feat: enable exporting logs via otel

CHANGELOG.md

@@ -9,10 +9,19 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/).
 ### Added
 
 - Predefined kind `telemetry-to-otlp` that creates exporters based on OTLP exporter configuration via environment variables
+- If `@opentelemetry/instrumentation-runtime-node` is in the project's dependencies but not in `cds.requires.telemetry.instrumentations`, it is registered automatically
+  - Disable via `cds.requires.telemetry.instrumentations.instrumentation-runtime-node = false`
 - Experimental!: Propagate W3C trace context to SAP HANA via session context `SAP_PASSPORT`
   - Enable via environment variable `SAP_PASSPORT`
-- If `@opentelemetry/instrumentation-runtime-node` is in the project's dependencies but not in `cds.env.requires.telemetry.instrumentations`, it is registered automatically
-  - Disable via `cds.env.requires.telemetry.instrumentations.instrumentation-runtime-node = false`
+- Experimental!: Intercept and export application logs (cf. `cds.log()`) via OpenTelemetry
+  - Enable by adding section `logging` to `cds.requires.telemetry` as follows (using `grpc` as an example):
+    ```json
+    "logging": {
+      "module": "@opentelemetry/exporter-logs-otlp-grpc",
+      "class": "OTLPLogExporter"
+    }
+    ```
+  - Requires additional dependencies `@opentelemetry/api-logs`, `@opentelemetry/sdk-logs`, and the configured exporter module (`cds.requires.telemetry.logging.module`)
 
 ### Changed
 
@@ -77,7 +86,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/).
 ### Added
 
 - Support for local modules (e.g., exporters) via `[...].module = '<path relative to cds.root>'`
-- Disable pool metrics via `cds.env.requires.telemetry.metrics._db_pool = false` (beta)
+- Disable pool metrics via `cds.requires.telemetry.metrics._db_pool = false` (beta)
 
 ### Fixed
 
@@ -90,7 +99,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/).
 ### Added
 
 - Support for own, high resolution timestamps
-  - Enable via `cds.env.requires.telemetry.tracing.hrtime = true`
+  - Enable via `cds.requires.telemetry.tracing.hrtime = true`
   - Enabled by default in development profile
 
 ## Version 0.0.5 - 2024-03-11
@@ -107,7 +116,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/).
   - Disable change via environment variable `HOST_METRICS_RETAIN_SYSTEM=true`
 - Metric exporter's property `temporalityPreference` always gets defaulted to `DELTA`
   - Was previously only done for kind `telemetry-to-dynatrace`
-  - Set custom value via `cds.env.requires.telemetry.metrics.exporter.config.temporalityPreference`
+  - Set custom value via `cds.requires.telemetry.metrics.exporter.config.temporalityPreference`
 
 ### Fixed
 

lib/index.js

@@ -7,6 +7,7 @@ const { SEMRESATTRS_SERVICE_NAME, SEMRESATTRS_SERVICE_VERSION } = require('@open
 
 const tracing = require('./tracing')
 const metrics = require('./metrics')
+const logging = require('./logging')
 const { getDiagLogLevel, getResource, _require } = require('./utils')
 
 function _getInstrumentations() {
@@ -63,13 +64,18 @@ module.exports = function () {
    */
   const meterProvider = metrics(resource)
 
+  /*
+   * setup logging
+   */
+  const loggerProvider = logging(resource)
+
   /*
    * register instrumentations
    */
   registerInstrumentations({
     tracerProvider,
     meterProvider,
-    // loggerProvider,
+    loggerProvider,
     instrumentations: _getInstrumentations()
   })
 }

