[Tarantool-patches] [PATCH vshard 06/11] util: introduce fiber_is_self_canceled()

[Oleg Babin]

Thanks for your patch. LGTM.


On 23.02.2021 03:15, Vladislav Shpilevoy wrote:
> Original fiber.testcancel() has an issue - it is not
> exception-safe. This makes it unusable for code which wants to do
> cleanup before cancellation.
>
> The patch introduces util.fiber_is_self_canceled() which checks if
> the current fiber is canceled but returns true/false instead of
> throwing an error.
>
> The patch is going to be used in the map-reduce patches where it
> will be necessary to check if the fiber is canceled. And if it
> is - perform cleanup and quit whatever the code was doing.
>
> Part of #147
> ---
>   test/unit/util.result   | 28 ++++++++++++++++++++++++++++
>   test/unit/util.test.lua | 14 ++++++++++++++
>   vshard/util.lua         |  8 ++++++++
>   3 files changed, 50 insertions(+)
>
> diff --git a/test/unit/util.result b/test/unit/util.result
> index 679c087..c83e80c 100644
> --- a/test/unit/util.result
> +++ b/test/unit/util.result
> @@ -266,3 +266,31 @@ assert(type(err) == 'table')
>   ---
>   - true
>   ...
> +--
> +-- Exception-safe fiber cancel check.
> +--
> +self_is_canceled = util.fiber_is_self_canceled
> +---
> +...
> +assert(not self_is_canceled())
> +---
> +- true
> +...
> +ok = nil
> +---
> +...
> +_ = fiber.create(function()                                                     \
> +    local f = fiber.self()                                                      \
> +    pcall(f.cancel, f)                                                          \
> +    ok = self_is_canceled()                                                     \
> +end)
> +---
> +...
> +test_run:wait_cond(function() return ok ~= nil end)
> +---
> +- true
> +...
> +assert(ok)
> +---
> +- true
> +...
> diff --git a/test/unit/util.test.lua b/test/unit/util.test.lua
> index df3db6f..881feb4 100644
> --- a/test/unit/util.test.lua
> +++ b/test/unit/util.test.lua
> @@ -107,3 +107,17 @@ _ = test_run:wait_cond(function() return ok or err end)
>   assert(not ok)
>   err.message
>   assert(type(err) == 'table')
> +
> +--
> +-- Exception-safe fiber cancel check.
> +--
> +self_is_canceled = util.fiber_is_self_canceled
> +assert(not self_is_canceled())
> +ok = nil
> +_ = fiber.create(function()                                                     \
> +    local f = fiber.self()                                                      \
> +    pcall(f.cancel, f)                                                          \
> +    ok = self_is_canceled()                                                     \
> +end)
> +test_run:wait_cond(function() return ok ~= nil end)
> +assert(ok)
> diff --git a/vshard/util.lua b/vshard/util.lua
> index d78f3a5..30a1e6e 100644
> --- a/vshard/util.lua
> +++ b/vshard/util.lua
> @@ -225,6 +225,13 @@ local function fiber_cond_wait(cond, timeout)
>       return nil, lerror.make(err)
>   end
>   
> +--
> +-- Exception-safe way to check if the current fiber is canceled.
> +--
> +local function fiber_is_self_canceled()
> +    return not pcall(fiber.testcancel)
> +end
> +
>   return {
>       tuple_extract_key = tuple_extract_key,
>       reloadable_fiber_create = reloadable_fiber_create,
> @@ -235,4 +242,5 @@ return {
>       table_copy_yield = table_copy_yield,
>       table_minus_yield = table_minus_yield,
>       fiber_cond_wait = fiber_cond_wait,
> +    fiber_is_self_canceled = fiber_is_self_canceled,
>   }