Errors

Occasionally a Whois command can raise an exception when an unexpected error occurs. This section describes the available error classes and the conventions adopted.

Base Error

The base exception class for Whois is called Whois::Error. Any Whois exception inherits from this class.

In turns, this class extends the Ruby StandardError exception class. So make sure to list rescue from a Whois::Error before any StandardError statement or your code might not work properly.

# Example:  Example of invalid rescue

begin
  Whois.whois("google.com")
rescue StandardError => e
  # do something
rescue Whois::Error => e
  # do something
end

# Example:  Example of valid rescue

begin
  Whois.whois("google.com")
rescue Whois::Error => e
  # do something
rescue StandardError => e
  # do something
end

Component Specific Errors

Different element of the library might raise different type of errors. For instance, a Whois::Server connecting to a WHOIS interface can raise a socket error while a Whois::Record::Parser trying to decompose a response can fail due to unexpected tokens.

Each component of the library defines its own base error classes.

  • ServerError < Error
  • ParserError < Error

and so on

  • AttributeNotImplemented < ParserError < Error
  • NoInterfaceError < InterfaceNotSupported < ServerError < Error
  • WebInterfaceError < InterfaceNotSupported < ServerError < Error

This encapsulation, along with the library conventions, makes your exception experience less painful.

Conventions

Whois never raises global exceptions outside the Whois namespace.

This encapsulation offers a bullet-proof approach if you need to rescue an exception and you want to be sure it originates from a Whois statement.

# Example:  How to rescue from a Whois::Error and Standard error at the same time.

begin
  r = Whois.whois("google.com")
  very_complex_operation_with(a.nameservers)
rescue Whois::Error => e
  abort("Whois Exception #{e.class}: #{e.message}")
rescue StandardError => e
  abort("Application Exception #{e.class}: #{e.message}")
end

Also, you can easily rescue from any Whois error with one line of code, for instance for debugging or logging purposes.

# Example:  How to rescue from a Whois::Error

begin
  r = Whois.whois("google.com")
  r.nameservers
rescue Whois::Error => e
  abort("Exception #{e.class}: #{e.message}")
end

This is a consistent behavior across the entire library. If a statement doesn't follow this rule, this is a bug. Component Specific errors follows the same convention.

The only exception to this rule is the Timeout::Error exception which is intentionally left unmanaged.