Unexpected ANSI color codes appearing in the severityText field

[mznet]

What version of OpenTelemetry are you using?

@opentelemetry/auto-instrumentations-node@0.62.0

What version of Node are you using?

v18.20.7

What did you do?

An example application prints logs at three different levels. In the OpenTelemetry logs emitted by this application, the severityText field contains both the log level and ANSI color codes—for example, \x1B[32minfo\x1B[39m, which represents the word “info” in green. Since severityText contains ANSI color codes, it’s difficult to search logs by log level.

OTLPExportDelegate items to be sent [ ...
LogRecordImpl {
    hrTime: [ 1753258688, 585000000 ],
    hrTimeObserved: [ 1753258688, 585000000 ],
    spanContext: undefined,
    resource: ResourceImpl {
      _rawAttributes: [Array],
      _asyncAttributesPending: false,
      _memoizedAttributes: undefined
    },
    instrumentationScope: {
      name: '@opentelemetry/winston-transport',
      version: '0.14.0',
      schemaUrl: undefined
    },
    attributes: { timestamp: '2025-07-23T08:18:08.585Z' },
    _severityText: '\x1B[32minfo\x1B[39m',
    _severityNumber: undefined,
    _body: 'Test error message',
    _eventName: undefined,
    totalAttributesCount: 1,
    _isReadonly: true,
    _logRecordLimits: { attributeCountLimit: 128, attributeValueLengthLimit: Infinity }
  }
]

What did you expect to see?

• SeverityText should contain only log level.

What did you see instead?

• SeverityText contains both log level and color code.

Additional context

https://gist.github.com/mznet/154f00599ae05a08f58a85454e73f90b

[trentm]

I can definintely repro. Using the example winston-using script from the gist above and running that instrumented with an SDK that enables instrumentation-winston (and its logSending feature), I see this OTLP data sent from the SDK:

ExportLogsServiceRequest {
  resourceLogs: [
    ResourceLogs {
      scopeLogs: [
        ScopeLogs {
          logRecords: [
            LogRecord {
              attributes: [ KeyValue { key: 'timestamp', value: AnyValue { stringValue: '2025-07-23T17:30:11.411Z' } } ],
              timeUnixNano: Long { low: -155125056, high: 408220060, unsigned: true },
              severityText: '\x1B[32minfo\x1B[39m',
              body: AnyValue { stringValue: 'Test info message' },
              droppedAttributesCount: 0,
              observedTimeUnixNano: Long { low: -155125056, high: 408220060, unsigned: true }
            },
            LogRecord {
              attributes: [ KeyValue { key: 'timestamp', value: AnyValue { stringValue: '2025-07-23T17:30:11.412Z' } } ],
              timeUnixNano: Long { low: -154125056, high: 408220060, unsigned: true },
              severityText: '\x1B[33mwarn\x1B[39m',
              body: AnyValue { stringValue: 'Test warning message' },
              droppedAttributesCount: 0,
              observedTimeUnixNano: Long { low: -154125056, high: 408220060, unsigned: true }
            },
            LogRecord {
              attributes: [ KeyValue { key: 'timestamp', value: AnyValue { stringValue: '2025-07-23T17:30:11.412Z' } } ],
              timeUnixNano: Long { low: -154125056, high: 408220060, unsigned: true },
              severityText: '\x1B[31merror\x1B[39m',
              body: AnyValue { stringValue: 'Test error message' },
              droppedAttributesCount: 0,
              observedTimeUnixNano: Long { low: -154125056, high: 408220060, unsigned: true }
            }
          ],
          scope: InstrumentationScope { attributes: [], name: '@opentelemetry/winston-transport', version: '0.14.0' }
        }
      ],
...

Note the ANSI codes in the severityText.
Almost certainly this will be interaction with the winston.format.colorize(), formatter being used for that Winston logger.

[trentm]

Here is a fix:

diff --git a/packages/winston-transport/src/utils.ts b/packages/winston-transport/src/utils.ts
index 976d0f55..9354efa8 100644
--- a/packages/winston-transport/src/utils.ts
+++ b/packages/winston-transport/src/utils.ts
@@ -60,19 +60,20 @@ function getSeverityNumber(level: string): SeverityNumber | undefined {
 }

 export function emitLogRecord(
-  record: Record<string, any>,
+  record: Record<string | symbol, any>,
   logger: Logger
 ): void {
   const { message, level, ...splat } = record;
   const attributes: LogAttributes = {};
+  const levelSym = record[Symbol.for('level')];
   for (const key in splat) {
     if (Object.prototype.hasOwnProperty.call(splat, key)) {
       attributes[key] = splat[key];
     }
   }
   const logRecord: LogRecord = {
-    severityNumber: getSeverityNumber(level),
-    severityText: level,
+    severityNumber: getSeverityNumber(levelSym),
+    severityText: levelSym,
     body: message,
     attributes: attributes,
   };

Now for a test case. Unfortunately the instr-winston tests are basically just not being run for winston@3 because of TAV-goofiness in the package.json file.

[trentm]

#2956 to fix this