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Unverified Commit b34068a9 authored by Dean's avatar Dean Committed by GitHub
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Merge pull request #5 from whats-this/feature/elastic-metrics 

Elasticsearch metrics
parents 714acaed ef25c3bf
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.editorconfig
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− 0
View file @ b34068a9
......@@ -2,6 +2,10 @@
indent_style = tab
indent_size = 8
[*.json]
indent_style = space
indent_size = 2
[*.sql]
indent_style = space
indent_size = 2
......
.gitignore
+ 3
− 0
View file @ b34068a9
......@@ -19,5 +19,8 @@ cdn-origin
# Package configuration file (not including sample configuration)
cdn-origin.toml
# MaxMind GeoLite2 Country database files
GeoLite2-Country.mmdb
# JetBrains .idea
.idea/
README.md
+ 15
− 21
View file @ b34068a9
# Whats-This CDN Origin
Simple but quick Golang webserver that serves requests to get files and
Simple but quick Golang webserver that serves requests to get files and
redirects from a [PostgreSQL](https://www.postgresql.org) and
[SeaweedFS](https://github.com/chrislusf/seaweedfs) backend.
......@@ -40,28 +40,22 @@ Information about configuration variables and their purpose can be found in
### Metrics
If `cdnUtil.serveMetrics` is enabled,
`/.cdn-util/prometheus/metrics?authKey={{cdnUtil.authKey}}` will return
Prometheus-compatible information about requests (and Go runtime information).
Here is a sample scrape configuration for accessing data from `cdn-origin`:
```yml
scrape_configs:
- job_name: 'cdn_origin'
scrape_interval: 5s
metrics_path: '/.cdn-util/prometheus/metrics'
params:
authKey: ['secret']
static_configs:
- targets: ['localhost:8080']
If `metrics.enable` is `true`, request metadata will be indexed in the provided
Elaticsearch server in the following format:
```js
{
"country_code": keyword,
"hostname": keyword,
"object_type": keyword,
"status_code": short,
"@timestamp": date // generated from `@timestamp` pipeline
}
```
Sample Grafana dashboards can be found in [dashboards.json](dashboards.json).
Custom metrics:
- HTTPRequestsTotal: `cdn_origin_http_requests_total{host="request Host header"}`
The index and `@timestamp` pipeline are created automatically if `cdn-origin`
has permission. Alternatively, the mapping and pipeline can be created by other
means using the `.json` files in [metrics/](metrics).
### TODO
......
cdn-origin.go
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This diff is collapsed.
cdn-origin.sample.toml
+ 37
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View file @ b34068a9
[cdnUtil]
# Authentication token for accessing /.cdn-util (supplied with query
# parameter "authKey")
authKey = "secret"
# Enable debug mode (logs requests and prints other information)
debug = false
# Serve Prometheus metrics (/.cdn-util/prometheus/metrics)
serveMetrics = true
[database]
# PostgreSQL connection URL, see
# https://godoc.org/github.com/lib/pq#hdr-Connection_String_Parameters for
# more information
connectionURL = "postgres://postgres:password@localhost/whats_this?sslmode=disable"
[http]
# Enable transparent response compression (only when the client Accepts it)
compressResponse = true
compressResponse = false
# TCP address to listen to for HTTP requests
listenAddress = ":8001"
listenAddress = ":8080"
# Trust X-Forwarded-For header from proxy (used in metrics collection)
trustProxy = false
[metrics]
# Enable metrics collection domain whitelist. When this is enabled, metrics
# will only be collected for requests with a Host header matching a domain
# in the list below.
enableWhitelist = false
# Metrics collection domain whitelist. Wildcards are supported at the
# beginning of each domain.
domainWhitelist = [
# Enable anonymized request recording (country code, hostname, object type,
# status code)
enable = false
# Elasticsearch URL to connect to for metrics, required if
# `metrics.enable == true`. See
# https://godoc.org/gopkg.in/olivere/elastic.v5/config#Parse for more
# information.
elasticURL = "http://elasticsearch:9200/cdn-origin_requests?shards=1&replicas=0"
