Re: [Tarantool-patches] [PATCH 0/6] Extending error functionality

[lvasiliev <lvasiliev@tarantool.org>]

Summary of discussion with Alexander Turenko, Vlad, Mons, Sergos and 
Kirill Yukhin:
1) Session parameters
Move negotiations to UPDATE (as for _vsession_settings).
As further optimization session settings can be moved to auth message 
for to remove an additional RTT

2) Backtrace
Leave adding to the error only Lua backtrace (which is added to the 
error at luaT_pusherror()).
We must have a per server option for enable/disable adding backtrace.
In addition a bactrace enable/disable adding can be forced by the 
creation function parametr.
The backtrace should be combined with the message if tostring is 
used.(@knazarov )
Notes:
To add a C bt is possible when error is created (for example) but unwind 
the Lua stack in diag.c is difficult (reason: the lua functions like 
lua_getstack, lua_getinfo are unavailable where)

3) About returning(return box.error.new(...)) an error through IPROTO
Now the error is serialized to string for marshaling through connection, 
which makes it difficult to add various error parameters.
In the first iteration format was changed to table. But after discussion 
was decided to add a new msgpack type for the errors transmitting(by 
analogy with MP_DECIMAL)
An intermediate type mp_error will be introduced for this purposes 
(reason: it is impossible to  create an object of the ClientError class 
(or some other classes) at the time of decoding)
Due to the need to use different serialization methods, depending on the 
session settings, the serializator context (containing fickle options) 
was added.

4) Payload
For storage the payload at struct error will be added ptr to data with 
data size.
For using a payload from Lua set/get_payload (worked with table as 
argument/return type) will be used. It is possible to use msgpack encode 
when set and decode on get, but not is rationally.
To reduce overhead is offered to save a link to the table and use it as 
response output.
For these purposes is proposed to use inheritance from the struct error 
in the C style with adding additional attributes like ptr to the Lua 
table. In the case of a marshaling through net the payload will be 
encoded/decoded with msgpack using.


On 24.03.2020 15:45, Leonid Vasiliev wrote:
> https://github.com/tarantool/tarantool/issues/4398
> https://github.com/tarantool/tarantool/tree/lvasiliev/gh-4398-expose-error-module-4
> 
> According to https://github.com/tarantool/tarantool/issues/4398
> (and after some discussion) we would like box.error to have:
> * Ability to create new error types
> * Transparent marshalling through net.box
> * Lua backtrace
> * payload (not implemented in patch)
> 
> 
> Leonid Vasiliev (6):
>    error: Add a Lua backtrace to error
>    error: Add the custom error type
>    iproto: Add negotiation phase
>    error: Add extended error transfer format
>    error: Add test for extended error
>    error: Transmit an error through IPROTO_OK as object
> 
>   src/box/errcode.h                    |   1 +
>   src/box/error.cc                     |  56 +++++++++
>   src/box/error.h                      |  32 ++++++
>   src/box/execute.c                    |   1 +
>   src/box/iproto.cc                    |  40 ++++++-
>   src/box/iproto_constants.h           |  25 +++++
>   src/box/lua/call.c                   |  29 +++--
>   src/box/lua/error.cc                 | 126 +++++++++++++++++----
>   src/box/lua/execute.c                |   2 +-
>   src/box/lua/net_box.c                |  34 ++++++
>   src/box/lua/net_box.lua              | 103 +++++++++++++++--
>   src/box/lua/tuple.c                  |  12 +-
>   src/box/session.cc                   |  16 +++
>   src/box/session.h                    |  20 ++++
>   src/box/sql/func.c                   |   4 +-
>   src/box/xrow.c                       | 160 ++++++++++++++++++++++++++
>   src/box/xrow.h                       |  48 +++++++-
>   src/lib/core/diag.c                  |  20 ++++
>   src/lib/core/diag.h                  |   5 +
>   src/lib/core/exception.cc            |   1 +
>   src/lib/core/mp_extension_types.h    |   4 +-
>   src/lib/core/port.h                  |   4 +-
>   src/lua/error.c                      |  45 +++++++-
>   src/lua/error.h                      |   6 +-
>   src/lua/error.lua                    |  65 ++++++++---
>   src/lua/msgpack.c                    |  26 +++--
>   src/lua/msgpack.h                    |   8 +-
>   src/lua/utils.c                      |  28 ++++-
>   src/lua/utils.h                      |  27 ++++-
>   test/app/fiber.result                |  35 ++++--
>   test/app/fiber.test.lua              |  11 +-
>   test/box-tap/extended_error.test.lua | 212 +++++++++++++++++++++++++++++++++++
>   test/box/misc.result                 |  51 +++++++--
>   test/box/misc.test.lua               |  19 +++-
>   34 files changed, 1161 insertions(+), 115 deletions(-)
>   create mode 100755 test/box-tap/extended_error.test.lua
>