ddl: reload and retry on sharding info mismatch

If sharding info mismatch has happened, sharding info will be reloaded
on router. After that, request will be retried with new sharding info
(expect for pairs requests due to its nature, they must be retried
manually).

There are no detectable performance drops introduced in this patch.

Closes #212

Author: DifferentialOrange

CHANGELOG.md

@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 * Fix processing storage error for tuple-merger implementation of
   select/pairs (#271).
 * Do not change input tuple object in requests.
+* Add automatic reload of DDL schema (#212).
 
 ## [0.10.0] - 01-12-21
 

README.md

@@ -117,26 +117,11 @@ Table below describe what operations supports custom sharding key:
 
 Current limitations for using custom sharding key:
 
-- It's not possible to update sharding keys automatically when schema is
-  updated on storages, see
-  [#212](https://github.com/tarantool/crud/issues/212). However it is possible
-  to do it manually with `require('crud.common.sharding_key').update_cache()`
-  (this function updates both caches: sharding key cache and sharding function
-  cache, but returned value is sharding key from cache).
 - No support of JSON path for sharding key, see
   [#219](https://github.com/tarantool/crud/issues/219).
 - `primary_index_fieldno_map` is not cached, see
   [#243](https://github.com/tarantool/crud/issues/243).
 
-Current limitations for using custom sharding functions:
-
-- It's not possible to update sharding functions automatically when schema is
-  updated on storages, see
-  [#212](https://github.com/tarantool/crud/issues/212). However it is possible
-  to do it manually with `require('crud.common.sharding_func').update_cache()`
-  (this function updates both caches: sharding key cache and sharding function
-  cache, but returned value is sharding function from cache).
-
 ### Insert
 
 ```lua

crud/borders.lua

@@ -2,6 +2,7 @@ local checks = require('checks')
 local errors = require('errors')
 local vshard = require('vshard')
 
+local const = require('crud.common.const')
 local dev_checks = require('crud.common.dev_checks')
 local call = require('crud.common.call')
 local utils = require('crud.common.utils')
@@ -76,7 +77,7 @@ local function call_get_border_on_router(border_name, space_name, index_name, op
 
     local space = utils.get_space(space_name, vshard.router.routeall())
     if space == nil then
-        return nil, BorderError:new("Space %q doesn't exist", space_name), true
+        return nil, BorderError:new("Space %q doesn't exist", space_name), const.NEED_SCHEMA_RELOAD
     end
 
     local index
@@ -87,7 +88,9 @@ local function call_get_border_on_router(border_name, space_name, index_name, op
     end
 
     if index == nil then
-        return nil, BorderError:new("Index %q of space %q doesn't exist", index_name, space_name), true
+        return nil,
+               BorderError:new("Index %q of space %q doesn't exist", index_name, space_name),
+               const.NEED_SCHEMA_RELOAD
     end
 
     local primary_index = space.index[0]
@@ -131,8 +134,14 @@ local function call_get_border_on_router(border_name, space_name, index_name, op
     for _, storage_result in pairs(results) do
         local storage_result = storage_result[1]
         if storage_result.err ~= nil then
+            local err_wrapped = BorderError:new("Failed to get %s: %s", border_name, storage_result.err)
+
             local need_reload = schema.result_needs_reload(space, storage_result)
-            return nil, BorderError:new("Failed to get %s: %s", border_name, storage_result.err), need_reload
+            if need_reload then
+                return nil, err_wrapped, const.NEED_SCHEMA_RELOAD
+            end
+
+            return nil, err_wrapped
         end
 
         local tuple = storage_result.res

crud/common/call.lua

@@ -3,6 +3,7 @@ local errors = require('errors')
 
 local dev_checks = require('crud.common.dev_checks')
 local utils = require('crud.common.utils')
+local sharding_utils = require('crud.common.sharding.utils')
 local fiber_clock = require('fiber').clock
 
 local CallError = errors.new_class('CallError')
@@ -40,6 +41,11 @@ function call.get_vshard_call_name(mode, prefer_replica, balance)
 end
 
 local function wrap_vshard_err(err, func_name, replicaset_uuid, bucket_id)
+    -- Do not rewrite ShardingHashMismatchError class.
+    if err.class_name == sharding_utils.ShardingHashMismatchError.name then
+        return errors.wrap(err)
+    end
+
     if err.type == 'ClientError' and type(err.message) == 'string' then
