nil {
return nil, err
}
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)
response.Body.Close()
txt := http.StatusText(code)
if n > 0 {
return nil, fmt.Errorf("%s (Status: %s)", msg[:n], txt)
}
return nil, fmt.Errorf("%s", txt)
}
return response.Body, nil
}
func (t *httpTransport) endpoint() string {
return t.traceURL
}
// resolveAgentAddr resolves the given agent address and fills in any missing host
// and port using the defaults. Some environment variable settings will
// take precedence over configuration.
func resolveAgentAddr() *url.URL {
var host, port string
if v := os.Getenv("DD_AGENT_HOST"); v != "" {
host = v
}
if v := os.Getenv("DD_TRACE_AGENT_PORT"); v != "" {
port = v
}
if _, err := os.Stat(defaultSocketAPM); host == "" && port == "" && err == nil {
return &url.URL{
Scheme: "unix",
Path: defaultSocketAPM,
}
}
if host == "" {
host = defaultHostname
}
if port == "" {
port = defaultPort
}
return &url.URL{
Scheme: "http",
Host: fmt.Sprintf("%s:%s", host, port),
}
}