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Posted to commits@kylin.apache.org by xx...@apache.org on 2022/09/20 05:10:42 UTC
[kylin] branch doc5.0 updated: Add design of metastore
This is an automated email from the ASF dual-hosted git repository.
xxyu pushed a commit to branch doc5.0
in repository https://gitbox.apache.org/repos/asf/kylin.git
The following commit(s) were added to refs/heads/doc5.0 by this push:
new 2ba5eb5ad4 Add design of metastore
2ba5eb5ad4 is described below
commit 2ba5eb5ad44d17dec6f1a309085f20ed29090b5d
Author: XiaoxiangYu <xx...@apache.org>
AuthorDate: Mon Sep 19 16:59:05 2022 +0800
Add design of metastore
---
.../write_and_read_persistent_entity.puml | 98 +++++++++++++++
.../write_and_read_persistent_entity_cn.png | Bin 0 -> 272752 bytes
.../write_and_read_persistent_entity_cn.puml | 68 ++++++++++
.../class_diagram/metastore_resource_store.png | Bin 0 -> 175673 bytes
.../class_diagram/metastore_resource_store.puml | 126 +++++++++++++++++++
.../development/dev_design/metastore_design.md | 139 +++++++++++++++++++++
website/docusaurus.config.js | 1 +
website/sidebars.js | 4 +
8 files changed, 436 insertions(+)
diff --git a/website/docs/development/dev_design/diagram/activity_diagram/write_and_read_persistent_entity.puml b/website/docs/development/dev_design/diagram/activity_diagram/write_and_read_persistent_entity.puml
new file mode 100644
index 0000000000..ce38478968
--- /dev/null
+++ b/website/docs/development/dev_design/diagram/activity_diagram/write_and_read_persistent_entity.puml
@@ -0,0 +1,98 @@
+@startuml
+
+start
+
+if (alreadyInTransaction?) then (yes)
+ :call process() of inner transaction;
+ end
+endif
+
+repeat
+ :Update Transaction Metrics;
+ :UnitOfWorkParams.getProcessor().preprocess();
+
+ :UnitOfWork#startTransaction;
+ partition #lightyellow "startTransaction" {
+ if (EpochNotOwnedByCurrentProcess?) then (no)
+ :throw Exception;
+ end
+ endif
+ : checkThreadLock;
+ : lockThreadLock;
+ if(isSandboxMode) then (yes)
+ : prepare thread kylin config;
+ : prepare thread ResourceStore(ThreadViewResourceStore);
+ endif
+ }
+
+ :UnitOfWorkParams.getProcessor().process();
+ :process(real business logic)// change is stored in ThreadViewResourceStore;
+ partition #azure "business logic" {
+ : copy new PersistentEntity for write;
+ : update on new PersistentEntity;
+ : create XXXManager;
+ : call XXXManager#save();
+ partition "XXXManager" {
+ : some check;
+ : CachedCrudAssist#save();
+ : ResourceStore#checkAndPutResource();
+ }
+ }
+
+
+ :UnitOfWork#endTransaction;
+ partition #powderblue "endTransaction" {
+ : remove thread kylin config;
+ if(isSandboxMode) then (yes)
+ : Fetch change from thread ResourceStore;
+ endif
+
+ :flushSandboxMeta;
+ :write_AuditLogStore;
+ :replay audit log into resource store;
+
+ }
+
+
+repeat while (Transaction failed and not hit max retry times?) is (retry) not (Succeed or not failed)
+ ->//return a object//;
+stop
+
+'autonumber 1.0
+'doInTransactionWithRetry -> isAlreadyInTransaction
+'
+'isAlreadyInTransaction --> doInTransactionWithRetry
+'
+'doInTransactionWithRetry -> updateMetrics
+'
+'loop "Retry-transaction" [123]
+' autonumber 2.0
+' updateMetrics -> preProcess
+'
+' group doTransaction []
+' autonumber 3.0
+' preProcess -> startTransaction
+'