# Enable metrics collection hostname whitelist. When this is enabled,
# metrics will only be collected for requests with a Host header matching a
# domain in the list below.
enableHostnameWhitelist = false
# Metrics collection hostname whitelist. Wildcards are supported at the
# beginning of each domain. It is recommended to rank this list by domain
# popularity at intervals to reduce match time.
#
# Since 0.4.0 `www.` prefixes will be stripped from all incoming `Host`
# headers, and don't need to be included in `metrics.hostnameWhitelist`.
hostnameWhitelist = [
"example.com",
"*.example.net",
"test.example.org"
]
[log]
# Enable debug mode (logs requests and prints other information)
debug = false
[database]
# PostgreSQL connection URL, see
# https://godoc.org/github.com/lib/pq#hdr-Connection_String_Parameters for
# more information
connectionURL = "postgres://postgres:password@localhost/whats_this?sslmode=disable"
# MaxMind GeoLite2 Country database location on disk. If omitted, no country
# code data will be collected. https://dev.maxmind.com/geoip/geoip2/geolite2
maxmindDBLocation = "/var/data/maxmind/GeoLite2-Country.mmdb"
[seaweed]
# SeaweedFS master URL (used for looking up volumes, volumes must be
......
dashboards.json deleted 100644 → 0
+ 0
− 407
View file @ 714acaed
{
"annotations": {
"list": []
},
"editable": true,
"gnetId": null,
"graphTooltip": 2,
"hideControls": false,
"id": 1,
"links": [],
"refresh": "5s",
"rows": [
{
"collapse": false,
"height": 125,
"panels": [
{
"cacheTimeout": null,
"colorBackground": false,
"colorValue": false,
"colors": [
"rgba(245, 54, 54, 0.9)",
"rgba(237, 129, 40, 0.89)",
"rgba(50, 172, 45, 0.97)"
],
"datasource": null,
"format": "none",
"gauge": {
"maxValue": 100,
"minValue": 0,
"show": false,
"thresholdLabels": false,
"thresholdMarkers": true
},
"hideTimeOverride": false,
"id": 3,
"interval": null,
"links": [],
"mappingType": 1,
"mappingTypes": [
{
"name": "value to text",
"value": 1
},
{
"name": "range to text",
"value": 2
}
],
"maxDataPoints": 100,
"minSpan": null,
"nullPointMode": "connected",
"nullText": null,
"postfix": "",
"postfixFontSize": "50%",
"prefix": "",
"prefixFontSize": "50%",
"rangeMaps": [
{
"from": "null",
"text": "N/A",
"to": "null"
}
],
"repeat": null,
"span": 6,
"sparkline": {
"fillColor": "rgba(31, 118, 189, 0.18)",
"full": false,
"lineColor": "rgb(31, 120, 193)",
"show": false
},
"tableColumn": "",
"targets": [
{
"expr": "sum(delta(cdn_origin_http_requests_total[24h]))",
"format": "time_series",
"interval": "",
"intervalFactor": 2,
"legendFormat": "",
"metric": "cdn_origin_http_requests_total",
"refId": "A",
"step": 4
}
],
"thresholds": "",
"timeFrom": null,
"title": "Requests in the Last 24 Hours",
"transparent": false,
"type": "singlestat",
"valueFontSize": "80%",
"valueMaps": [
{
"op": "=",
"text": "N/A",
"value": "null"
}
],
"valueName": "avg"
},
{
"cacheTimeout": null,
"colorBackground": false,
"colorValue": false,
"colors": [
"rgba(245, 54, 54, 0.9)",
"rgba(237, 129, 40, 0.89)",
"rgba(50, 172, 45, 0.97)"
],
"datasource": null,
"format": "none",
"gauge": {
"maxValue": 100,
"minValue": 0,
"show": false,
"thresholdLabels": false,
"thresholdMarkers": true
},
"id": 4,
"interval": null,
"links": [],
"mappingType": 1,
"mappingTypes": [
{
"name": "value to text",
"value": 1
},
{
"name": "range to text",
"value": 2
}
],
"maxDataPoints": 100,
"nullPointMode": "connected",
"nullText": null,
"postfix": "",
"postfixFontSize": "50%",
"prefix": "",
"prefixFontSize": "50%",
"rangeMaps": [
{
"from": "null",
"text": "N/A",
"to": "null"
}
],
"span": 6,
"sparkline": {
"fillColor": "rgba(31, 118, 189, 0.18)",
"full": false,
"lineColor": "rgb(31, 120, 193)",
"show": false
},
"tableColumn": "",
"targets": [
{
"expr": "sum(cdn_origin_http_requests_total)",
"format": "time_series",
"intervalFactor": 2,
"legendFormat": "",
"metric": "cdn_origin_http_requests_total",
