[Tarantool-patches] [PATCH vshard 2/2] storage: introduce vshard.storage._call()

[Vladislav Shpilevoy]

It is a new internal function which is supposed to absorb all the
other internal functions to make it easier to change them, to
simplify adding new and drop old functions.

This also hides them from vshard.storage.* namespace so users
can't try to use them not knowing they are private.

Additionally, _call() allows to change internal function set even
on read-only instances, because it has nothing to do with the
schema. Internal function set can be updated by reload.

Closes #227
Part of #210
---

_call can't be properly integrated at this moment, because that
would break rebalancing from old nodes. The new function is only
added. Its usage and drop of old functions will happen in 0.1.17
when I will finish and merge top commit from this branch:
https://github.com/tarantool/vshard/tree/gerold103/gh-227-drop-old-functions

 test/upgrade/upgrade.result   | 12 ++++++++++++
 test/upgrade/upgrade.test.lua |  3 +++
 vshard/storage/init.lua       | 26 ++++++++++++++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/test/upgrade/upgrade.result b/test/upgrade/upgrade.result
index 0fb68c7..6c9bf2c 100644
--- a/test/upgrade/upgrade.result
+++ b/test/upgrade/upgrade.result
@@ -92,6 +92,10 @@ vshard.storage.internal.schema_latest_version
  | ---
  | - null
  | ...
+vshard.storage._call == nil
+ | ---
+ | - true
+ | ...
 bucket_count = vshard.consts.DEFAULT_BUCKET_COUNT / 2
  | ---
  | ...
@@ -157,6 +161,10 @@ vshard.storage.internal.schema_latest_version
  |   - 16
  |   - 0
  | ...
+vshard.storage._call ~= nil
+ | ---
+ | - true
+ | ...
 
 test_run:switch('storage_1_b')
  | ---
@@ -180,6 +188,10 @@ vshard.storage.internal.schema_latest_version
  |   - 16
  |   - 0
  | ...
+vshard.storage._call ~= nil
+ | ---
+ | - true
+ | ...
 
 test_run:switch('default')
  | ---
diff --git a/test/upgrade/upgrade.test.lua b/test/upgrade/upgrade.test.lua
index 3a4d113..422920e 100644
--- a/test/upgrade/upgrade.test.lua
+++ b/test/upgrade/upgrade.test.lua
@@ -31,6 +31,7 @@ test_run:switch('storage_2_a')
 box.space._schema:get({'oncevshard:storage:1'}) or box.space._schema:select()
 vshard.storage.internal.schema_current_version
 vshard.storage.internal.schema_latest_version
+vshard.storage._call == nil
 bucket_count = vshard.consts.DEFAULT_BUCKET_COUNT / 2
 first_bucket = vshard.consts.DEFAULT_BUCKET_COUNT / 2 + 1
 vshard.storage.bucket_force_create(first_bucket, bucket_count)
@@ -51,11 +52,13 @@ test_run:switch('storage_1_a')
 box.space._schema:get({'vshard_version'})
 vshard.storage.internal.schema_current_version()
 vshard.storage.internal.schema_latest_version
+vshard.storage._call ~= nil
 
 test_run:switch('storage_1_b')
 box.space._schema:get({'vshard_version'})
 vshard.storage.internal.schema_current_version()
 vshard.storage.internal.schema_latest_version
+vshard.storage._call ~= nil
 
 test_run:switch('default')
 -- Main purpose of the test - ensure that data can be safely moved
diff --git a/vshard/storage/init.lua b/vshard/storage/init.lua
index a87a50b..0af075b 100644
--- a/vshard/storage/init.lua
+++ b/vshard/storage/init.lua
@@ -325,6 +325,20 @@ local function schema_upgrade_to_0_1_16_0(username)
     log.info('Insert vshard_version into _schema')
     box.space._schema:replace({'vshard_version', 0, 1, 16, 0})
     box.space._schema:delete({'oncevshard:storage:1'})
+
+    -- vshard.storage._call() is supposed to replace some internal
+    -- functions exposed in _func; to allow introduction of new
+    -- functions on replicas; to allow change of internal
+    -- functions without touching the schema.
+    local func = 'vshard.storage._call'
+    log.info('Create function %s()', func)
+    box.schema.func.create(func, {setuid = true})
+    box.schema.user.grant(username, 'execute', 'function', func)
+    -- Don't drop old functions in the same version. Removal can
+    -- happen only after 0.1.16. Or there should appear support of
+    -- rebalancing from too old versions. Drop of these functions
+    -- now would immediately make it impossible to rebalance from
+    -- old instances.
 end
 
 local function schema_current_version()
@@ -2154,6 +2168,17 @@ local function storage_call(bucket_id, mode, name, args)
     return ok, ret1, ret2, ret3
 end
 
+local service_call_api = {
+    bucket_recv = bucket_recv,
+    rebalancer_apply_routes = rebalancer_apply_routes,
+    rebalancer_request_state = rebalancer_request_state,
+}
+
+local function service_call(...)
+    local service_name = select(1, ...)
+    return service_call_api[service_name](select(2, ...))
+end
+
 --------------------------------------------------------------------------------
 -- Configuration
 --------------------------------------------------------------------------------
@@ -2609,6 +2634,7 @@ return {
     rebalancing_is_in_progress = rebalancing_is_in_progress,
     recovery_wakeup = recovery_wakeup,
     call = storage_call,
+    _call = service_call,
     cfg = function(cfg, uuid) return storage_cfg(cfg, uuid, false) end,
     info = storage_info,
     buckets_info = storage_buckets_info,
-- 
2.21.1 (Apple Git-122.3)