Timing number 0b" + timingNumber.toString(2) + " has more th

Error message

Timing number 0b" + timingNumber.toString(2) + " has more than two bits of info

What it means

JavaClassNameLookup.__init__ raises ValueError when both expansion_service and classpath are given. These are mutually exclusive ways to control how the expansion service is launched: either a fully specified service address/spec, or just a classpath for the default service. Providing both is treated as a conflicting configuration.

Source

Thrown at sdks/typescript/src/apache_beam/coders/required_coders.ts:525

export class PaneInfoCoder implements Coder<PaneInfo> {
  static INSTANCE = new PaneInfoCoder();
  static ONE_AND_ONLY_FIRING = PaneInfoCoder.INSTANCE.decode(
    new Reader(new Uint8Array([0x09])),
    null!,
  );

  private static decodeTiming(timingNumber): Timing {
    switch (timingNumber) {
      case 0b00:
        return Timing.EARLY;
      case 0b01:
        return Timing.ON_TIME;
      case 0b10:
        return Timing.LATE;
      case 0b11:
        return Timing.UNKNOWN;
      default:
        throw new Error(
          "Timing number 0b" +
            timingNumber.toString(2) +
            " has more than two bits of info",
        );
    }
  }

  private static encodeTiming(timing: Timing): number {
    switch (timing) {
      case Timing.EARLY:
        return 0b00;
      case Timing.ON_TIME:
        return 0b01;
      case Timing.LATE:
        return 0b10;
      case Timing.UNKNOWN:
        return 0b11;
      default:

View on GitHub (pinned to 12126d8942)

Solutions

Remove the classpath argument if you want to use a specific expansion_service.
Remove the expansion_service argument and pass classpath to let Beam start a default service with extra jars.

Example fix

// before
JavaClassNameLookup('com.example.T', expansion_service='localhost:1234', classpath=['a.jar'])
// after
JavaClassNameLookup('com.example.T', classpath=['a.jar'])

Defensive patterns

Strategy: validation

Validate before calling

assert not (expansion_service and classpath), 'pass either expansion_service or classpath, not both'

Type guard

def service_config_ok(expansion_service, classpath) -> bool:
    return not (expansion_service and classpath)

Try / catch

try:
    lookup = JavaClassNameLookup(cls, expansion_service=svc, classpath=cp)
except ValueError as e:
    logger.error('Conflicting service config: %s', e)

Prevention

Centralize expansion service configuration in one place
When switching from classpath to a fixed service, delete the other argument
Document which of the two options each pipeline uses

When it happens

Trigger: JavaClassNameLookup(class_name, expansion_service='localhost:1234', classpath=['/path/x.jar']) — both parameters non-None/non-empty in the same constructor call.

Common situations: Copy-pasting example code that sets classpath into code that already passes expansion_service; layering configuration from two sources without clearing one.

Related errors

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/e4d8f339e7e6fe39. Report an issue: GitHub.