SpringBoot-MongoDB 索引衝突分析及解決
一、背景
spring-data-mongo 實現了基於 MongoDB 的 ORM-Mapping 能力,
通過一些簡單的註解、Query封裝以及工具類,就可以通過物件操作來實現集合、文件的增刪改查;
在 SpringBoot 體系中,spring-data-mongo 是 MongoDB Java 工具庫的不二之選。
二、問題產生
在一次專案問題的追蹤中,發現SpringBoot 應用啟動失敗,報錯資訊如下:
Error creating bean with name 'mongoTemplate' defined in class path resource [org/bootfoo/BootConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.data.mongodb.core.MongoTemplate]: Factory method 'mongoTemplate' threw exception; nested exception is org.springframework.dao.DataIntegrityViolationException: Cannot create index for 'deviceId' in collection 'T_MDevice' with keys '{ "deviceId" : 1}' and options '{ "name" : "deviceId"}'. Index already defined as '{ "v" : 1 , "unique" : true , "key" : { "deviceId" : 1} , "name" : "deviceId" , "ns" : "appdb.T_MDevice"}'.; nested exception is com.mongodb.MongoCommandException: Command failed with error 85: 'exception: Index with name: deviceId already exists with different options' on server 127.0.0.1:27017. The full response is { "createdCollectionAutomatically" : false, "numIndexesBefore" : 6, "errmsg" : "exception: Index with name: deviceId already exists with different options", "code" : 85, "ok" : 0.0 } at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:588) at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:366) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1264) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553) ... Caused by: org.springframework.dao.DataIntegrityViolationException: Cannot create index for 'deviceId' in collection 'T_MDevice' with keys '{ "deviceId" : 1}' and options '{ "name" : "deviceId"}'. Index already defined as '{ "v" : 1 , "unique" : true , "key" : { "deviceId" : 1} , "name" : "deviceId" , "ns" : "appdb.T_MDevice"}'.; nested exception is com.mongodb.MongoCommandException: Command failed with error 85: 'exception: Index with name: deviceId already exists with different options' on server 127.0.0.1:27017. The full response is { "createdCollectionAutomatically" : false, "numIndexesBefore" : 6, "errmsg" : "exception: Index with name: deviceId already exists with different options", "code" : 85, "ok" : 0.0 } at org.springframework.data.mongodb.core.index.MongoPersistentEntityIndexCreator.createIndex(MongoPersistentEntityIndexCreator.java:157) at org.springframework.data.mongodb.core.index.MongoPersistentEntityIndexCreator.checkForAndCreateIndexes(MongoPersistentEntityIndexCreator.java:133) at org.springframework.data.mongodb.core.index.MongoPersistentEntityIndexCreator.checkForIndexes(MongoPersistentEntityIndexCreator.java:125) at org.springframework.data.mongodb.core.index.MongoPersistentEntityIndexCreator.<init>(MongoPersistentEntityIndexCreator.java:91) at org.springframework.data.mongodb.core.index.MongoPersistentEntityIndexCreator.<init>(MongoPersistentEntityIndexCreator.java:68) at org.springframework.data.mongodb.core.MongoTemplate.<init>(MongoTemplate.java:229) at org.bootfoo.BootConfiguration.mongoTemplate(BootConfiguration.java:121) at org.bootfoo.BootConfiguration$$EnhancerBySpringCGLIB$$1963a75.CGLIB$mongoTemplate$2(<generated>) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:162) ... 58 more Caused by: com.mongodb.MongoCommandException: Command failed with error 85: 'exception: Index with name: deviceId already exists with different options' on server 127.0.0.1:27017. The full response is { "createdCollectionAutomatically" : false, "numIndexesBefore" : 6, "errmsg" : "exception: Index with name: deviceId already exists with different options", "code" : 85, "ok" : 0.0 } at com.mongodb.connection.ProtocolHelper.getCommandFailureException(ProtocolHelper.java:115) at com.mongodb.connection.CommandProtocol.execute(CommandProtocol.java:114) at com.mongodb.connection.DefaultServer$DefaultServerProtocolExecutor.execute(DefaultServer.java:168)
關鍵資訊:org.springframework.dao.DataIntegrityViolationException: Cannot create index
從異常資訊上看,出現的是索引衝突(Command failed with error 85),spring-data-mongo 元件在程式啟動時會實現根據註解建立索引的功能。
檢視業務實體定義:
@Document(collection = "T_MDevice") public class MDevice { @Id private String id; @Indexed(unique=true) private String deviceId;
deviceId 這個欄位上定義了一個索引,unique=true表示這是一個唯一索引。
我們繼續 檢視 MongoDB中表的定義:
db.getCollection('T_MDevice').getIndexes() >> [ { "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "appdb.T_MDevice" }, { "v" : 1, "key" : { "deviceId" : 1 }, "name" : "deviceId", "ns" : "appdb.T_MDevice" } ]
發現數據庫表中同樣存在一個名為 deviceId的索引,但是並非唯一索引!
