Instana tracer implementation

vendor/github.com/instana/go-sensor/agent.go

@@ -0,0 +1,183 @@
+package instana
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"strconv"
+	"time"
+)
+
+const (
+	agentDiscoveryURL = "/com.instana.plugin.golang.discovery"
+	agentTracesURL    = "/com.instana.plugin.golang/traces."
+	agentDataURL      = "/com.instana.plugin.golang."
+	agentEventURL     = "/com.instana.plugin.generic.event"
+	agentDefaultHost  = "localhost"
+	agentDefaultPort  = 42699
+	agentHeader       = "Instana Agent"
+)
+
+type agentResponse struct {
+	Pid    uint32 `json:"pid"`
+	HostID string `json:"agentUuid"`
+}
+
+type discoveryS struct {
+	PID   int      `json:"pid"`
+	Name  string   `json:"name"`
+	Args  []string `json:"args"`
+	Fd    string   `json:"fd"`
+	Inode string   `json:"inode"`
+}
+
+type fromS struct {
+	PID    string `json:"e"`
+	HostID string `json:"h"`
+}
+
+type agentS struct {
+	sensor *sensorS
+	fsm    *fsmS
+	from   *fromS
+	host   string
+	client *http.Client
+}
+
+func (r *agentS) init() {
+	r.client = &http.Client{Timeout: 5 * time.Second}
+	r.fsm = r.initFsm()
+	r.setFrom(&fromS{})
+}
+
+func (r *agentS) makeURL(prefix string) string {
+	return r.makeHostURL(r.host, prefix)
+}
+
+func (r *agentS) makeHostURL(host string, prefix string) string {
+	envPort := os.Getenv("INSTANA_AGENT_PORT")
+	port := agentDefaultPort
+	if r.sensor.options.AgentPort > 0 {
+		return r.makeFullURL(host, r.sensor.options.AgentPort, prefix)
+	}
+	if envPort == "" {
+		return r.makeFullURL(host, port, prefix)
+	}
+	port, err := strconv.Atoi(envPort)
+	if err != nil {
+		return r.makeFullURL(host, agentDefaultPort, prefix)
+	}
+	return r.makeFullURL(host, port, prefix)
+}
+
+func (r *agentS) makeFullURL(host string, port int, prefix string) string {
+	var buffer bytes.Buffer
+
+	buffer.WriteString("http://")
+	buffer.WriteString(host)
+	buffer.WriteString(":")
+	buffer.WriteString(strconv.Itoa(port))
+	buffer.WriteString(prefix)
+	if prefix[len(prefix)-1:] == "." && r.from.PID != "" {
+		buffer.WriteString(r.from.PID)
+	}
+
+	return buffer.String()
+}
+
+func (r *agentS) head(url string) (string, error) {
+	return r.request(url, "HEAD", nil)
+}
+
+func (r *agentS) request(url string, method string, data interface{}) (string, error) {
+	return r.fullRequestResponse(url, method, data, nil, "")
+}
+
+func (r *agentS) requestResponse(url string, method string, data interface{}, ret interface{}) (string, error) {
+	return r.fullRequestResponse(url, method, data, ret, "")
+}
+
+func (r *agentS) requestHeader(url string, method string, header string) (string, error) {
+	return r.fullRequestResponse(url, method, nil, nil, header)
+}
+
+func (r *agentS) fullRequestResponse(url string, method string, data interface{}, body interface{}, header string) (string, error) {
+	var j []byte
+	var ret string
+	var err error
+	var resp *http.Response
+	var req *http.Request
+	if data != nil {
+		j, err = json.Marshal(data)
+	}
+
+	if err == nil {
+		if j != nil {
+			req, err = http.NewRequest(method, url, bytes.NewBuffer(j))
+		} else {
+			req, err = http.NewRequest(method, url, nil)
+		}
+
+		if err == nil {
+			req.Header.Set("Content-Type", "application/json")
+			resp, err = r.client.Do(req)
+			if err == nil {
+				defer resp.Body.Close()
+
+				if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+					err = errors.New(resp.Status)
+				} else {
+
+					log.debug("agent response:", url, resp.Status)
+
+					if body != nil {
+						var b []byte
+						b, err = ioutil.ReadAll(resp.Body)
+						json.Unmarshal(b, body)
+					}
+
+					if header != "" {
+						ret = resp.Header.Get(header)
+					}
+				}
+			}
+		}
+	}
+
+	if err != nil {
+		// Ignore errors while in announced stated (before ready) as
+		// this is the time where the entity is registering in the Instana
+		// backend and it will return 404 until it's done.
+		if !r.sensor.agent.fsm.fsm.Is("announced") {
+			log.info(err, url)
+		}
+	}
+
+	return ret, err
+}
+
+func (r *agentS) setFrom(from *fromS) {
+	r.from = from
+}
+
+func (r *agentS) setHost(host string) {
+	r.host = host
+}
+
+func (r *agentS) reset() {
+	r.fsm.reset()
+}
+
+func (r *sensorS) initAgent() *agentS {
+
+	log.debug("initializing agent")
+
+	ret := new(agentS)
+	ret.sensor = r
+	ret.init()
+
+	return ret
+}