[Tarantool-patches] [PATCH 1/1] test: fix flaky box/gh-4627-session-use-after-free

[Alexander Turenko]

This fix itself is okay for me, but, please, look at a few minor
comments below.

WBR, Alexander Turenko.

On Tue, Dec 03, 2019 at 01:05:30AM +0100, Vladislav Shpilevoy wrote:
> The problem was in that the test uses the global trigger
> box.session.on_disconnect() to set a global variable by one
> connection. But test-run can do multiple connects/reconnects to
> the same instance. That led to multiple invocations of
> box.session.on_disconnect(), which could override the global
> variable in unexpected ways and moments.
> 
> The patch makes only one session execute that trigger.
> 
> Probably related to https://github.com/tarantool/test-run/issues/46
> Follow up #4627
> ---
> Branch: https://github.com/tarantool/tarantool/tree/gerold103/session-flaky-test
> 
>  .../box/gh-4627-session-use-after-free.result | 28 +++++++++++++++++++
>  .../gh-4627-session-use-after-free.test.lua   | 20 +++++++++++++
>  2 files changed, 48 insertions(+)

> diff --git a/test/box/gh-4627-session-use-after-free.test.lua b/test/box/gh-4627-session-use-after-free.test.lua
> index 70624a96a..1b2ebfdc4 100644
> --- a/test/box/gh-4627-session-use-after-free.test.lua
> +++ b/test/box/gh-4627-session-use-after-free.test.lua
> @@ -15,15 +15,33 @@
>  net_box = require('net.box')
>  fiber = require('fiber')
>  
> +box.schema.user.grant('guest', 'execute', 'universe')
> +
> +-- This is a workaround for flakiness of the test
> +-- appearing when another test tries to connect to

I tentative that another test may access to a unix socket (tarantool's
binary port) that run on another worker: all those sockets are placed in
worker's directory. It seems that test-run itself doing some reconnects.

> +-- this one. By setting a flag for only one
> +-- session, others won't interfere in
> +-- session.on_disconnect().
> +function enable_on_disconnect()                 \
> +    box.session.storage.is_enabled = true       \
> +end
> +
>  sid_before_yield = nil
>  sid_after_yield = nil
>  func = box.session.on_disconnect(function()     \
> +    if not box.session.storage.is_enabled then  \
> +        return                                  \
> +    end                                         \
>      sid_before_yield = box.session.id()         \
>      fiber.yield()                               \
>      sid_after_yield = box.session.id()          \
>  end)
>  
>  connection = net_box.connect(box.cfg.listen)
> +-- Connections, not related to this one, won't
> +-- call this function, and therefore won't do
> +-- anything in session.on_disconnect() trigger.
> +connection:call('enable_on_disconnect')
>  connection:ping()

It seems that :ping() is not needed anymore.

>  connection:close()
>  
> @@ -33,3 +51,5 @@ sid_after_yield == sid_before_yield and sid_after_yield ~= 0 or \
>      {sid_after_yield, sid_before_yield}
>  
>  box.session.on_disconnect(nil, func)
> +
> +box.schema.user.revoke('guest', 'execute', 'universe')
> -- 
> 2.21.0 (Apple Git-122.2)
>