ddl: store sharding info hashes on storage

Compute and store sharding key and sharding func hashes on storages.
Hashes are updated with on_replace triggers.

Part of #212

Author: DifferentialOrange

crud/common/sharding/sharding_metadata.lua

@@ -5,8 +5,10 @@ local call = require('crud.common.call')
 local const = require('crud.common.const')
 local dev_checks = require('crud.common.dev_checks')
 local cache = require('crud.common.sharding.sharding_metadata_cache')
+local storage_cache = require('crud.common.sharding.storage_metadata_cache')
 local sharding_func = require('crud.common.sharding.sharding_func')
 local sharding_key = require('crud.common.sharding.sharding_key')
+local sharding_utils = require('crud.common.sharding.utils')
 
 local FetchShardingMetadataError = errors.new_class('FetchShardingMetadataError', {capture_stack = false})
 
@@ -39,25 +41,6 @@ local function locked(f)
     end
 end
 
-local function extract_sharding_func_def(tuple)
-    if not tuple then
-        return nil
-    end
-
-    local SPACE_SHARDING_FUNC_NAME_FIELDNO = 2
-    local SPACE_SHARDING_FUNC_BODY_FIELDNO = 3
-
-    if tuple[SPACE_SHARDING_FUNC_BODY_FIELDNO] ~= nil then
-        return {body = tuple[SPACE_SHARDING_FUNC_BODY_FIELDNO]}
-    end
-
-    if tuple[SPACE_SHARDING_FUNC_NAME_FIELDNO] ~= nil then
-        return tuple[SPACE_SHARDING_FUNC_NAME_FIELDNO]
-    end
-
-    return nil
-end
-
 -- Return a map with metadata or nil when spaces box.space._ddl_sharding_key and
 -- box.space._ddl_sharding_func are not available on storage.
 function sharding_metadata_module.fetch_on_storage()
@@ -68,14 +51,12 @@ function sharding_metadata_module.fetch_on_storage()
         return nil
     end
 
-    local SPACE_NAME_FIELDNO = 1
-    local SPACE_SHARDING_KEY_FIELDNO = 2
     local metadata_map = {}
 
     if sharding_key_space ~= nil then
         for _, tuple in sharding_key_space:pairs() do
-            local space_name = tuple[SPACE_NAME_FIELDNO]
-            local sharding_key_def = tuple[SPACE_SHARDING_KEY_FIELDNO]
+            local space_name = tuple[sharding_utils.SPACE_NAME_FIELDNO]
+            local sharding_key_def = tuple[sharding_utils.SPACE_SHARDING_KEY_FIELDNO]
             local space_format = box.space[space_name]:format()
             metadata_map[space_name] = {
                 sharding_key_def = sharding_key_def,
@@ -86,8 +67,8 @@ function sharding_metadata_module.fetch_on_storage()
 
     if sharding_func_space ~= nil then
         for _, tuple in sharding_func_space:pairs() do
-            local space_name = tuple[SPACE_NAME_FIELDNO]
-            local sharding_func_def = extract_sharding_func_def(tuple)
+            local space_name = tuple[sharding_utils.SPACE_NAME_FIELDNO]
+            local sharding_func_def = sharding_utils.extract_sharding_func_def(tuple)
             metadata_map[space_name] = metadata_map[space_name] or {}
             metadata_map[space_name].sharding_func_def = sharding_func_def
         end

