collect and propagate process tags

packages/dd-trace/src/process-tags/index.js

@@ -0,0 +1,68 @@
+'use strict'
+
+const path = require('node:path')
+const pkg = require('../pkg')
+const { tags } = require('../config_defaults')
+
+const CURRENT_WORKING_DIRECTORY = process.cwd()
+const ENTRYPOINT_PATH = require.main?.filename || ''
+console.log('ENTRYPOINT_PATH:', ENTRYPOINT_PATH)
+console.log('CURRENT_WORKING_DIRECTORY:', CURRENT_WORKING_DIRECTORY)
+
+// if we don't have a value we should send nothing at all
+// e.g. undefined which is dropped upon JSON serialization
+
+// $ cd /foo/bar && node baz/banana.js
+// entrypoint.workdir = bar
+// entrypoint.name = banana
+// entrypoint.type = script
+// entrypoint.basedir = baz
+// package.json.name = <from package.json>
+
+module.exports = function getProcessTags () {
+  // this list is sorted alphabetically for consistent serialization
+  const tags = [
+    // the immediate parent directory name of the entrypoint script, e.g. /foo/bar/baz/banana.js -> baz
+    ['entrypoint.basedir', ENTRYPOINT_PATH === '' ? undefined : path.basename(path.dirname(ENTRYPOINT_PATH))],
+
+    // the entrypoint script filename without the extension, e.g. /foo/bar/baz/banana.js -> banana
+    ['entrypoint.name', path.basename(ENTRYPOINT_PATH, path.extname(ENTRYPOINT_PATH)) || undefined],
+
+    // always script for JavaScript applications
+    ['entrypoint.type', 'script'],
+
+    // last segment of the current working directory, e.g. /foo/bar/baz/ -> baz
+    ['entrypoint.workdir', path.basename(CURRENT_WORKING_DIRECTORY) || undefined],
+
+    // the .name field from the application's package.json
+    ['package.json.name', pkg.name || undefined]
+  ]
+
+  const serialized = serialize(tags)
+
+  return {
+    tags,
+    serialized
+  }
+}
+
+function serialize(tags) {
+  const intermediary = []
+  for (let [name, value] of tags) {
+    if (value === undefined) continue
+    intermediary.push(`${name}:${sanitize(value)}`)
+  }
+  return intermediary.join(',')
+}
+
+/**
+ * Sanitize a process tag value
+ * 
+ * @param {string} value 
+ * @returns {string}
+ */
+function sanitize(value) {
+  return String(value)
+    .toLowerCase()
+    .replaceAll(/[^a-zA-Z0-9/_.-]/g, '_')
+}

packages/dd-trace/src/proxy.js

@@ -18,6 +18,7 @@ const {
   removeBaggageItem,
   removeAllBaggageItems
 } = require('./baggage')
+const getProcessTags = require('./process-tags')
 
 class LazyModule {
   constructor (provider) {
@@ -78,6 +79,7 @@ class Tracer extends NoopProxy {
     this.getAllBaggageItems = getAllBaggageItems
     this.removeBaggageItem = removeBaggageItem
     this.removeAllBaggageItems = removeAllBaggageItems
+    this.processTags = getProcessTags()
 
     // these requires must work with esm bundler
     this._modules = {