Add alertmanager exporter implementation (open-telemetry#28906)

**Description:** Export Implementation of Alertmanager Exporter
Second PR - exporter implementation

**Link to tracking Issue:**
[open-telemetry#23659](open-telemetry#23569)

**Testing:** Unit tests for exporter implementation

**Documentation:** Readme and Sample Configs to use Alertmanager
exporter

.chloggen/alertmanager-exporter-implementation.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: 'new_component'
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: alertmanagerexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Add Alertmanager exporter implementation and tests"
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [23569]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

exporter/alertmanagerexporter/README.md

@@ -20,7 +20,7 @@ Supported pipeline types: traces
 The following settings are required:
 
 - `endpoint` : Alertmanager endpoint to send events
-- `severity` (default info): Default severity for Alerts
+- `severity`: Default severity for Alerts
 
 
 The following settings are optional:
@@ -33,7 +33,6 @@ The following settings are optional:
    eg: If severity_attribute is set to "foo" and the SpanEvent has an attribute called foo, foo's attribute value will be used as the severity value for that particular Alert generated from the SpanEvent.
 
 
-
 Example config:
 
 ```yaml

exporter/alertmanagerexporter/alertmanager_exporter.go

@@ -4,17 +4,27 @@
 package alertmanagerexporter // import "github.com/open-telemetry/opentelemetry-collector-contrib/exporter/alertmanagerexporter"
 
 import (
+	"bytes"
 	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
 
+	"github.com/prometheus/common/model"
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/consumer"
 	"go.opentelemetry.io/collector/exporter"
 	"go.opentelemetry.io/collector/exporter/exporterhelper"
+	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/ptrace"
+	"go.uber.org/zap"
 )
 
 type alertmanagerExporter struct {
 	config            *Config
+	client            *http.Client
 	tracesMarshaler   ptrace.Marshaler
 	settings          component.TelemetrySettings
 	endpoint          string
@@ -23,20 +33,167 @@ type alertmanagerExporter struct {
 	severityAttribute string
 }
 
-func (s *alertmanagerExporter) pushTraces(_ context.Context, _ ptrace.Traces) error {
+type alertmanagerEvent struct {
+	spanEvent ptrace.SpanEvent
+	traceID   string
+	spanID    string
+	severity  string
+}
+
+func (s *alertmanagerExporter) convertEventSliceToArray(eventSlice ptrace.SpanEventSlice, traceID pcommon.TraceID, spanID pcommon.SpanID) []*alertmanagerEvent {
+	if eventSlice.Len() > 0 {
+		events := make([]*alertmanagerEvent, eventSlice.Len())
 
-	// To Be Implemented
+		for i := 0; i < eventSlice.Len(); i++ {
+			var severity string
+			severityAttrValue, ok := eventSlice.At(i).Attributes().Get(s.severityAttribute)
+			if ok {
+				severity = severityAttrValue.AsString()
+			} else {
+				severity = s.defaultSeverity
+			}
+			event := alertmanagerEvent{
+				spanEvent: eventSlice.At(i),
+				traceID:   traceID.String(),
+				spanID:    spanID.String(),
+				severity:  severity,
+			}
+
+			events[i] = &event
+		}
+		return events
+	}
 	return nil
 }
 
-func (s *alertmanagerExporter) start(_ context.Context, _ component.Host) error {
+func (s *alertmanagerExporter) extractEvents(td ptrace.Traces) []*alertmanagerEvent {
+
+	// Stitch parent trace ID and span ID
+	rss := td.ResourceSpans()
+	var events []*alertmanagerEvent
+	if rss.Len() == 0 {
+		return nil
+	}
+
+	for i := 0; i < rss.Len(); i++ {
+		resource := rss.At(i).Resource()
+		ilss := rss.At(i).ScopeSpans()
+
+		if resource.Attributes().Len() == 0 && ilss.Len() == 0 {
+			return nil
+		}
+
+		for j := 0; j < ilss.Len(); j++ {
+			spans := ilss.At(j).Spans()
+			for k := 0; k < spans.Len(); k++ {
+				traceID := spans.At(k).TraceID()
+				spanID := spans.At(k).SpanID()
+				events = append(events, s.convertEventSliceToArray(spans.At(k).Events(), traceID, spanID)...)
