collector-topologylisted

# OpenTelemetry Collector Topology ## Two modes: agent and gateway ### Agent mode Runs on every host/pod alongside the application. Receives OTLP from the app, applies basic processing, forwards to a gateway or directly to a backend. ```yaml receivers: otlp: protocols: grpc: endpoint: 0.0.0.0:4317 # app sends here http: endpoint: 0.0.0.0:4318 processors: batch: timeout: 1s send_batch_size: 1024 memory_limiter: check_interval: 1s limit_mib: 256 exporters: otlp: endpoint: gateway.internal:4317 # or backend endpoint tls: insecure: false service: pipelines: traces: receivers: [otlp] processors: [memory_limiter, batch] exporters: [otlp] metrics: receivers: [otlp] processors: [memory_limiter, batch] exporters: [otlp] logs: receivers: [otlp] processors: [memory_limiter, batch] exporters: [otlp] ``` ### Gateway mode Centralized aggregation tier. Receives from agents, applies tail sampling, exports to backend(s). Adds `tail_sampling` processor between `memory_limiter` and `batch`: ```yaml processors: tail_sampling: decision_wait: 10s num_traces: 100000 expected_new_traces_per_sec: 10000 policies: - name: errors-policy type: status_code status_code: {status_codes: [ERROR]} - name: slow-traces-policy type: latency latency: {threshold_ms: 1000} - name: debug-policy