feat: add alloy

docker/alloy/config.alloy

@@ -0,0 +1,45 @@
+// =============================================================================
+// Grafana Alloy Pipeline Configuration
+// Centralized OpenTelemetry collector for the curated compose stacks.
+// Receives OTLP traces/metrics/logs and forwards to the LGTM backend.
+// =============================================================================
+
+// ---------------------------------------------------------------------------
+// OTLP Receiver — gRPC + HTTP
+// All stacks push telemetry here via OTLP gRPC (port 4317) or OTLP HTTP (port
+// 4318). Other stacks reference this service on the `pipeline` network as `otel`
+// or `alloy`.
+// ---------------------------------------------------------------------------
+otelcol.receiver.otlp "default" {
+    grpc {
+        endpoint = "0.0.0.0:4317"
+    }
+    http {
+        endpoint = "0.0.0.0:4318"
+    }
+}
+
+// ---------------------------------------------------------------------------
+// OTLP Exporter — Forward to LGTM
+// Sends all received telemetry to the LGTM backend (grafana/otel-lgtm).
+// The target endpoint is configurable via the ALLOY_OTLP_FORWARD_ENDPOINT env
+// var, defaulting to http://lgtm:4318 (LGTM's OTLP HTTP endpoint on pipeline).
+// ---------------------------------------------------------------------------
+otelcol.exporter.otlp "lgtm" {
+    client {
+        endpoint = env("OTEL_EXPORTER_OTLP_ENDPOINT", "http://lgtm:4318")
+        tls {
+            insecure             = true
+            insecure_skip_verify = true
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Pipeline — Connect receiver to exporter(s)
+// Routes telemetry from the OTLP receiver to the LGTM exporter.
+// ---------------------------------------------------------------------------
+otelcol.pipeline "default" {
+    receiver = otelcol.receiver.otlp.default
+    exporter = otelcol.exporter.otlp.lgtm
+}