Alerting: Refactor readiness check (#78799)

* Alerting: Refactor readiness check

Moves the readiness check to the mimir client and removes the need to assert that we have senders - it already has a queue and can hold notifications until we're ready to send them.
---------

Signed-off-by: gotjosh <josue.abreu@gmail.com>

pkg/services/ngalert/remote/alertmanager.go

@@ -6,26 +6,20 @@ import (
 	"fmt"
 	"net/http"
 	"net/url"
-	"strings"
-	"time"
 
-	httptransport "github.com/go-openapi/runtime/client"
 	"github.com/go-openapi/strfmt"
 	"github.com/grafana/grafana/pkg/infra/log"
 	apimodels "github.com/grafana/grafana/pkg/services/ngalert/api/tooling/definitions"
 	"github.com/grafana/grafana/pkg/services/ngalert/models"
 	"github.com/grafana/grafana/pkg/services/ngalert/notifier"
-	mimirClient "github.com/grafana/grafana/pkg/services/ngalert/remote/client"
+	remoteClient "github.com/grafana/grafana/pkg/services/ngalert/remote/client"
 	"github.com/grafana/grafana/pkg/services/ngalert/sender"
-	amclient "github.com/prometheus/alertmanager/api/v2/client"
 	amalert "github.com/prometheus/alertmanager/api/v2/client/alert"
 	amalertgroup "github.com/prometheus/alertmanager/api/v2/client/alertgroup"
 	amreceiver "github.com/prometheus/alertmanager/api/v2/client/receiver"
 	amsilence "github.com/prometheus/alertmanager/api/v2/client/silence"
 )
 
-const readyPath = "/-/ready"
-
 type stateStore interface {
 	GetFullState(ctx context.Context, keys ...string) (string, error)
 }
@@ -39,9 +33,8 @@ type Alertmanager struct {
 	tenantID string
 	url      string
 
-	amClient    *amclient.AlertmanagerAPI
-	httpClient  *http.Client
-	mimirClient mimirClient.MimirClient
+	amClient    *remoteClient.Alertmanager
+	mimirClient remoteClient.MimirClient
 }
 
 type AlertmanagerConfig struct {
@@ -50,15 +43,7 @@ type AlertmanagerConfig struct {
 	BasicAuthPassword string
 }
 
-func NewAlertmanager(cfg AlertmanagerConfig, orgID int64, stateStore stateStore) (*Alertmanager, error) {
-	client := http.Client{
-		Transport: &mimirClient.MimirAuthRoundTripper{
-			TenantID: cfg.TenantID,
-			Password: cfg.BasicAuthPassword,
-			Next:     http.DefaultTransport,
-		},
-	}
-
+func NewAlertmanager(cfg AlertmanagerConfig, orgID int64, store stateStore) (*Alertmanager, error) {
 	if cfg.URL == "" {
 		return nil, fmt.Errorf("empty remote Alertmanager URL for tenant '%s'", cfg.TenantID)
 	}
@@ -70,31 +55,36 @@ func NewAlertmanager(cfg AlertmanagerConfig, orgID int64, stateStore stateStore)
 
 	logger := log.New("ngalert.remote.alertmanager")
 
-	mcCfg := &mimirClient.Config{
+	mcCfg := &remoteClient.Config{
 		URL:      u,
 		TenantID: cfg.TenantID,
 		Password: cfg.BasicAuthPassword,
 		Logger:   logger,
 	}
-
-	mc, err := mimirClient.New(mcCfg)
+	mc, err := remoteClient.New(mcCfg)
 	if err != nil {
 		return nil, err
 	}
 
-	u = u.JoinPath("/alertmanager", amclient.DefaultBasePath)
-	transport := httptransport.NewWithClient(u.Host, u.Path, []string{u.Scheme}, &client)
+	amcCfg := &remoteClient.AlertmanagerConfig{
+		URL:      u,
+		TenantID: cfg.TenantID,
+		Password: cfg.BasicAuthPassword,
+		Logger:   logger,
+	}
+	amc, err := remoteClient.NewAlertmanager(amcCfg)
+	if err != nil {
+		return nil, err
+	}
 