"refId": "A",
"step": 4
}
],
"thresholds": "",
"title": "Total Requests",
"type": "singlestat",
"valueFontSize": "80%",
"valueMaps": [
{
"op": "=",
"text": "N/A",
"value": "null"
}
],
"valueName": "avg"
}
],
"repeat": null,
"repeatIteration": null,
"repeatRowId": null,
"showTitle": false,
"title": "Dashboard Row",
"titleSize": "h6"
},
{
"collapse": false,
"height": 250,
"panels": [
{
"aliasColors": {},
"bars": false,
"dashLength": 10,
"dashes": false,
"datasource": null,
"fill": 1,
"id": 5,
"legend": {
"alignAsTable": false,
"avg": false,
"current": false,
"max": false,
"min": false,
"show": true,
"total": false,
"values": false
},
"lines": true,
"linewidth": 1,
"links": [],
"nullPointMode": "null",
"percentage": false,
"pointradius": 5,
"points": false,
"renderer": "flot",
"seriesOverrides": [],
"spaceLength": 10,
"span": 12,
"stack": false,
"steppedLine": false,
"targets": [
{
"expr": "sum(idelta(cdn_origin_http_requests_total[5m]))",
"format": "time_series",
"intervalFactor": 2,
"legendFormat": "",
"refId": "A",
"step": 2
}
],
"thresholds": [],
"timeFrom": null,
"timeShift": null,
"title": "Total Requests",
"tooltip": {
"shared": true,
"sort": 0,
"value_type": "individual"
},
"type": "graph",
"xaxis": {
"buckets": null,
"mode": "time",
"name": null,
"show": true,
"values": []
},
"yaxes": [
{
"format": "short",
"label": "Requests/5s",
"logBase": 1,
"max": null,
"min": "0",
"show": true
},
{
"format": "short",
"label": null,
"logBase": 1,
"max": null,
"min": null,
"show": true
}
]
}
],
"repeat": null,
"repeatIteration": null,
"repeatRowId": null,
"showTitle": false,
"title": "Dashboard Row",
"titleSize": "h6"
},
{
"collapse": false,
"height": 284,
"panels": [
{
"aliasColors": {},
"bars": false,
"dashLength": 10,
"dashes": false,
"datasource": "PrometheusLocalhost",
"fill": 1,
"id": 2,
"legend": {
"alignAsTable": true,
"avg": true,
"current": true,
"hideEmpty": false,
"max": true,
"min": true,
"rightSide": false,
"show": true,
"total": true,
"values": true
},
"lines": true,
"linewidth": 1,
"links": [],
"nullPointMode": "null",
"percentage": false,
"pointradius": 5,
"points": false,
"renderer": "flot",
"seriesOverrides": [],
"spaceLength": 10,
"span": 12,
"stack": false,
"steppedLine": false,
"targets": [
{
"expr": "idelta(cdn_origin_http_requests_total[5m])",
"format": "time_series",
"intervalFactor": 2,
"legendFormat": "{{host}}",
"metric": "cdn_origin_http_requests_total",
"refId": "A",
"step": 2
}
],
"thresholds": [],
"timeFrom": null,
"timeShift": null,
"title": "Requests Per Host",
"tooltip": {
"shared": true,
"sort": 1,
"value_type": "individual"
},
"type": "graph",
"xaxis": {
"buckets": null,
"mode": "time",
"name": null,
"show": true,
"values": []
},
"yaxes": [
{
"format": "short",
"label": "Requests/5s",
"logBase": 1,
"max": null,
"min": "0",
"show": true
},
{
"format": "short",
"label": null,
"logBase": 1,
"max": null,
"min": null,
"show": false
}
]
}
],
"repeat": null,
"repeatIteration": null,
"repeatRowId": null,
"showTitle": false,
"title": "Dashboard Row",
"titleSize": "h6"
}
],
"schemaVersion": 14,
"style": "dark",
"tags": [],
"templating": {
"list": []
},
"time": {
"from": "now-5m",
"to": "now"
},
"timepicker": {
"refresh_intervals": [
"5s",
"10s",
"30s",
"1m",
"5m",
"15m",
"30m",
"1h",
"2h",
"1d"
],
"time_options": [
"5m",
"15m",
"1h",
"6h",
"12h",
"24h",
"2d",
"7d",
"30d"
]
},
"timezone": "browser",
"title": "cdn-origin Requests",
"version": 1
}
\ No newline at end of file
metrics/collector.go 0 → 100644
+ 229
− 0
View file @ b34068a9
package metrics
import (
"context"
"errors"
"fmt"
"net"
"strings"
log "github.com/Sirupsen/logrus"
"github.com/oschwald/maxminddb-golang"
"gopkg.in/olivere/elastic.v5"
"gopkg.in/olivere/elastic.v5/config"
)
// mapping is the default mapping to use when creating the index if it doesn't exist. This JSON data is also maintained
// in `./mapping.elasticsearch.json`.
