chore: Port loki.source.heroku to use server abstraction (#5962)

### Pull Request Details
Followup to #5895. Port
`loki.source.heroku` to use the shared server abstraction.

This will also make it so that this server don't require a restart if
labels, relabel rules or timestamp config changes.

### Issue(s) fixed by this Pull Request

Part of #5803


### Notes to the Reviewer

Changes so that each component pass the `EntriesWritten` counter since
they unfortunately have different naming conventions..

### PR Checklist

<!-- Remove items that do not apply. For completed items, change [ ] to
[x]. -->

- [ ] Documentation added
- [x] Tests updated
- [ ] Config converters updated

Author: kalleep

internal/component/loki/source/api/api.go

@@ -56,6 +56,7 @@ func (a *Arguments) labelSet() model.LabelSet {
 
 type Component struct {
 	opts               component.Options
+	metrics            *metrics
 	handler            loki.LogsBatchReceiver
 	uncheckedCollector *util.UncheckedCollector
 
@@ -68,6 +69,7 @@ type Component struct {
 func New(opts component.Options, args Arguments) (*Component, error) {
 	c := &Component{
 		opts:               opts,
+		metrics:            newMetrics(opts.Registerer),
 		handler:            loki.NewLogsBatchReceiver(),
 		uncheckedCollector: util.NewUncheckedCollector(nil),
 
@@ -134,8 +136,9 @@ func (c *Component) Update(args component.Arguments) error {
 
 		var err error
 		c.server, err = source.NewServer(c.opts.Logger, reg, c.handler, source.ServerConfig{
-			Namespace: "loki_source_api",
-			NetConfig: newArgs.Server,
+			Namespace:      "loki_source_api",
+			EntriesWritten: c.metrics.entriesWritten,
+			NetConfig:      newArgs.Server,
 			LogsConfig: &source.LogsConfig{
 				FixedLabels:          newArgs.labelSet(),
 				RelabelRules:         relabel.ComponentToPromRelabelConfigs(newArgs.RelabelRules),

internal/component/loki/source/api/metrics.go

@@ -0,0 +1,20 @@
+package api
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+
+	"github.com/grafana/alloy/internal/util"
+)
+
+type metrics struct {
+	entriesWritten prometheus.Counter
+}
+
+func newMetrics(reg prometheus.Registerer) *metrics {
+	return &metrics{
+		entriesWritten: util.MustRegisterOrGet(reg, prometheus.NewCounter(prometheus.CounterOpts{
+			Name: "loki_source_api_entries_written",
+			Help: "Total number of entries written.",
+		})).(prometheus.Counter),
+	}
+}

internal/component/loki/source/heroku/heroku.go

@@ -3,20 +3,18 @@ package heroku
 import (
 	"context"
 	"fmt"
-	"reflect"
 	"sync"
 
 	"github.com/grafana/alloy/internal/component"
 	"github.com/grafana/alloy/internal/component/common/loki"
 	fnet "github.com/grafana/alloy/internal/component/common/net"
 	alloy_relabel "github.com/grafana/alloy/internal/component/common/relabel"
-	ht "github.com/grafana/alloy/internal/component/loki/source/heroku/internal/herokutarget"
+	"github.com/grafana/alloy/internal/component/loki/source"
 	"github.com/grafana/alloy/internal/featuregate"
 	"github.com/grafana/alloy/internal/runtime/logging/level"
 	"github.com/grafana/alloy/internal/util"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/common/model"
-	"github.com/prometheus/prometheus/model/relabel"
 )
 
 func init() {
@@ -51,14 +49,14 @@ func (a *Arguments) SetToDefault() {
 // Component implements the loki.source.heroku component.
 type Component struct {
 	opts          component.Options
-	metrics       *ht.Metrics              // Metrics about Heroku entries.
+	metrics       *metrics                 // Metrics about Heroku entries.
 	serverMetrics *util.UncheckedCollector // Metircs about the HTTP server managed by the component.
 
