Re: [Tarantool-patches] [PATCH 1/9] rlist: move rlist to a new module

[Oleg Babin via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

Hi! Thanks for your patch. LGTM.

On 10/02/2021 02:46, Vladislav Shpilevoy wrote:
> Rlist in storage/init.lua implemented a container similar to rlist
> in libsmall in Tarantool core. Doubly-linked list.
>
> It does not depend on anything in storage/init.lua, and should
> have been done in a separate module from the beginning.
>
> Now init.lua is going to grow even more in scope of map-reduce
> feature, beyond 3k lines if nothing would be moved out. It was
> decided (by me) that it crosses the border of when it is time to
> split init.lua into separate modules.
>
> The patch takes the low hanging fruit by moving rlist into its
> own module.
> ---
>   test/unit/rebalancer.result   |  99 -----------------------------
>   test/unit/rebalancer.test.lua |  27 --------
>   test/unit/rlist.result        | 114 ++++++++++++++++++++++++++++++++++
>   test/unit/rlist.test.lua      |  33 ++++++++++
>   vshard/rlist.lua              |  53 ++++++++++++++++
>   vshard/storage/init.lua       |  68 +++-----------------
>   6 files changed, 208 insertions(+), 186 deletions(-)
>   create mode 100644 test/unit/rlist.result
>   create mode 100644 test/unit/rlist.test.lua
>   create mode 100644 vshard/rlist.lua
>
> diff --git a/test/unit/rebalancer.result b/test/unit/rebalancer.result
> index 2fb30e2..19aa480 100644
> --- a/test/unit/rebalancer.result
> +++ b/test/unit/rebalancer.result
> @@ -1008,105 +1008,6 @@ build_routes(replicasets)
>   -- the latter is a dispenser. It is a structure which hands out
>   -- destination UUIDs in a round-robin manner to worker fibers.
>   --
> -list = rlist.new()
> ----
> -...
> -list
> ----
> -- count: 0
> -...
> -obj1 = {i = 1}
> ----
> -...
> -rlist.remove(list, obj1)
> ----
> -...
> -list
> ----
> -- count: 0
> -...
> -rlist.add_tail(list, obj1)
> ----
> -...
> -list
> ----
> -- count: 1
> -  last: &0
> -    i: 1
> -  first: *0
> -...
> -rlist.remove(list, obj1)
> ----
> -...
> -list
> ----
> -- count: 0
> -...
> -obj1
> ----
> -- i: 1
> -...
> -rlist.add_tail(list, obj1)
> ----
> -...
> -obj2 = {i = 2}
> ----
> -...
> -rlist.add_tail(list, obj2)
> ----
> -...
> -list
> ----
> -- count: 2
> -  last: &0
> -    i: 2
> -    prev: &1
> -      i: 1
> -      next: *0
> -  first: *1
> -...
> -obj3 = {i = 3}
> ----
> -...
> -rlist.add_tail(list, obj3)
> ----
> -...
> -list
> ----
> -- count: 3
> -  last: &0
> -    i: 3
> -    prev: &1
> -      i: 2
> -      next: *0
> -      prev: &2
> -        i: 1
> -        next: *1
> -  first: *2
> -...
> -rlist.remove(list, obj2)
> ----
> -...
> -list
> ----
> -- count: 2
> -  last: &0
> -    i: 3
> -    prev: &1
> -      i: 1
> -      next: *0
> -  first: *1
> -...
> -rlist.remove(list, obj1)
> ----
> -...
> -list
> ----
> -- count: 1
> -  last: &0
> -    i: 3
> -  first: *0
> -...
>   d = dispenser.create({uuid = 15})
>   ---
>   ...
> diff --git a/test/unit/rebalancer.test.lua b/test/unit/rebalancer.test.lua
> index a4e18c1..8087d42 100644
> --- a/test/unit/rebalancer.test.lua
> +++ b/test/unit/rebalancer.test.lua
> @@ -246,33 +246,6 @@ build_routes(replicasets)
>   -- the latter is a dispenser. It is a structure which hands out
>   -- destination UUIDs in a round-robin manner to worker fibers.
>   --
> -list = rlist.new()
> -list
> -
> -obj1 = {i = 1}
> -rlist.remove(list, obj1)
> -list
> -
> -rlist.add_tail(list, obj1)
> -list
> -
> -rlist.remove(list, obj1)
> -list
> -obj1
> -
> -rlist.add_tail(list, obj1)
> -obj2 = {i = 2}
> -rlist.add_tail(list, obj2)
> -list
> -obj3 = {i = 3}
> -rlist.add_tail(list, obj3)
> -list
> -
> -rlist.remove(list, obj2)
> -list
> -rlist.remove(list, obj1)
> -list
> -
>   d = dispenser.create({uuid = 15})
>   dispenser.pop(d)
>   for i = 1, 14 do assert(dispenser.pop(d) == 'uuid', i) end
> diff --git a/test/unit/rlist.result b/test/unit/rlist.result
> new file mode 100644
> index 0000000..c8aabc0
> --- /dev/null
> +++ b/test/unit/rlist.result
> @@ -0,0 +1,114 @@
> +-- test-run result file version 2
> +--
> +-- gh-161: parallel rebalancer. One of the most important part of the latter is
> +-- a dispenser. It is a structure which hands out destination UUIDs in a
> +-- round-robin manner to worker fibers. It uses rlist data structure.
