Add support for proxying user connection to Alertmanager

docs/CONFIGURATION.md

@@ -49,6 +49,7 @@ alertmanager:
     - name: string
       uri: string
       timeout: duration
+      proxy: bool
 ```
 
 * `interval` - how often alerts should be refreshed, a string in
@@ -70,8 +71,12 @@ alertmanager:
    of unsee with `make run`.
 * `timeout` - timeout for requests send to this Alertmanager server, a string in
   [time.Duration](https://golang.org/pkg/time/#ParseDuration) format.
+* `proxy` - if enabled requests from user browsers to this Alertmanager will be
+            proxied via unsee. This applies to requests made when managing
+            silences via unsee (creating or expiring silences).
 
-Example:
+Example with two production Alertmanager instances running in HA mode and a
+staging instance that is also proxied:
 
 ```yaml
 alertmanager:
@@ -80,12 +85,15 @@ alertmanager:
     - name: production1
       uri: https://alertmanager1.prod.example.com
       timeout: 20s
+      proxy: false
     - name: production2
       uri: https://alertmanager2.prod.example.com
       timeout: 20s
+      proxy: false
     - name: staging
       uri: https://alertmanager.staging.example.com
       timeout: 30s
+      proxy: true
 ```
 
 Defaults:

docs/example.yaml

@@ -1,9 +1,10 @@
 alertmanager:
   interval: 60s
   servers:
-    - name: mock
-      uri: file://internal/mock/0.11.0
+    - name: local
+      uri: http://localhost:9093
       timeout: 10s
+      proxy: true
 annotations:
   default:
     hidden: false
@@ -29,6 +30,7 @@ listen:
   port: 8080
   prefix: /
 log:
+  config: false
   level: info
 jira:
   - regex: DEVOPS-[0-9]+

internal/alertmanager/dedup_test.go

@@ -16,7 +16,9 @@ import (
 func init() {
 	log.SetLevel(log.ErrorLevel)
 	for i, uri := range mock.ListAllMockURIs() {
-		alertmanager.NewAlertmanager(fmt.Sprintf("dedup-mock-%d", i), uri, time.Second)
+		name := fmt.Sprintf("dedup-mock-%d", i)
+		am := alertmanager.NewAlertmanager(name, uri, alertmanager.WithRequestTimeout(time.Second))
+		alertmanager.RegisterAlertmanager(am)
 	}
 }
 

internal/alertmanager/models.go

@@ -2,10 +2,13 @@ package alertmanager
 
 import (
 	"fmt"
+	"path"
 	"sort"
+	"strings"
 	"sync"
 	"time"
 
+	"github.com/cloudflare/unsee/internal/config"
 	"github.com/cloudflare/unsee/internal/mapper"
 	"github.com/cloudflare/unsee/internal/models"
 	"github.com/cloudflare/unsee/internal/transform"
@@ -26,9 +29,11 @@ type alertmanagerMetrics struct {
 
 // Alertmanager represents Alertmanager upstream instance
 type Alertmanager struct {
-	URI     string        `json:"uri"`
-	Timeout time.Duration `json:"timeout"`
-	Name    string        `json:"name"`
+	URI            string        `json:"uri"`
+	RequestTimeout time.Duration `json:"timeout"`
+	Name           string        `json:"name"`
+	// whenever this instance should be proxied
+	ProxyRequests bool
 	// lock protects data access while updating
 	lock sync.RWMutex
 	// fields for storing pulled data
@@ -51,7 +56,7 @@ func (am *Alertmanager) detectVersion() string {
 		return defaultVersion
 	}
 	ver := alertmanagerVersion{}
-	err = transport.ReadJSON(url, am.Timeout, &ver)
+	err = transport.ReadJSON(url, am.RequestTimeout, &ver)
 	if err != nil {
 		log.Errorf("[%s] %s request failed: %s", am.Name, url, err.Error())
 		return defaultVersion
@@ -87,7 +92,7 @@ func (am *Alertmanager) pullSilences(version string) error {
 	}
 
 	start := time.Now()
-	silences, err := mapper.GetSilences(am.URI, am.Timeout)
+	silences, err := mapper.GetSilences(am.URI, am.RequestTimeout)
 	if err != nil {
 		return err
 	}
@@ -107,14 +112,30 @@ func (am *Alertmanager) pullSilences(version string) error {
 	return nil
 }
 
+// this is the URI of this Alertmanager we put in JSON reponse
+// it's either real full URI or a proxy relative URI