+			}
+		}
+	}
+	return events
+}
+
+func createAnnotations(event *alertmanagerEvent) model.LabelSet {
+	labelMap := make(model.LabelSet, event.spanEvent.Attributes().Len()+2)
+	event.spanEvent.Attributes().Range(func(key string, attr pcommon.Value) bool {
+		labelMap[model.LabelName(key)] = model.LabelValue(attr.AsString())
+		return true
+	})
+	labelMap["TraceID"] = model.LabelValue(event.traceID)
+	labelMap["SpanID"] = model.LabelValue(event.spanID)
+	return labelMap
+}
+
+func (s *alertmanagerExporter) convertEventsToAlertPayload(events []*alertmanagerEvent) []model.Alert {
+
+	payload := make([]model.Alert, len(events))
+
+	for i, event := range events {
+		annotations := createAnnotations(event)
+
+		alert := model.Alert{
+			StartsAt:     time.Now(),
+			Labels:       model.LabelSet{"severity": model.LabelValue(event.severity), "event_name": model.LabelValue(event.spanEvent.Name())},
+			Annotations:  annotations,
+			GeneratorURL: s.generatorURL,
+		}
+
+		payload[i] = alert
+	}
+	return payload
+}
+
+func (s *alertmanagerExporter) postAlert(ctx context.Context, payload []model.Alert) error {
+
+	msg, err := json.Marshal(payload)
+	if err != nil {
+		return fmt.Errorf("error marshaling alert to JSON: %w", err)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, "POST", s.endpoint, bytes.NewBuffer(msg))
+	if err != nil {
+		return fmt.Errorf("error creating HTTP request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
 
-	// To Be Implemented
+	resp, err := s.client.Do(req)
+	if err != nil {
+		return fmt.Errorf("error sending HTTP request: %w", err)
+	}
+
+	defer func() {
+		if closeErr := resp.Body.Close(); closeErr != nil {
+			s.settings.Logger.Warn("failed to close response body", zap.Error(closeErr))
+		}
+	}()
+
+	_, err = io.ReadAll(resp.Body)
+	if err != nil {
+		return fmt.Errorf("failed to read response body %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		s.settings.Logger.Debug("post request to Alertmanager failed", zap.Error(err))
+		return fmt.Errorf("request POST %s failed - %q", req.URL.String(), resp.Status)
+	}
+	return nil
+}
+
+func (s *alertmanagerExporter) pushTraces(ctx context.Context, td ptrace.Traces) error {
+
+	events := s.extractEvents(td)
+
+	if len(events) == 0 {
+		return nil
+	}
+
+	alert := s.convertEventsToAlertPayload(events)
+	err := s.postAlert(ctx, alert)
+
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (s *alertmanagerExporter) start(_ context.Context, host component.Host) error {
+
+	client, err := s.config.HTTPClientSettings.ToClient(host, s.settings)
+	if err != nil {
+		return fmt.Errorf("failed to create HTTP Client: %w", err)
+	}
+	s.client = client
 	return nil
 }
 
 func (s *alertmanagerExporter) shutdown(context.Context) error {
-	// To Be Implemented
+
+	if s.client != nil {
+		s.client.CloseIdleConnections()
+	}
 	return nil
 }
 
@@ -46,14 +203,15 @@ func newAlertManagerExporter(cfg *Config, set component.TelemetrySettings) *aler
 		config:            cfg,
 		settings:          set,
 		tracesMarshaler:   &ptrace.JSONMarshaler{},
-		endpoint:          cfg.HTTPClientSettings.Endpoint,
+		endpoint:          fmt.Sprintf("%s/api/v1/alerts", cfg.HTTPClientSettings.Endpoint),
 		generatorURL:      cfg.GeneratorURL,
 		defaultSeverity:   cfg.DefaultSeverity,
 		severityAttribute: cfg.SeverityAttribute,
 	}
 }
 
 func newTracesExporter(ctx context.Context, cfg component.Config, set exporter.CreateSettings) (exporter.Traces, error) {
+
 	config := cfg.(*Config)
 
 	s := newAlertManagerExporter(config, set.TelemetrySettings)
@@ -64,7 +222,6 @@ func newTracesExporter(ctx context.Context, cfg component.Config, set exporter.C
 		cfg,
 		s.pushTraces,
 		exporterhelper.WithCapabilities(consumer.Capabilities{MutatesData: false}),
-		// Disable Timeout/RetryOnFailure and SendingQueue
 		exporterhelper.WithStart(s.start),
 		exporterhelper.WithTimeout(config.TimeoutSettings),
 		exporterhelper.WithRetry(config.RetrySettings),