const mapping = `
{
"settings": {
"number_of_shards": 1
},
"mappings": {
"request": {
"properties": {
"country_code": {
"type": "keyword",
"ignore_above": 2,
"index": true
},
"hostname": {
"type": "keyword",
"ignore_above": 30,
"index": true
},
"object_type": {
"type": "keyword",
"ignore_above": 30,
"index": true
},
"status_code": {
"type": "short",
"index": true
},
"@timestamp": {
"type": "date",
"index": true
}
}
}
}
}`
// The default `@timestamp` pipeline. Sets the `@timestamp` field to the ingest timestamp (date type). This JSON data is
// also maintained in `./timestampPipeline.elasticsearch.json`.
const timestampPipeline = `
{
"description": "Stores the ingest timestamp as a date field in the document.",
"processors": [
{
"set": {
"field": "@timestamp",
"value": "{{_ingest.timestamp}}"
}
},
{
"date": {
"field": "@timestamp",
"target_field": "@timestamp",
"formats": ["EEE MMM d HH:mm:ss z yyyy"]
}
}
]
}`
// Collector collects request metadata and sends it to Elasticsearch.
type Collector struct {
ctx context.Context
elastic *elastic.Client
index string
geoIPDatabase *maxminddb.Reader
enableHostnameWhitelist bool
hostnameWhitelist *treeNode
}
// New creates a new Elasticsearch connection and returns a Collector using that connection.
func New(elasticURL string, maxmindLoc string, enableHostnameWhitelist bool, hostnameWhitelist []string) (*Collector, error) {
// Parse elasticURL
cfg, err := config.Parse(elasticURL)
if err != nil {
return nil, fmt.Errorf("failed to parse elasticURL: %s", err)
}
if cfg.Index == "" {
log.Info(`empty index name in elasticURL, using "cdn-origin_requests"`)
cfg.Index = "cdn-origin_requests"
}
// Create client and ping Elasticsearch server
client, err := elastic.NewClientFromConfig(cfg)
if err != nil {
return nil, fmt.Errorf("failed to create elastic client: %s", err)
}
ctx := context.Background()
info, code, err := client.Ping(cfg.URL).Do(ctx)
if err != nil {
return nil, fmt.Errorf("failed to ping Elasticsearch server: %s", err)
}
// TODO: if code != 200
log.WithFields(log.Fields{
"statusCode": code,
"version": info.Version.Number,
}).Debug("elasticsearch ping success")
// Check if the index exists or create it
exists, err := client.IndexExists(cfg.Index).Do(ctx)
if err != nil {
return nil, fmt.Errorf("failed to determine if the index exists: %s", err)
}
if !exists {
log.WithField("index", cfg.Index).Info("creating Elasticsearch index")
createIndex, err := client.CreateIndex(cfg.Index).
BodyString(mapping).
Do(ctx)
if err != nil {
return nil, fmt.Errorf("failed to create missing index on Elasticsearchr: %s", err)
}
if !createIndex.Acknowledged {
return nil, errors.New("failed to create missing index on Elasticsearch: no acknowledged")
}
}
// Check if the timestamp pipeline exists or create it
pipelines, err := elastic.NewIngestGetPipelineService(client).
Id("timestamp").
Do(ctx)
if err != nil && !strings.Contains(err.Error(), "404") {
return nil, fmt.Errorf("failed to determine if the timestamp pipeline exists: %s", err)
}
if len(pipelines) == 0 {
log.WithField("pipeline", "timestamp").Info("creating Elasticsearch ingest pipeline")
putPipeline, err := elastic.NewIngestPutPipelineService(client).
Id("timestamp").
BodyString(timestampPipeline).
