chore(llmobs): Add llmobs product enabled telemetry metrics (#5475)

* Add product_enabled metric, need to add tags

* Add llmobs enabled metrics - wip, add more tags

* Add manual flag

* Use env var check

* Allow optional envs

* fmt

Author: Yun-Kim

packages/dd-trace/src/llmobs/index.js

@@ -6,6 +6,7 @@ const { storage } = require('./storage')
 
 const LLMObsSpanProcessor = require('./span_processor')
 
+const telemetry = require('./telemetry')
 const { channel } = require('dc-polyfill')
 const spanProcessCh = channel('dd-trace:span:process')
 const evalMetricAppendCh = channel('llmobs:eval-metric:append')
@@ -29,6 +30,7 @@ let spanWriter
 let evalWriter
 
 function enable (config) {
+  const startTime = performance.now()
   // create writers and eval writer append and flush channels
   // span writer append is handled by the span processor
   evalWriter = new LLMObsEvalMetricsWriter(config)
@@ -44,6 +46,7 @@ function enable (config) {
 
   // distributed tracing for llmobs
   injectCh.subscribe(handleLLMObsParentIdInjection)
+  telemetry.recordLLMObsEnabled(startTime, config)
 }
 
 function disable () {

packages/dd-trace/src/llmobs/telemetry.js

@@ -74,6 +74,23 @@ function incrementLLMObsSpanFinishedCount (span, value = 1) {
   llmobsMetrics.count('span.finished', tags).inc(value)
 }
 
+function recordLLMObsEnabled (startTime, config, value = 1) {
+  const initTimeMs = performance.now() - startTime
+  // There isn't an easy way to determine if a user automatically enabled LLMObs via
+  // in-code or command line setup. We'll use the presence of DD_LLMOBS_ENABLED env var
+  // as a rough heuristic, but note that this isn't perfect since
+  // a user may have env vars but enable manually in code.
+  const autoEnabled = !!config._env?.['llmobs.enabled']
+  const tags = {
+    error: 0,
+    agentless: Number(config.llmobs.agentlessEnabled),
+    site: config.site,
+    auto: Number(autoEnabled)
+  }
+  llmobsMetrics.count('product_enabled', tags).inc(value)
+  llmobsMetrics.distribution('init_time', tags).track(initTimeMs)
+}
+
 function recordLLMObsRawSpanSize (event, rawEventSize) {
   const tags = extractTagsFromSpanEvent(event)
   llmobsMetrics.distribution('span.raw_size', tags).track(rawEventSize)
@@ -86,6 +103,7 @@ function recordLLMObsSpanSize (event, eventSize, shouldTruncate) {
 }
 
 module.exports = {
+  recordLLMObsEnabled,
   incrementLLMObsSpanStartCount,
   incrementLLMObsSpanFinishedCount,
   recordLLMObsRawSpanSize,