+' group startTransaction [hello]
+' startTransaction -> checkEpoch
+'
+' checkEpoch -> fetchLock
+'
+' fetchLock -> lock
+' end
+'
+' lock -> process : 业务逻辑
+'
+'
+' process -> flushSandboxMeta
+'
+' group endTransaction []
+' autonumber 4.0
+' flushSandboxMeta -> write_AuditLogStore
+'
+' write_AuditLogStore -> write_Metastore
+' end
+'
+'end
+
+@enduml
\ No newline at end of file
diff --git a/website/docs/development/dev_design/diagram/activity_diagram/write_and_read_persistent_entity_cn.png b/website/docs/development/dev_design/diagram/activity_diagram/write_and_read_persistent_entity_cn.png
new file mode 100644
index 0000000000..170f84cfaf
Binary files /dev/null and b/website/docs/development/dev_design/diagram/activity_diagram/write_and_read_persistent_entity_cn.png differ
diff --git a/website/docs/development/dev_design/diagram/activity_diagram/write_and_read_persistent_entity_cn.puml b/website/docs/development/dev_design/diagram/activity_diagram/write_and_read_persistent_entity_cn.puml
new file mode 100644
index 0000000000..a5d1f7e435
--- /dev/null
+++ b/website/docs/development/dev_design/diagram/activity_diagram/write_and_read_persistent_entity_cn.puml
@@ -0,0 +1,68 @@
+@startuml
+
+start
+
+note right
+ 这个是 Kylin 5.0 **元数据事务** 的提交流程分析
+ ======
+ 1. 元数据事务的相关代码在 UnitOfWork, 本活动图是对代码的说明;
+ 2. Epoch 是全局级别的, 项目粒度的元数据写锁, 用于确保同一时刻只有一个进程会修改指定项目下的元数据;
+ 3. 为了避免获得 Epoch 的进程多线程同时变更元数据, 所以获得 Epoch 的进程, 还需要进行一个进程内的写锁的锁定, 以确保获得 Epoch 的进程对元数据的变更, 是串行的;
+ 4. 调用 endTransaction 方法前, 元数据变更会发生在一个沙盒模式的 ResourceStore;
+ 5. 在 endTransaction 方法, 会将元数据变更持久化到 Metastore(RDBMS) 和 AuditLogStore(RDBMS), 这里使用 RDBMS 的事务保证元数据操作的一致性;
+ 6. 其他 Kylin 进程会定期获取 AuditLogStore 的变更, 重放到自己的 ResourceStore.
+end note
+
+if (是否已经在事务?) then (yes)
+ :调用"被包含"的子事务的 process 方法并且退出子事务;
+ end
+endif
+
+repeat
+ :更新元数据事务相关的 Metrics;
+ :调用 UnitOfWorkParams.getProcessor().preprocess(), 目前没有太多作用;
+
+ partition #lightyellow "startTransaction" {
+
+ if (当前进程是否拥有 Epoch?) then (no)
+ :抛出异常并且结束事务;
+ end
+ endif
+ : 获取进程内写锁;
+ : 对进程内写锁进行锁定;
+ if(是否启用沙盒模式?) then (yes)
+ : 创建 KylinConfig 的快照并且进行设置到 ThreadLocal;
+ : 创建 ThreadViewResourceStore, 以保证事务提交前\n事务内的元数据变更, 不会对外部可见;
+ endif
+ }
+ floating note #pink: 开始元数据事务的准备工作, \n相关代码在 UnitOfWork#startTransaction
+
+ partition #azure "process 方法包含的元数据修改逻辑(业务逻辑)" {
+ : 获取 startTransaction 准备的 KylinConfig;
+ : 创建 XXXManager 和 PersistentEntity;
+ : 使用 XXXManager 对变更后的 PersistentEntity 进行保存;
+ floating note #pink: 调用 UnitOfWorkParams.getProcessor().process()\n, process 方法由 Service 层传递, process 方法包含业务逻辑,\n在这一阶段元数据变更会发生在沙盒内(也就是 ThreadViewResourceStore)
+ partition "XXXManager" {
+ : XXXManager 对变更后的 PersistentEntity 进行约束性检查;
+ : XXXManager 调用 CachedCrudAssist#save() 写入 Cache;
+ : CachedCrudAssist 调用 ResourceStore#checkAndPutResource() \n写入 ThreadViewResourceStore 的 overlay;
+ }
+ }
+
+ partition #powderblue "endTransaction" {
+ floating note #pink: 调用 UnitOfWork#endTransaction 来将\n ThreadViewResourceStore 的元数据变更提交;
+ : 清理 ThreadLocal 级别的 KylinConfig;
+ : 再次检查当前进程是否持有 Epoch;
+ if(是否启用沙盒模式?) then (yes)
+ : 从 ThreadViewResourceStore 的 overlay 收集元数据变更, 保存到 UnitMessages;
+ : 在一个 RDBMS 事务内, 提交 UnitMessages 的变更到\n MetadataStore 和 AuditLogStore 对应的表;
+ : 通过 MessageSynchronization 将 UnitMessages 缓存的元数据变更\n重放到原先的 ResourceStore(此时对外部可见);
+ endif
+ :更新元数据事务的耗时指标;
+ }
+