Do(ctx)
if err != nil {
return nil, fmt.Errorf("failed to put missing pipeline on Elasticsearch: %s", err)
}
if !putPipeline.Acknowledged {
return nil, errors.New("failed to put missing pipeline on Elasticsearch: not acknowledged")
}
}
// Create Maxmind GeoLite2 Country database reader
var geoIPDatabase *maxminddb.Reader
if maxmindLoc != "" {
geoIPDatabase, err = maxminddb.Open(maxmindLoc)
if err != nil {
return nil, fmt.Errorf("failed to open MaxMind GeoLite2 Country database: %s", err)
}
}
// Construct hostname whitelist *treeNode
var hostnameWhitelistTree *treeNode
if enableHostnameWhitelist {
hostnameWhitelistTree = parseWhitelistSlice(hostnameWhitelist)
}
// Create Collector
return &Collector{
ctx: ctx,
elastic: client,
index: cfg.Index,
geoIPDatabase: geoIPDatabase,
enableHostnameWhitelist: enableHostnameWhitelist,
hostnameWhitelist: hostnameWhitelistTree,
}, nil
}
// Put indexes a record in the Elasticsearch server.
func (c *Collector) Put(record *Record) error {
_, err := c.elastic.Index().
Index(c.index).
Type("request").
Pipeline("timestamp").
BodyJson(record).
Do(c.ctx)
if err != nil {
return fmt.Errorf("failed to index record: %s", err)
}
return nil
}
// MatchHostname returns an anonymized hostname and whether or not the hostname is in the whitelist.
func (c *Collector) MatchHostname(hostname string) (string, bool) {
if c.enableHostnameWhitelist {
hostSplit := strings.Split(hostname, ".")
if hostSplit[0] == "www" {
hostSplit = hostSplit[1:]
}
if match := c.hostnameWhitelist.getMatch(hostSplit); match != "" {
if strings.HasPrefix(match, "*.") {
hostSplit[0] = "*"
}
return strings.Join(hostSplit, "."), true
}
return "", false
}
return hostname, true
}
// GetCountryCode returns the country code for an IP address from the MaxMind GeoLite2 Country database.
func (c *Collector) GetCountryCode(ip net.IP) (string, error) {
if c.geoIPDatabase == nil {
return "", nil
}
geoIPRecord := getGeoIPCountryRecord()
defer returnGeoIPCountryRecord(geoIPRecord)
err := c.geoIPDatabase.Lookup(ip, &geoIPRecord)
if err != nil {
return "", err
}
return geoIPRecord.Country.IsoCode, nil
}
metrics/geoip.go 0 → 100644
+ 26
− 0
View file @ b34068a9
package metrics
import "sync"
var geoIPPool = &sync.Pool{
New: func() interface{} {
return &geoIPCountryRecord{}
},
}
func getGeoIPCountryRecord() *geoIPCountryRecord {
return geoIPPool.Get().(*geoIPCountryRecord)
}
func returnGeoIPCountryRecord(record *geoIPCountryRecord) {
go func() {
record.Country.IsoCode = ""
geoIPPool.Put(record)
}()
}
type geoIPCountryRecord struct {
Country struct {
IsoCode string `maxminddb:"iso_code"`
} `maxminddb:"country"`
}
metrics/mapping.elasticsearch.json 0 → 100644
+ 36
− 0
View file @ b34068a9
{
"settings": {
"number_of_shards": 1
},
"mappings": {
"request": {
"properties": {
"country_code": {
"type": "keyword",
"ignore_above": 2,
"index": true
},
"hostname": {
"type": "keyword",
"ignore_above": 30,
"index": true
},
"object_type": {
"type": "keyword",
"ignore_above": 30,
"index": true
},
"status_code": {
"type": "short",
"index": true
},
"@timestamp": {
"type": "date",
"index": true
}
}
}
}
}
metrics/match.go 0 → 100644
+ 69
− 0
View file @ b34068a9
package metrics
import "strings"
// treeNode is used for domain whitelisting.
