Use multiple mongo DBs in same application for same model & same Repository - mongodb

Question

I need to implement Spring boot - MongoDb application where There are 2 mongo DBs which have exact same database name & collections. Based on User making a request, i need to choose whether to fetch data from DB1 or DB2 (only difference in mongo URI host - IP).
E.g. I need some way to create 2 mongoTemplates like mTempA & mTempB in my Repository & based on some condition, use either of the template to execute query as below:
#Repository
public class MyCustomRepository {
private Logger logger = LoggerFactory.getLogger(MyCustomRepository.class);
#Autowired
private MongoTemplateA mongoTemplateA;// Need to know if this is possible & how
#Autowired
private MongoTemplateB mongoTemplateB;// Need to know if this is possible & how
public List<MyModel> findByCriteria(MyRequest request) {
List<MyModel> result;
//Query query = <build query based on request>
if (request.getUserType().equals("A")) {
result = mongoTemplateA.find(query, MyModel.class);
} else {
result = mongoTemplateB.find(query, MyModel.class);
}
logger.debug("Result fetched with {} records", result.size());
return result;
}
}
I don't want to have 2 separate Repo (Class or Interfaces) or different models to be used. Just want to have 2 different mongoTemplates to be injected in single repo.
Is this possible? If yes, please give some example code.
I have followed below tutorial:
https://dzone.com/articles/multiple-mongodb-connectors-with-spring-boot

Answer 1

As rightly pointed out by #Lucia, below is how it can be done:
Have 2 different configuration placeholders
#Configuration
#EnableMongoRepositories(basePackages = "com.snk.repository", mongoTemplateRef = "mongoTemplateA")
public class MongoConfigA {
// Configuration class for DB 1 access
}
#Configuration
#EnableMongoRepositories(basePackages = "com.snk.repository", mongoTemplateRef = "mongoTemplateB")
public class MongoConfigB {
// Configuration class for DB 2 access
}
Get one class which will help in reading custom properties for mongo db properties in application.properties:
#ConfigurationProperties(prefix = "mongodb")
public class MultipleMongoProperties {
private MongoProperties adb = new MongoProperties();
private MongoProperties bdb = new MongoProperties();
public MongoProperties getAdb() {
return adb;
}
public MongoProperties getBdb() {
return bdb;
}
}
Add a configuration class to create mongoTemplates:
#Configuration
#EnableConfigurationProperties(MultipleMongoProperties.class)
public class MultipleMongoConfig {
#Autowired
private MultipleMongoProperties mongoProperties = new MultipleMongoProperties();
#Bean(name = "mongoTemplateA")
#Primary
public MongoTemplate mongoTemplateA() {
return new MongoTemplate(aDbFactory(this.mongoProperties.getAdb()));
}
#Bean(name = "mongoTemplateB")
public MongoTemplate mongoTemplateB() {
return new MongoTemplate(bDbFactory(this.mongoProperties.getBdb()));
}
#Bean
#Primary
public MongoDbFactory aDbFactory(final MongoProperties mongo) {
return new SimpleMongoDbFactory(new MongoClientURI(mongo.getUri()));
}
#Bean
public MongoDbFactory bDbFactory(final MongoProperties mongo) {
return new SimpleMongoDbFactory(new MongoClientURI(mongo.getUri()));
}
}
Add below decelerations to your service/repository:
#Autowired
#Qualifier("mongoTemplateA")
private MongoTemplate mongoTemplateA;
#Autowired
#Qualifier("MongoTemplateB")
private MongoTemplate MongoTemplateB;
Add below properties in your application.properties:
mongodb.adb.uri=mongodb://user:pass#myhost1:27017/adb
mongodb.bdb.uri=mongodb://user:pass#myhost2:27017/bdb
If you have mongo rplica set, URL can be set as:
mongodb.adb.uri=mongodb://user:pass#myhost1,myhost2,myhost13/adb?replicaSet=rsName
mongodb.bdb.uri=mongodb://user:pass#myhost1,myhost2,myhost13/bdb?replicaSet=rsName
Based on your logic, use either of the template.
Thought, there are few catches:
Notice the #Primary annotation, one bean needs to be marked as primary. I haven't find any solution if no template is marked primary.
If any of the mongo DB is down & application is started/restarted, application will not start/deploy. to avoid this, #Autowired needs to be changed to #Autowired(required = false).
If any of the mongo DB is down & application is already running, it automatically uses 2nd mongo BD (which is not down). So, even if you want to use A DB, if it's down, requests are processed with B DB & vice-versa.