crud/common/sharding/storage_metadata_cache.lua

@@ -0,0 +1,95 @@
+local stash = require('crud.common.stash')
+local utils = require('crud.common.sharding.utils')
+
+local storage_metadata_cache = {}
+
+local FUNC = 1
+local KEY = 2
+
+local cache_data = {
+    [FUNC] = nil,
+    [KEY] = nil,
+}
+
+local ddl_space = {
+    [FUNC] = '_ddl_sharding_func',
+    [KEY] = '_ddl_sharding_key',
+}
+
+local trigger_stash = stash.get(stash.name.ddl_triggers)
+
+local function update_sharding_func_hash(tuple)
+    local space_name = tuple[utils.SPACE_NAME_FIELDNO]
+    local sharding_func_def = utils.extract_sharding_func_def(tuple)
+    cache_data[FUNC][space_name] = utils.compute_hash(sharding_func_def)
+end
+
+local function update_sharding_key_hash(tuple)
+    local space_name = tuple[utils.SPACE_NAME_FIELDNO]
+    local sharding_key_def = tuple[utils.SPACE_SHARDING_KEY_FIELDNO]
+    cache_data[KEY][space_name] = utils.compute_hash(sharding_key_def)
+end
+
+local update_hash = {
+    [FUNC] = update_sharding_func_hash,
+    [KEY] = update_sharding_key_hash,
+}
+
+local function init_cache(section)
+    cache_data[section] = {}
+
+    local space = box.space[ddl_space[section]]
+
+    local update_hash_func = update_hash[section]
+
+    -- Remove old trigger if there was some code reload.
+    -- It is possible that ddl space was dropped and created again,
+    -- so removing non-existing trigger will cause fail;
+    -- thus we use pcall.
+    pcall(space.on_replace, space, nil, trigger_stash[section])
+
+    trigger_stash[section] = space:on_replace(
+        function(_, new)
+            return update_hash_func(new)
+        end
+    )
+
+    for _, tuple in space:pairs() do
+        local space_name = tuple[utils.SPACE_NAME_FIELDNO]
+        -- If the cache record for a space is not nil, it means
+        -- that it was already set to up-to-date value with trigger.
+        -- It is more like an overcautiousness since the cycle
+        -- isn't expected to yield, but let it be here.
+        if cache_data[section][space_name] == nil then
+            update_hash_func(tuple)
+        end
+    end
+end
+
+local function get_sharding_hash(space_name, section)
+    if box.space[ddl_space[section]] == nil then
+        return nil
+    end
+
+    -- If one would drop and rebuild ddl spaces fom scratch manually,
+    -- caching is likely to break.
+    if cache_data[section] == nil then
+        init_cache(section)
+    end
+
+    return cache_data[section][space_name]
+end
+
+function storage_metadata_cache.get_sharding_func_hash(space_name)
+    return get_sharding_hash(space_name, FUNC)
+end
+
+function storage_metadata_cache.get_sharding_key_hash(space_name)
+    return get_sharding_hash(space_name, KEY)
+end
+
+function storage_metadata_cache.drop_caches()
+    cache_data = {}
+end
+
+return storage_metadata_cache

crud/common/sharding/utils.lua

@@ -0,0 +1,31 @@
+local digest = require('digest')
+local msgpack = require('msgpack')
+
+local utils = {}
+
+utils.SPACE_NAME_FIELDNO = 1
+utils.SPACE_SHARDING_KEY_FIELDNO = 2
+utils.SPACE_SHARDING_FUNC_NAME_FIELDNO = 2
+utils.SPACE_SHARDING_FUNC_BODY_FIELDNO = 3
+
+function utils.extract_sharding_func_def(tuple)
+    if not tuple then
+        return nil
+    end
+
+    if tuple[utils.SPACE_SHARDING_FUNC_BODY_FIELDNO] ~= nil then
+        return {body = tuple[utils.SPACE_SHARDING_FUNC_BODY_FIELDNO]}
+    end
+
+    if tuple[utils.SPACE_SHARDING_FUNC_NAME_FIELDNO] ~= nil then
+        return tuple[utils.SPACE_SHARDING_FUNC_NAME_FIELDNO]
+    end
+
+    return nil
+end
+
+function utils.compute_hash(val)
+    return digest.murmur(msgpack.encode(val))
+end
+
+return utils

crud/common/stash.lua

@@ -23,7 +23,8 @@ stash.name = {
     cfg = '__crud_cfg',
     stats_internal = '__crud_stats_internal',
     stats_local_registry = '__crud_stats_local_registry',
-    stats_metrics_registry = '__crud_stats_metrics_registry'
+    stats_metrics_registry = '__crud_stats_metrics_registry',
+    ddl_triggers = '__crud_ddl_spaces_triggers',
 }
 
 --- Setup Tarantool Cartridge reload.