-	// Using our client with custom headers and basic auth credentials.
+	// Configure and start the components that sends alerts.
+	c := amc.GetAuthedClient()
 	doFunc := func(ctx context.Context, _ *http.Client, req *http.Request) (*http.Response, error) {
-		return client.Do(req.WithContext(ctx))
+		return c.Do(req.WithContext(ctx))
 	}
 	s := sender.NewExternalAlertmanagerSender(sender.WithDoFunc(doFunc))
 	s.Run()
-
-	err = s.ApplyConfig(orgID, 0, []sender.ExternalAMcfg{{
-		URL: cfg.URL + "/alertmanager",
-	}})
+	err = s.ApplyConfig(orgID, 0, []sender.ExternalAMcfg{{URL: cfg.URL + "/alertmanager"}})
 	if err != nil {
 		return nil, err
 	}
@@ -102,9 +92,8 @@ func NewAlertmanager(cfg AlertmanagerConfig, orgID int64, stateStore stateStore)
 	return &Alertmanager{
 		log:         logger,
 		mimirClient: mc,
-		amClient:    amclient.New(transport, nil),
-		httpClient:  &client,
-		state:       stateStore,
+		state:       store,
+		amClient:    amc,
 		sender:      s,
 		orgID:       orgID,
 		tenantID:    cfg.TenantID,
@@ -157,45 +146,18 @@ func (am *Alertmanager) ApplyConfig(ctx context.Context, config *models.AlertCon
 }
 
 func (am *Alertmanager) checkReadiness(ctx context.Context) error {
-	readyURL := strings.TrimSuffix(am.url, "/") + "/alertmanager" + readyPath
-	req, err := http.NewRequestWithContext(ctx, http.MethodGet, readyURL, nil)
+	ready, err := am.amClient.IsReadyWithBackoff(ctx)
 	if err != nil {
-		return fmt.Errorf("error creating readiness request: %w", err)
+		return err
 	}
 
-	res, err := am.httpClient.Do(req)
-	if err != nil {
-		return fmt.Errorf("error performing readiness check: %w", err)
+	if ready {
+		am.log.Debug("Alertmanager readiness check successful")
+		am.ready = true
+		return nil
 	}
 
-	defer func() {
-		if err := res.Body.Close(); err != nil {
-			am.log.Warn("Error closing response body", "err", err)
-		}
-	}()
-
-	if res.StatusCode != http.StatusOK {
-		return fmt.Errorf("%w, status code: %d", notifier.ErrAlertmanagerNotReady, res.StatusCode)
-	}
-
-	// Wait for active senders.
-	var attempts int
-	ticker := time.NewTicker(100 * time.Millisecond)
-	defer ticker.Stop()
-
-	for {
-		select {
-		case <-ticker.C:
-			attempts++
-			if len(am.sender.Alertmanagers()) > 0 {
-				am.log.Debug("Alertmanager readiness check successful", "attempts", attempts)
-				am.ready = true
-				return nil
-			}
-		case <-time.After(10 * time.Second):
-			return notifier.ErrAlertmanagerNotReady
-		}
-	}
+	return notifier.ErrAlertmanagerNotReady
 }
 
 func (am *Alertmanager) SaveAndApplyConfig(ctx context.Context, cfg *apimodels.PostableUserConfig) error {

pkg/services/ngalert/remote/alertmanager_test.go

@@ -78,7 +78,6 @@ func TestNewAlertmanager(t *testing.T) {
 			require.Equal(tt, am.url, test.url)
 			require.Equal(tt, am.orgID, test.orgID)
 			require.NotNil(tt, am.amClient)
-			require.NotNil(tt, am.httpClient)
 		})
 	}
 }
@@ -340,6 +339,9 @@ func TestIntegrationRemoteAlertmanagerAlerts(t *testing.T) {
 	// Wait until the Alertmanager is ready to send alerts.
 	require.NoError(t, am.checkReadiness(context.Background()))
 	require.True(t, am.Ready())
+	require.Eventually(t, func() bool {
+		return len(am.sender.Alertmanagers()) > 0
+	}, 10*time.Second, 500*time.Millisecond)
 
