SpringBoot MongoDB 索引冲突分析及解决方法

时间:2021-12-20 06:02:16

一、背景

spring-data-mongo 实现了基于 mongodb 的 orm-mapping 能力,

通过一些简单的注解、query封装以及工具类,就可以通过对象操作来实现集合、文档的增删改查;

在 springboot 体系中,spring-data-mongo 是 mongodb java 工具库的不二之选。

二、问题产生

在一次项目问题的追踪中,发现springboot 应用启动失败,报错信息如下:

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)

关键信息: org.springframework.dao.dataintegrityviolationexception: cannot create index

从异常信息上看,出现的是索引冲突( command failed with error 85 ),spring-data-mongo 组件在程序启动时会实现根据注解创建索引的功能。

查看业务实体定义:

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@document(collection = "t_mdevice")
public class mdevice {
 
  @id
  private string id;
 
  @indexed(unique=true)
  private string deviceid;

deviceid 这个字段上定义了一个索引, unique=true 表示这是一个唯一索引。

我们继续 查看 mongodb中表的定义:

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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"
  }
]

发现数据库表中同样存在一个名为 deviceid的索引,但是并非唯一索引!

三、详细分析

为了核实错误产生的原因,我们尝试通过 mongo shell去执行索引的创建,发现返回了同样的错误。

通过将数据库中的索引删除,或更正为 unique=true 之后可以解决当前的问题。

从严谨度上看,一个索引冲突导致 springboot 服务启动不了,是可以接受的。

但从灵活性来看,是否有某些方式能 禁用索引的自动创建 ,或者仅仅是打印日志呢?

尝试 google spring data mongodb disable index creation

发现 jira-datamongo-1201 在2015年就已经提出,至今未解决。

SpringBoot MongoDB 索引冲突分析及解决方法

* 找到许多  同样问题 

但大多数的解答是不采用索引注解,选择其他方式对索引进行管理。

这些结果并不能令人满意。

尝试查看 spring-data-mongo 的机制,定位到 mongopersistententityindexcreator 类:

初始化方法中,会根据 mappingcontext(实体映射上下文)中已有的实体去创建索引

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public mongopersistententityindexcreator(mongomappingcontext mappingcontext, mongodbfactory mongodbfactory,
      indexresolver indexresolver) {
    ...
    //根据已有实体创建
    for (mongopersistententity<?> entity : mappingcontext.getpersistententities()) {
      checkforindexes(entity);
    }
  }

在接收到mappingcontextevent时,创建对应实体的索引

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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) {
     //创建单个实体索引
     checkforindexes((mongopersistententity<?>) entity);
   }
 }

mongopersistententityindexcreator是通过mongotemplate引入的,如下:

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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实现了 applicationcontextaware,当applicationcontext被实例化时被感知
public void setapplicationcontext(applicationcontext applicationcontext) throws beansexception {
 
  prepareindexcreator(applicationcontext);
 
  eventpublisher = applicationcontext;
  if (mappingcontext instanceof applicationeventpublisheraware) {
    //mappingcontext作为事件来源,向applicationcontext发布
    ((applicationeventpublisheraware) mappingcontext).setapplicationeventpublisher(eventpublisher);
  }
  resourceloader = applicationcontext;
}
 
...
//注入事件监听
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 监听 applicationcontext的事件
    ((configurableapplicationcontext) context).addapplicationlistener(indexcreator);
  }
}

由此可见, mongotemplate 在初始化时,先通过 mongoconverter 带入 mongomappingcontext,

随后完成一系列初始化,整个过程如下:

  • 实例化 mongotemplate;
  • 实例化 mongoconverter;
  • 实例化 mongopersistententityindexcreator;
  • 初始化索引(通过mappingcontext已有实体);
  • repository初始化 -> mappingcontext 发布映射事件;
  • applicationcontext 将事件通知到 indexcreator;
  • indexcreator 创建索引

在实例化过程中,没有任何配置可以阻止索引的创建。

四、解决问题

从前面的分析中,可以发现问题关键在 indexcreator,能否提供一个自定义的实现呢,答案是可以的!

实现的要点如下

  • 实现一个indexcreator,可继承mongopersistententityindexcreator,去掉索引的创建功能;
  • 实例化 mongoconverter和 mongotemplate时,使用一个空的 mongomappingcontext对象避免初始化索引;
  • 将自定义的indexcreator作为bean进行注册,这样在prepareindexcreator方法执行时,原来的 mongopersistententityindexcreator不会监听applicationcontext的事件
  • indexcreator 实现了applicationcontext监听,接管 mappingevent事件处理。

实例化bean

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@bean
 public mongomappingcontext mappingcontext() {
   return new mongomappingcontext();
 }
 
 // 使用 mappingcontext 实例化 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;
 }

自定义indexcreator

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// 自定义indexcreator实现
@component
public static class customindexcreator extends mongopersistententityindexcreator {
 
  // 构造器引用mappingcontext
  public customindexcreator(mongomappingcontext mappingcontext, mongodbfactory mongodbfactory) {
    super(mappingcontext, mongodbfactory);
  }
 
  public void onapplicationevent(mappingcontextevent<?, ?> event) {
    persistententity<?, ?> entity = event.getpersistententity();
 
    // 获得mongo实体类
    if (entity instanceof mongopersistententity) {
      system.out.println("detected mongoentity " + entity.getname());
      
      //可实现索引处理..
    }
  }
}

在这里 customindexcreator继承了 mongopersistententityindexcreator ,将自动接管mappingcontextevent事件的监听。

在业务实现上可以根据需要完成索引的处理!

小结

spring-data-mongo 提供了非常大的便利性,但在灵活性支持上仍然不足。上述的方法实际上有些隐晦,在官方文档中并未提及这样的方式。

orm-mapping 框架在实现schema映射处理时需要考虑校验级别,比如 hibernate便提供了 none/create/update/validation 多种选择,毕竟这对开发者来说更加友好。

期待 spring-data-mongo 在后续的演进中能尽快完善 schema的管理功能!

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。

原文链接:http://www.cnblogs.com/littleatp/p/10043447.html