+repeat while (事务失败, 并且事务失败次数尚未超出重试最大次数?) is (是, 则触发事务重试) not (否, 那么事务成功, 或者事务失败次数超出阈值)
+ ->\n//返回 Pair<Boolean, T>, 其中 Boolean 标示事务是否成功, T 是业务逻辑(也就是 process方法)的返回值 //;
+stop
+
+@enduml
\ No newline at end of file
diff --git a/website/docs/development/dev_design/diagram/class_diagram/metastore_resource_store.png b/website/docs/development/dev_design/diagram/class_diagram/metastore_resource_store.png
new file mode 100644
index 0000000000..03ece7d787
Binary files /dev/null and b/website/docs/development/dev_design/diagram/class_diagram/metastore_resource_store.png differ
diff --git a/website/docs/development/dev_design/diagram/class_diagram/metastore_resource_store.puml b/website/docs/development/dev_design/diagram/class_diagram/metastore_resource_store.puml
new file mode 100644
index 0000000000..b2712369ff
--- /dev/null
+++ b/website/docs/development/dev_design/diagram/class_diagram/metastore_resource_store.puml
@@ -0,0 +1,126 @@
+@startuml
+
+namespace business_layer {
+ class DataModelManager #pink {
+ 'CRUD operation of DataModel // first kind method;
+ 'complex business logic of DataModel // second kind method;
+
+ private NDataModel saveDataModelDesc(NDataModel dataModelDesc); // metadata write path, level 1
+ }
+
+ class CachedCrudAssist<T extends RootPersistentEntity> #pink {
+ protected Cache<String, T extends RootPersistentEntity> cache; // cache of RootPersistentEntity
+ ResourceStore resourceStore;
+
+ public T save(T entity); // metadata write path, level 2
+ }
+}
+
+
+namespace resource_store {
+
+
+ class RawResource {
+ private String resPath;
+ private ByteSource byteSource;
+ private long timestamp;
+ private long mvcc;
+ }
+
+ class VersionedRawResource {
+ RawResource resource;
+ Integer mvcc;
+ }
+
+ abstract class ResourceStore {
+ static Cache<KylinConfig, ResourceStore> META_CACHE;
+ volatile ConcurrentSkipListMap<String, VersionedRawResource> data; // cache of byte array
+
+ public final <T extends RootPersistentEntity> void checkAndPutResource(String resPath, T obj,
+ Serializer<T> serializer); // metadata write path, level 3
+ }
+
+ class InMemResourceStore
+
+ class ThreadViewResourceStore {
+ // ThreadViewResourceStore like a sandbox, update on ThreadViewResourceStore won't impact outside.\n ThreadViewResourceStore is used in transaction(UnitOfContext) only. */
+
+ InMemResourceStore overlay; // store local change of an uncommitted transaction
+ InMemResourceStore underlying; // real ResourceStore
+ }
+}
+
+
+namespace metastore {
+ abstract class MetadataStore {
+ void putResource(RawResource res, String unitPath, long epochId); // metadata write path, level 4
+ }
+
+
+ class JDBCMetadataStore {
+ DataSourceTransactionManager transactionManager;
+ JdbcTemplate jdbcTemplate;
+ RowMapper<RawResource> RAW_RESOURCE_ROW_MAPPER;
+ }
+
+ class HDFSMetadataStore
+ class FileMetadataStore
+
+ class JdbcUtil {
+
+ }
+
+ abstract class EpochStore {
+
+ }
+}
+
+
+namespace sync {
+ abstract class AuditLogStore {
+ void save(UnitMessages unitMessages); // metadata write path, level 5
+ }
+
+ class JDBCAuditLogStore
+}
+
+
+'---------------------- Class Relation(extends) ---------------------
+
+resource_store.InMemResourceStore --|> resource_store.ResourceStore : extends
+
+resource_store.ThreadViewResourceStore --|> resource_store.ResourceStore : extends
