feat: add tail sampling for traces

charts/k8s-monitoring/templates/alloy_config/_processors.alloy.txt

@@ -212,6 +212,40 @@ otelcol.processor.transform "default" {
   }
 }
 
+
+{{- if and .Values.traces.enabled .Values.traces.receiver.tailsampling.policies }}
+otelcol.processor.tail_sampling "default" {
+  {{- range $policy := .Values.traces.receiver.tailsampling.policies }}
+  policy {
+    name    = {{ $policy.name | quote }}
+    type    = {{ $policy.type | quote }}
+  {{- if and (eq $policy.type "latency") (hasKey $policy "latency") }}
+    latency = {
+      threshold_ms = {{ $policy.latency.thresholdMs | int }},
+    }
+  {{- end }}
+
+  {{- if and (eq $policy.type "string_attribute") (hasKey $policy "stringAttribute") }}
+    stringAttribute = {
+      key = {{ $policy.stringAttribute.key | quote }}
+      values = [
+      {{- range $value := $policy.stringAttribute.values }}
+        {{ $value }},
+      {{- end }}
+      ]
+      enabled_regex_matching = {{ $policy.stringAttribute.enabledRegexMatching | default true }}
+      invert_match = {{ $policy.stringAttribute.invertMatch | default false }}
+    }
+  {{- end }}
+  }
+  {{- end }}
+
+	output {
+		traces = [otelcol.processor.batch.batch_processor.input]
+	}
+}
+{{- end }}
+
 otelcol.processor.filter "default" {
   error_mode = "ignore"
 

examples/tail-sampling/README.md

@@ -0,0 +1,42 @@
+# Tail sampling
+
+This example contains an example of [tail sampling](https://grafana.com/docs/grafana-cloud/monitor-applications/application-observability/setup/sampling/tail/).
+
+```yaml
+cluster:
+  name: tail-sampling-test
+
+externalServices:
+  prometheus:
+    host: https://prometheus.example.com
+    basicAuth:
+      username: 12345
+      password: "It's a secret to everyone"
+  loki:
+    host: https://loki.example.com
+    basicAuth:
+      username: 12345
+      password: "It's a secret to everyone"
+  tempo:
+    host: https://tempo.example.com
+    basicAuth:
+      username: 12345
+      password: "It's a secret to everyone"
+
+metrics:
+  enabled: false
+
+logs:
+  enabled: false
+
+traces:
+  enabled: true
+  receiver:
+    tailsampling:
+      policies:
+        - name: all_traces_above_500
+          type: latency
+          latency:
+            thresholdMs: 500
+
+```