Added contributor docs for SigNoz. (#39402)

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**Related issue:** Resolves #38607

docs/Contributing/reference/configuration-for-contributors.md

@@ -229,6 +229,8 @@ By default, OpenTelemetry is used. Set `tracing_type` to `elasticapm` only if yo
 
 Enables exporting logs to an OpenTelemetry collector in addition to stderr output. When enabled, logs are sent to the OTLP endpoint configured via the standard `OTEL_EXPORTER_OTLP_ENDPOINT` environment variable. Logs are automatically correlated with traces via `trace_id` and `span_id` attributes.
 
+> **Note:** All log levels, including debug, are always sent to the OpenTelemetry collector regardless of the `logging.debug` setting. The `logging.debug` flag only controls what appears in stderr output.
+
 > **Note:** This option requires `logging.tracing_enabled` to be set to `true`. Fleet will fail to start if `otel_logs_enabled` is `true` but `tracing_enabled` is `false`.
 
 - Default value: `false`

tools/README.md

@@ -242,6 +242,7 @@ go run ./tools/run-scripts -scripts-disabled -content 'echo "Test"'
 | `percona/` | Percona testing | Percona MySQL testing configs - See [percona/test/README.md](percona/test/README.md) |
 | `sentry-self-hosted/` | Self-hosted Sentry | See [sentry-self-hosted/README.md](sentry-self-hosted/README.md) |
 | `smtp4dev/` | Local SMTP testing | SMTP4Dev server with TLS certs for email testing |
+| `signoz/` | SigNoz for traces, metrics, and logs | See [signoz/README.md](signoz/README.md) |
 | `telemetry/` | Jaeger + Prometheus for tracing | `docker compose up` - See [telemetry/README.md](telemetry/README.md) |
 | `terraform/` | Terraform provider for Fleet teams | `make install && make apply` - See [terraform/README.md](terraform/README.md) |
 | **MDM Tools** | | |

tools/signoz/README.md

@@ -0,0 +1,86 @@
+# Running SigNoz locally with Fleet
+
+[SigNoz](https://signoz.io/) is an open-source observability platform that provides traces, metrics, and logs in a single UI. This guide explains how to run SigNoz locally for Fleet development with optimized settings for reduced latency.
+
+## Prerequisites
+
+- Docker and Docker Compose
+- A locally-built Fleet server (see [Testing and local development](../../docs/Contributing/getting-started/testing-and-local-development.md))
+
+## Setup
+
+1. Clone the SigNoz repository at a specific release:
+
+```bash
+git clone --branch v0.110.1 --depth 1 https://github.com/SigNoz/signoz.git
+cd signoz/deploy
+```
+
+2. Modify the SigNoz UI port to avoid conflict with Fleet (which uses port 8080):
+
+In `docker/docker-compose.yaml`, change the signoz service port mapping:
+
+```yaml
+services:
+  signoz:
+    ports:
+      - "8085:8080"  # Changed from 8080:8080 to avoid conflict with Fleet
+```
+
+3. (Optional) For reduced latency during development, modify `docker/otel-collector-config.yaml`:
+
+```yaml
+processors:
+  batch:
+    send_batch_size: 10000
+    send_batch_max_size: 11000
+    timeout: 200ms  # reduced from 10s for dev
+  # ...
+  signozspanmetrics/delta:
+    # ...
+    metrics_flush_interval: 5s  # reduced from 60s for dev
+```
+
+4. Start SigNoz:
+
+```bash
+cd docker
+docker compose up -d
+```
+
+Give it a minute for all services to initialize. The SigNoz UI will be available at http://localhost:8085.
+
+## Configuring Fleet
+
+Start the Fleet server with OpenTelemetry tracing and logging enabled:
+
+```bash
+export FLEET_LOGGING_TRACING_ENABLED=true
+export FLEET_LOGGING_OTEL_LOGS_ENABLED=true
+export OTEL_SERVICE_NAME=fleet
+export OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4317
+
+./build/fleet serve
+```
+
+> **Note:** All log levels (including debug) are always sent to SigNoz regardless of the `--logging_debug` flag. That flag only controls stderr output.
+
+### Low-latency configuration (optional)
+
+For faster feedback during development, you can reduce the batch processing delays on the Fleet side:
+
+```bash
+# Batch span processor delay (default 5000ms)
+export OTEL_BSP_SCHEDULE_DELAY=1000
+
+# Log batch processor settings
+export OTEL_BLRP_EXPORT_TIMEOUT=1000
+export OTEL_BLRP_SCHEDULE_DELAY=500
+export OTEL_BLRP_MAX_EXPORT_BATCH_SIZE=1
+
+./build/fleet serve
+```
+
+## Using SigNoz
+
+After starting Fleet with the above configuration, you should start seeing traces, logs, and metrics in SigNoz UI at http://localhost:8085.

tools/telemetry/README.md

@@ -20,3 +20,7 @@ OTEL_EXPORTER_OTLP_ENDPOINT="http://localhost:4317" \
 ```
 
 Afterwards, you can navigate to http://localhost:16686/ to access the Jaeger UI.
+
+## Alternatives
+
+For a more full-featured observability platform that includes traces, metrics, and logs in a single UI, see [SigNoz](../signoz/README.md).