三、詳細分析
為了核實錯誤產生的原因,我們嘗試通過 Mongo Shell去執行索引的建立,發現返回了同樣的錯誤。
通過將資料庫中的索引刪除,或更正為 unique=true 之後可以解決當前的問題。
從嚴謹度上看,一個索引衝突導致 SpringBoot 服務啟動不了,是可以接受的。
但從靈活性來看,是否有某些方式能禁用索引的自動建立,或者僅僅是列印日誌呢?
嘗試 google spring data mongodb disable index creation
發現 JIRA-DATAMONGO-1201在2015年就已經提出,至今未解決。
圖
stackoverflow 找到許多同樣問題,
但大多數的解答是不採用索引註解,選擇其他方式對索引進行管理。
這些結果並不能令人滿意。
嘗試檢視 spring-data-mongo 的機制,定位到 MongoPersistentEntityIndexCreator類:
- 初始化方法中,會根據 MappingContext(實體對映上下文)中已有的實體去建立索引
public MongoPersistentEntityIndexCreator(MongoMappingContext mappingContext, MongoDbFactory mongoDbFactory,
IndexResolver indexResolver) {
...
//根據已有實體建立
for (MongoPersistentEntity<?> entity : mappingContext.getPersistentEntities()) {
checkForIndexes(entity);
}
}
- 在接收到MappingContextEvent時,建立對應實體的索引
public void onApplicationEvent(MappingContextEvent<?, ?> event) {
if (!event.wasEmittedBy(mappingContext)) {
return;
}
PersistentEntity<?, ?> entity = event.getPersistentEntity();
// Double check type as Spring infrastructure does not consider nested generics
if (entity instanceof MongoPersistentEntity) {
//建立單個實體索引
checkForIndexes((MongoPersistentEntity<?>) entity);
}
}
MongoPersistentEntityIndexCreator是通過MongoTemplate引入的,如下:
public MongoTemplate(MongoDbFactory mongoDbFactory, MongoConverter mongoConverter) {
Assert.notNull(mongoDbFactory);
this.mongoDbFactory = mongoDbFactory;
this.exceptionTranslator = mongoDbFactory.getExceptionTranslator();
this.mongoConverter = mongoConverter == null ? getDefaultMongoConverter(mongoDbFactory) : mongoConverter;
...
// We always have a mapping context in the converter, whether it's a simple one or not
mappingContext = this.mongoConverter.getMappingContext();
// We create indexes based on mapping events
if (null != mappingContext && mappingContext instanceof MongoMappingContext) {
indexCreator = new MongoPersistentEntityIndexCreator((MongoMappingContext) mappingContext, mongoDbFactory);
eventPublisher = new MongoMappingEventPublisher(indexCreator);
if (mappingContext instanceof ApplicationEventPublisherAware) {
((ApplicationEventPublisherAware) mappingContext).setApplicationEventPublisher(eventPublisher);
}
}
}
...
//MongoTemplate實現了 ApplicationContextAware,當ApplicationContext被例項化時被感知
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
prepareIndexCreator(applicationContext);
eventPublisher = applicationContext;
if (mappingContext instanceof ApplicationEventPublisherAware) {
//MappingContext作為事件來源,向ApplicationContext釋出
((ApplicationEventPublisherAware) mappingContext).setApplicationEventPublisher(eventPublisher);
}
resourceLoader = applicationContext;
}
...
