提案：service configs via dns

// A list of one or more service config choices.
// The first matching entry wins.
[
  {
    // Criteria used to select this choice.
    // If a field is absent or empty, it matches all clients.
    // All fields must match a client for this choice to be selected.
    // If any unexpected field name is present in this object, the entire
    // config is considered invalid.
    //
    // Client language(s): a list of strings (e.g., "c++", "java", "go",
    // "python", etc).  Each string is case insensitive.
    "clientLanguage": [string],
    // Percentage: integer from 0 to 100 indicating the percentage of
    // clients that should use this choice.  If present, the number must
    // match the regular expression `^0|[0-9]|[1-9][0-9]|100$`
    // All other numbers are considered invalid.
    "percentage": number,
    // Client hostname(s): a list of strings.  Each name is case 
    // sensitive and must be an exact match of the hostname according to
    // the system.
    "clientHostname": [string],

    // The service config data object for clients that match the above
    // criteria.  (The format for this object is defined in
    // https://github.com/grpc/grpc/blob/master/doc/service_config.md.)
    // If this field is not an object, or is missing, or is otherwise 
    // invalid, the entire config is considered invalid.
    "serviceConfig": object
  }
]

_grpc_config.myserver  3600  TXT "grpc_config=[{\"serviceConfig\":{\"loadBalancingPolicy\":\"round_robin\",\"methodConfig\":[{\"name\":[{\"service\":\"MyService\",\"method\":\"Foo\"}],\"waitForReady\":true}]}}]"