feat: add OpenTelemetry Collector configuration

Add example OTel Collector config that scrapes DBLab's Prometheus
endpoint and exports to OTLP-compatible backends. Update documentation
with integration instructions.

Author: claude

PROMETHEUS.md

@@ -166,3 +166,58 @@ dblab_clone_cpu_usage_percent{clone_id="my-clone"}
     summary: "DBLab has many clones"
     description: "DBLab has {{ $value }} clones running"
 ```
+
+## OpenTelemetry Integration
+
+DBLab metrics can be exported to OpenTelemetry-compatible backends using the OpenTelemetry Collector. This allows you to send metrics to Grafana Cloud, Datadog, New Relic, and other observability platforms.
+
+### Quick Start
+
+1. Install the OpenTelemetry Collector:
+   ```bash
+   # Using Docker
+   docker pull otel/opentelemetry-collector-contrib:latest
+   ```
+
+2. Copy the example configuration:
+   ```bash
+   cp engine/configs/otel-collector.example.yml otel-collector.yml
+   ```
+
+3. Edit `otel-collector.yml` to configure your backend:
+   ```yaml
+   exporters:
+     otlp:
+       endpoint: "your-otlp-endpoint:4317"
+       headers:
+         Authorization: "Bearer <your-token>"
+   ```
+
+4. Run the collector:
+   ```bash
+   docker run -v $(pwd)/otel-collector.yml:/etc/otelcol/config.yaml \
+     -p 4317:4317 -p 8889:8889 \
+     otel/opentelemetry-collector-contrib:latest
+   ```
+
+### Architecture
+
+```
+┌─────────────┐     scrape      ┌──────────────────┐      OTLP       ┌─────────────┐
+│   DBLab     │ ──────────────► │  OTel Collector  │ ──────────────► │  Backend    │
+│  /metrics   │    :2345        │                  │    :4317        │ (Grafana,   │
+└─────────────┘                 └──────────────────┘                 │  Datadog)   │
+                                                                     └─────────────┘
+```
+
+### Supported Backends
+
+The OTel Collector can export to:
+- **Grafana Cloud** - Use OTLP exporter with Grafana Cloud endpoint
+- **Datadog** - Use the datadog exporter
+- **New Relic** - Use OTLP exporter with New Relic endpoint
+- **Prometheus Remote Write** - Use prometheusremotewrite exporter
+- **AWS CloudWatch** - Use awsemf exporter
+- **Any OTLP-compatible backend**
+
+See `engine/configs/otel-collector.example.yml` for a complete configuration example.

engine/configs/otel-collector.example.yml

@@ -0,0 +1,115 @@
+# OpenTelemetry Collector Configuration for Database Lab Engine
+#
+# This configuration scrapes Prometheus metrics from DBLab's /metrics endpoint
+# and exports them via OTLP protocol to observability backends.
+#
+# Usage:
+#   1. Install the OpenTelemetry Collector: https://opentelemetry.io/docs/collector/installation/
+#   2. Copy this file and adjust the configuration for your environment
+#   3. Run: otelcol --config otel-collector.yml
+#
+# For Docker:
+#   docker run -v $(pwd)/otel-collector.yml:/etc/otelcol/config.yaml \
+#     otel/opentelemetry-collector-contrib:latest
+
+receivers:
+  # Scrape Prometheus metrics from DBLab Engine
+  prometheus:
+    config:
+      scrape_configs:
+        - job_name: 'dblab'
+          scrape_interval: 15s
+          scrape_timeout: 10s
+          static_configs:
+            - targets: ['localhost:2345']
+          # Optional: Add labels to identify this instance
+          relabel_configs:
+            - source_labels: []
+              target_label: environment
+              replacement: 'production'
+
+  # Optional: Collect host metrics
+  hostmetrics:
+    collection_interval: 30s
+    scrapers:
+      cpu:
+      memory:
+      disk:
+      filesystem:
+      network:
+
+processors:
+  # Batch metrics for efficient export
+  batch:
+    timeout: 10s
+    send_batch_size: 1000
+
+  # Add resource attributes
+  resource:
+    attributes:
+      - key: service.name
+        value: dblab-engine
+        action: upsert
+      - key: service.version
+        value: "3.0"
+        action: upsert
+
+  # Optional: Filter or transform metrics
+  filter:
+    metrics:
+      include:
+        match_type: regexp
+        metric_names:
+          - dblab_.*
+
+exporters:
+  # Export to OTLP-compatible backends (Grafana Cloud, Datadog, etc.)
+  otlp:
+    endpoint: "your-otlp-endpoint:4317"
+    tls:
+      insecure: false
+    headers:
+      # Add authentication headers as needed
+      # Authorization: "Bearer <token>"
+
+  # Alternative: Export to Prometheus remote write
+  prometheusremotewrite:
+    endpoint: "https://prometheus.example.com/api/v1/write"
+    # tls:
+    #   ca_file: /path/to/ca.crt
+    # headers:
+    #   Authorization: "Bearer <token>"
+
+  # Debug: Log metrics to console (useful for testing)
+  debug:
+    verbosity: detailed
+
+  # Alternative: Keep Prometheus format for local scraping
+  prometheus:
+    endpoint: "0.0.0.0:8889"
+    namespace: dblab
+
+extensions:
+  health_check:
+    endpoint: 0.0.0.0:13133
+
+  zpages:
+    endpoint: 0.0.0.0:55679
+
+service:
+  extensions: [health_check, zpages]
+  pipelines:
+    metrics:
+      receivers: [prometheus]
+      processors: [batch, resource]
+      # Choose your exporter(s):
+      # - Use 'otlp' for OTLP-compatible backends
+      # - Use 'prometheusremotewrite' for Prometheus remote write
+      # - Use 'debug' for testing
+      exporters: [debug]
+
+  telemetry:
+    logs:
+      level: info
+    metrics:
+      address: 0.0.0.0:8888