type treeNode struct {
Leaf bool
Value string
FullValue string
SubNodes []*treeNode
}
func (t *treeNode) findOrCreateSubNode(v string) *treeNode {
if t.SubNodes == nil {
t.SubNodes = []*treeNode{}
}
for _, n := range t.SubNodes {
if !n.Leaf && n.Value == v {
return n
}
}
node := &treeNode{Value: v}
t.SubNodes = append(t.SubNodes, node)
return node
}
func (t *treeNode) getMatch(s []string) string {
if t.Leaf || len(t.SubNodes) == 0 || len(s) == 0 {
return ""
}
for _, node := range t.SubNodes {
if node.Value == "*" || node.Value == s[0] {
if node.Leaf {
return node.FullValue
}
if match := node.getMatch(s[1:]); match != "" {
return match
}
}
}
return ""
}
func parseWhitelistSlice(hostnameWhitelist []string) *treeNode {
// NOTE: using arrays because the provided order is important (maps would be a check if part in in map,
// then check for *, which works but doesn't maintain order)
tree := &treeNode{SubNodes: []*treeNode{}}
for _, d := range hostnameWhitelist {
split := strings.Split(d, ".")
currentNode := tree
for i, s := range split {
currentNode = currentNode.findOrCreateSubNode(s)
if i+1 == len(split) {
currentNode.Leaf = true
currentNode.FullValue = d
continue
}
if currentNode.SubNodes == nil {
currentNode.SubNodes = []*treeNode{}
}
}
}
return tree
}
metrics/record.go 0 → 100644
+ 35
− 0
View file @ b34068a9
package metrics
import "sync"
var recordPool = &sync.Pool{
New: func() interface{} {
return &Record{}
},
}
// GetRecord returns a `*Record` with all properties set to their zero values.
func GetRecord() *Record {
return recordPool.Get().(*Record)
}
// ReturnRecord returns a record to the `Record` pool. Once a record has been returned, its properties must not be
// altered.
func ReturnRecord(record *Record) {
go func() {
record.CountryCode = ""
record.Hostname = ""
record.ObjectType = ""
record.StatusCode = 0
recordPool.Put(record)
}()
}
// Record represents request metadata to be stored in Elasticsearch. When using `Record`s, it is recommended to use the
// pool methods `GetRecord()` and `ReturnRecord(*Record)` to reduce garbage colllector load and improve performance.
type Record struct {
CountryCode string `json:"country_code,omitempty"`
Hostname string `json:"hostname,omitempty"`
ObjectType string `json:"object_type,omitempty"`
StatusCode int `json:"status_code"`
}
metrics/timestampPipeline.elasticsearch.json 0 → 100644
+ 18
− 0
View file @ b34068a9
{
"description": "Stores the ingest timestamp as a date field in the document.",
"processors": [
{
"set": {
"field": "@timestamp",
"value": "{{_ingest.timestamp}}"
}
},
{
"date": {
"field": "@timestamp",
"target_field": "@timestamp",
"formats": ["EEE MMM d HH:mm:ss z yyyy"]
}
}
]
}
prometheus/metrics.go deleted 100644 → 0
+ 0
− 24
View file @ 714acaed
package prometheus
import "github.com/prometheus/client_golang/prometheus"
// namespace for use with metric names.
const namespace = "cdn_origin"
// Additional metrics to expose, prometheus.DefaultGatherer includes runtime metrics by default.
var (
// HTTPRequestsTotal records the total number of HTTP requests, partitioned by hostname.
HTTPRequestsTotal = prometheus.NewCounterVec(
prometheus.CounterOpts{
Namespace: namespace,
Name: "http_requests_total",
Help: "Total number of HTTP requests, partitioned by hostname.",
},
[]string{"host"},
)
)
func init() {
// Register metrics
prometheus.MustRegister(HTTPRequestsTotal)
}
prometheus/writer.go deleted 100644 → 0
+ 0
− 32
View file @ 714acaed
package prometheus
import (
"io"
"net/http"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/common/expfmt"
)
// WriteMetrics writes data to the supplied io.Writer in the format specified by the `Accept` header (where possible).
// The `Content-Type` of the response is returned.
func WriteMetrics(writer io.Writer, acceptHeader string) (string, error) {
metricFamilies, err := prometheus.DefaultGatherer.Gather()
if err != nil {
return "", nil
}
contentType := expfmt.Negotiate(http.Header{
"Accept": []string{acceptHeader},
})
enc := expfmt.NewEncoder(writer, contentType)
for _, metricFamily := range metricFamilies {
if err := enc.Encode(metricFamily); err != nil {
return "", err
}
}
if closer, ok := writer.(io.Closer); ok {
closer.Close()
}
return string(contentType), nil
}
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