> +--
> +rlist = require('vshard.rlist')
> + | ---
> + | ...
> +
> +list = rlist.new()
> + | ---
> + | ...
> +list
> + | ---
> + | - count: 0
> + | ...
> +
> +obj1 = {i = 1}
> + | ---
> + | ...
> +list:remove(obj1)
> + | ---
> + | ...
> +list
> + | ---
> + | - count: 0
> + | ...
> +
> +list:add_tail(obj1)
> + | ---
> + | ...
> +list
> + | ---
> + | - count: 1
> + |   last: &0
> + |     i: 1
> + |   first: *0
> + | ...
> +
> +list:remove(obj1)
> + | ---
> + | ...
> +list
> + | ---
> + | - count: 0
> + | ...
> +obj1
> + | ---
> + | - i: 1
> + | ...
> +
> +list:add_tail(obj1)
> + | ---
> + | ...
> +obj2 = {i = 2}
> + | ---
> + | ...
> +list:add_tail(obj2)
> + | ---
> + | ...
> +list
> + | ---
> + | - count: 2
> + |   last: &0
> + |     i: 2
> + |     prev: &1
> + |       i: 1
> + |       next: *0
> + |   first: *1
> + | ...
> +obj3 = {i = 3}
> + | ---
> + | ...
> +list:add_tail(obj3)
> + | ---
> + | ...
> +list
> + | ---
> + | - count: 3
> + |   last: &0
> + |     i: 3
> + |     prev: &1
> + |       i: 2
> + |       next: *0
> + |       prev: &2
> + |         i: 1
> + |         next: *1
> + |   first: *2
> + | ...
> +
> +list:remove(obj2)
> + | ---
> + | ...
> +list
> + | ---
> + | - count: 2
> + |   last: &0
> + |     i: 3
> + |     prev: &1
> + |       i: 1
> + |       next: *0
> + |   first: *1
> + | ...
> +list:remove(obj1)
> + | ---
> + | ...
> +list
> + | ---
> + | - count: 1
> + |   last: &0
> + |     i: 3
> + |   first: *0
> + | ...
> diff --git a/test/unit/rlist.test.lua b/test/unit/rlist.test.lua
> new file mode 100644
> index 0000000..db52955
> --- /dev/null
> +++ b/test/unit/rlist.test.lua
> @@ -0,0 +1,33 @@
> +--
> +-- gh-161: parallel rebalancer. One of the most important part of the latter is
> +-- a dispenser. It is a structure which hands out destination UUIDs in a
> +-- round-robin manner to worker fibers. It uses rlist data structure.
> +--
> +rlist = require('vshard.rlist')
> +
> +list = rlist.new()
> +list
> +
> +obj1 = {i = 1}
> +list:remove(obj1)
> +list
> +
> +list:add_tail(obj1)
> +list
> +
> +list:remove(obj1)
> +list
> +obj1
> +
> +list:add_tail(obj1)
> +obj2 = {i = 2}
> +list:add_tail(obj2)
> +list
> +obj3 = {i = 3}
> +list:add_tail(obj3)
> +list
> +
> +list:remove(obj2)
> +list
> +list:remove(obj1)
> +list
> diff --git a/vshard/rlist.lua b/vshard/rlist.lua
> new file mode 100644
> index 0000000..4be5382
> --- /dev/null
> +++ b/vshard/rlist.lua
> @@ -0,0 +1,53 @@
> +--
> +-- A subset of rlist methods from the main repository. Rlist is a
> +-- doubly linked list, and is used here to implement a queue of
> +-- routes in the parallel rebalancer.