+
+resource_store.VersionedRawResource --|> resource_store.RawResource : extends
+
+
+metastore.JDBCMetadataStore --|> metastore.MetadataStore : extends
+metastore.HDFSMetadataStore --|> metastore.MetadataStore : extends
+metastore.FileMetadataStore --|> metastore.MetadataStore : extends
+
+sync.JDBCAuditLogStore --|> sync.AuditLogStore : extends
+
+'---------------------- Class Relation(contains) ---------------------
+
+
+business_layer.DataModelManager *-- "business_layer.CachedCrudAssist" : contains
+
+"business_layer.CachedCrudAssist" *-- resource_store.ResourceStore : contains
+
+resource_store.ResourceStore *-- metastore.MetadataStore : contains
+
+metastore.MetadataStore *-- sync.AuditLogStore : contains
+
+metastore.MetadataStore *-- metastore.EpochStore : contains
+
+resource_store.ThreadViewResourceStore *-- resource_store.InMemResourceStore : contains
+
+
+
+'---------------------- Class Relation(relate) ---------------------
+
+resource_store.ResourceStore --> resource_store.VersionedRawResource : store
+
+
+
+@enduml
\ No newline at end of file
diff --git a/website/docs/development/dev_design/metastore_design.md b/website/docs/development/dev_design/metastore_design.md
new file mode 100644
index 0000000000..2022f3b9ab
--- /dev/null
+++ b/website/docs/development/dev_design/metastore_design.md
@@ -0,0 +1,139 @@
+---
+title: Metastore Design of Kylin 5
+language: en
+sidebar_label: Metastore Design of Kylin 5
+pagination_label: Metastore Design of Kylin 5
+toc_min_heading_level: 2
+toc_max_heading_level: 6
+pagination_prev: null
+pagination_next: null
+showLastUpdateAuthor: true
+showLastUpdateTime: true
+keywords:
+ - dev-design
+draft: false
+last_update:
+ date: 09/16/2022
+ author: Xiaoxiang Yu
+---
+
+### Target Audience
+
+这篇文档是为有以下需求的用户和开发者而准备的:
+1. 对 Kylin 5.0 元数据存储, 元数据缓存, 以及节点间元数据同步机制感兴趣的用户和开发者.
+2. 在二次开发过程中, 想了解对 Kylin 5.0 进行元数据读写操作的最佳实践和注意事项的开发者.
+3. 想对 Kylin 5.0 的元数据进行升级改造的开发者.
+
+### Terminology
+
+#### Core Class and Interface
+
+| Class | Comment |
+|-----------------------------|----------------------------------------------------|
+| ResourceStore | 用于管理内存中对元数据的操作 |
+| InMemResourceStore | ResourceStore 的实现类, 用于绝大部分情况 |
+| ThreadViewResourceStore | ResourceStore 的实现类, 作为一个沙盒式的 ResourceStore, 在事务中使用 |
+| MetadataStore | 用于管理元数据持久化的操作 |
+| AuditLogStore | 用于节点间元数据同步, 以及诊断元数据异常情况 |
+| Epoch | 用于保证同时只有一个进程对指定项目下的元数据进行修改操作, 或者提交作业 |
+| EpochStore | 用于持久化 Epoch |
+
+
+### Question and Answer
+
+#### 1. Why Kylin 5.0 need transaction(of metadata) ?
+因为用户操作可能同时操作多个元数据, 这些元数据变更必须保持一致性, 要么同时变更成功要么同时变更失败, 不允许出现中间状态.
+例如, 如果用户修改 DataModel 的维度和度量, IndexPlan 也需要随之同时变更, 两者必须保持一致性.
+
+#### 2. How transaction was implemented？
+检查 [元数据更新流程图](#metadata_write)
+
+#### 3. How do meta was synced in Kylin Cluster？
+对于指定项目, Kylin 节点要获取 Epoch 才能对元数据进行写操作, 所以对于这个项目下面元数据, 没有获取 Epoch 的 Kylin 节点
+将作为 Follower 通过 AuditLogReplayWorker 获取元数据更新.
+
+Follower 同步元数据变更，通过两个方式，代码在 AuditLogReplayWorker
+1. 第一个是 Follower 自己定期调度同步任务，默认间隔是 5s；
+2. 第二个方式是元数据变更的节点发送 AuditLogBroadcastEventNotifier 告知所有 Follower, Follower 主动 replay
+
+按照设计，Follower 元数据的 delay 在 1-2s 左右(被动广播同步)，最多 5s(主动定期同步).
+
+#### 4. How to read meta from metastore？
+todo
+
+#### 5. As a kylin developer, how should I write my code to update metadata?