//注入事件監聽
private void prepareIndexCreator(ApplicationContext context) {
String[] indexCreators = context.getBeanNamesForType(MongoPersistentEntityIndexCreator.class);
for (String creator : indexCreators) {
MongoPersistentEntityIndexCreator creatorBean = context.getBean(creator, MongoPersistentEntityIndexCreator.class);
if (creatorBean.isIndexCreatorFor(mappingContext)) {
return;
}
}
if (context instanceof ConfigurableApplicationContext) {
//使 IndexCreator 監聽 ApplicationContext的事件
((ConfigurableApplicationContext) context).addApplicationListener(indexCreator);
}
}
由此可見,MongoTemplate在初始化時,先通過MongoConverter 帶入 MongoMappingContext,
隨後完成一系列初始化,整個過程如下:
- 例項化 MongoTemplate;
- 例項化 MongoConverter;
- 例項化 MongoPersistentEntityIndexCreator;
- 初始化索引(通過MappingContext已有實體);
- Repository初始化 -> MappingContext 釋出對映事件;
- ApplicationContext 將事件通知到 IndexCreator;
- IndexCreator 建立索引
在例項化過程中,沒有任何配置可以阻止索引的建立。
四、解決問題
從前面的分析中,可以發現問題關鍵在 IndexCreator,能否提供一個自定義的實現呢,答案是可以的!
實現的要點如下
- 實現一個IndexCreator,可繼承MongoPersistentEntityIndexCreator,去掉索引的建立功能;
- 例項化 MongoConverter和 MongoTemplate時,使用一個空的 MongoMappingContext物件避免初始化索引;
- 將自定義的IndexCreator作為Bean進行註冊,這樣在prepareIndexCreator方法執行時,
原來的 MongoPersistentEntityIndexCreator不會監聽ApplicationContext的事件 - IndexCreator 實現了ApplicationContext監聽,接管 MappingEvent事件處理。
例項化Bean
@Bean
public MongoMappingContext mappingContext() {
return new MongoMappingContext();
}
// 使用 MappingContext 例項化 MongoTemplate
@Bean
public MongoTemplate mongoTemplate(MongoDbFactory mongoDbFactory, MongoMappingContext mappingContext) {
MappingMongoConverter converter = new MappingMongoConverter(new DefaultDbRefResolver(mongoDbFactory),
mappingContext);
converter.setTypeMapper(new DefaultMongoTypeMapper(null));
MongoTemplate mongoTemplate = new MongoTemplate(mongoDbFactory, converter);
return mongoTemplate;
}
自定義IndexCreator
// 自定義IndexCreator實現
@Component
public static class CustomIndexCreator extends MongoPersistentEntityIndexCreator {
// 構造器引用MappingContext
public CustomIndexCreator(MongoMappingContext mappingContext, MongoDbFactory mongoDbFactory) {
super(mappingContext, mongoDbFactory);
}
public void onApplicationEvent(MappingContextEvent<?, ?> event) {
PersistentEntity<?, ?> entity = event.getPersistentEntity();
// 獲得Mongo實體類
if (entity instanceof MongoPersistentEntity) {
System.out.println("Detected MongoEntity " + entity.getName());
//可實現索引處理..
}
}
}
在這裡 CustomIndexCreator繼承了MongoPersistentEntityIndexCreator,將自動接管MappingContextEvent事件的監聽。
在業務實現上可以根據需要完成索引的處理!
小結
spring-data-mongo 提供了非常大的便利性,但在靈活性支援上仍然不足。上述的方法實際上有些隱晦,在官方文件中並未提及這樣的方式。
ORM-Mapping 框架在實現Schema對映處理時需要考慮校驗級別,比如 Hibernate便提供了 none/create/update/validation 多種選擇,畢竟這對開發者來說更加友好。
期待 spring-data-mongo 在後續的演進中能儘快完善 Schema的管理功能!