         if err.message == string.format("Procedure '%s' is not defined", func_name) then
             if func_name:startswith('_crud.') then

crud/common/const.lua

@@ -3,5 +3,9 @@ local const = {}
 const.RELOAD_RETRIES_NUM = 1
 const.RELOAD_SCHEMA_TIMEOUT = 3 -- 3 seconds
 const.FETCH_SHARDING_METADATA_TIMEOUT = 3 -- 3 seconds
+const.SHARDING_RELOAD_RETRIES_NUM = 1
 
-return const
+const.NEED_SCHEMA_RELOAD   = 0x0001000
+const.NEED_SHARDING_RELOAD = 0x0001001
+
+return const

crud/common/schema.lua

@@ -87,7 +87,7 @@ function schema.wrap_func_reload(func, ...)
     while true do
         res, err, need_reload = func(...)
 
-        if err == nil or not need_reload then
+        if err == nil or need_reload ~= const.NEED_SCHEMA_RELOAD then
             break
         end
 

crud/common/sharding/init.lua

@@ -3,12 +3,13 @@ local errors = require('errors')
 
 local BucketIDError = errors.new_class("BucketIDError", {capture_stack = false})
 local GetReplicasetsError = errors.new_class('GetReplicasetsError', {capture_stack = false})
-local ShardingHashMismatchError = errors.new_class("ShardingHashMismatchError", {capture_stack = false})
 
+local const = require('crud.common.const')
 local utils = require('crud.common.utils')
 local dev_checks = require('crud.common.dev_checks')
 local sharding_metadata_module = require('crud.common.sharding.sharding_metadata')
 local storage_metadata_cache = require('crud.common.sharding.storage_metadata_cache')
+local sharding_utils = require('crud.common.sharding.utils')
 
 local sharding = {}
 
@@ -114,12 +115,72 @@ function sharding.check_sharding_hash(space_name, sharding_func_hash, sharding_k
 
     if storage_func_hash ~= sharding_func_hash or storage_key_hash ~= sharding_key_hash then
         local err_msg = ('crud: Sharding hash mismatch for space %s. ' ..
-                         'Please refresh sharding data and retry your request.'
+                         'Sharding info will be refreshed after receiving this error. ' ..
+                         'Please retry your request.'
                         ):format(space_name)
-        return nil, ShardingHashMismatchError:new(err_msg)
+        return nil, sharding_utils.ShardingHashMismatchError:new(err_msg)
     end
 
     return true
 end
 
+function sharding.result_needs_sharding_reload(err)
+    return err.class_name == sharding_utils.ShardingHashMismatchError.name
+end
+
+function sharding.wrap_method(method, space_name, ...)
+    local i = 0
+
+    local res, err, need_reload
+    while true do
+        res, err, need_reload = method(space_name, ...)
+
+        if err == nil or need_reload ~= const.NEED_SHARDING_RELOAD then
+            break
+        end
+
+        sharding_metadata_module.reload_sharding_cache(space_name)
+
+        i = i + 1
+
+        if i > const.SHARDING_RELOAD_RETRIES_NUM then
+            break
+        end
+    end
+
+    return res, err, need_reload
+end
+
+-- This wrapper assumes reload is performed inside the method and
+-- expect ShardingHashMismatchError error to be thrown.
+function sharding.wrap_select_method(method, space_name, ...)
+    local i = 0
+
+    local ok, res, err
+    while true do
+        ok, res, err = pcall(method, space_name, ...)
+
+        if ok == true then
+            break
+        end
+
+        -- Error thrown from merger casted to string,
+        -- so the only way to identify it is string.find.
+        local str_err = tostring(res)
+        if (str_err:find(sharding_utils.ShardingHashMismatchError.name) == nil) then
+            error(res)
+        end
+
+        -- Reload is performed inside the merger.
+
+        i = i + 1
+
+        if i > const.SHARDING_RELOAD_RETRIES_NUM then
+            error(res)
+        end
+    end
+
+    return res, err
+end
+
 return sharding

crud/common/sharding/sharding_metadata.lua

@@ -1,5 +1,6 @@
 local fiber = require('fiber')
 local errors = require('errors')
+local log = require('log')
 
 local call = require('crud.common.call')
 local const = require('crud.common.const')
@@ -85,10 +86,11 @@ end
 -- a sharding metadata by a single one, other fibers will wait while
 -- cache.fetch_lock become unlocked during timeout passed to
 -- _fetch_on_router().
+-- metadata_map_name == nil means forced reload.
 local _fetch_on_router = locked(function(timeout, space_name, metadata_map_name)
-    dev_checks('number', 'string', 'string')
+    dev_checks('number', 'string', '?string')
 
-    if cache[metadata_map_name] ~= nil then
+    if (metadata_map_name ~= nil) and (cache[metadata_map_name]) ~= nil then
         return
     end
 
