From 6001078abf5e754d8ccdea26d7869142ffcdb1c0 Mon Sep 17 00:00:00 2001
From: sjvans <30337871+sjvans@users.noreply.github.com>
Date: Tue, 8 Oct 2024 12:32:06 +0200
Subject: [PATCH] feat: propagate trace context to hana via sap passport
 session context (#230)

---
 CHANGELOG.md         |  9 +++++++--
 README.md            |  1 +
 lib/tracing/index.js |  9 +++++++++
 lib/tracing/trace.js | 31 +++++++++++++++++++++++++++++++
 4 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 865229e..4b559b5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,7 +4,12 @@ All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 The format is based on [Keep a Changelog](http://keepachangelog.com/).
 
-## Version 1.0.2 - tbd
+## Version 1.1.0 - tbd
+
+### Added
+
+- Experimental!: Propagate W3C trace context to SAP HANA via session context `SAP_PASSPORT`
+  - Enable via environment variable `SAP_PASSPORT`
 
 ### Fixed
 
@@ -24,7 +29,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/).
 - Support for SAP Cloud Logging credentials via user-provided service
 - Support for adding `@opentelemetry/instrumentation-runtime-node`
   - `npm add @opentelemetry/instrumentation-runtime-node`
-  -  to `cds.requires.telemetry.instrumentations`, add:
+  -  To `cds.requires.telemetry.instrumentations`, add:
       ```json
       "instrumentation-runtime-node": {
         "class": "RuntimeNodeInstrumentation",
diff --git a/README.md b/README.md
index de09af0..b3bb7f5 100644
--- a/README.md
+++ b/README.md
@@ -438,6 +438,7 @@ Hence, the `hrtime` mode is on by default in development but not in production.
 
 - `NO_TELEMETRY`: Disables the plugin
 - `NO_LOCATE`: Disables function location in tracing
+- `SAP_PASSPORT`: Enables propagating W3C trace context to SAP HANA (experimental!)
 - `OTEL_LOG_LEVEL`: If not specified, the log level of cds logger `telemetry` is used
 - `OTEL_SERVICE_NAME`: If not specified, the name is determined from package.json (defaulting to "CAP Application")
 - `OTEL_SERVICE_VERSION`: If not specified, the version is determined from package.json (defaulting to "1.0.0")
diff --git a/lib/tracing/index.js b/lib/tracing/index.js
index 0a44b51..0b0367c 100644
--- a/lib/tracing/index.js
+++ b/lib/tracing/index.js
@@ -147,6 +147,15 @@ module.exports = resource => {
     cds._telemetry.tracer._active = true
   })
 
+  // clear sap passport for new tx
+  if (process.env.SAP_PASSPORT) {
+    cds.on('served', () => {
+      cds.db?.before('BEGIN', async function () {
+        if (this.dbc?.constructor.name in { HDBDriver: 1, HANAClientDriver: 1 }) this.dbc.set({ SAP_PASSPORT: '' })
+      })
+    })
+  }
+
   /*
    * add tracing
    */
diff --git a/lib/tracing/trace.js b/lib/tracing/trace.js
index 787e7e1..c76cbff 100644
--- a/lib/tracing/trace.js
+++ b/lib/tracing/trace.js
@@ -1,4 +1,5 @@
 const cds = require('@sap/cds')
+const LOG = cds.log('telemetry')
 
 const otel = require('@opentelemetry/api')
 const { SpanKind, SpanStatusCode, ROOT_CONTEXT } = otel
@@ -244,6 +245,36 @@ function trace(name, fn, targetObj, args, options = {}) {
 
     _setAttributes(span, _getDynamicDBAttributes(options, args, parentSpan))
 
+    // SAP Passport
+    if (process.env.SAP_PASSPORT && targetObj.dbc?.constructor.name in { HDBDriver: 1, HANAClientDriver: 1 }) {
+      const { spanId, traceId } = span.spanContext()
+      // prettier-ignore
+      let passport = [
+        /* EYECATCHER      */ '2A54482A',
+        /* VERSION         */ '03',
+        /* LENGTH          */ '00E6',
+        /* TRACELEVEL      */ '0000',
+        /* COMPONENTID     */ '2020202020202020202020202020202020202020202020202020202020202020',
+        /* SERVICE         */ '0000',
+        /* USER            */ '2020202020202020202020202020202020202020202020202020202020202020',
+        /* ACTION          */ '20202020202020202020202020202020202020202020202020202020202020202020202020202020',
+        /* ACTIONTYPE      */ '0000',
+        /* PREVCOMPONENTID */ Buffer.from(span.resource.attributes['service.name'].substr(0, 32).padEnd(32, ' ')).toString('hex'),
+        /* TRANSACTIONID   */ Buffer.from(traceId.toUpperCase()).toString('hex'),
+        /* CLIENT          */ '202020',
+        /* COMPONENTTYPE   */ '0000',
+        /* ROOTCONTEXTID   */ traceId.toUpperCase(),
+        /* CONNECTIONID    */ '0000000000000001' + spanId.toUpperCase(),
+        /* CONNECTIONCNT   */ '00000001',
+        /* VARPARTCOUNT    */ '0000',
+        /* VARPARTOFFSET   */ '0000', // REVISIT: @sap/dsrpassport uses '0226'
+        /* EYECATCHER      */ '2A54482A'
+      ]
+      passport = passport.join('')
+      LOG._debug && LOG.debug('Setting SAP Passport:', passport)
+      targetObj.dbc.set({ SAP_PASSPORT: passport })
+    }
+
     // augment db.statement at parent, if necessary
     if (
       span.attributes[SEMATTRS_DB_STATEMENT] &&