NETOBSERV-584: Support for writing logs to Loki (distributor) using gRPC (#1086)

* grpc support to write logs to Loki

* update vendors

* addressed feedback

Author: leandroberetta

docs/api.md

@@ -324,6 +324,10 @@ Following is the supported API format for writing to loki:
          timestampScale: timestamp units scale (e.g. for UNIX = 1s)
          format: the format of each line: printf (writes using golang's default map printing), fields (writes one key and value field per line) or json (default)
          reorder: reorder json map keys
+         clientProtocol: type of client protocol to use: 'http' or 'grpc' (default: 'http')
+         grpcConfig: gRPC client configuration (used only for gRPC client type)
+             keepAlive: keep alive interval
+             keepAliveTimeout: keep alive timeout
 </pre>
 ## Write Standard Output
 Following is the supported API format for writing to standard output:

go.mod

@@ -17,7 +17,7 @@ require (
 	github.com/minio/minio-go/v7 v7.0.95
 	github.com/mitchellh/mapstructure v1.5.0
 	github.com/netobserv/gopipes v0.3.0
-	github.com/netobserv/loki-client-go v0.0.0-20250425113517-526b43e51847
+	github.com/netobserv/loki-client-go v0.0.0-20251014110557-40bc8d2e6cf3
 	github.com/netobserv/netobserv-ebpf-agent v1.9.2-community
 	github.com/netsampler/goflow2 v1.3.7
 	github.com/pkg/errors v0.9.1

go.sum

@@ -255,8 +255,8 @@ github.com/mxk/go-flowrate v0.0.0-20140419014527-cca7078d478f h1:y5//uYreIhSUg3J
 github.com/mxk/go-flowrate v0.0.0-20140419014527-cca7078d478f/go.mod h1:ZdcZmHo+o7JKHSa8/e818NopupXU1YMK5fe1lsApnBw=
 github.com/netobserv/gopipes v0.3.0 h1:IYmPnnAVCdSK7VmHmpFhrVBOEm45qpgbZmJz1sSW+60=
 github.com/netobserv/gopipes v0.3.0/go.mod h1:N7/Gz05EOF0CQQSKWsv3eof22Cj2PB08Pbttw98YFYU=
-github.com/netobserv/loki-client-go v0.0.0-20250425113517-526b43e51847 h1:hjzhVZSSKIOmAzHbGUV4JhVIPkgKs/UtrWDx6JSVKMw=
-github.com/netobserv/loki-client-go v0.0.0-20250425113517-526b43e51847/go.mod h1:Zb/jtD3Lnu88Poo+jnhTASzxYnvncmHOoZaT93xQjJ8=
+github.com/netobserv/loki-client-go v0.0.0-20251014110557-40bc8d2e6cf3 h1:rxQipq0xpoiao7ifls/82JCcOVALC4n08ppTLCUFGL4=
+github.com/netobserv/loki-client-go v0.0.0-20251014110557-40bc8d2e6cf3/go.mod h1:Zb/jtD3Lnu88Poo+jnhTASzxYnvncmHOoZaT93xQjJ8=
 github.com/netobserv/netobserv-ebpf-agent v1.9.2-community h1:ghW16OO4QRWj0Uh1gMYX+NjAlgx2sZmCsO3Tkwoj4Do=
 github.com/netobserv/netobserv-ebpf-agent v1.9.2-community/go.mod h1:17OaUNAwx0LxoeV/SaHlJIJP6bpN7zSvUP3GtZelESQ=
 github.com/netsampler/goflow2 v1.3.7 h1:XZaTy8kkMnGXpJ9hS3KbO1McyrFTpVNhVFEx9rNhMmc=

pkg/api/write_loki.go

@@ -20,6 +20,7 @@ package api
 import (
 	"errors"
 	"fmt"
+	"time"
 
 	promConfig "github.com/prometheus/common/config"
 	"github.com/prometheus/common/model"
@@ -46,6 +47,15 @@ type WriteLoki struct {
 	TimestampScale string `yaml:"timestampScale,omitempty" json:"timestampScale,omitempty" doc:"timestamp units scale (e.g. for UNIX = 1s)"`
 	Format         string `yaml:"format,omitempty" json:"format,omitempty" doc:"the format of each line: printf (writes using golang's default map printing), fields (writes one key and value field per line) or json (default)"`
 	Reorder        bool   `yaml:"reorder,omitempty" json:"reorder,omitempty" doc:"reorder json map keys"`
+
+	// Client protocol selection
+	ClientProtocol string          `yaml:"clientProtocol,omitempty" json:"clientProtocol,omitempty" doc:"type of client protocol to use: 'http' or 'grpc' (default: 'http')"`
+	GRPCConfig     *GRPCLokiConfig `yaml:"grpcConfig,omitempty" json:"grpcConfig,omitempty" doc:"gRPC client configuration (used only for gRPC client type)"`
+}
+
+type GRPCLokiConfig struct {
+	KeepAlive        string `yaml:"keepAlive,omitempty" json:"keepAlive,omitempty" doc:"keep alive interval"`
+	KeepAliveTimeout string `yaml:"keepAliveTimeout,omitempty" json:"keepAliveTimeout,omitempty" doc:"keep alive timeout"`
 }
 
