What causes "invalid value for 'max_buffer_size': %w" in crowdsecurity/crowdsec?

Provide max_buffer_size as a plain integer number of bytes, e.g. max_buffer_size=10485760.

invalid value for 'max_buffer_size': %w

Error message

invalid value for 'max_buffer_size': %w

What it means

ConfigureByDSN parses the 'max_buffer_size' DSN parameter with strconv.Atoi. If the value is not a plain integer, the parse error is wrapped and returned. The parameter controls the bufio.Scanner buffer size for reading objects.

Source

Thrown at pkg/acquisition/modules/s3/config.go:241

			case "log_level":
				if len(value) != 1 {
					return errors.New("expected zero or one value for 'log_level'")
				}

				lvl, err := log.ParseLevel(value[0])
				if err != nil {
					return fmt.Errorf("unknown level %s: %w", value[0], err)
				}

				s.logger.Logger.SetLevel(lvl)
			case "max_buffer_size":
				if len(value) != 1 {
					return errors.New("expected zero or one value for 'max_buffer_size'")
				}

				maxBufferSize, err := strconv.Atoi(value[0])
				if err != nil {
					return fmt.Errorf("invalid value for 'max_buffer_size': %w", err)
				}

				s.logger.Debugf("Setting max buffer size to %d", maxBufferSize)
				s.Config.MaxBufferSize = maxBufferSize
			default:
				return fmt.Errorf("unknown parameter %s", key)
			}
		}
	}

	s.Config.Labels = labels
	s.Config.Mode = configuration.CAT_MODE
	s.Config.UniqueId = uuid

	pathParts := strings.Split(args[0], "/")
	s.logger.Debugf("pathParts: %v", pathParts)

	// FIXME: handle s3://bucket/

View on GitHub (pinned to 909b515798)

Solutions

Provide max_buffer_size as a plain integer number of bytes, e.g. max_buffer_size=10485760.
Remove units or separators from the value.
Omit the parameter to keep the default buffer size.

Example fix

// before
crowdsec-s3://mybucket?max_buffer_size=10MB
// after
crowdsec-s3://mybucket?max_buffer_size=10485760

Defensive patterns

Strategy: validation

Validate before calling

if _, err := strconv.Atoi(bufSize); err != nil {
    return fmt.Errorf("max_buffer_size must be an integer byte count, got %q", bufSize)
}

Prevention

Always emit plain byte counts, never sizes with units.
Centralize DSN construction in one helper with parameter validation.
Document accepted parameters where DSNs are templated.

When it happens

Trigger: DSN contains `max_buffer_size=10MB`, `max_buffer_size=abc`, or a value with spaces/units — anything strconv.Atoi cannot parse as an int.

Common situations: Users specifying units (KB/MB) or separators (underscores, commas) in the value, expecting the library to parse human-friendly sizes.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

AI-assisted analysis of crowdsecurity/crowdsec@909b515798 (2026-09-06). Data as JSON: /api/errors/14be7a07ebc20d10. Report an issue: GitHub.