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server.go
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server.go
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package server
import (
"flag"
"fmt"
"net/http"
"net/url"
"os"
"os/signal"
"path"
"sort"
"strings"
"syscall"
"text/template"
"github.com/felixge/fgprof"
"github.com/go-kit/log"
"github.com/go-kit/log/level"
"github.com/pkg/errors"
"github.com/prometheus/common/version"
serverww "github.com/weaveworks/common/server"
"github.com/pao214/loki/v2/clients/pkg/promtail/server/ui"
"github.com/pao214/loki/v2/clients/pkg/promtail/targets"
"github.com/pao214/loki/v2/clients/pkg/promtail/targets/target"
)
var (
readinessProbeFailure = "Not ready: Unable to find any logs to tail. Please verify permissions, volumes, scrape_config, etc."
readinessProbeSuccess = []byte("Ready")
)
type Server interface {
Shutdown()
Run() error
}
// Server embed weaveworks server with static file and templating capability
type server struct {
*serverww.Server
log log.Logger
tms *targets.TargetManagers
externalURL *url.URL
healthCheckTarget bool
promtailCfg string
}
// Config extends weaveworks server config
type Config struct {
serverww.Config `yaml:",inline"`
ExternalURL string `yaml:"external_url"`
HealthCheckTarget *bool `yaml:"health_check_target"`
Disable bool `yaml:"disable"`
}
// RegisterFlags with prefix registers flags where every name is prefixed by
// prefix. If prefix is a non-empty string, prefix should end with a period.
func (cfg *Config) RegisterFlagsWithPrefix(prefix string, f *flag.FlagSet) {
// NOTE: weaveworks server's config can't be registered with a prefix.
cfg.Config.RegisterFlags(f)
f.BoolVar(&cfg.Disable, prefix+"server.disable", false, "Disable the http and grpc server.")
}
// RegisterFlags adds the flags required to config this to the given FlagSet
func (cfg *Config) RegisterFlags(f *flag.FlagSet) {
cfg.RegisterFlagsWithPrefix("", f)
}
// New makes a new Server
func New(cfg Config, log log.Logger, tms *targets.TargetManagers, promtailCfg string) (Server, error) {
if cfg.Disable {
return newNoopServer(log), nil
}
wws, err := serverww.New(cfg.Config)
if err != nil {
return nil, err
}
externalURL, err := computeExternalURL(cfg.ExternalURL, cfg.HTTPListenPort)
if err != nil {
return nil, errors.Wrapf(err, "parse external URL %q", cfg.ExternalURL)
}
externalURL.Path += cfg.PathPrefix
healthCheckTargetFlag := true
if cfg.HealthCheckTarget != nil {
healthCheckTargetFlag = *cfg.HealthCheckTarget
}
serv := &server{
Server: wws,
log: log,
tms: tms,
externalURL: externalURL,
healthCheckTarget: healthCheckTargetFlag,
promtailCfg: promtailCfg,
}
serv.HTTP.Path("/").Handler(http.RedirectHandler(path.Join(serv.externalURL.Path, "/targets"), 303))
serv.HTTP.Path("/ready").Handler(http.HandlerFunc(serv.ready))
serv.HTTP.PathPrefix("/static/").Handler(http.StripPrefix(externalURL.Path, http.FileServer(ui.Assets)))
serv.HTTP.Path("/service-discovery").Handler(http.HandlerFunc(serv.serviceDiscovery))
serv.HTTP.Path("/targets").Handler(http.HandlerFunc(serv.targets))
serv.HTTP.Path("/config").Handler(http.HandlerFunc(serv.config))
serv.HTTP.Path("/debug/fgprof").Handler(fgprof.Handler())
return serv, nil
}
// serviceDiscovery serves the service discovery page.
func (s *server) serviceDiscovery(rw http.ResponseWriter, req *http.Request) {
var index []string
allTarget := s.tms.AllTargets()
for job := range allTarget {
index = append(index, job)
}
sort.Strings(index)
scrapeConfigData := struct {
Index []string
Targets map[string][]target.Target
Active []int
Dropped []int
Total []int
}{
Index: index,
Targets: make(map[string][]target.Target),
Active: make([]int, len(index)),
Dropped: make([]int, len(index)),
Total: make([]int, len(index)),
}
for i, job := range scrapeConfigData.Index {
scrapeConfigData.Targets[job] = make([]target.Target, 0, len(allTarget[job]))
scrapeConfigData.Total[i] = len(allTarget[job])
for _, t := range allTarget[job] {
// Do not display more than 100 dropped targets per job to avoid
// returning too much data to the clients.
