Add example

Signed-off-by: Shizuo Fujita <fujita@clear-code.com>

Author: Watson1978

.gitignore

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 /spec/reports/
 /tmp/
 
+/example/node_modules/
+
 Gemfile.lock

example/README.md

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+# Fluentd Observability Demo
+
+This is demo based on [fluent-bit-observability-demo](https://github.com/fluent/fluent-bit-observability-demo)
+for using Fluentd to export OpenTelemetry traces and metrics.
+
+The telemetry data have been provided by js application in `app` directory.
+
+* metrics.js: OpenTelemetry instrumented application that exports metrics to an endpoint (Fluentd) using the otlp protocol
+* tracing.js: OpenTelemetry instrumented application that exports trace data to an endpoint (Fluentd) using the otlp protocol
+
+### Setup
+
+1. Run `docker-compose up -d --build` to start the application
+
+### Visualize metrics data
+
+1. Go to [`localhost:3000`](http://localhost:3000) and login to Grafana using credentials admin, admin
+
+2. Then, show `demo > Basic Service Trace` in [dashboard](http://localhost:3000/dashboards).
+
+![dashboard](./assets/dashboard.png)
+
+
+### Visualize trace data
+
+1. Navigate to [`localhost:16686`](http://localhost:16686/), select the correct service and find traces.
+
+![find-traces](./assets/find-traces.png)
+
+
+![trace-data](./assets/trace-data.png)
+

example/app/Dockerfile

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+FROM node:22
+WORKDIR /usr/src/app
+COPY package*.json ./
+RUN npm install
+COPY . .
+CMD ["/bin/bash", "-c", "node tracing.js & node metrics.js"]

example/app/metrics.js

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+/*  Copyright (C) 2022 The Fluent Bit authors
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+'use strict';
+
+const { DiagConsoleLogger, DiagLogLevel, diag } = require('@opentelemetry/api');
+const { OTLPMetricExporter } = require('@opentelemetry/exporter-metrics-otlp-proto');
+const { MeterProvider, PeriodicExportingMetricReader } = require('@opentelemetry/sdk-metrics-base');
+const { Resource } = require('@opentelemetry/resources');
+const { SemanticResourceAttributes } = require('@opentelemetry/semantic-conventions');
+
+// Optional and only needed to see the internal diagnostic logging (during development)
+diag.setLogger(new DiagConsoleLogger(), DiagLogLevel.DEBUG);
+
+const metricExporter = new OTLPMetricExporter({'url':'http://fluentd:4318/v1/metrics'});
+
+const meterProvider = new MeterProvider({
+  resource: new Resource({
+    [SemanticResourceAttributes.SERVICE_NAME]: 'basic-metric-service',
+  }),
+});
+
+meterProvider.addMetricReader(new PeriodicExportingMetricReader({
+  exporter: metricExporter,
+  exportIntervalMillis: 1000,
+}));
+
+const meter = meterProvider.getMeter('example-exporter-collector');
+
+const requestCounter = meter.createCounter('requests', {
+  description: 'Example of a Counter',
+});
+
+const upDownCounter = meter.createUpDownCounter('test_up_down_counter', {
+  description: 'Example of a UpDownCounter',
+});
+
+const attributes = { pid: process.pid, environment: 'staging' };
+
+setInterval(() => {
+  requestCounter.add(15, attributes);
+  upDownCounter.add(Math.random() > 0.5 ? 1 : -1, attributes);
+}, 1000);