feat(esbuild-plugin): esbuild plugin to prepare bundled modules for instrumentation

packages/esbuild-plugin/README.md

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+# OTel esbuild-plugin
+
+This is a proposal for a `diagnostics_channel`-based mechanism for bundlers
+to hand off a loaded module, at runtime, to possibly active OTel
+instrumentations. This is an alternative proposal to
+https://github.com/open-telemetry/opentelemetry-js-contrib/pull/1856
+
+More details in the PR.
+
+XXX obviously I need to fill this all in
+
+
+## Dev Notes
+
+While this is all still in a development state, here is roughly how I work on this:
+
+Get a clone of the https://github.com/open-telemetry/opentelemetry-js/pull/4818 feature branch (e.g. to `~/tm/opentelemetry-js10` in the example below).
+Get a clone of the https://github.com/open-telemetry/opentelemetry-js-contrib/pull/2295 feature branch (e.g. to `~/tm/opentelemetry-js-contrib5` in the example below).
+
+Setup the node_modules in the example in the contrib repo.
+
+```bash
+cd ~/tm/opentelemetry-js-contrib5/packages/esbuild-plugin/example   # my tm-esbuild-plugin-alternative branch
+npm install   # get the initial layout
+```
+
+Build and copy in the changes from `@opentelemetry/instrumentation` in the core repo clone.
+
+```bash
+cd ~/tm/opentelemetry-js10/experimental/packages/opentelemetry-instrumentation   # my tm-esbuild-plugin-alternative branch
+vi ...   # make whatever edits I need
+npm run compile
+rsync -av ~/tm/opentelemetry-js10/experimental/packages/opentelemetry-instrumentation/build/ ~/tm/opentelemetry-js-contrib5/packages/esbuild-plugin/example/node_modules/@opentelemetry/instrumentation/build/
+```
+
+Back to the opentelemetry-js-contrib clone.
+
+```bash
+cd ~/tm/opentelemetry-js-contrib5/packages/esbuild-plugin/example
+```
+
+Run services used by app.js in a separate terminal:
+
+```bash
+docker run --name redis -ti --rm -p 6379:6379 redis:7   # run redis in a terminal for app.js to use
+```
+
+To watch OTel telemetry data for dev, I personally use `mockotlpserver` (https://github.com/elastic/elastic-otel-node/tree/main/packages/mockotlpserver#readme) which I and co-workers have written at Elastic. It is a smallish Node.js app that listens on the OTLP/HTTP and gRPC default ports and dumps a text representation of the data it receives. You can use it as follows, or use whatever you are used to:
+
+```bash
+npx @elastic/mockotlpserver
+```
+
+Now, run the *unbundled* app with instrumentation to see what to expect:
+
+```bash
+export OTEL_NODE_DISABLED_INSTRUMENTATIONS=net,dns,fs # disable some distracting instrumentations
+export OTEL_NODE_RESOURCE_DETECTORS=env,host,os,process,serviceinstance  # avoid cloud detectors to reduce noise
+node -r @opentelemetry/auto-instrumentations-node/register app.js
+```
+
+If you get the same as me, the "mockotlpserver" summary output shows this tracing data:
+
+```
+------ trace b3fbd7 (1 span) ------
+       span c0f9c8 "redis-connect" (6.2ms, SPAN_KIND_CLIENT)
+------ trace a9186c (1 span) ------
+       span 8666f5 "redis-SET" (0.7ms, SPAN_KIND_CLIENT)
+------ trace 2f54b8 (4 spans) ------
+       span 65d728 "GET" (7.7ms, SPAN_KIND_CLIENT, GET http://localhost:3000/ping -> 200)
+  +3ms `- span 91109f "GET /ping" (4.4ms, SPAN_KIND_SERVER, GET http://localhost:3000/ping -> 200)
+  +0ms   `- span f4aaca "request handler - fastify" (3.1ms, SPAN_KIND_INTERNAL)
+  +1ms     `- span 92f5d1 "redis-GET" (1.4ms, SPAN_KIND_CLIENT)
+```
+
+Now run the *bundled* app with instrumentation and compare:
+
+```bash
+vi esbuild.mjs  # edit the `otelPlugin` function
+npm run build   # build the bundle (in build/app.js)
+node -r @opentelemetry/auto-instrumentations-node/register build/app.js
+```
+
+Verify that the bundle isn't using `node_modules/{redis,fastify}`:
+
+```bash
+rm -rf node_modules/fastify node_modules/redis
+node -r @opentelemetry/auto-instrumentations-node/register build/app.js
+```

packages/esbuild-plugin/example/.npmrc

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+package-lock=false

packages/esbuild-plugin/example/app.js

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+const http = require('http');
+const fastify = require('fastify');
+const {createClient} = require('redis');
+// const clientS3 = require('@aws-sdk/client-s3');
+// console.log('XXX client-s3: ', !!clientS3);
+
+const redis = createClient();
+
+const server = fastify();
+server.get('/ping', async (req, reply) => {
+    const bar = await redis.get('bar');
+    reply.send(`pong (redis key "bar" is: ${bar})`);
+});
+
+async function main() {
+    await redis.connect();
+    await redis.set('bar', 'baz');
+
+    await server.listen({port: 3000});
+    const port = server.server.address().port;
+    await new Promise((resolve) => {
+        http.get(`http://localhost:${port}/ping`, (res) => {
+            const chunks = [];
+            res.on('data', (chunk) => { chunks.push(chunk); });
+            res.on('end', () => {
+              console.log('client res: status=%s headers=%s body=%s',
+                res.statusCode, res.headers, Buffer.concat(chunks).toString());
+              resolve();
+            });
+        });
+    });
+    server.close();
+
+    await redis.quit();
+}
+
+main();