+
+
+1. 使用 `@org.apache.kylin.rest.aspect.Transaction` 对你的业务方法进行注解, 这个在你的方法比较简短(轻量)的情况比较推荐
+ ```java
+ class JobService{
+
+ @Transaction(project = 0)
+ public ExecutableResponse manageJob(String project, ExecutableResponse job, String action) throws IOException {
+ Preconditions.checkNotNull(project);
+ Preconditions.checkNotNull(job);
+ Preconditions.checkArgument(!StringUtils.isBlank(action));
+
+ if (JobActionEnum.DISCARD == JobActionEnum.valueOf(action)) {
+ return job;
+ }
+
+ updateJobStatus(job.getId(), project, action);
+ return getJobInstance(job.getId());
+ }
+ }
+ ```
+2. 使用 `EnhancedUnitOfWork.doInTransactionWithCheckAndRetry` 来包含你的业务代码(元数据修改代码)
+
+```java
+class SomeService {
+ public void renameDataModel() {
+ // some codes not in transaction
+ EnhancedUnitOfWork.doInTransactionWithCheckAndRetry(() -> {
+ // 1. Get XXXManager, such as NDataModelManager
+ KylinConfig config = KylinConfig.getInstanceFromEnv(); // thread local KylinConfig was created in startTransaction
+ NDataModelManager manager = config.getManager(project, NDataModelManager.class);
+ // 2. Get RootPersistentEntity by XXXManager and Update XXX
+ NDataModel nDataModel = modelManager.getDataModelDesc(modelId);
+ checkAliasExist(modelId, newAlias, project);
+ nDataModel.setAlias(newAlias);
+ NDataModel modelUpdate = modelManager.copyForWrite(nDataModel);
+ // 3. Call updateXXX method of XXXManager
+ modelManager.updateDataModelDesc(modelUpdate);
+ }, project);
+ // some more codes not in transaction
+ }
+}
+```
+
+:::info 元数据操作须知
+1. KylinConfig 和 XXXManager(例如:NDataModelManager) 需要在事务内获取,
+原因在于事务开启时准备了一个事务专用的单独的 KylinConfig, 单独的 KylinConfig 绑定了事务需要的 ResourceStore
+2. 开启多线程修改元数据需要注意, 原因在于新的线程并不能获取事务开启时准备的 KylinConfig, 而是全局的 KylinConfig
+3. 两个事务写的时候别复用同一个对象, 以避免元数据更新时, MVCC 检查失败
+:::
+
+#### 6. AuditLog replay and clean
+
+todo
+
+#### 7. Metadata dumped logic
+
+todo
+
+### <span id="metadata_write">Diagram of write a piece of meta </span>
+
+#### About Activity Diagram
+1. 元数据事务的相关代码在 `UnitOfWork`, 本活动图是对代码的说明;
+2. `Epoch` 是全局级别的, 项目粒度的元数据写锁, 用于确保同一时刻只有一个进程会修改指定项目下的元数据;
+3. 为了避免多线程同时变更元数据, 所以获得 Epoch 的进程, 还需要进行一个进程内的写锁的锁定, 以确保获得 `Epoch` 的进程对元数据的变更, 是串行的;
+4. 调用 `endTransaction` 方法前, 元数据变更会发生在一个沙盒模式的 `ResourceStore`;
+5. 在 `endTransaction` 方法, 会将元数据变更持久化到 `Metastore`(RDBMS) 和 `AuditLogStore`(RDBMS), 这里使用 RDBMS 的事务保证元数据操作的一致性;
+6. 关于事物的异常和回滚, 在 `process` 方法发生的异常因为元数据变更是发生在沙盒的, 所以直接舍弃沙盒即可;
+在 `endTransaction` 发生的异常, 由 RDBMS 事务保证对 Metastore 和 AudiLogStore 操作的原子性;
+7. 其他 Kylin 进程会定期获取 `AuditLogStore` 的变更, 重放到自己的 `ResourceStore`, 来保持节点间的元数据的一致性.
+
+
+
+### <span id="class_metastore">Class Diagram of Metastore</span>
+
diff --git a/website/docusaurus.config.js b/website/docusaurus.config.js
index 008c020c89..7e640b14f3 100644
--- a/website/docusaurus.config.js
+++ b/website/docusaurus.config.js
@@ -239,6 +239,7 @@ const config = {
Built with Docusaurus.`,
},
prism: {
+ additionalLanguages: ['java'],
theme: lightCodeTheme,
darkTheme: darkCodeTheme,
},
diff --git a/website/sidebars.js b/website/sidebars.js
index 10f48ce8e6..94cabbf514 100644
--- a/website/sidebars.js
+++ b/website/sidebars.js
@@ -970,6 +970,10 @@ const sidebars = {
type: 'doc',
id: 'development/how_to_subscribe_mailing_list'
},
+ {
+ type: 'doc',
+ id: 'development/dev_design/metastore_design'
+ },
],
},