box.iproto.override()

Since version 2.11.0. Set a new IPROTO request handler callback for the given request type.

Parameters:

• request_type (number) — a request type code. Possible values:

• a type code from box.iproto.type (except box.iproto.type.UNKNOWN) – override the existing request type handler.

• box.iproto.type.UNKNOWN – override the handler of unknown request types.

• handler (function) — IPROTO request handler. The signature of a handler function: function(sid, header, body), where

  • header (userdata): a request header encoded as a msgpack_object
  • body (userdata): a request body encoded as a msgpack_object

  Returns true on success, otherwise false. On false, there is a fallback to the default handler. Also, you can indicate an error by throwing an exception. In this case, the return value is false, but this does not always mean a failure.

  To reset the request handler, set the handler parameter to nil.

Returns

none

Possible errors:

If a Lua handler throws an exception, the behavior is similar to that of a remote procedure call. The following errors are returned to the client over IPROTO (see src/lua/utils.h):

• ER_PROC_LUA – an exception is thrown from a Lua handler, diagnostic is not set.
• diagnostics from src/box/errcode.h – an exception is thrown, diagnostic is set.

For details, see src/box/errcode.h.

Example:

Define a handler function for the box.iproto.type.SELECT request type:

 
local function iproto_select_handler_lua(header, body)    if body.space_id == 512 then        box.iproto.send(box.session.id(),                { request_type = box.iproto.type.OK,                  sync = header.SYNC,                  schema_version = box.info.schema_version },                { data = { 1, 2, 3 } })        return true    end    return falseend

Override box.iproto.type.SELECT handler:

 
box.iproto.override(box.iproto.type.SELECT, iproto_select_handler_lua)

Reset box.iproto.type.SELECT handler:

 
box.iproto.override(box.iproto.type.SELECT, nil)

Override a handler function for the unknown request type:

 
box.iproto.override(box.iproto.type.UNKNOWN, iproto_unknown_request_handler_lua)