 	mut  sync.RWMutex
 	args Arguments
 
 	fanout *loki.Fanout
-	server *ht.HerokuServer
+	server *source.Server
 
 	handler loki.LogsBatchReceiver
 }
@@ -67,7 +65,7 @@ type Component struct {
 func New(o component.Options, args Arguments) (*Component, error) {
 	c := &Component{
 		opts:          o,
-		metrics:       ht.NewMetrics(o.Registerer),
+		metrics:       newMetrics(o.Registerer),
 		mut:           sync.RWMutex{},
 		args:          Arguments{},
 		fanout:        loki.NewFanout(args.ForwardTo),
@@ -107,19 +105,14 @@ func (c *Component) Update(args component.Arguments) error {
 	defer c.mut.Unlock()
 
 	newArgs := args.(Arguments)
+
 	c.fanout.UpdateChildren(newArgs.ForwardTo)
 
-	var rcs []*relabel.Config
-	if len(newArgs.RelabelRules) > 0 {
-		rcs = alloy_relabel.ComponentToPromRelabelConfigs(newArgs.RelabelRules)
+	if newArgs.Server == nil {
+		newArgs.Server = &fnet.ServerConfig{}
 	}
 
-	restartRequired := changed(c.args.Server, newArgs.Server) ||
-		changed(c.args.RelabelRules, newArgs.RelabelRules) ||
-		changed(c.args.Labels, newArgs.Labels) ||
-		c.args.UseIncomingTimestamp != newArgs.UseIncomingTimestamp
-
-	if restartRequired {
+	if c.server.NeedsRestart(newArgs.Server) {
 		if c.server != nil {
 			c.server.Shutdown()
 		}
@@ -131,54 +124,67 @@ func (c *Component) Update(args component.Arguments) error {
 		registry := prometheus.NewRegistry()
 		c.serverMetrics.SetCollector(registry)
 
-		server, err := ht.NewHerokuServer(c.metrics, c.opts.Logger, c.handler, rcs, newArgs.Convert(), registry)
+		server, err := source.NewServer(c.opts.Logger, registry, c.handler, source.ServerConfig{
+			Namespace:      "loki_source_heroku_drain_target",
+			EntriesWritten: c.metrics.entriesWritten,
+			NetConfig:      newArgs.Server,
+			LogsConfig: &source.LogsConfig{
+				FixedLabels:          newArgs.labelSet(),
+				RelabelRules:         alloy_relabel.ComponentToPromRelabelConfigs(newArgs.RelabelRules),
+				UseIncomingTimestamp: newArgs.UseIncomingTimestamp,
+			},
+		})
+
 		if err != nil {
 			return fmt.Errorf("failed to create heroku server: %w", err)
 		}
 
-		if err := server.Run(); err != nil {
+		if err := server.Run(newRoutes(c.opts.Logger, c.metrics), []source.HandlerRoute{newHealthyHandler()}); err != nil {
 			return fmt.Errorf("failed to run heroku server: %w", err)
 		}
 
 		c.server = server
-		c.args = newArgs
+		return nil
+	}
+
+	if c.server != nil {
+		c.server.Update(&source.LogsConfig{
+			FixedLabels:          newArgs.labelSet(),
+			RelabelRules:         alloy_relabel.ComponentToPromRelabelConfigs(newArgs.RelabelRules),
+			UseIncomingTimestamp: newArgs.UseIncomingTimestamp,
+		})
 	}
 
+	c.args = newArgs
+
 	return nil
 }
 
-// Convert is used to bridge between the Alloy and Promtail types.
-func (args *Arguments) Convert() *ht.HerokuConfig {
+func (args *Arguments) labelSet() model.LabelSet {
 	lbls := make(model.LabelSet, len(args.Labels))
 	for k, v := range args.Labels {
 		lbls[model.LabelName(k)] = model.LabelValue(v)
 	}
 
