feat: logs signal support (#54)

The Elastic SDK now adds a global Logger Provider.
mockotlpserver now has a 'logs-summary' printer to nicely show
received 'ExportLogsServiceRequest' data, and the 'json' printer
will normalize the service request data similar to as is being
done for Trace and Metrics service requests.

'examples/bunyan-logging-app.js' shows using a Bunyan logger with
'examples/start-elastic-sdk.js' which shows how to start the
Elastic distro SDK manually, including how to specify custom
instrumentations -- in this case the Bunyan instrumentation.

Refs: #41

examples/bunyan-logging-app.js

@@ -0,0 +1,18 @@
+// Usage:
+//  node -r @elastic/opentelemetry-node/start.js bunyan-logging-app.js
+
+const path = require('path');
+const otel = require('@opentelemetry/api');
+const bunyan = require('bunyan');
+
+const log = bunyan.createLogger({name: path.parse(__filename).name});
+
+log.info({foo: 'bar'}, 'hi there');
+log.warn(new Error('boom'), 'oops');
+log.debug('hi at debug-level');
+
+const tracer = otel.trace.getTracer('example');
+tracer.startActiveSpan('manual-span', (span) => {
+    log.info('this record will have trace-correlation fields');
+    span.end();
+});

examples/package.json

@@ -4,8 +4,10 @@
   "private": true,
   "version": "0.1.0",
   "scripts": {},
-  "dependencies": {
+  "devDependencies": {
     "@elastic/opentelemetry-node": "*",
+    "@opentelemetry/instrumentation-bunyan": "^0.35.0",
+    "bunyan": "^1.8.15",
     "express": "^4.18.2"
   }
 }

examples/start-elastic-sdk.js

@@ -0,0 +1,49 @@
+/**
+ * Setup and start the Elastic OpenTelemetry Node.js SDK distro.
+ *
+ * This is an alternative to the `node -r @elastic/opentelemetry-node/start.js`
+ * convenience for starting the SDK. Starting the SDK manually via a local
+ * file can be useful to allow configuring the SDK with code.
+ *
+ * Usage:
+ *      node -r ./start-elastic-sdk.js SCRIPT.js
+ */
+
+const path = require('path');
+
+const {ElasticNodeSDK} = require('@elastic/opentelemetry-node');
+
+// TODO: remove BunyanInstrumentation manual usage when the distro includes it by default
+const {
+    BunyanInstrumentation,
+} = require('@opentelemetry/instrumentation-bunyan');
+
+const sdk = new ElasticNodeSDK({
+    serviceName: path.parse(process.argv[1]).name,
+    instrumentations: [
+        // One can **override** the instrumentations provided by ElasticNodeSDK
+        // by specifying `instrumentations`. How to **extended** the set of
+        // instrumentations provided by ElasticNodeSDK is to be determined (TODO).
+        new BunyanInstrumentation(),
+    ],
+});
+
+process.on('SIGTERM', async () => {
+    try {
+        await sdk.shutdown();
+    } catch (err) {
+        console.warn('warning: error shutting down OTel SDK', err);
+    }
+    process.exit();
+});
+
+process.once('beforeExit', async () => {
+    // Flush recent telemetry data if about the shutdown.
+    try {
+        await sdk.shutdown();
+    } catch (err) {
+        console.warn('warning: error shutting down OTel SDK', err);
+    }
+});
+
+sdk.start();