 func (w *WriteLoki) SetDefaults() {
@@ -76,6 +86,26 @@ func (w *WriteLoki) SetDefaults() {
 	if w.Format == "" {
 		w.Format = "json"
 	}
+	if w.ClientProtocol == "" {
+		w.ClientProtocol = "http"
+	}
+
+	// Set defaults for gRPC config if gRPC client protocol is selected
+	if w.ClientProtocol == "grpc" {
+		if w.GRPCConfig == nil {
+			w.GRPCConfig = &GRPCLokiConfig{}
+		}
+		w.GRPCConfig.SetDefaults()
+	}
+}
+
+func (g *GRPCLokiConfig) SetDefaults() {
+	if g.KeepAlive == "" {
+		g.KeepAlive = "30s"
+	}
+	if g.KeepAliveTimeout == "" {
+		g.KeepAliveTimeout = "5s"
+	}
 }
 
 func (w *WriteLoki) Validate() error {
@@ -85,11 +115,51 @@ func (w *WriteLoki) Validate() error {
 	if w.TimestampScale == "" {
 		return errors.New("timestampUnit must be a valid Duration > 0 (e.g. 1m, 1s or 1ms)")
 	}
-	if w.URL == "" {
-		return errors.New("url can't be empty")
-	}
 	if w.BatchSize <= 0 {
 		return fmt.Errorf("invalid batchSize: %v. Required > 0", w.BatchSize)
 	}
+
+	// Validate client protocol
+	if w.ClientProtocol != "" && w.ClientProtocol != "http" && w.ClientProtocol != "grpc" {
+		return fmt.Errorf("invalid clientProtocol: %s. Must be 'http' or 'grpc'", w.ClientProtocol)
+	}
+
+	// Validate based on client protocol
+	switch w.ClientProtocol {
+	case "http", "":
+		if w.URL == "" {
+			return errors.New("url can't be empty for HTTP client")
+		}
+	case "grpc":
+		if w.URL == "" {
+			return errors.New("url can't be empty for gRPC client")
+		}
+		if w.GRPCConfig == nil {
+			return errors.New("grpcConfig is required when using gRPC client protocol")
+		}
+		if err := w.GRPCConfig.Validate(); err != nil {
+			return fmt.Errorf("gRPC config validation failed: %w", err)
+		}
+	}
+
+	return nil
+}
+
+func (g *GRPCLokiConfig) Validate() error {
+	if g == nil {
+		return errors.New("gRPC config cannot be nil")
+	}
+	// Validate duration fields
+	if g.KeepAlive != "" {
+		if _, err := time.ParseDuration(g.KeepAlive); err != nil {
+			return fmt.Errorf("invalid keepAlive duration: %w", err)
+		}
+	}
+	if g.KeepAliveTimeout != "" {
+		if _, err := time.ParseDuration(g.KeepAliveTimeout); err != nil {
+			return fmt.Errorf("invalid keepAliveTimeout duration: %w", err)
+		}
+	}
+
 	return nil
 }

pkg/pipeline/write/write_loki.go

@@ -30,6 +30,7 @@ import (
 	"github.com/netobserv/flowlogs-pipeline/pkg/utils"
 
 	logAdapter "github.com/go-kit/kit/log/logrus"
+	"github.com/netobserv/loki-client-go/grpc"
 	"github.com/netobserv/loki-client-go/loki"
 	"github.com/netobserv/loki-client-go/pkg/backoff"
 	"github.com/netobserv/loki-client-go/pkg/urlutil"
@@ -49,7 +50,6 @@ type emitter interface {
 
 // Loki record writer
 type Loki struct {
-	lokiConfig     loki.Config
 	apiConfig      api.WriteLoki
 	timestampScale float64
 	saneLabels     map[string]model.LabelName
@@ -61,7 +61,46 @@ type Loki struct {
 	formatter      func(config.GenericMap) string
 }
 
