prometheus

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// Copyright 2020 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package eureka
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import (
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	"context"
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	"encoding/xml"
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	"fmt"
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	"io"
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	"net/http"
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	"github.com/prometheus/common/version"
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)
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var userAgent = fmt.Sprintf("Prometheus/%s", version.Version)
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type Applications struct {
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	VersionsDelta int           `xml:"versions__delta"`
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	AppsHashcode  string        `xml:"apps__hashcode"`
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	Applications  []Application `xml:"application"`
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}
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type Application struct {
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	Name      string     `xml:"name"`
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	Instances []Instance `xml:"instance"`
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}
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type Port struct {
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	Port    int  `xml:",chardata"`
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	Enabled bool `xml:"enabled,attr"`
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}
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type Instance struct {
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	HostName                      string          `xml:"hostName"`
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	HomePageURL                   string          `xml:"homePageUrl"`
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	StatusPageURL                 string          `xml:"statusPageUrl"`
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	HealthCheckURL                string          `xml:"healthCheckUrl"`
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	App                           string          `xml:"app"`
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	IPAddr                        string          `xml:"ipAddr"`
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	VipAddress                    string          `xml:"vipAddress"`
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	SecureVipAddress              string          `xml:"secureVipAddress"`
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	Status                        string          `xml:"status"`
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	Port                          *Port           `xml:"port"`
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	SecurePort                    *Port           `xml:"securePort"`
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	DataCenterInfo                *DataCenterInfo `xml:"dataCenterInfo"`
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	Metadata                      *MetaData       `xml:"metadata"`
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	IsCoordinatingDiscoveryServer bool            `xml:"isCoordinatingDiscoveryServer"`
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	ActionType                    string          `xml:"actionType"`
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	CountryID                     int             `xml:"countryId"`
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	InstanceID                    string          `xml:"instanceId"`
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}
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type MetaData struct {
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	Items []Tag `xml:",any"`
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}
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type Tag struct {
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	XMLName xml.Name
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	Content string `xml:",innerxml"`
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}
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type DataCenterInfo struct {
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	Name     string    `xml:"name"`
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	Class    string    `xml:"class,attr"`
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	Metadata *MetaData `xml:"metadata"`
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}
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const appListPath string = "/apps"
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func fetchApps(ctx context.Context, server string, client *http.Client) (*Applications, error) {
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	url := fmt.Sprintf("%s%s", server, appListPath)
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	request, err := http.NewRequest(http.MethodGet, url, nil)
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	if err != nil {
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		return nil, err
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	}
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	request = request.WithContext(ctx)
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	request.Header.Add("User-Agent", userAgent)
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	resp, err := client.Do(request)
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	if err != nil {
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		return nil, err
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	}
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	defer func() {
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		io.Copy(io.Discard, resp.Body)
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		resp.Body.Close()
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	}()
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	if resp.StatusCode/100 != 2 {
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		return nil, fmt.Errorf("non 2xx status '%d' response during eureka service discovery", resp.StatusCode)
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	}
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	var apps Applications
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	err = xml.NewDecoder(resp.Body).Decode(&apps)
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	if err != nil {
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		return nil, fmt.Errorf("%q: %w", url, err)
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	}
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	return &apps, nil
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}
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