@@ -186,6 +188,15 @@ function sharding_metadata_module.update_sharding_func_cache(space_name)
     return sharding_metadata_module.fetch_sharding_func_on_router(space_name)
 end
 
+function sharding_metadata_module.reload_sharding_cache(space_name)
+    cache.drop_caches()
+
+    local err = _fetch_on_router(const.FETCH_SHARDING_METADATA_TIMEOUT, space_name, nil)
+    if err ~= nil then
+        log.warn('Failed to reload sharding cache: %s', err)
+    end
+end
+
 function sharding_metadata_module.init()
    _G._crud.fetch_on_storage = sharding_metadata_module.fetch_on_storage
 end

crud/common/sharding/utils.lua

@@ -1,4 +1,5 @@
 local digest = require('digest')
+local errors = require('errors')
 local msgpack = require('msgpack')
 
 local utils = {}
@@ -8,6 +9,8 @@ utils.SPACE_SHARDING_KEY_FIELDNO = 2
 utils.SPACE_SHARDING_FUNC_NAME_FIELDNO = 2
 utils.SPACE_SHARDING_FUNC_BODY_FIELDNO = 3
 
+utils.ShardingHashMismatchError = errors.new_class("ShardingHashMismatchError", {capture_stack = false})
+
 function utils.extract_sharding_func_def(tuple)
     if not tuple then
         return nil

crud/common/sharding_func.lua

@@ -4,6 +4,7 @@ local vshard = require('vshard')
 local fun = require('fun')
 local bit = require('bit')
 
+local const = require('crud.common.const')
 local schema = require('crud.common.schema')
 local dev_checks = require('crud.common.dev_checks')
 
@@ -631,12 +632,12 @@ end
 local function flatten_obj(space_name, obj)
     local space_format, err = utils.get_space_format(space_name, vshard.router.routeall())
     if err ~= nil then
-        return nil, FlattenError:new("Failed to get space format: %s", err), true
+        return nil, FlattenError:new("Failed to get space format: %s", err), const.NEED_SCHEMA_RELOAD
     end
 
     local tuple, err = utils.flatten(obj, space_format)
     if err ~= nil then
-        return nil, FlattenError:new("Object is specified in bad format: %s", err), true
+        return nil, FlattenError:new("Object is specified in bad format: %s", err), const.NEED_SCHEMA_RELOAD
     end
 
     return tuple

crud/common/sharding_key.lua

@@ -4,6 +4,7 @@ local vshard = require('vshard')
 local fiber = require('fiber')
 
 local call = require('crud.common.call')
+local const = require('crud.common.const')
 local utils = require('crud.common.utils')
 local sharding = require('crud.common.sharding')
 local filters = require('crud.compare.filters')
@@ -122,7 +123,7 @@ local function call_count_on_router(space_name, user_conditions, opts)
 
     local space = utils.get_space(space_name, replicasets)
     if space == nil then
-        return nil, CountError:new("Space %q doesn't exist", space_name), true
+        return nil, CountError:new("Space %q doesn't exist", space_name), const.NEED_SCHEMA_RELOAD
     end
 
     local sharding_key_data, err = sharding_metadata_module.fetch_sharding_key_on_router(space_name)
@@ -135,7 +136,7 @@ local function call_count_on_router(space_name, user_conditions, opts)
         sharding_key_as_index_obj = sharding_key_data.value,
     })
     if err ~= nil then
-        return nil, CountError:new("Failed to plan count: %s", err), true
+        return nil, CountError:new("Failed to plan count: %s", err), const.NEED_SCHEMA_RELOAD
     end
 
     -- set replicasets to count from
@@ -188,7 +189,7 @@ local function call_count_on_router(space_name, user_conditions, opts)
         local err
         replicasets_to_count, err = sharding.get_replicasets_by_bucket_id(bucket_id_data.bucket_id)
         if err ~= nil then
-            return nil, err, true
+            return nil, err, const.NEED_SCHEMA_RELOAD
         end
     else
         skip_sharding_hash_check = true
@@ -219,7 +220,13 @@ local function call_count_on_router(space_name, user_conditions, opts)
     }, call_opts)
 
     if err ~= nil then
-        return nil, CountError:new("Failed to call count on storage-side: %s", err)
+        local err_wrapped = CountError:new("Failed to call count on storage-side: %s", err)
+
+        if sharding.result_needs_sharding_reload(err) then
+            return nil, err_wrapped, const.NEED_SHARDING_RELOAD
+        end
+
+        return nil, err_wrapped
     end
 
     if results.err ~= nil then
@@ -289,7 +296,8 @@ function count.call(space_name, user_conditions, opts)
         mode = '?string',
     })
 
-    return schema.wrap_func_reload(call_count_on_router, space_name, user_conditions, opts)
+    return schema.wrap_func_reload(sharding.wrap_method,
+                                   call_count_on_router, space_name, user_conditions, opts)
 end
 
 return count