-func buildLokiConfig(c *api.WriteLoki) (loki.Config, error) {
+func createLokiClient(c *api.WriteLoki) (emitter, error) {
+	switch c.ClientProtocol {
+	case "grpc":
+		return createGRPCClient(c)
+	case "http", "":
+		return createHTTPClient(c)
+	default:
+		return nil, fmt.Errorf("unsupported client protocol: %s", c.ClientProtocol)
+	}
+}
+
+func createHTTPClient(c *api.WriteLoki) (emitter, error) {
+	cfg, err := buildHTTPLokiConfig(c)
+	if err != nil {
+		return nil, err
+	}
+
+	client, err := loki.NewWithLogger(cfg, logAdapter.NewLogger(log.WithField("module", "export/loki")))
+	if err != nil {
+		return nil, fmt.Errorf("failed to create HTTP Loki client: %w", err)
+	}
+
+	return client, nil
+}
+
+func createGRPCClient(c *api.WriteLoki) (emitter, error) {
+	cfg, err := buildGRPCLokiConfig(c)
+	if err != nil {
+		return nil, err
+	}
+
+	client, err := grpc.NewWithLogger(cfg, logAdapter.NewLogger(log.WithField("module", "export/loki-grpc")))
+	if err != nil {
+		return nil, fmt.Errorf("failed to create gRPC Loki client: %w", err)
+	}
+
+	return client, nil
+}
+
+func buildHTTPLokiConfig(c *api.WriteLoki) (loki.Config, error) {
 	batchWait, err := time.ParseDuration(c.BatchWait)
 	if err != nil {
 		return loki.Config{}, fmt.Errorf("failed in parsing BatchWait : %w", err)
@@ -105,6 +144,69 @@ func buildLokiConfig(c *api.WriteLoki) (loki.Config, error) {
 	return cfg, nil
 }
 
+func buildGRPCLokiConfig(c *api.WriteLoki) (grpc.Config, error) {
+	if c.GRPCConfig == nil {
+		return grpc.Config{}, fmt.Errorf("gRPC config is required for gRPC client protocol")
+	}
+
+	batchWait, err := time.ParseDuration(c.BatchWait)
+	if err != nil {
+		return grpc.Config{}, fmt.Errorf("failed in parsing BatchWait: %w", err)
+	}
+
+	timeout, err := time.ParseDuration(c.Timeout)
+	if err != nil {
+		return grpc.Config{}, fmt.Errorf("failed in parsing Timeout: %w", err)
+	}
+
+	minBackoff, err := time.ParseDuration(c.MinBackoff)
+	if err != nil {
+		return grpc.Config{}, fmt.Errorf("failed in parsing MinBackoff: %w", err)
+	}
+
+	maxBackoff, err := time.ParseDuration(c.MaxBackoff)
+	if err != nil {
+		return grpc.Config{}, fmt.Errorf("failed in parsing MaxBackoff: %w", err)
+	}
+
+	keepAlive, err := time.ParseDuration(c.GRPCConfig.KeepAlive)
+	if err != nil {
+		return grpc.Config{}, fmt.Errorf("failed in parsing KeepAlive: %w", err)
+	}
+
+	keepAliveTimeout, err := time.ParseDuration(c.GRPCConfig.KeepAliveTimeout)
+	if err != nil {
+		return grpc.Config{}, fmt.Errorf("failed in parsing KeepAliveTimeout: %w", err)
+	}
+
+	cfg := grpc.Config{
+		ServerAddress:    c.URL,
+		TenantID:         c.TenantID,
+		BatchWait:        batchWait,
+		BatchSize:        c.BatchSize,
+		Timeout:          timeout,
+		KeepAlive:        keepAlive,
+		KeepAliveTimeout: keepAliveTimeout,
+		BackoffConfig: backoff.BackoffConfig{
+			MinBackoff: minBackoff,
+			MaxBackoff: maxBackoff,
+			MaxRetries: c.MaxRetries,
+		},
+	}
+
+	// Set external labels from static labels
+	if len(c.StaticLabels) > 0 {
+		cfg.ExternalLabels.LabelSet = c.StaticLabels
+	}
+
+	// Configure TLS from shared ClientConfig (same as HTTP client)
+	if c.ClientConfig != nil {
+		cfg.TLS = c.ClientConfig.TLSConfig
+	}
+
+	return cfg, nil
+}
+
 func (l *Loki) ProcessRecord(in config.GenericMap) error {
 	labels, lines := l.splitLabelsLines(in)
 
@@ -219,13 +321,10 @@ func NewWriteLoki(opMetrics *operational.Metrics, params config.StageParam) (*Lo
 		return nil, fmt.Errorf("the provided config is not valid: %w", err)
 	}
 
-	lokiConfig, buildconfigErr := buildLokiConfig(&lokiConfigIn)
-	if buildconfigErr != nil {
-		return nil, buildconfigErr
-	}
-	client, newWithLoggerErr := loki.NewWithLogger(lokiConfig, logAdapter.NewLogger(log.WithField("module", "export/loki")))
-	if newWithLoggerErr != nil {
-		return nil, newWithLoggerErr
+	// Create the appropriate client based on clientProtocol
+	client, err := createLokiClient(&lokiConfigIn)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create Loki client: %w", err)
 	}
 
 	timestampScale, err := time.ParseDuration(lokiConfigIn.TimestampScale)
@@ -253,7 +352,6 @@ func NewWriteLoki(opMetrics *operational.Metrics, params config.StageParam) (*Lo
 
 	f := formatter(lokiConfigIn.Format, lokiConfigIn.Reorder)
 	l := &Loki{
-		lokiConfig:     lokiConfig,
 		apiConfig:      lokiConfigIn,
 		timestampScale: float64(timestampScale),
 		saneLabels:     saneLabels,