-	return &ht.HerokuConfig{
-		Server:               args.Server,
-		Labels:               lbls,
-		UseIncomingTimestamp: args.UseIncomingTimestamp,
-	}
+	return lbls
 }
 
 // DebugInfo returns information about the status of listener.
 func (c *Component) DebugInfo() any {
 	c.mut.RLock()
 	defer c.mut.RUnlock()
 
-	var res = readerDebugInfo{
-		Ready:   c.server.Ready(),
-		Address: c.server.HTTPListenAddress(),
+	if c.server == nil {
+		return readerDebugInfo{}
 	}
 
-	return res
+	return readerDebugInfo{
+		Ready:   ready(c.server.HTTPAddr()),
+		Address: c.server.HTTPAddr(),
+	}
 }
 
 type readerDebugInfo struct {
 	Ready   bool   `alloy:"ready,attr"`
 	Address string `alloy:"address,attr"`
 }
-
-func changed(prev, next any) bool {
-	return !reflect.DeepEqual(prev, next)
-}

internal/component/loki/source/heroku/heroku_test.go

@@ -12,7 +12,7 @@ import (
 	"github.com/grafana/alloy/internal/component/common/loki"
 	fnet "github.com/grafana/alloy/internal/component/common/net"
 	alloy_relabel "github.com/grafana/alloy/internal/component/common/relabel"
-	"github.com/grafana/alloy/internal/component/loki/source/heroku/internal/herokutarget"
+	"github.com/grafana/alloy/internal/component/loki/source"
 	"github.com/grafana/alloy/internal/util"
 	"github.com/grafana/regexp"
 	"github.com/prometheus/client_golang/prometheus"
@@ -97,25 +97,25 @@ func TestUpdate_detectsWhenTargetRequiresARestart(t *testing.T) {
 			restartRequired: false,
 		},
 		{
-			name: "change in labels requires server restart",
+			name: "change in labels does not require server restart",
 			mutateNewArgs: func(_ *testing.T, args *Arguments) {
 				args.Labels = map[string]string{"some": "label"}
 			},
-			restartRequired: true,
+			restartRequired: false,
 		},
 		{
-			name: "change in relabel rules requires server restart",
+			name: "change in relabel rules does not require server restart",
 			mutateNewArgs: func(_ *testing.T, args *Arguments) {
 				args.RelabelRules = alloy_relabel.Rules{}
 			},
-			restartRequired: true,
+			restartRequired: false,
 		},
 		{
-			name: "change in use incoming timestamp requires server restart",
+			name: "change in use incoming timestamp does not require server restart",
 			mutateNewArgs: func(_ *testing.T, args *Arguments) {
 				args.UseIncomingTimestamp = !args.UseIncomingTimestamp
 			},
-			restartRequired: true,
+			restartRequired: false,
 		},
 	}
 	for _, tc := range tests {
@@ -253,7 +253,7 @@ func waitForServerToBeReady(t *testing.T, comp *Component) {
 	require.Eventuallyf(t, func() bool {
 		resp, err := http.Get(fmt.Sprintf(
 			"http://%v/wrong/url",
-			comp.server.HTTPListenAddress(),
+			comp.server.HTTPAddr(),
 		))
 		return err == nil && resp.StatusCode == 404
 	}, 5*time.Second, 20*time.Millisecond, "server failed to start before timeout")
@@ -275,6 +275,6 @@ func newRegexp() alloy_relabel.Regexp {
 	return alloy_relabel.Regexp{Regexp: re}
 }
 
-func getEndpoint(target *herokutarget.HerokuServer) string {
-	return fmt.Sprintf("http://%s%s", target.HTTPListenAddress(), target.DrainEndpoint())
+func getEndpoint(target *source.Server) string {
+	return fmt.Sprintf("http://%s%s", target.HTTPAddr(), pathDrain)
 }