+func (am *Alertmanager) publicURI() string {
+	if am.ProxyRequests {
+		sub := fmt.Sprintf("/proxy/alertmanager/%s", am.Name)
+		uri := path.Join(config.Config.Listen.Prefix, sub)
+		if strings.HasSuffix(sub, "/") {
+			// if sub path had trailing slash then add it here, since path.Join will
+			// skip it
+			return uri + "/"
+		}
+		return uri
+	}
+	return am.URI
+}
+
 func (am *Alertmanager) pullAlerts(version string) error {
 	mapper, err := mapper.GetAlertMapper(version)
 	if err != nil {
 		return err
 	}
 
 	start := time.Now()
-	groups, err := mapper.GetAlerts(am.URI, am.Timeout)
+	groups, err := mapper.GetAlerts(am.URI, am.RequestTimeout)
 	if err != nil {
 		return err
 	}
@@ -163,7 +184,7 @@ func (am *Alertmanager) pullAlerts(version string) error {
 			alert.Alertmanager = []models.AlertmanagerInstance{
 				models.AlertmanagerInstance{
 					Name:     am.Name,
-					URI:      am.URI,
+					URI:      am.publicURI(),
 					State:    alert.State,
 					StartsAt: alert.StartsAt,
 					EndsAt:   alert.EndsAt,

internal/alertmanager/upstream.go

@@ -10,31 +10,24 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
+// Option allows to pass functional options to NewAlertmanager()
+type Option func(am *Alertmanager)
+
 var (
 	upstreams = map[string]*Alertmanager{}
 )
 
 // NewAlertmanager creates a new Alertmanager instance
-func NewAlertmanager(name, uri string, timeout time.Duration) error {
-	if _, found := upstreams[name]; found {
-		return fmt.Errorf("Alertmanager upstream '%s' already exist", name)
-	}
-
-	for _, am := range upstreams {
-		if am.URI == uri {
-			return fmt.Errorf("Alertmanager upstream '%s' already collects from '%s'", am.Name, am.URI)
-		}
-	}
-
-	upstreams[name] = &Alertmanager{
-		URI:          uri,
-		Timeout:      timeout,
-		Name:         name,
-		lock:         sync.RWMutex{},
-		alertGroups:  []models.AlertGroup{},
-		silences:     map[string]models.Silence{},
-		colors:       models.LabelsColorMap{},
-		autocomplete: []models.Autocomplete{},
+func NewAlertmanager(name, uri string, opts ...Option) *Alertmanager {
+	am := &Alertmanager{
+		URI:            uri,
+		RequestTimeout: time.Second * 10,
+		Name:           name,
+		lock:           sync.RWMutex{},
+		alertGroups:    []models.AlertGroup{},
+		silences:       map[string]models.Silence{},
+		colors:         models.LabelsColorMap{},
+		autocomplete:   []models.Autocomplete{},
 		metrics: alertmanagerMetrics{
 			errors: map[string]float64{
 				labelValueErrorsAlerts:   0,
@@ -43,8 +36,27 @@ func NewAlertmanager(name, uri string, timeout time.Duration) error {
 		},
 	}
 
-	log.Infof("[%s] Configured Alertmanager source at %s", name, uri)
+	for _, opt := range opts {
+		opt(am)
+	}
+
+	return am
+}
+
+// RegisterAlertmanager will add an Alertmanager instance to the list of
+// instances used when pulling alerts from upstreams
+func RegisterAlertmanager(am *Alertmanager) error {
+	if _, found := upstreams[am.Name]; found {
+		return fmt.Errorf("Alertmanager upstream '%s' already exist", am.Name)
+	}
 
+	for _, existingAM := range upstreams {
+		if existingAM.URI == am.URI {
+			return fmt.Errorf("Alertmanager upstream '%s' already collects from '%s'", existingAM.Name, existingAM.URI)
+		}
+	}
+	upstreams[am.Name] = am
+	log.Infof("[%s] Configured Alertmanager source at %s (proxied: %v)", am.Name, am.URI, am.ProxyRequests)
 	return nil
 }
 
@@ -66,3 +78,19 @@ func GetAlertmanagerByName(name string) *Alertmanager {
 	}
 	return nil
 }
+
+// WithProxy option can be passed to NewAlertmanager in order to enable request
+// proxying for unsee clients
+func WithProxy(proxied bool) Option {
+	return func(am *Alertmanager) {
+		am.ProxyRequests = proxied
+	}
+}
+
+// WithRequestTimeout option can be passed to NewAlertmanager in order to set
+// a custom timeout for Alertmanager upstream requests