> +--
> +local rlist_mt = {}
> +
> +function rlist_mt.add_tail(rlist, object)
> +    local last = rlist.last
> +    if last then
> +        last.next = object
> +        object.prev = last
> +    else
> +        rlist.first = object
> +    end
> +    rlist.last = object
> +    rlist.count = rlist.count + 1
> +end
> +
> +function rlist_mt.remove(rlist, object)
> +    local prev = object.prev
> +    local next = object.next
> +    local belongs_to_list = false
> +    if prev then
> +        belongs_to_list = true
> +        prev.next = next
> +    end
> +    if next then
> +        belongs_to_list = true
> +        next.prev = prev
> +    end
> +    object.prev = nil
> +    object.next = nil
> +    if rlist.last == object then
> +        belongs_to_list = true
> +        rlist.last = prev
> +    end
> +    if rlist.first == object then
> +        belongs_to_list = true
> +        rlist.first = next
> +    end
> +    if belongs_to_list then
> +        rlist.count = rlist.count - 1
> +    end
> +end
> +
> +local function rlist_new()
> +    return setmetatable({count = 0}, {__index = rlist_mt})
> +end
> +
> +return {
> +    new = rlist_new,
> +}
> diff --git a/vshard/storage/init.lua b/vshard/storage/init.lua
> index 5464824..1b48bf1 100644
> --- a/vshard/storage/init.lua
> +++ b/vshard/storage/init.lua
> @@ -13,12 +13,13 @@ if rawget(_G, MODULE_INTERNALS) then
>           'vshard.consts', 'vshard.error', 'vshard.cfg',
>           'vshard.replicaset', 'vshard.util',
>           'vshard.storage.reload_evolution',
> -        'vshard.lua_gc',
> +        'vshard.lua_gc', 'vshard.rlist'
>       }
>       for _, module in pairs(vshard_modules) do
>           package.loaded[module] = nil
>       end
>   end
> +local rlist = require('vshard.rlist')
>   local consts = require('vshard.consts')
>   local lerror = require('vshard.error')
>   local lcfg = require('vshard.cfg')
> @@ -1786,54 +1787,6 @@ local function rebalancer_build_routes(replicasets)
>       return bucket_routes
>   end
>   
> ---
> --- A subset of rlist methods from the main repository. Rlist is a
> --- doubly linked list, and is used here to implement a queue of
> --- routes in the parallel rebalancer.
> ---
> -local function rlist_new()
> -    return {count = 0}
> -end
> -
> -local function rlist_add_tail(rlist, object)
> -    local last = rlist.last
> -    if last then
> -        last.next = object
> -        object.prev = last
> -    else
> -        rlist.first = object
> -    end
> -    rlist.last = object
> -    rlist.count = rlist.count + 1
> -end
> -
> -local function rlist_remove(rlist, object)
> -    local prev = object.prev
> -    local next = object.next
> -    local belongs_to_list = false
> -    if prev then
> -        belongs_to_list = true
> -        prev.next = next
> -    end
> -    if next then
> -        belongs_to_list = true
> -        next.prev = prev
> -    end
> -    object.prev = nil
> -    object.next = nil
> -    if rlist.last == object then
> -        belongs_to_list = true
> -        rlist.last = prev
> -    end
> -    if rlist.first == object then
> -        belongs_to_list = true
> -        rlist.first = next
> -    end
> -    if belongs_to_list then
> -        rlist.count = rlist.count - 1
> -    end
> -end
> -
>   --
>   -- Dispenser is a container of routes received from the
>   -- rebalancer. Its task is to hand out the routes to worker fibers
> @@ -1842,7 +1795,7 @@ end
>   -- receiver nodes.
>   --
>   local function route_dispenser_create(routes)
> -    local rlist = rlist_new()
> +    local rlist = rlist.new()
>       local map = {}
>       for uuid, bucket_count in pairs(routes) do
>           local new = {
> @@ -1873,7 +1826,7 @@ local function route_dispenser_create(routes)
>           --    the main applier fiber does some analysis on the
>           --    destinations.
>           map[uuid] = new
> -        rlist_add_tail(rlist, new)
> +        rlist:add_tail(new)
>       end
>       return {
>           rlist = rlist,
> @@ -1892,7 +1845,7 @@ local function route_dispenser_put(dispenser, uuid)
>           local bucket_count = dst.bucket_count + 1
>           dst.bucket_count = bucket_count
>           if bucket_count == 1 then
> -            rlist_add_tail(dispenser.rlist, dst)
> +            dispenser.rlist:add_tail(dst)
>           end
>       end
>   end
> @@ -1909,7 +1862,7 @@ local function route_dispenser_skip(dispenser, uuid)
>       local dst = map[uuid]
>       if dst then
>           map[uuid] = nil
> -        rlist_remove(dispenser.rlist, dst)
> +        dispenser.rlist:remove(dst)
>       end
>   end
>   
> @@ -1952,9 +1905,9 @@ local function route_dispenser_pop(dispenser)
>       if dst then
>           local bucket_count = dst.bucket_count - 1
>           dst.bucket_count = bucket_count
> -        rlist_remove(rlist, dst)
> +        rlist:remove(dst)
>           if bucket_count > 0 then
> -            rlist_add_tail(rlist, dst)
> +            rlist:add_tail(dst)
>           end
>           return dst.uuid
>       end
> @@ -2742,11 +2695,6 @@ M.route_dispenser = {
>       pop = route_dispenser_pop,
>       sent = route_dispenser_sent,
>   }
> -M.rlist = {
> -    new = rlist_new,
> -    add_tail = rlist_add_tail,
> -    remove = rlist_remove,
> -}
>   M.schema_latest_version = schema_latest_version
>   M.schema_current_version = schema_current_version
>   M.schema_upgrade_master = schema_upgrade_master