lib/logging/index.js

@@ -0,0 +1,104 @@
+const cds = require('@sap/cds')
+const LOG = cds.log('telemetry')
+
+const { getEnv, getEnvWithoutDefaults } = require('@opentelemetry/core')
+
+const { getCredsForCLSAsUPS, augmentCLCreds, _require } = require('../utils')
+
+const _protocol2module = {
+  grpc: '@opentelemetry/exporter-logs-otlp-grpc',
+  'http/protobuf': '@opentelemetry/exporter-logs-otlp-proto',
+  'http/json': '@opentelemetry/exporter-logs-otlp-http'
+}
+
+function _getExporter() {
+  let {
+    kind,
+    logging: { exporter: loggingExporter },
+    credentials
+  } = cds.env.requires.telemetry
+
+  // for kind telemetry-to-otlp based on env vars
+  if (loggingExporter === 'env') {
+    const otlp_env = getEnvWithoutDefaults()
+    const dflt_env = getEnv()
+    const protocol =
+      otlp_env.OTEL_EXPORTER_OTLP_LOGS_PROTOCOL ??
+      otlp_env.OTEL_EXPORTER_OTLP_PROTOCOL ??
+      dflt_env.OTEL_EXPORTER_OTLP_LOGS_PROTOCOL ??
+      dflt_env.OTEL_EXPORTER_OTLP_PROTOCOL
+    loggingExporter = { module: _protocol2module[protocol], class: 'OTLPLogExporter' }
+  }
+
+  // use _require for better error message
+  const loggingExporterModule = _require(loggingExporter.module)
+  if (!loggingExporterModule[loggingExporter.class])
+    throw new Error(`Unknown logs exporter "${loggingExporter.class}" in module "${loggingExporter.module}"`)
+  const loggingConfig = { ...(loggingExporter.config || {}) }
+
+  if (kind.match(/to-cloud-logging$/)) {
+    if (!credentials) credentials = getCredsForCLSAsUPS()
+    if (!credentials) throw new Error('No SAP Cloud Logging credentials found.')
+    augmentCLCreds(credentials)
+    loggingConfig.url ??= credentials.url
+    loggingConfig.credentials ??= credentials.credentials
+  }
+
+  const exporter = new loggingExporterModule[loggingExporter.class](loggingConfig)
+  LOG._debug && LOG.debug('Using logs exporter:', exporter)
+
+  return exporter
+}
+
+module.exports = resource => {
+  if (!cds.env.requires.telemetry.logging?.exporter) return
+
+  const { logs, SeverityNumber } = require('@opentelemetry/api-logs')
+  const { LoggerProvider, BatchLogRecordProcessor } = require('@opentelemetry/sdk-logs')
+
+  let loggerProvider = logs.getLoggerProvider()
+  if (!loggerProvider.getDelegateLogger()) {
+    loggerProvider = new LoggerProvider({ resource })
+    logs.setGlobalLoggerProvider(loggerProvider)
+  } else {
+    LOG._warn && LOG.warn('LoggerProvider already initialized by a different module. It will be used as is.')
+    loggerProvider = loggerProvider.getDelegateLogger()
+  }
+
+  const exporter = _getExporter()
+  loggerProvider.addLogRecordProcessor(new BatchLogRecordProcessor(exporter))
+
+  const loggers = {}
+  const l2s = { 1: 'ERROR', 2: 'WARN', 3: 'INFO', 4: 'DEBUG', 5: 'TRACE' }
+
+  // intercept logs via format
+  const { format } = cds.log
+  cds.log.format = (module, level, ...args) => {
+    const res = format(module, level, ...args)
+
+    let log
+    try {
+      log = res.length === 1 && res[0].startsWith?.('{"') && JSON.parse(res[0])
+    } catch {
+      // ignore
+    }
+    if (log) {
+      const logger = loggers[module] || (loggers[module] = loggerProvider.getLogger(module))
+      const severity = l2s[level]
+      // TODO: what to log?
+      logger.emit({
+        severityNumber: SeverityNumber[severity],
+        severityText: severity,
+        body: log.msg,
+        attributes: { 'log.type': 'LogRecord' }
+      })
+    }
+
+    return res
+  }
+
+  // clear cached loggers
+  cds.log.loggers = {}
+
+  return loggerProvider
+}

lib/metrics/index.js

@@ -73,6 +73,7 @@ function _getExporter() {
 
   const exporter = new metricsExporterModule[metricsExporter.class](metricsConfig)
   LOG._debug && LOG.debug('Using metrics exporter:', exporter)
+
   return exporter
 }
 

lib/tracing/index.js

@@ -99,7 +99,7 @@ function _getExporter() {
   const tracingExporterModule =
     tracingExporter.module === '@cap-js/telemetry' ? require('../exporter') : _require(tracingExporter.module)
   if (!tracingExporterModule[tracingExporter.class])
-    throw new Error(`Unknown tracing exporter "${tracingExporter.class}" in module "${tracingExporter.module}"`)
+    throw new Error(`Unknown trace exporter "${tracingExporter.class}" in module "${tracingExporter.module}"`)
   const tracingConfig = { ...(tracingExporter.config || {}) }
 
   if (kind.match(/to-dynatrace$/)) {
@@ -124,7 +124,8 @@ function _getExporter() {
   }
 
   const exporter = new tracingExporterModule[tracingExporter.class](tracingConfig)
-  LOG._debug && LOG.debug('Using tracing exporter:', exporter)
+  LOG._debug && LOG.debug('Using trace exporter:', exporter)
+
   return exporter
 }
 
@@ -150,7 +151,7 @@ module.exports = resource => {
     !hasDependency('@opentelemetry/exporter-trace-otlp-proto')
   if (via_one_agent) {
     // if Dynatrace OneAgent is present, no exporter is needed
-    LOG._info && LOG.info('Dynatrace OneAgent detected, disabling tracing exporter')
+    LOG._info && LOG.info('Dynatrace OneAgent detected, disabling trace exporter')
   } else {
     const exporter = _getExporter()
     const spanProcessor =