+func WithRequestTimeout(timeout time.Duration) Option {
+	return func(am *Alertmanager) {
+		am.RequestTimeout = timeout
+	}
+}

internal/config/config_test.go

@@ -53,6 +53,7 @@ func testReadConfig(t *testing.T) {
   - name: default
     uri: http://localhost
     timeout: 40s
+    proxy: false
 annotations:
   default:
     hidden: true

internal/config/models.go

@@ -6,6 +6,7 @@ type alertmanagerConfig struct {
 	Name    string
 	URI     string
 	Timeout time.Duration
+	Proxy   bool
 }
 
 type jiraRule struct {

internal/filters/filter_test.go

@@ -485,11 +485,7 @@ var tests = []filterTest{
 func TestFilters(t *testing.T) {
 	log.SetLevel(log.ErrorLevel)
 
-	err := alertmanager.NewAlertmanager("test", "http://localhost", time.Second)
-	am := alertmanager.GetAlertmanagerByName("test")
-	if err != nil {
-		t.Error(err)
-	}
+	am := alertmanager.NewAlertmanager("test", "http://localhost", alertmanager.WithRequestTimeout(time.Second))
 	for _, ft := range tests {
 		alert := models.Alert(ft.Alert)
 		if &ft.Silence != nil {

main.go

@@ -60,7 +60,8 @@ func setupRouter(router *gin.Engine) {
 
 func setupUpstreams() {
 	for _, s := range config.Config.Alertmanager.Servers {
-		err := alertmanager.NewAlertmanager(s.Name, s.URI, s.Timeout)
+		am := alertmanager.NewAlertmanager(s.Name, s.URI, alertmanager.WithRequestTimeout(s.Timeout), alertmanager.WithProxy(s.Proxy))
+		err := alertmanager.RegisterAlertmanager(am)
 		if err != nil {
 			log.Fatalf("Failed to configure Alertmanager '%s' with URI '%s': %s", s.Name, s.URI, err)
 		}
@@ -151,6 +152,9 @@ func main() {
 	}
 
 	setupRouter(router)
+	for _, am := range alertmanager.GetAlertmanagers() {
+		setupRouterProxyHandlers(router, am)
+	}
 	listen := fmt.Sprintf("%s:%d", config.Config.Listen.Address, config.Config.Listen.Port)
 	log.Infof("Listening on %s", listen)
 	err := router.Run(listen)

proxy.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httputil"
+	"net/url"
+
+	"github.com/cloudflare/unsee/internal/alertmanager"
+	"github.com/cloudflare/unsee/internal/config"
+	"github.com/gin-gonic/gin"
+
+	log "github.com/sirupsen/logrus"
+)
+
+func proxyPathPrefix(name string) string {
+	return fmt.Sprintf("%sproxy/alertmanager/%s", config.Config.Listen.Prefix, name)
+}
+
+func proxyPath(name, path string) string {
+	return fmt.Sprintf("%s%s", proxyPathPrefix(name), path)
+}
+
+// NewAlertmanagerProxy creates a proxy instance for given alertmanager instance
+func NewAlertmanagerProxy(alertmanager *alertmanager.Alertmanager) (*httputil.ReverseProxy, error) {
+	upstreamURL, err := url.Parse(alertmanager.URI)
+	if err != nil {
+		return nil, err
+	}
+	proxy := httputil.ReverseProxy{
+		Director: func(req *http.Request) {
+			req.URL.Scheme = upstreamURL.Scheme
+			req.URL.Host = upstreamURL.Host
+			// drop Accept-Encoding header so we always get uncompressed reponses from
+			// upstream, there's a gzip middleware that's global so we don't want it
+			// to gzip twice
+			req.Header.Del("Accept-Encoding")
+			log.Debugf("[%s] Proxy request for %s", alertmanager.Name, req.URL.Path)
+		},
+		ModifyResponse: func(resp *http.Response) error {
+			// drop Content-Length header from upstream responses, gzip middleware
+			// will compress those and that could cause a mismatch
+			resp.Header.Del("Content-Length")
+			return nil
+		},
+	}
+	return &proxy, nil
+}
+
+func setupRouterProxyHandlers(router *gin.Engine, alertmanager *alertmanager.Alertmanager) error {
+	proxy, err := NewAlertmanagerProxy(alertmanager)
+	if err != nil {
+		return err
+	}
+	router.POST(
+		proxyPath(alertmanager.Name, "/api/v1/silences"),
+		gin.WrapH(http.StripPrefix(proxyPathPrefix(alertmanager.Name), proxy)))
+	router.DELETE(
+		proxyPath(alertmanager.Name, "/api/v1/silence/*id"),
+		gin.WrapH(http.StripPrefix(proxyPathPrefix(alertmanager.Name), proxy)))
+	return nil
+}