 	// We should have no alerts and no groups at first.
 	alerts, err := am.GetAlerts(context.Background(), true, true, true, []string{}, "")

pkg/services/ngalert/remote/client/alertmanager.go

@@ -0,0 +1,114 @@
+package client
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/url"
+	"time"
+
+	httptransport "github.com/go-openapi/runtime/client"
+	"github.com/grafana/grafana/pkg/infra/log"
+	amclient "github.com/prometheus/alertmanager/api/v2/client"
+)
+
+const alertmanagerAPIMountPath = "/alertmanager"
+const alertmanagerReadyPath = "/-/ready"
+
+type AlertmanagerConfig struct {
+	TenantID string
+	Password string
+	URL      *url.URL
+	Logger   log.Logger
+}
+
+type Alertmanager struct {
+	*amclient.AlertmanagerAPI
+	httpClient *http.Client
+	url        *url.URL
+	logger     log.Logger
+}
+
+func NewAlertmanager(cfg *AlertmanagerConfig) (*Alertmanager, error) {
+	// First, add the authentication middleware.
+	c := &http.Client{Transport: &MimirAuthRoundTripper{
+		TenantID: cfg.TenantID,
+		Password: cfg.Password,
+		Next:     http.DefaultTransport,
+	}}
+
+	apiEndpoint := *cfg.URL
+
+	// Next, make sure you set the right path.
+	u := apiEndpoint.JoinPath(alertmanagerAPIMountPath, amclient.DefaultBasePath)
+	transport := httptransport.NewWithClient(u.Host, u.Path, []string{u.Scheme}, c)
+
+	return &Alertmanager{
+		logger:          cfg.Logger,
+		url:             cfg.URL,
+		AlertmanagerAPI: amclient.New(transport, nil),
+		httpClient:      c,
+	}, nil
+}
+
+// GetAuthedClient returns a *http.Client that includes a configured MimirAuthRoundTripper.
+// Requests using this client are fully authenticated.
+func (am *Alertmanager) GetAuthedClient() *http.Client {
+	return am.httpClient
+}
+
+// IsReadyWithBackoff executes a readiness check against the `/-/ready` Alertmanager endpoint.
+// If it takes more than 10s to get a response back - we abort the check.
+func (am *Alertmanager) IsReadyWithBackoff(ctx context.Context) (bool, error) {
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	readyURL := am.url.JoinPath(am.url.Path, alertmanagerAPIMountPath, alertmanagerReadyPath)
+
+	attempt := func() (int, error) {
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, readyURL.String(), nil)
+		if err != nil {
+			return 0, fmt.Errorf("error creating the readiness request: %w", err)
+		}
+
+		res, err := am.httpClient.Do(req)
+		if err != nil {
+			return 0, fmt.Errorf("error performing the readiness check: %w", err)
+		}
+
+		defer func() {
+			if err := res.Body.Close(); err != nil {
+				am.logger.Warn("Error closing response body", "err", err)
+			}
+		}()
+
+		return res.StatusCode, nil
+	}
+
+	var attempts int
+	ticker := time.NewTicker(100 * time.Millisecond)
+	deadlineCh := time.After(10 * time.Second)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			attempts++
+			status, err := attempt()
+			if err != nil {
+				am.logger.Debug("Ready check attempt failed", "attempt", attempts, "err", err)
+				continue
+			}
+
+			if status != http.StatusOK {
+				am.logger.Debug("Ready check failed, status code is not 200", "attempt", attempts, "status", status, "err", err)
+				continue
+			}
+
+			return true, nil
+		case <-deadlineCh:
+			cancel()
+			return false, fmt.Errorf("ready check timed out after %d attempts", attempts)
+		}
+	}
+}