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server.go
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server.go
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// Copyright (c) 2017 Uber Technologies, Inc.
//
// 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 httpserver
import (
"encoding/json"
"errors"
"fmt"
"net/http"
"strings"
"github.com/uber/jaeger-lib/metrics"
tSampling "github.com/jaegertracing/jaeger/thrift-gen/sampling"
)
const mimeTypeApplicationJSON = "application/json"
var (
errBadRequest = errors.New("Bad request")
)
// NewHTTPServer creates a new server that hosts an HTTP/JSON endpoint for clients
// to query for sampling strategies and baggage restrictions.
func NewHTTPServer(hostPort string, manager ClientConfigManager, mFactory metrics.Factory) *http.Server {
handler := newHTTPHandler(manager, mFactory)
mux := http.NewServeMux()
mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
handler.serveSamplingHTTP(w, r, true /* thriftEnums092 */)
})
mux.HandleFunc("/sampling", func(w http.ResponseWriter, r *http.Request) {
handler.serveSamplingHTTP(w, r, false /* thriftEnums092 */)
})
mux.HandleFunc("/baggageRestrictions", func(w http.ResponseWriter, r *http.Request) {
handler.serveBaggageHTTP(w, r)
})
return &http.Server{Addr: hostPort, Handler: mux}
}
func newHTTPHandler(manager ClientConfigManager, mFactory metrics.Factory) *httpHandler {
handler := &httpHandler{manager: manager}
metrics.Init(&handler.metrics, mFactory, nil)
return handler
}
type httpHandler struct {
manager ClientConfigManager
metrics struct {
// Number of good sampling requests
SamplingRequestSuccess metrics.Counter `metric:"http-server.requests" tags:"type=sampling"`
// Number of good sampling requests against the old endpoint / using Thrift 0.9.2 enum codes
LegacySamplingRequestSuccess metrics.Counter `metric:"http-server.requests" tags:"type=sampling-legacy"`
// Number of good baggage requests
BaggageRequestSuccess metrics.Counter `metric:"http-server.requests" tags:"type=baggage"`
// Number of bad requests (400s)
BadRequest metrics.Counter `metric:"http-server.errors" tags:"status=4xx,source=all"`
// Number of collector proxy failures
TCollectorProxyFailures metrics.Counter `metric:"http-server.errors" tags:"status=5xx,source=tcollector-proxy"`
// Number of bad responses due to malformed thrift
BadThriftFailures metrics.Counter `metric:"http-server.errors" tags:"status=5xx,source=thrift"`
// Number of failed response writes from http server
WriteFailures metrics.Counter `metric:"http-server.errors" tags:"status=5xx,source=write"`
}
}
func (h *httpHandler) serviceFromRequest(w http.ResponseWriter, r *http.Request) (string, error) {
services := r.URL.Query()["service"]
if len(services) != 1 {
h.metrics.BadRequest.Inc(1)
http.Error(w, "'service' parameter must be provided once", http.StatusBadRequest)
return "", errBadRequest
}
return services[0], nil
}
func (h *httpHandler) writeJSON(w http.ResponseWriter, json []byte) error {
w.Header().Add("Content-Type", mimeTypeApplicationJSON)
if _, err := w.Write(json); err != nil {
h.metrics.WriteFailures.Inc(1)
return err
}
return nil
}
func (h *httpHandler) serveSamplingHTTP(w http.ResponseWriter, r *http.Request, thriftEnums092 bool) {
service, err := h.serviceFromRequest(w, r)
if err != nil {
return
}
resp, err := h.manager.GetSamplingStrategy(service)
if err != nil {
h.metrics.TCollectorProxyFailures.Inc(1)
http.Error(w, fmt.Sprintf("tcollector error: %+v", err), http.StatusInternalServerError)
return
}
jsonBytes, err := json.Marshal(resp)
if err != nil {
h.metrics.BadThriftFailures.Inc(1)
http.Error(w, "Cannot marshall Thrift to JSON", http.StatusInternalServerError)
return
}
if thriftEnums092 {
jsonBytes = h.encodeThriftEnums092(jsonBytes)
}
if err = h.writeJSON(w, jsonBytes); err != nil {
return
}
if thriftEnums092 {
h.metrics.LegacySamplingRequestSuccess.Inc(1)
} else {
h.metrics.SamplingRequestSuccess.Inc(1)
}
}
func (h *httpHandler) serveBaggageHTTP(w http.ResponseWriter, r *http.Request) {
service, err := h.serviceFromRequest(w, r)
if err != nil {
return
}
resp, err := h.manager.GetBaggageRestrictions(service)
if err != nil {
h.metrics.TCollectorProxyFailures.Inc(1)
http.Error(w, fmt.Sprintf("tcollector error: %+v", err), http.StatusInternalServerError)
return
}
// NB. it's literally impossible for this Marshal to fail
jsonBytes, _ := json.Marshal(resp)
if err = h.writeJSON(w, jsonBytes); err != nil {
return
}
h.metrics.BaggageRequestSuccess.Inc(1)
}
var samplingStrategyTypes = []tSampling.SamplingStrategyType{
tSampling.SamplingStrategyType_PROBABILISTIC,
tSampling.SamplingStrategyType_RATE_LIMITING,
}
// Replace string enum values produced from Thrift 0.9.3 generated classes
// with integer codes produced from Thrift 0.9.2 generated classes.
//
// For example:
//
// Thrift 0.9.2 classes generate this JSON:
// {"strategyType":0,"probabilisticSampling":{"samplingRate":0.5},"rateLimitingSampling":null,"operationSampling":null}
//
// Thrift 0.9.3 classes generate this JSON:
// {"strategyType":"PROBABILISTIC","probabilisticSampling":{"samplingRate":0.5}}
func (h *httpHandler) encodeThriftEnums092(json []byte) []byte {
str := string(json)
for _, strategyType := range samplingStrategyTypes {
str = strings.Replace(
str,
fmt.Sprintf(`"strategyType":"%s"`, strategyType.String()),
fmt.Sprintf(`"strategyType":%d`, strategyType),
1,
)
}
return []byte(str)
}