if target.IsDropped(t) {
scrapeConfigData.Dropped[i]++
if scrapeConfigData.Dropped[i] > 100 {
continue
}
} else {
scrapeConfigData.Active[i]++
}
scrapeConfigData.Targets[job] = append(scrapeConfigData.Targets[job], t)
}
}
executeTemplate(req.Context(), rw, templateOptions{
Data: scrapeConfigData,
BuildVersion: version.Info(),
Name: "service-discovery.html",
PageTitle: "Service Discovery",
ExternalURL: s.externalURL,
TemplateFuncs: template.FuncMap{
"fileTargetDetails": func(details interface{}) map[string]int64 {
// you can't cast with a text template in go so this is a helper
return details.(map[string]int64)
},
"dropReason": func(details interface{}) string {
if reason, ok := details.(string); ok {
return reason
}
return ""
},
"numReady": func(ts []target.Target) (readies int) {
for _, t := range ts {
if t.Ready() {
readies++
}
}
return
},
},
})
}
func (s *server) config(rw http.ResponseWriter, req *http.Request) {
executeTemplate(req.Context(), rw, templateOptions{
Data: s.promtailCfg,
BuildVersion: version.Info(),
Name: "config.html",
PageTitle: "Config",
ExternalURL: s.externalURL,
})
}
// targets serves the targets page.
func (s *server) targets(rw http.ResponseWriter, req *http.Request) {
executeTemplate(req.Context(), rw, templateOptions{
Data: struct {
TargetPools map[string][]target.Target
}{
TargetPools: s.tms.ActiveTargets(),
},
BuildVersion: version.Info(),
Name: "targets.html",
PageTitle: "Targets",
ExternalURL: s.externalURL,
TemplateFuncs: template.FuncMap{
"fileTargetDetails": func(details interface{}) map[string]int64 {
// you can't cast with a text template in go so this is a helper
return details.(map[string]int64)
},
"journalTargetDetails": func(details interface{}) map[string]string {
// you can't cast with a text template in go so this is a helper
return details.(map[string]string)
},
"numReady": func(ts []target.Target) (readies int) {
for _, t := range ts {
if t.Ready() {
readies++
}
}
return
},
},
})
}
// ready serves the ready endpoint
func (s *server) ready(rw http.ResponseWriter, _ *http.Request) {
if s.healthCheckTarget && !s.tms.Ready() {
http.Error(rw, readinessProbeFailure, http.StatusInternalServerError)
return
}
rw.WriteHeader(http.StatusOK)
if _, err := rw.Write(readinessProbeSuccess); err != nil {
level.Error(s.log).Log("msg", "error writing success message", "error", err)
}
}
// computeExternalURL computes a sanitized external URL from a raw input. It infers unset
// URL parts from the OS and the given listen address.
func computeExternalURL(u string, port int) (*url.URL, error) {
if u == "" {
hostname, err := os.Hostname()
if err != nil {
return nil, err
}
u = fmt.Sprintf("http://%s:%d/", hostname, port)
}
eu, err := url.Parse(u)
if err != nil {
return nil, err
}
ppref := strings.TrimRight(eu.Path, "/")
if ppref != "" && !strings.HasPrefix(ppref, "/") {
ppref = "/" + ppref
}
eu.Path = ppref
return eu, nil
}
type noopServer struct {
log log.Logger
sigs chan os.Signal
}
func newNoopServer(log log.Logger) *noopServer {
return &noopServer{
log: log,
sigs: make(chan os.Signal, 1),
}
}
func (s *noopServer) Run() error {
signal.Notify(s.sigs, syscall.SIGINT, syscall.SIGTERM)
sig := <-s.sigs
level.Info(s.log).Log("msg", "received shutdown signal", "sig", sig)
return nil
}
func (s *noopServer) Shutdown() {
s.sigs <- syscall.SIGTERM
}